Streptococcus suis serotype 2(S.suis 2)is a zoonotic pathogen that clinically causes severe swine and human infections(such as meningitis,endocarditis,and septicemia).In order to cause widespread diseases in different...Streptococcus suis serotype 2(S.suis 2)is a zoonotic pathogen that clinically causes severe swine and human infections(such as meningitis,endocarditis,and septicemia).In order to cause widespread diseases in different organs,S.suis 2 must colonize the host,break the blood barrier,and cause exaggerated inflammation.In the last few years,most studies have focused on a single virulence factor and its influences on the host.Membrane vesicles(MVs)can be actively secreted into the extracellular environment contributing to bacteria-host interactions.Gram-negative bacteria-derived outer membrane vesicles(OMVs)were recently shown to activate host Caspase-11-mediated non-canonical inflammasome pathway via deliverance of OMV-bound lipopolysaccharide(LPS),causing host cell pyroptosis.However,little is known about the effect of the MVs from S.suis 2(Gram-positive bacteria without LPS)on cell pyroptosis.Thus,we investigated the molecular mechanism by which S.suis 2 MVs participate in endothelial cell pyroptosis.In this study,we used proteomics,electron scanning microscopy,fluorescence microscope,Western blotting,and bioassays,to investigate the MVs secreted by S.suis 2.First,we demonstrated that S.suis 2 secreted MVs with an average diameter of 72.04 nm,and 200 proteins in MVs were identified.Then,we showed that MVs were transported to cells via mainly dynamin-dependent endocytosis.The S.suis 2 MVs activated NLRP3/Caspase-1/GSDMD canonical inflammasome signaling pathway,resulting in cell pyroptosis,but it did not activate the Caspase-4/-5 pathway.More importantly,endothelial cells produce large amounts of reactive oxygen species(ROS)and lost their mitochondrial membrane potential under induction by S.suis 2 MVs.The results in this study suggest for the first time that MVs from S.suis 2 were internalized by endothelial cells via mainly dynamin-dependent endocytosis and might promote NLRP3/Caspase-1/GSDMD pathway by mitochondrial damage,which produced mtDNA and ROS under induction,leading to the pyroptosis of endothelial cells.展开更多
Muramidase-released protein(MRP)is now being recognized as a critical indicator of the virulence and pathogenicity of Streptococcus suis(S.suis).However,the identification of viable therapeutics for S.suis infection w...Muramidase-released protein(MRP)is now being recognized as a critical indicator of the virulence and pathogenicity of Streptococcus suis(S.suis).However,the identification of viable therapeutics for S.suis infection was hindered by the absence of an explicit mechanism for MRP-actuated inflammation.Dihydroartemisinin(DhA)is an artemisinin derivative with potential anti-inflammatory activity.The modulatory effect of DhA on the inflammatory response mediated by the virulence factor MRP remains obscure.This research aimed to identify the signaling mechanism by which MRP triggers the innate immune response in mouse spleen and cultured macrophages.With the candidate mechanism in mind,we investigated DhA for its ability to dampen the pro-inflammatory response induced by MRP.The innate immune response in mice was drastically triggered by MRP,manifesting as splenic and systemic inflammation with splenomegaly,immune cell infiltration,and an elevation in pro-inflammatory cytokines.A crucial role for Toll-like receptor 4(TLR4)in coordinating the MRP-mediated inflammatory response via nuclear factor-kappa B(NF-kB)activation was revealed by TLR4 blockade.In addition,NFkB-dependent transducer and activator of transcription 3(STAT3)and mitogen-activated protein kinases(MAPKs)activation was required for the inflammatory signal transduction engendered by MRP.Intriguingly,we observed an alleviation effect of DhA on the MRP-induced immune response,which referred to the suppression of TLR4-mediated actuation of NF-kB-STAT3/MAPK cascades.The inflammatory response elicited by MRP is relevant to TLR4-dependent NF-kB activation,followed by an increase in the activity of STAT3 or MAPKs.DhA mitigates the inflammation process induced by MRP via blocking the TLR4 cascade,highlighting the therapeutic potential of DhA in targeting S.suis infection diseases.展开更多
[Objective] This study aimed to establish a method for quantitative detection of mRNA transcriptional level of SS2 adhesive related-factors of Streptococcus suis serotype 2 （SS2） by fluorescent quantitative PCR. []V...[Objective] This study aimed to establish a method for quantitative detection of mRNA transcriptional level of SS2 adhesive related-factors of Streptococcus suis serotype 2 （SS2） by fluorescent quantitative PCR. []Vlethod] The gene fragments en- coding SS2 adhesive related-factors MRP, FBPS and CPS2J and a housekeeping gene aroA were amplified by reverse transcription PCR from the total RNA of SS2, cloned, and sequenced. The recombinant plasmids containing the target genes were constructed, and used as templates in Real-time PCR. [Result] Dynamic curves, stan- dard curves and melting curves of the adhesive related-factors and aroA were ob- tained by the optimized Real-time PCR system. The standard curves showed a good linear relationship between template copy number and circulation number, and the correlation coefficients （FF） of the standard curves were over 0.995. Also, these as- says were highly specific a^d there was single specific melting peak for every gene. Moreover, the assays were highly sensitive and had a detection limit of 1.0×102 copies in 1 μl of initial templates. Finally, it was highly repeatable and had a coeffi- cient of variation less than 2% for intra-assay. [Conclusion] This study will provide a way to reveal the adhesion mechanism of SS2 to different host cells at molecular level.展开更多
Respiratory diseases are one of the most important health problems in pig herds. The porcine respiratory disease complex (PRDC) is the term used to describe pneumonic diseases caused by multiple infectious agents that...Respiratory diseases are one of the most important health problems in pig herds. The porcine respiratory disease complex (PRDC) is the term used to describe pneumonic diseases caused by multiple infectious agents that provoke weight loss in animals or death. In the PRDC multiple pathogens (bacteria and/or viruses) work in combination to induce this respiratory disease. Within this complex, Actinobacillus pleuropneumoniae, Streptococcus suis, Pasteurella multocida, Bordetella bronchiseptica, Haemophilus parasuis and Mycoplasma hyopneumoniae are the main bacterial pathogens involved in great economic losses to the swine industry. The aim of this work was to estimate the presence of A. pleuropneumoniae, S. suis, P. multocida, B. bronchiseptica, H. parasuis and M. hyopneumoniae in the upper respiratory tract of pigs in representative swine farms inAguascalientes,Mexico, using PCR technique. The study was performed in 14 swine farms. We obtained a total of 212 nasal swabs. Near 20% of samples were positive for A. pleuropneumoniae (located in the 79% of farms);17% were positive for S. suis (in 86% of farms), of these, 3% were S. suis serovar 2;30% were positive for H. parasuis (93% of farms);23% of the samples to P. multocida (in 79% of farms);and 19% to M. hyopneumoniae (in 64% of farms). B. bronchiseptica was not detected in this study. The results obtained show that bacterial pathogens of PRDC were present in the upper respiratory tract of pigs in all farms studied;therefore, these pathogens are widely disseminated in pig farms of Aguascalientes, Mexico.展开更多
Brucellosis is a bacterial anthropozoonosis usually caused by Brucella abortus, Brucella melitensis, Brucella suis and Brucella canis. Brucella suis, the causative agent of swine brucellosis, is classified into five b...Brucellosis is a bacterial anthropozoonosis usually caused by Brucella abortus, Brucella melitensis, Brucella suis and Brucella canis. Brucella suis, the causative agent of swine brucellosis, is classified into five biovars and preferentially infects different animal hostsIll. In China, brucellosis is a national notifiable communicable disease both in animals and in human. In 2009, 35 816 brucellosis cases were reported. The annual incidence was 2.7 per 100 000 population.展开更多
对四川猪链球菌2型(S.suis 2)强毒株05ZYH33溶血素样蛋白(hemolysin-like protein,HLP)编码基因hlp进行序列信息分析、分子克隆表达及溶血活性检测,深入探讨HLP的致病机制.用Blast和Clustal X程序对HLP进行基因同源性分析,用Signal P 4....对四川猪链球菌2型(S.suis 2)强毒株05ZYH33溶血素样蛋白(hemolysin-like protein,HLP)编码基因hlp进行序列信息分析、分子克隆表达及溶血活性检测,深入探讨HLP的致病机制.用Blast和Clustal X程序对HLP进行基因同源性分析,用Signal P 4.1和TMHMM Server 2.0分析HLP氨基酸序列.设计合成hlp引物进行PCR扩增,先后将hlp克隆入p MD-18T载体和p ET30a表达载体中,构建p ET30a::hly原核表达质粒.将重组质粒转化至E.coli BL21中诱导表达,并对重组HLP蛋白进行纯化和溶血活性检测.同源性分析表明HLP与多种具有溶血活性的蛋白相似性较高.氨基酸序列分析发现HLP具有信号肽和跨膜区,且由DUF21、CBS和Cor CHly C 3部分组成.序列测定显示hly片段全长1 335 bp,编码445个氨基酸.重组质粒经诱导表达和纯化后电泳显示,HLP分子量约为70 k Da,具有溶血活性.结果表明,HLP是一个膜结合蛋白,不同于能够分泌到细胞外的溶血素Suilysin.重组HLP具有一定的溶血效价,此可能与致病相关.展开更多
[Objectives]This study aimed to investigate the pathogenicity,growth characteristics and drug resistance of Streptococcus suis type 2.[Methods]Bacterial isolation and identification,biochemical experiments,determinati...[Objectives]This study aimed to investigate the pathogenicity,growth characteristics and drug resistance of Streptococcus suis type 2.[Methods]Bacterial isolation and identification,biochemical experiments,determination of growth curve and correlation curve between OD 600 values and viable counts,drug susceptibility tests,pathogenicity analysis,and histopathological observations were carried out.[Results]The Streptococcus strain isolated from infected pigs was identified as Streptococcus suis type 2,which was named TA01 strain.TA01 strain reached the growth peak at 6-8 h post-incubation,and viable counts gradually declined after 8 h of incubation.The correlation equation between OD 600 values and viable counts is y=24.659 x-1.076 1,R^2=0.996 7.TA01 strain was sensitive to penicillin,erythromycin,florfenicol and oxacillin,and resistant to ciprofloxacin,polymyxin B and clindamycin.According to the results of pathogenicity analysis,all the mice in 3.6×10^9 cfu/mouse group died within 48,and these dead mice exhibited acute pyaemia septica.Based on the Reed-Muench formula,it was calculated that LD 50 of TA01 strain was 1.137×10^8 cfu/mouse.Pathological examination showed obvious blue-stained bacteria clusters,accompanied by neutrophil infiltration.[Conclusions]TA01 strain was a virulent strain of Streptococcus suis type 2.Compared with Streptococcus strains which were isolated and reported in China,TA01 strain exhibited strong virulence and rapid proliferation.展开更多
BACKGROUND Streptococcus suis(S.suis)is an anthropozoonotic pathogen that shows clinical manifestations of meningitis,septicemia,and arthritis in infected humans.Nocardia is another type of anthropozoonotic bacteria,w...BACKGROUND Streptococcus suis(S.suis)is an anthropozoonotic pathogen that shows clinical manifestations of meningitis,septicemia,and arthritis in infected humans.Nocardia is another type of anthropozoonotic bacteria,with clinical manifestations of skin,lung,and brain abscesses in infected humans.Few intracranial infections caused by S.suis or Nocardia have been reported.To the best of our knowledge,no study has reported a patient with simultaneous intracranial infection by S.suis and Nocardia.CASE SUMMARY A 66-year-old male presented at Liaocheng People’s Hospital(Liaocheng,Shandong Province,China)reporting dizziness with nausea and vomiting.Metagenomic next-generation sequencing(m NGS)was performed on cerebrospinal fluid for examination,and the patient was diagnosed with suppurative meningitis caused by S.suis infection.He received anti-infection treatment with penicillin sodium and ceftriaxone.The patient’s condition initially improved but then deteriorated.Further m NGS of cerebrospinal fluid revealed both S.suis and Nocardia.Imaging examination revealed a brain abscess.Furthermore,a mixed infection of S.suis and Nocardia was detected in the patient’s central nervous system.The patient was treated with antibiotics and sulfamethoxazole.He was discharged after his condition improved.CONCLUSION This case shows that the disease can be recurrent in patients with intracranial infection of a rare pathogen.The possibility of mixed infection should also be considered,especially in patients treated with immunosuppressive agents.m NGS of cerebrospinal fluid is a supplement to conventional microbial pathogen identification methods.Patients with unknown pathogen diagnosis,early extensive use of antibiotics and infection with rare pathogens can be diagnosed by the combination of conventional methods and m NGS of cerebrospinal fluid.展开更多
Streptococcus suis is an important pathogen in pigs. Transmission of this pathogen is generally believed to occur between healthy carrier sows and their offspring, so the carrier status of S. suis in healthy sows is i...Streptococcus suis is an important pathogen in pigs. Transmission of this pathogen is generally believed to occur between healthy carrier sows and their offspring, so the carrier status of S. suis in healthy sows is important for the control of S. suis infections in pigs, especially in suckling and growing pigs. In this study, the prevalence of S. suis isolated from clinically healthy sows in China was studied for the first time. A total of 1 043 tonsil samples were collected from clinically healthy sows from 10 regions in China from 2005 to 2007. Among the 421 S. suis isolates, 31 strains were identified as capsular type 2. The results showed that S. suis was widespread in swine herds in China with the carrier rates in different herds ranging from 19.5 to 93.9%. Overall, 40.4 and 3.0% of clinically healthy sows harbored S. suis and capsular type 2 in their palatine tonsils, respectively. Statistically significant differences of carrier rates of S. suis and capsular type 2 between the different farms were observed, which was independent of herd sizes and geographic distributions of different herds.展开更多
[ Objective] To obtain detection antigen for diagnosis of Streptococcus suis infection. [ Method] The complete ORF of glutamate dehy- drogenase （GDH） gene was amplified from the genomic DNA of Streptococcus suis ser...[ Objective] To obtain detection antigen for diagnosis of Streptococcus suis infection. [ Method] The complete ORF of glutamate dehy- drogenase （GDH） gene was amplified from the genomic DNA of Streptococcus suis serotype 2 strain SC22 isolated in Sichuan Province by poly- merase chain reaction （PCR）. The resulting product was cloned into the prokaryotic expression vector pET-30a, which was then transformed into E. coil BL21 （DE3）. The identified positive transformants were screened for expression induced by IPTG. The expression products were subjected to SDS-PAGE and the recombinant protein was purified by nickel ion-agarose affinity chromatography. New Zealand rabbits were immunized with the purified recombinant GDH protein to prepare polyclonal antibodies. Titers of the anti-serum were determined by indirect ELISA and Western blot assay. [ Result] The recombinant GDH protein was effectively expressed in the host bacteria, and highly pure recombinant protein was obtained by nickel ion-agarose affinity chromatography. High-titer anti-serum against the recombinant protein was obtained. As evidenced by western blot as- say, the sera could react specifically with the lysates of all detected Streptococcus suis strains. In addition, the recombinant GDH protein could re- act specifically with serum samples collected from five pigs experimentally infected by strain SC22. [ Conclusion] The expressed GDH fusion protein has some common epitopes of natural GDH and can be used as detection antigen to develop ELISA and other diagnostic methods.展开更多
Streptococcus suis （S. suis） is a Gram-positive, facultatively anaerobic coccus that has been implicated as the cause of a wide range of clinical disease syndromes in swine and other domestic animals. S. suis has al...Streptococcus suis （S. suis） is a Gram-positive, facultatively anaerobic coccus that has been implicated as the cause of a wide range of clinical disease syndromes in swine and other domestic animals. S. suis has also been implicated in disease in humans, especially anaong abattoir workers, swine and pork handlers. Here we report a case of streptococcal toxic shock syndrome（STSS） caused by S. suis in a 59-year-old man. Despite of intensive treatment, the patient died of shock with multiple organ failure 14 h after admission. One bacterial isolate obtained from blood culture was identified to the species level by biochemical tests and serological tests as S. suis serotype 2. Identification was confirmed by PCR amplification of genes encoding 16sRNA of S. suis and the capsule of S. suis serotype 2（cps 23）. Genes encoding virulence factors were also detected. An investigation to identify the source of S. suis revealed that several days before admission the affected man had been handling sick pigs or their meat. Transmission may occur through breaks in the skin of feet with tinea due to that no measures for personal protection was taken. This case should highten awareness of the potential for occupational exposure and human infection with S. suis.展开更多
Antimicrobial resistance is undoubtedly one of the greatest global health threats. The emergence of multidrug-resistant(MDR) Gram-positive pathogens, such as methicillin-resistant Staphylococcus aureus(MRSA), vancomyc...Antimicrobial resistance is undoubtedly one of the greatest global health threats. The emergence of multidrug-resistant(MDR) Gram-positive pathogens, such as methicillin-resistant Staphylococcus aureus(MRSA), vancomycin-resistant Enterococcus faecium(VRE), and β-lactamase-resistant Streptococcus pneumonia, has severely limited our antibiotic arsenal. Numerous ribosome-targeting antibiotics, especially pleuromutilins, oxazolidinones, and streptogramins, are viewed as promising alternatives against aggressive MDR pathogens. In this study, we identified a new adenosine triphosphate(ATP)-binding cassete(ABC)-F family determinant, srp A, in Streptococcus suis(S. suis) by means of a comparative analysis of the whole-genome sequences of tiamulin(TIA)-resistant and TIA-sensitive bacteria. Functional cloning confirmed that the deduced gene can mediate cross-resistance to pleuromutilins, lincosamides, and streptogramin A in S. suis and S. aureus. A sequence alignment revealed that Srp A shares the highest amino acid identity with Vga(E)(36%) and shows canonical characteristics of ABC-F family members.In Srp A-ribosome docked compounds, the extended loop region of Srp A approaches the valnemulinbinding pocket in the ribosome peptidyl-transferase center and competes with bound valnemulin. A detailed mutational analysis of the loop residues confirmed that this domain is crucial for Srp A activity,as substitutions or truncations of this region affect the efficiency and specificity of antibiotic resistance.Intracellular antibiotics accumulation indicated that Srp A does not act as an efflux pump, while a ribosome binding assay supported the protective effects of Srp A on the ribosome by preventing antibiotic binding as well as displacing bound drugs. These findings clarify the mechanisms underlying resistance to ribosomal antibiotics.展开更多
Streptococcus suis(S. suis) is a Gram-positive zoonotic pathogen. S. suis infection in humans commonly causes meningitis, septicemia, arthritis,and streptococcal toxic shock-like syndrome(STSLS). S. suis has 29 seroty...Streptococcus suis(S. suis) is a Gram-positive zoonotic pathogen. S. suis infection in humans commonly causes meningitis, septicemia, arthritis,and streptococcal toxic shock-like syndrome(STSLS). S. suis has 29 serotypes, of which S. suis serotype 2(SS2) has the highest clinical isolation rate and strongest pathogenicity and causes most S. suis human infections.About 1,000 different sequence types(STs)were identified in S.suis based on multilocus sequence typing(MLST).Among these,STs,ST1,and ST7 belong to serotype 2 and are the major hazards of S.suis.in 1998 and 2005,two cases of SS2 human infection outbreak were reported in Jiangsu and Sichuan,China,causing 14 deaths and 38 deaths,respectively.展开更多
Streptococcus suis is one of the major pathogens of swine streptococcosis. Among them, the strongest virulence and highest rate of clinical isolation serotype is S. suis serotype 2（SS2）. Moreover, SS2 is also an imp...Streptococcus suis is one of the major pathogens of swine streptococcosis. Among them, the strongest virulence and highest rate of clinical isolation serotype is S. suis serotype 2（SS2）. Moreover, SS2 is also an important zoonosis pathogen, which caused severe public health issues in China. It has been reported that SS2 has several virulence factors, including muramidase released protein, extracellular factors, capsule, fibronectin-binding protein, enolase, hemolysin, small RNA, biofilm, two-component regulatory systems, STK/STP, etc., whose functions involved in adhesion, anti-phagocytosis, inflammatory pathway activation, invasion, etc. Actually, SS2 has developed a variety of ways to escape from host immune system during evolution. In particularly, capsule could resist phagocytosis through inhibiting sphingosine dependent immune cell recognition, which plays an important role in escaping host inflammation response; moreover, superoxide dismutase encoding by sod A enables SS2 escaping reactive oxygen species（ROS） in host immune cells; besides, binding complement factor h with Fhb could suppress the activation of complement alternative pathway and bactericidal effect. And SS2 could also hinder the formation of neutrophil extracellular traps（NETs） to avoid trapping by swine neutrophils, while host immune globulin could be degraded by Ig A1 hydrolase and Ig M protease. In addition, SS2 could escape host immune defense with the help of multiple transcriptional factors and micro-RNA. So far, the pathogenesis of meningitis, arthritis caused by SS2 infection, is still unclear, and the virulence regulatory mechanism of phosphorylation, micro-RNA need to be further clarified. Importantly, the study of interaction mechanism of pathogen and host contribute to further demonstration the pathogenesis of SS2.展开更多
[ Objectlve] This study aimed to investigate the antimicrobial effect of Chinese herbal preparation Yinqiaotiangan against Streptococcus suis serotype II in vivo. [ Method ] The prevention and treatment tests were con...[ Objectlve] This study aimed to investigate the antimicrobial effect of Chinese herbal preparation Yinqiaotiangan against Streptococcus suis serotype II in vivo. [ Method ] The prevention and treatment tests were conducted with Kunming mice weighing about 18 -22 g. In the prevention test, Kunming mice were inocu- lated with Streptococcus suis serotype II and simultaneously taken orally 0.5, 1.0 and 2.0 g/ml Chinese herbal preparation Yinqiaotiangan respectively for continu- ous 3 d, once a day; the incidence rate, mortality rate and protective rate were detected after 7 d. In the treatment test, Kunming mice were inoculated with Strepto- coccus suis serotype II to establish the Streptococcus suis serotype II pathogenic model, and then taken orally 0.5, 1.0 and 2.0 g/ml Chinese herbal preparation Yin- qiaotiangan respectively for continuous 3 d, twice a day; the mortality rate, cure rate and effective rate were detected after 7 d. [ Result ] Results of the prevention test showed that the protective rate in experimental groups was extremely significantly higher than that in control group （P 〈0.01 ）, while the incidence rate and mortality rate were extremely significantly lower than that in control group （P 〈0.01 ）. Results of the treatment test showed that the incidence rate in experimental groups was extremely significantly lower than that in control group （P 〈0.01 ）, the cure rate in 0.5 g/ml group was extremely significantly higher than that in 1.0 g/ml group and 2.0 g/ml group （P 〈 0.01 ）, the effective rate in 0.5 g/ml group was significantly higher than that in 1.0 g/ml group and 2.0 g/ml group （ P 〈 0.05 ）, with no significant difference from the positive group （P 〉 0.05 ）. [ Conclusion ] The pathologic model of Streptococcus su/s serotype II could be effec- tively prevented and treated by oral intake of low dose of Chinese herbal preparation Yinqiaotiangan in Kunming mice.展开更多
In order to study erythromycin resistance of Streptococcus suis under high or low concentration of selective drug pressure, Streptococcus suis strain LN was isolated from a diseased pig in 2005 and showed to be suscep...In order to study erythromycin resistance of Streptococcus suis under high or low concentration of selective drug pressure, Streptococcus suis strain LN was isolated from a diseased pig in 2005 and showed to be susceptible to erythromycin as determined by disc diffusion and tube dilution tests. In this study, clean level rabbits were divided into three groups of six rabbits each, including a prevention dosage group, a treatment dosage group, and a control group. After injection with S. suis strain LN, erythromycin （20 μg mL^-1） was taken orally in the prevention dosage group, erythromycin （5 mg kg^-1） was injected intramuscularly in the treatment dosage group, and no treatment was given in the control group. S. suis with intermediate resistance to erythromycin was isolated on the 5th day after infection from the prevention dosage group （5th PDG） and on the 7th day after infection from the treatment dosage group （7th TDG）. Both isolates were determined to be the constitutive macrolide-lincosamide-streptogramin B （cMLSB） resistance phenotype. The resistance gene ermB was detected in all of the isolates. The results suggested that both the 5th PDG and 7th TDG isolates had a mutation （A2372T） in the 23S rRNA gene. In addition, the 5th PDG isolates had a mutation in ribosomal protein L4 （detected as G268A） and a mutation in ribosomal protein L22 （A345C）; and the 7th TDG isolates had a C insertion at site 564. Each of these mutations is considered as a possible mechanism of erythromycin resistance in S. suis strain LN. This study demonstrated that erythromycin resistance was readily induced in S. suis at a low erythromycin dose creating selective pressure in vivo. Resistance appeared to be mediated by ribosome methylation, encoded by the ermB gene.展开更多
seven week old hybrid healthy pigs (weighted 25.5±1.4 kg ) from a source were randomly allotted to four groups (six each): the blank group, the negative group, the positive group and the test group. Pigs in the...seven week old hybrid healthy pigs (weighted 25.5±1.4 kg ) from a source were randomly allotted to four groups (six each): the blank group, the negative group, the positive group and the test group. Pigs in the negative group and the test group were developed into a typical subacute Streptococcosis suis by inoculating subcutaneously 0.45 billion of pure living Streptococcus suis (type C 55126 ) per kilogram body weight. Pigs in the positive group and the test group were intravenously injected ciprofloxacin (5 mg kg 1 of BW) for 8 consecutive days (twice daily). Pigs in the blank group and positive group were inoculated with a placebo ( 0.85% NaCl). Some immunity parameters were tested on day 0, 7, 14, 21 and 28 after inoculation. Total leukocytes were counted with microscope. Differential leukocyte counts were performed on Giemsa stained blood smears. The effect on the nitroblue tetrazolium (NBT) reduction of neutrophil was used to determine its phagocytic ability. Lymphocyte proliferation was determined by using the mitogens PHA. The total serum IgG concentration was measured by radial single immunodiffusion. A 50% hemolytic test was used to investigate the complement activity in serum. Whereas, a phytohemagglutinin (PHA) skin test was used to investigate in vivo immunity. We got the following results: Ciprofloxacin can retard the clinical signs of an increase of leukocyte counts, a large percent of lymphocytes and a relative percentage decrease of neutrophis. Ciprofloxacin could promote nitroblue tetrazolium (NBT) reduction by neutrophil. Though there was no obvious difference ( P > 0.05 ) between the test group and the negative group, the interaction of both Streptococcosis suis and ciprofloxacin was significantly different( P <0.01, on day 14, 21, 28 post inoculation). The two factors enhanced NBT reduction by neutrophils of pigs in the test group in coordination ( P <0.01, significantly higher than the blank group). In vitro proliferation to phytohemagglutinin (PHA) of lymphocytes from ciprofloxacin treated diseased pigs was increased finally. Mean index, which was stimulated (SI) by PHA, of proliferation on lymphocytes in negative group, was significantly lower ( P <0.01) than the blank group on days after inoculation, so do the SI of the test group on day 7, 14, 21 after inoculation. However, the drug increased the lymphocyte proliferation and led to the markedly higher response ( P <0.01) in test group at the 28th day post inoculation than the negative group, though there was no difference ( P >0.05) between the test group and the blank group. Delayed type hypersensitivity (DTH) to PHA was increased in diseased animals after receiving the treatment with ciprofloxacin. Owing to the difference of interaction ( P <0.01, on day 21, 28 after inoculation), the DTH response was increased on the 21st day after inoculation ( P <0.01. in comparison with both the negative group and the blank group). At the same time, the DTH response in negative group was lower than the blank group ( P <0.05). The drug caused the decrease of IgG level in serum ( P <0.05, on day 14 after inoculation, lower than the negative group). On day 14 after inoculation, the complement activity in se rum in the test group was lower than the blank group ( P <0.05), but on day 28, it was higher ( P <0.05) than the negative group.展开更多
基金supported by the National Natural Science Foundation of China(U22A20520)the Innovation Team Project of Modern Agricultural Industrial Technology System of Guangdong Province,China(2023KJ119)the Natural Science Foundation Program of Guangdong Province,China(2023A1515012206)。
文摘Streptococcus suis serotype 2(S.suis 2)is a zoonotic pathogen that clinically causes severe swine and human infections(such as meningitis,endocarditis,and septicemia).In order to cause widespread diseases in different organs,S.suis 2 must colonize the host,break the blood barrier,and cause exaggerated inflammation.In the last few years,most studies have focused on a single virulence factor and its influences on the host.Membrane vesicles(MVs)can be actively secreted into the extracellular environment contributing to bacteria-host interactions.Gram-negative bacteria-derived outer membrane vesicles(OMVs)were recently shown to activate host Caspase-11-mediated non-canonical inflammasome pathway via deliverance of OMV-bound lipopolysaccharide(LPS),causing host cell pyroptosis.However,little is known about the effect of the MVs from S.suis 2(Gram-positive bacteria without LPS)on cell pyroptosis.Thus,we investigated the molecular mechanism by which S.suis 2 MVs participate in endothelial cell pyroptosis.In this study,we used proteomics,electron scanning microscopy,fluorescence microscope,Western blotting,and bioassays,to investigate the MVs secreted by S.suis 2.First,we demonstrated that S.suis 2 secreted MVs with an average diameter of 72.04 nm,and 200 proteins in MVs were identified.Then,we showed that MVs were transported to cells via mainly dynamin-dependent endocytosis.The S.suis 2 MVs activated NLRP3/Caspase-1/GSDMD canonical inflammasome signaling pathway,resulting in cell pyroptosis,but it did not activate the Caspase-4/-5 pathway.More importantly,endothelial cells produce large amounts of reactive oxygen species(ROS)and lost their mitochondrial membrane potential under induction by S.suis 2 MVs.The results in this study suggest for the first time that MVs from S.suis 2 were internalized by endothelial cells via mainly dynamin-dependent endocytosis and might promote NLRP3/Caspase-1/GSDMD pathway by mitochondrial damage,which produced mtDNA and ROS under induction,leading to the pyroptosis of endothelial cells.
基金supported by the National Key R&D Program of China(Grant Nos.:2022YFF1100104 and 2022YFF1100102)the National Natural Science Foundation of China(Grant Nos.:31625025,32172749,and 32202701)+1 种基金the 2115 Talent Development Program of China Agricultural University(Grant No.:00109016)the Zhengzhou 1125 Talent Program,China(Grant No.:2016XT016).
文摘Muramidase-released protein(MRP)is now being recognized as a critical indicator of the virulence and pathogenicity of Streptococcus suis(S.suis).However,the identification of viable therapeutics for S.suis infection was hindered by the absence of an explicit mechanism for MRP-actuated inflammation.Dihydroartemisinin(DhA)is an artemisinin derivative with potential anti-inflammatory activity.The modulatory effect of DhA on the inflammatory response mediated by the virulence factor MRP remains obscure.This research aimed to identify the signaling mechanism by which MRP triggers the innate immune response in mouse spleen and cultured macrophages.With the candidate mechanism in mind,we investigated DhA for its ability to dampen the pro-inflammatory response induced by MRP.The innate immune response in mice was drastically triggered by MRP,manifesting as splenic and systemic inflammation with splenomegaly,immune cell infiltration,and an elevation in pro-inflammatory cytokines.A crucial role for Toll-like receptor 4(TLR4)in coordinating the MRP-mediated inflammatory response via nuclear factor-kappa B(NF-kB)activation was revealed by TLR4 blockade.In addition,NFkB-dependent transducer and activator of transcription 3(STAT3)and mitogen-activated protein kinases(MAPKs)activation was required for the inflammatory signal transduction engendered by MRP.Intriguingly,we observed an alleviation effect of DhA on the MRP-induced immune response,which referred to the suppression of TLR4-mediated actuation of NF-kB-STAT3/MAPK cascades.The inflammatory response elicited by MRP is relevant to TLR4-dependent NF-kB activation,followed by an increase in the activity of STAT3 or MAPKs.DhA mitigates the inflammation process induced by MRP via blocking the TLR4 cascade,highlighting the therapeutic potential of DhA in targeting S.suis infection diseases.
基金Supported by National Natural Science Foundation of China(31072155)Natural Science Foundation of Jiangsu Province(BK2010068)+1 种基金Fund for Independent Innovation of Agricultural Science in Jiangsu Province[CX(11)2060]Special Fund for Agroscientific Research in the Public Interest(201303041)~~
文摘[Objective] This study aimed to establish a method for quantitative detection of mRNA transcriptional level of SS2 adhesive related-factors of Streptococcus suis serotype 2 （SS2） by fluorescent quantitative PCR. []Vlethod] The gene fragments en- coding SS2 adhesive related-factors MRP, FBPS and CPS2J and a housekeeping gene aroA were amplified by reverse transcription PCR from the total RNA of SS2, cloned, and sequenced. The recombinant plasmids containing the target genes were constructed, and used as templates in Real-time PCR. [Result] Dynamic curves, stan- dard curves and melting curves of the adhesive related-factors and aroA were ob- tained by the optimized Real-time PCR system. The standard curves showed a good linear relationship between template copy number and circulation number, and the correlation coefficients （FF） of the standard curves were over 0.995. Also, these as- says were highly specific a^d there was single specific melting peak for every gene. Moreover, the assays were highly sensitive and had a detection limit of 1.0×102 copies in 1 μl of initial templates. Finally, it was highly repeatable and had a coeffi- cient of variation less than 2% for intra-assay. [Conclusion] This study will provide a way to reveal the adhesion mechanism of SS2 to different host cells at molecular level.
文摘Respiratory diseases are one of the most important health problems in pig herds. The porcine respiratory disease complex (PRDC) is the term used to describe pneumonic diseases caused by multiple infectious agents that provoke weight loss in animals or death. In the PRDC multiple pathogens (bacteria and/or viruses) work in combination to induce this respiratory disease. Within this complex, Actinobacillus pleuropneumoniae, Streptococcus suis, Pasteurella multocida, Bordetella bronchiseptica, Haemophilus parasuis and Mycoplasma hyopneumoniae are the main bacterial pathogens involved in great economic losses to the swine industry. The aim of this work was to estimate the presence of A. pleuropneumoniae, S. suis, P. multocida, B. bronchiseptica, H. parasuis and M. hyopneumoniae in the upper respiratory tract of pigs in representative swine farms inAguascalientes,Mexico, using PCR technique. The study was performed in 14 swine farms. We obtained a total of 212 nasal swabs. Near 20% of samples were positive for A. pleuropneumoniae (located in the 79% of farms);17% were positive for S. suis (in 86% of farms), of these, 3% were S. suis serovar 2;30% were positive for H. parasuis (93% of farms);23% of the samples to P. multocida (in 79% of farms);and 19% to M. hyopneumoniae (in 64% of farms). B. bronchiseptica was not detected in this study. The results obtained show that bacterial pathogens of PRDC were present in the upper respiratory tract of pigs in all farms studied;therefore, these pathogens are widely disseminated in pig farms of Aguascalientes, Mexico.
文摘Brucellosis is a bacterial anthropozoonosis usually caused by Brucella abortus, Brucella melitensis, Brucella suis and Brucella canis. Brucella suis, the causative agent of swine brucellosis, is classified into five biovars and preferentially infects different animal hostsIll. In China, brucellosis is a national notifiable communicable disease both in animals and in human. In 2009, 35 816 brucellosis cases were reported. The annual incidence was 2.7 per 100 000 population.
文摘对四川猪链球菌2型(S.suis 2)强毒株05ZYH33溶血素样蛋白(hemolysin-like protein,HLP)编码基因hlp进行序列信息分析、分子克隆表达及溶血活性检测,深入探讨HLP的致病机制.用Blast和Clustal X程序对HLP进行基因同源性分析,用Signal P 4.1和TMHMM Server 2.0分析HLP氨基酸序列.设计合成hlp引物进行PCR扩增,先后将hlp克隆入p MD-18T载体和p ET30a表达载体中,构建p ET30a::hly原核表达质粒.将重组质粒转化至E.coli BL21中诱导表达,并对重组HLP蛋白进行纯化和溶血活性检测.同源性分析表明HLP与多种具有溶血活性的蛋白相似性较高.氨基酸序列分析发现HLP具有信号肽和跨膜区,且由DUF21、CBS和Cor CHly C 3部分组成.序列测定显示hly片段全长1 335 bp,编码445个氨基酸.重组质粒经诱导表达和纯化后电泳显示,HLP分子量约为70 k Da,具有溶血活性.结果表明,HLP是一个膜结合蛋白,不同于能够分泌到细胞外的溶血素Suilysin.重组HLP具有一定的溶血效价,此可能与致病相关.
基金Supported by National Key Basic Research Program of China(973 Program)(2017YFD0500605)
文摘[Objectives]This study aimed to investigate the pathogenicity,growth characteristics and drug resistance of Streptococcus suis type 2.[Methods]Bacterial isolation and identification,biochemical experiments,determination of growth curve and correlation curve between OD 600 values and viable counts,drug susceptibility tests,pathogenicity analysis,and histopathological observations were carried out.[Results]The Streptococcus strain isolated from infected pigs was identified as Streptococcus suis type 2,which was named TA01 strain.TA01 strain reached the growth peak at 6-8 h post-incubation,and viable counts gradually declined after 8 h of incubation.The correlation equation between OD 600 values and viable counts is y=24.659 x-1.076 1,R^2=0.996 7.TA01 strain was sensitive to penicillin,erythromycin,florfenicol and oxacillin,and resistant to ciprofloxacin,polymyxin B and clindamycin.According to the results of pathogenicity analysis,all the mice in 3.6×10^9 cfu/mouse group died within 48,and these dead mice exhibited acute pyaemia septica.Based on the Reed-Muench formula,it was calculated that LD 50 of TA01 strain was 1.137×10^8 cfu/mouse.Pathological examination showed obvious blue-stained bacteria clusters,accompanied by neutrophil infiltration.[Conclusions]TA01 strain was a virulent strain of Streptococcus suis type 2.Compared with Streptococcus strains which were isolated and reported in China,TA01 strain exhibited strong virulence and rapid proliferation.
文摘BACKGROUND Streptococcus suis(S.suis)is an anthropozoonotic pathogen that shows clinical manifestations of meningitis,septicemia,and arthritis in infected humans.Nocardia is another type of anthropozoonotic bacteria,with clinical manifestations of skin,lung,and brain abscesses in infected humans.Few intracranial infections caused by S.suis or Nocardia have been reported.To the best of our knowledge,no study has reported a patient with simultaneous intracranial infection by S.suis and Nocardia.CASE SUMMARY A 66-year-old male presented at Liaocheng People’s Hospital(Liaocheng,Shandong Province,China)reporting dizziness with nausea and vomiting.Metagenomic next-generation sequencing(m NGS)was performed on cerebrospinal fluid for examination,and the patient was diagnosed with suppurative meningitis caused by S.suis infection.He received anti-infection treatment with penicillin sodium and ceftriaxone.The patient’s condition initially improved but then deteriorated.Further m NGS of cerebrospinal fluid revealed both S.suis and Nocardia.Imaging examination revealed a brain abscess.Furthermore,a mixed infection of S.suis and Nocardia was detected in the patient’s central nervous system.The patient was treated with antibiotics and sulfamethoxazole.He was discharged after his condition improved.CONCLUSION This case shows that the disease can be recurrent in patients with intracranial infection of a rare pathogen.The possibility of mixed infection should also be considered,especially in patients treated with immunosuppressive agents.m NGS of cerebrospinal fluid is a supplement to conventional microbial pathogen identification methods.Patients with unknown pathogen diagnosis,early extensive use of antibiotics and infection with rare pathogens can be diagnosed by the combination of conventional methods and m NGS of cerebrospinal fluid.
基金supported by the National Key Tech-nologies R&D Program of China (2004BA519A60,2006BAK02A03-1)
文摘Streptococcus suis is an important pathogen in pigs. Transmission of this pathogen is generally believed to occur between healthy carrier sows and their offspring, so the carrier status of S. suis in healthy sows is important for the control of S. suis infections in pigs, especially in suckling and growing pigs. In this study, the prevalence of S. suis isolated from clinically healthy sows in China was studied for the first time. A total of 1 043 tonsil samples were collected from clinically healthy sows from 10 regions in China from 2005 to 2007. Among the 421 S. suis isolates, 31 strains were identified as capsular type 2. The results showed that S. suis was widespread in swine herds in China with the carrier rates in different herds ranging from 19.5 to 93.9%. Overall, 40.4 and 3.0% of clinically healthy sows harbored S. suis and capsular type 2 in their palatine tonsils, respectively. Statistically significant differences of carrier rates of S. suis and capsular type 2 between the different farms were observed, which was independent of herd sizes and geographic distributions of different herds.
基金supported by the grants of the Independent Innovation Fund of Shandong Binzhou Animal Science & Veterinary Medicine Academy (200802)
文摘[ Objective] To obtain detection antigen for diagnosis of Streptococcus suis infection. [ Method] The complete ORF of glutamate dehy- drogenase （GDH） gene was amplified from the genomic DNA of Streptococcus suis serotype 2 strain SC22 isolated in Sichuan Province by poly- merase chain reaction （PCR）. The resulting product was cloned into the prokaryotic expression vector pET-30a, which was then transformed into E. coil BL21 （DE3）. The identified positive transformants were screened for expression induced by IPTG. The expression products were subjected to SDS-PAGE and the recombinant protein was purified by nickel ion-agarose affinity chromatography. New Zealand rabbits were immunized with the purified recombinant GDH protein to prepare polyclonal antibodies. Titers of the anti-serum were determined by indirect ELISA and Western blot assay. [ Result] The recombinant GDH protein was effectively expressed in the host bacteria, and highly pure recombinant protein was obtained by nickel ion-agarose affinity chromatography. High-titer anti-serum against the recombinant protein was obtained. As evidenced by western blot as- say, the sera could react specifically with the lysates of all detected Streptococcus suis strains. In addition, the recombinant GDH protein could re- act specifically with serum samples collected from five pigs experimentally infected by strain SC22. [ Conclusion] The expressed GDH fusion protein has some common epitopes of natural GDH and can be used as detection antigen to develop ELISA and other diagnostic methods.
文摘Streptococcus suis （S. suis） is a Gram-positive, facultatively anaerobic coccus that has been implicated as the cause of a wide range of clinical disease syndromes in swine and other domestic animals. S. suis has also been implicated in disease in humans, especially anaong abattoir workers, swine and pork handlers. Here we report a case of streptococcal toxic shock syndrome（STSS） caused by S. suis in a 59-year-old man. Despite of intensive treatment, the patient died of shock with multiple organ failure 14 h after admission. One bacterial isolate obtained from blood culture was identified to the species level by biochemical tests and serological tests as S. suis serotype 2. Identification was confirmed by PCR amplification of genes encoding 16sRNA of S. suis and the capsule of S. suis serotype 2（cps 23）. Genes encoding virulence factors were also detected. An investigation to identify the source of S. suis revealed that several days before admission the affected man had been handling sick pigs or their meat. Transmission may occur through breaks in the skin of feet with tinea due to that no measures for personal protection was taken. This case should highten awareness of the potential for occupational exposure and human infection with S. suis.
基金supported by grants from the National Key Research and Development Program of China(2016YFD0501304 and 2016YFD0501305)supported by the grants from the National Natural Science Foundation of China (31722057)
文摘Antimicrobial resistance is undoubtedly one of the greatest global health threats. The emergence of multidrug-resistant(MDR) Gram-positive pathogens, such as methicillin-resistant Staphylococcus aureus(MRSA), vancomycin-resistant Enterococcus faecium(VRE), and β-lactamase-resistant Streptococcus pneumonia, has severely limited our antibiotic arsenal. Numerous ribosome-targeting antibiotics, especially pleuromutilins, oxazolidinones, and streptogramins, are viewed as promising alternatives against aggressive MDR pathogens. In this study, we identified a new adenosine triphosphate(ATP)-binding cassete(ABC)-F family determinant, srp A, in Streptococcus suis(S. suis) by means of a comparative analysis of the whole-genome sequences of tiamulin(TIA)-resistant and TIA-sensitive bacteria. Functional cloning confirmed that the deduced gene can mediate cross-resistance to pleuromutilins, lincosamides, and streptogramin A in S. suis and S. aureus. A sequence alignment revealed that Srp A shares the highest amino acid identity with Vga(E)(36%) and shows canonical characteristics of ABC-F family members.In Srp A-ribosome docked compounds, the extended loop region of Srp A approaches the valnemulinbinding pocket in the ribosome peptidyl-transferase center and competes with bound valnemulin. A detailed mutational analysis of the loop residues confirmed that this domain is crucial for Srp A activity,as substitutions or truncations of this region affect the efficiency and specificity of antibiotic resistance.Intracellular antibiotics accumulation indicated that Srp A does not act as an efflux pump, while a ribosome binding assay supported the protective effects of Srp A on the ribosome by preventing antibiotic binding as well as displacing bound drugs. These findings clarify the mechanisms underlying resistance to ribosomal antibiotics.
基金supported by the National Natural Science Foundation of China [82172332]Gusu health youth talent of Suzhou [GSWS2019039,GSWS2020030]+2 种基金the Science and Technology Program of Suzhou [SKY2021007]Discipline Construction of The Second Affiliated Hospital of Soochow University [XKTJ-TD202001]Postgraduate Research&Practice Innovation Program of Jiangsu Province
文摘Streptococcus suis(S. suis) is a Gram-positive zoonotic pathogen. S. suis infection in humans commonly causes meningitis, septicemia, arthritis,and streptococcal toxic shock-like syndrome(STSLS). S. suis has 29 serotypes, of which S. suis serotype 2(SS2) has the highest clinical isolation rate and strongest pathogenicity and causes most S. suis human infections.About 1,000 different sequence types(STs)were identified in S.suis based on multilocus sequence typing(MLST).Among these,STs,ST1,and ST7 belong to serotype 2 and are the major hazards of S.suis.in 1998 and 2005,two cases of SS2 human infection outbreak were reported in Jiangsu and Sichuan,China,causing 14 deaths and 38 deaths,respectively.
基金supported by the National Key R&D Program of China (2017YFD0500203)the National Transgenic Major Program of China (2014ZX0800946B)+3 种基金the National NaturalScience Foundation of China (31672574)the Special Fund for Agro-scientific Research in the Public Interest, China (201403054)the Jiangsu Agricultural Science and Technology Innovation Fund, China ([CX (16) 1028])the Priority Academic Program Development of Jiangsu Higher Education Institutions, China (PAPD)
文摘Streptococcus suis is one of the major pathogens of swine streptococcosis. Among them, the strongest virulence and highest rate of clinical isolation serotype is S. suis serotype 2（SS2）. Moreover, SS2 is also an important zoonosis pathogen, which caused severe public health issues in China. It has been reported that SS2 has several virulence factors, including muramidase released protein, extracellular factors, capsule, fibronectin-binding protein, enolase, hemolysin, small RNA, biofilm, two-component regulatory systems, STK/STP, etc., whose functions involved in adhesion, anti-phagocytosis, inflammatory pathway activation, invasion, etc. Actually, SS2 has developed a variety of ways to escape from host immune system during evolution. In particularly, capsule could resist phagocytosis through inhibiting sphingosine dependent immune cell recognition, which plays an important role in escaping host inflammation response; moreover, superoxide dismutase encoding by sod A enables SS2 escaping reactive oxygen species（ROS） in host immune cells; besides, binding complement factor h with Fhb could suppress the activation of complement alternative pathway and bactericidal effect. And SS2 could also hinder the formation of neutrophil extracellular traps（NETs） to avoid trapping by swine neutrophils, while host immune globulin could be degraded by Ig A1 hydrolase and Ig M protease. In addition, SS2 could escape host immune defense with the help of multiple transcriptional factors and micro-RNA. So far, the pathogenesis of meningitis, arthritis caused by SS2 infection, is still unclear, and the virulence regulatory mechanism of phosphorylation, micro-RNA need to be further clarified. Importantly, the study of interaction mechanism of pathogen and host contribute to further demonstration the pathogenesis of SS2.
基金Supported by Youth Science and Technology Start-up Fund of Liaoning Medical University(Y2012Z023)Project of Agricultural Science and Technology Achievement Transformation from the Ministry of Science and Technology of China(2012GB2B000097)
文摘[ Objectlve] This study aimed to investigate the antimicrobial effect of Chinese herbal preparation Yinqiaotiangan against Streptococcus suis serotype II in vivo. [ Method ] The prevention and treatment tests were conducted with Kunming mice weighing about 18 -22 g. In the prevention test, Kunming mice were inocu- lated with Streptococcus suis serotype II and simultaneously taken orally 0.5, 1.0 and 2.0 g/ml Chinese herbal preparation Yinqiaotiangan respectively for continu- ous 3 d, once a day; the incidence rate, mortality rate and protective rate were detected after 7 d. In the treatment test, Kunming mice were inoculated with Strepto- coccus suis serotype II to establish the Streptococcus suis serotype II pathogenic model, and then taken orally 0.5, 1.0 and 2.0 g/ml Chinese herbal preparation Yin- qiaotiangan respectively for continuous 3 d, twice a day; the mortality rate, cure rate and effective rate were detected after 7 d. [ Result ] Results of the prevention test showed that the protective rate in experimental groups was extremely significantly higher than that in control group （P 〈0.01 ）, while the incidence rate and mortality rate were extremely significantly lower than that in control group （P 〈0.01 ）. Results of the treatment test showed that the incidence rate in experimental groups was extremely significantly lower than that in control group （P 〈0.01 ）, the cure rate in 0.5 g/ml group was extremely significantly higher than that in 1.0 g/ml group and 2.0 g/ml group （P 〈 0.01 ）, the effective rate in 0.5 g/ml group was significantly higher than that in 1.0 g/ml group and 2.0 g/ml group （ P 〈 0.05 ）, with no significant difference from the positive group （P 〉 0.05 ）. [ Conclusion ] The pathologic model of Streptococcus su/s serotype II could be effec- tively prevented and treated by oral intake of low dose of Chinese herbal preparation Yinqiaotiangan in Kunming mice.
基金funded by the National Basic Research Program of China (973 Program,2006CB504400)the National Key Techology R&D Program of China(2004BA519A60)
文摘In order to study erythromycin resistance of Streptococcus suis under high or low concentration of selective drug pressure, Streptococcus suis strain LN was isolated from a diseased pig in 2005 and showed to be susceptible to erythromycin as determined by disc diffusion and tube dilution tests. In this study, clean level rabbits were divided into three groups of six rabbits each, including a prevention dosage group, a treatment dosage group, and a control group. After injection with S. suis strain LN, erythromycin （20 μg mL^-1） was taken orally in the prevention dosage group, erythromycin （5 mg kg^-1） was injected intramuscularly in the treatment dosage group, and no treatment was given in the control group. S. suis with intermediate resistance to erythromycin was isolated on the 5th day after infection from the prevention dosage group （5th PDG） and on the 7th day after infection from the treatment dosage group （7th TDG）. Both isolates were determined to be the constitutive macrolide-lincosamide-streptogramin B （cMLSB） resistance phenotype. The resistance gene ermB was detected in all of the isolates. The results suggested that both the 5th PDG and 7th TDG isolates had a mutation （A2372T） in the 23S rRNA gene. In addition, the 5th PDG isolates had a mutation in ribosomal protein L4 （detected as G268A） and a mutation in ribosomal protein L22 （A345C）; and the 7th TDG isolates had a C insertion at site 564. Each of these mutations is considered as a possible mechanism of erythromycin resistance in S. suis strain LN. This study demonstrated that erythromycin resistance was readily induced in S. suis at a low erythromycin dose creating selective pressure in vivo. Resistance appeared to be mediated by ribosome methylation, encoded by the ermB gene.
文摘seven week old hybrid healthy pigs (weighted 25.5±1.4 kg ) from a source were randomly allotted to four groups (six each): the blank group, the negative group, the positive group and the test group. Pigs in the negative group and the test group were developed into a typical subacute Streptococcosis suis by inoculating subcutaneously 0.45 billion of pure living Streptococcus suis (type C 55126 ) per kilogram body weight. Pigs in the positive group and the test group were intravenously injected ciprofloxacin (5 mg kg 1 of BW) for 8 consecutive days (twice daily). Pigs in the blank group and positive group were inoculated with a placebo ( 0.85% NaCl). Some immunity parameters were tested on day 0, 7, 14, 21 and 28 after inoculation. Total leukocytes were counted with microscope. Differential leukocyte counts were performed on Giemsa stained blood smears. The effect on the nitroblue tetrazolium (NBT) reduction of neutrophil was used to determine its phagocytic ability. Lymphocyte proliferation was determined by using the mitogens PHA. The total serum IgG concentration was measured by radial single immunodiffusion. A 50% hemolytic test was used to investigate the complement activity in serum. Whereas, a phytohemagglutinin (PHA) skin test was used to investigate in vivo immunity. We got the following results: Ciprofloxacin can retard the clinical signs of an increase of leukocyte counts, a large percent of lymphocytes and a relative percentage decrease of neutrophis. Ciprofloxacin could promote nitroblue tetrazolium (NBT) reduction by neutrophil. Though there was no obvious difference ( P > 0.05 ) between the test group and the negative group, the interaction of both Streptococcosis suis and ciprofloxacin was significantly different( P <0.01, on day 14, 21, 28 post inoculation). The two factors enhanced NBT reduction by neutrophils of pigs in the test group in coordination ( P <0.01, significantly higher than the blank group). In vitro proliferation to phytohemagglutinin (PHA) of lymphocytes from ciprofloxacin treated diseased pigs was increased finally. Mean index, which was stimulated (SI) by PHA, of proliferation on lymphocytes in negative group, was significantly lower ( P <0.01) than the blank group on days after inoculation, so do the SI of the test group on day 7, 14, 21 after inoculation. However, the drug increased the lymphocyte proliferation and led to the markedly higher response ( P <0.01) in test group at the 28th day post inoculation than the negative group, though there was no difference ( P >0.05) between the test group and the blank group. Delayed type hypersensitivity (DTH) to PHA was increased in diseased animals after receiving the treatment with ciprofloxacin. Owing to the difference of interaction ( P <0.01, on day 21, 28 after inoculation), the DTH response was increased on the 21st day after inoculation ( P <0.01. in comparison with both the negative group and the blank group). At the same time, the DTH response in negative group was lower than the blank group ( P <0.05). The drug caused the decrease of IgG level in serum ( P <0.05, on day 14 after inoculation, lower than the negative group). On day 14 after inoculation, the complement activity in se rum in the test group was lower than the blank group ( P <0.05), but on day 28, it was higher ( P <0.05) than the negative group.
