| Streptococcus suis is a Gram-positive bacteria commonly found in the upper respiratory tract of pigs.It can cause various diseases such as septicemia,meningitis,and endocarditis.It is usually found in the nasal cavity,tonsils,genitals and digestion of pigs.Road and other parts.In the past few decades,Streptococcus suis infection has been a major problem that has plagued the global pig industry,causing huge economic losses to the breeding industry and has been classified as a national category 2 animal disease.At the same time,it can infect people through wounds and respiratory tracts,causing people with suppurative arthritis,meningoencephalitis and endocarditis.which can seriously cause death,making Streptococcus suis infection a serious public health problem.In China,there have been outbreaks of human infection with Streptococcus suis in Sichuan and Jiangsu.The widespread presence of Streptococcus suis poses a great threat to human and animal health.The use of antibiotics is closely related to drugresistant pathogens,and the emergence of multiple drug-resistant bacteria poses a serious threat to public health.The results of domestic and foreign investigations on the resistance of Streptococcus suis showed that the drug resistance has been very serious.Among them,the optrA resistance gene can mediate the resistance of oxazolidinones and amido alcohols,while oxazolidinones The drug linezolid(LZD)acts as a “last line of defense”against Gram-positive bacteria and can be used to treat leather including methicillin-resistant Staphylococcus aureus(MRSA)and vancomycin-resistant Enterococcus Lan positive bacteria infection.To understand the prevalence of serotype,drug sensitivity,and the prevalence of optrA gene in healthy pigs.The samples tested in this study were collected from some farms and slaughterhouses in Chongqing and Guizhou Province from November 2018 to January 2020.A total of 907 swine nasal swabs or cardiopulmonary tissue samples were collected and isolated for identification of Streptococcus suis.Select by using Colombian agar containing crystal violet(0.0002 g/L),sodium sulfite(0.1 g/L),nalidixic acid,polymyxin B(0.15 g/L),and 5% defibrillated sheep blood.Streptococcus suis specific gene gdh has been identified in the culture medium.Multiplex PCR method was used to diagnose the prevalent serotype of Streptococcus suis in healthy herds.Antibiotic sensitivity test for Streptococcus suis recommended by the Clinical and Laboratory Standards Lnstitute(CLSI)Resistance to Streptococcus suis.A plasmid extraction kit was used to extract bacterial plasmids,and the PCR method was used to detect the carrying of optr A gene in clinical isolates.After sequencing the plasmid,its sequence was analyzed by bioinformatics.Results 58 Streptococcus suis strains were detected from 907 samples,the total isolation rate was 6.4%.From the regional point of view,the isolation rate of Streptococcus suis was the highest in Dianjiang County,Chongqing(11%),and the lowest in Tongliang County(5.2%).In terms of time,the isolation rate of Streptococcus suis was 3.17% in the first quarter,7.23% in the second quarter,7.4% in the third quarter,and 6.6% in the fourth quarter.The isolation rate of Streptococcus suis in the second and third quarters was higher than that in the first and second quarters.Among 58 strains of Streptococcus suis from different sources,45 strains were successfully identified,covering 6 serotypes.The most common serotype was Streptococcus suis 29(25 strains,accounting for 43.1%),followed by Streptococcus suis 28(7 strains,accounting for 12%)and Streptococcus suis 21(6 strains,accounting for 10.3%).The results showed that the drug resistance rate to tetracycline,clindamycin,azithromycin and clarithromycin was more than 80%,and the drug resistance rate to erythromycin was more than 50%.In addition,it is resistant to amide alcohols and quinolones.All of the clinical isolates showed multi drug resistance ranging from 0-9 drugs,and the multi drug resistance rate was as high as 90%.There were 25 drug resistance profiles,among which the highest 9 drug resistance was isolate in Beibei Chongqing.It is suggested that penicillins and cephalosporins may be the first choice for the treatment of Streptococcus suis in Chongqing and Guizhou.Only one of the 58 strains of Streptococcus suis was optrA positive,with a prevalence of 1.7%(1/58).The MIC of P69 strain florfenicol was induced from 4 ?g / mL to 32 ?g / mL by in vitro induction,but accompanied by Reduced growth rate.By sequencing the entire genome sequence of the plasmid,using IPRscan,BLAST software,integrated VFDB,Swiss-port,CAZy,GO and KEGG and other databases,annotate protein function,virulence factors and drug resistance genes,and draw a complete plasmid circle diagram,the results show P69 is a circular plasmid with a total length of 8 012 bp.Through functional annotation of the obtained ORFs through the database,it was found that the P69 plasmid contains optrA,erm(A),erm(B),erm(C)resistance genes,ABC transporter and IS insertion sequence,in order to explore the function and Its biological significance. |
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