Analysis Of Drug Resistance And Detection Of ESBLs Gene Of Animal-derived Salmonella Isolated In Some Areas Of Chongqing

Salmonella is an important zoonotic pathogen that can be transmitted through the digestive tract and has a wide range of hosts.People,livestock,wild mammals,reptiles,birds and even insects can be infected.People infected with it can cause typhoid fever,paratyphoid fever,acute gastroenteritis,sepsis and other diseases.Young and young animals infected with it can cause sepsis,gastroenteritis and other tissue and local inflammation,and can lead to abortion of pregnant females.There is a close relationship between the use of antibiotics and drug-resistant pathogens.The emergence of multi-drug resistant bacteria is a serious threat to public health,especially resistance to broadspectrum cephalosporins and fluoroquinolone antibiotics.With the widespread use of the third and fourth generation cephalosporins,the resistance rate of bacteria has also gradually increased.There is mainly a class of enzymes capable of hydrolyzing the third or even fourth generation cephalosporins.It is called extended spectrumplactamases(ESBLs).Salmonella carrying ESBLs typically uses antibiotic-resistant plasmids,integrons,and transposable elements carried by mobile elements as donors for the transmission of antibiotic resistance.Certain ESBLs genes involved in pathogenesis mechanism are often transferred along with these antibiotic resistance gene elements.Transfer of the coding gene ESBLs into the genome or plasmid of the bacterial host promotes the emergence of more toxic and resistant strains,and thus leads to infections that are more difficult to treat.To understand the serotype prevalence,drug sensitivity and ESBLs gene prevalence of Salmonella in animal origin in some areas of Chongqing.The experimental samples of this study were collected from farms,slaughterhouses and animal hospitals in 14 districts and counties of Chongqing from March 2014 to January 2019,including Beibei District,Yubei District,Fuling District,Nanchuan District,Jiangjin District,Dazu District,Bishan District,Hechuan District,Rongchang District,Changshou District,Fengdu County,Dianjiang County,Wanzhou District and Pengshui County of Chongqing City.A total of 1850 samples of anal swab or cardiopulmonary tissue from 7 animals including pig,sheep,dog,chicken,cow,rabbit and duck were collected and identified by Salmonella.Selective culture is carried out by buffer protein hydrophobic water(BPW),sodium tetrasulfonate brilliant green enrichment liquid(TTB),xylose lysine Tergitol-4(XLT-4)agar medium,and Salmonella chromogenic medium.The Salmonella-specific gene invA was then amplified to confirm Salmonella.Serotype identification of clinical isolates identified as Salmonella using Salmonella diagnostic serum to determine the epidemic serotype of Salmonella in animal origin in some areas of Chongqing.According to the Salmonella antibacterial susceptibility test standard recommended by the Clinical and Laboratory Standards Lnstitute(CLSI).K-B disc diffusion method was used to test the susceptibility of 27 drugs to understand the drug resistance of Salmonella in some areas of Chongqing.To detect the prevalence of ESBL gene of Salmonella in animal origin in some areas of Chongqing,bacterial plasmids were extracted using a plasmid extraction kit and the carrying status of 11 ESBL genes in clinical isolates was detected by PCR.After sequencing the PCR product,the results were compared by BLAST analysis to determine the ESBL subtype.1,850 samples from different animals were collected and 76 strains of Salmonella isolated were isolated.Its total separation rate is as low as 4.1%.73 strains of 76 strains of Salmonella can be typed.3 strains are rough type and can not be classified by selfcoagulation.The Salmonella identified 12 serotypes of 4 serogroups,of which the dominant serotypes were Salmonella Derby,Salmonella Argona and Salmonella Typhimurium.the dominant serotypes belonged to group B.Salmonella from different animal origins and from the same animal source showed different resistance to 27 antimicrobial agents,but it also showed a certain regularity.The isolated strains of this test are the most resistant to ampicillin.The resistance to tetracyclines and amides is also serious.It is also resistant to sulfonamides,aminoglycosides and quinolones,However,it is completely sensitive to the fourthgeneration cephalosporin cefepime.All isolates strains showed multi-drug resistance ranging from 0-23 drugs,of which the highest resistance to 23 drugs was 1 Salmonella chicken.The lowest resistance to 0 drugs appeared in Salmonella pig,accounting for 6.6% of the total isolation rate.In general,Salmonella pig showed the rule of resistance to 0-8 drugs.Eleven ESBL genes were detected in 76 strains of Salmonella,and 68 strains carried at least one ESBL gene with a positive rate of 89.5%.The detection rates of TEM,OXA-1,CTX-M,OXA-10,and CMY were 85.5%,25%,6.6%,5.3%,and 5.3%,respectively.The SHV,VEB,PER,GES,OXA-2,and PSE genes were not detected in this test.The TEM gene is widely distributed in each type of animal-derived Salmonella.The sequencing analysis showed that the genetic subtypes of 65 strains of TEM gene were mainly TEM-1 and TEM-1a.Different Salmonella serotypes carry different ESBL genes.Among the dominant serotypes of Salmonella Derby,there are five ESBL genes including TEM,OXA-1,CTX-M,OXA-10 and CMY.The TEM and OXA-1 genes are present in Salmonella Argona.By comparing the ?-lactam drug resistance phenotype and ESBL gene carrying status of the test strain,it was found that the coincidence rate was 97%,which was highly consistent.Conclusion: In this experiment,76 strains of Salmonella from different animals were isolated from 1850 samples.Among them,73 strains of Salmonella can be divided into 12 serotypes.The dominant serotypes are Salmonella Derby,Salmonella Argona and Salmonella Typhimurium.76 strains showed the most serious resistance to ampicillin,However,it is completely sensitive to the fourth-generation cephalosporin cefepime,and the multi-drug resistance ranged from 0-23 drugs.A total of 5 drug resistance genes were detected in TEM,OXA-1,CTX-M,OXA-10 and CMY,among which TEM gene detection rate was the highest,followed by OXA-1.ESBL gene carrying is highly consistent with the ?-lactam drug resistance phenotype.