Isolation And Drug Resistance Analysis Of ESBLs Producing Salmonella In Some Areas Of Hubei Province

Salmonella is a zoonotic bacteria that is widely distributed throughout the world.The presence of salmonella bacteria poses a great threat to human and animal health,and also causes a series of public health problems.Antimicrobial drugs as an important means of preventing and controlling bacterial diseases,antibiotics have been playing an important role since the discovery of penicillin.However,with the overuse of antibacterial drugs,bacteria have evolved new resistance abilities under the pressure of drug screening and selection,increasing the difficulty of prevention and treatment.Moreover,with the passage of time,the rate of bacterial drug resistance is getting higher and higher,from single drug resistance to multiple drug resistance.The situation of global drug resistance is grim,and Samana,as an important public health prevention and control goal,is the top priority.Salmonella is a common high risk foodborne pathogenic bacteria.The analysis of different sources of Salmonella can understand the epidemic situation,sequence type,drug resistance spectrum,drug resistance gene and the mechanism of drug resistance.It plays a positive and necessary role in the clinical treatment and follow-up research of salmonellosis.The main research contents and results are as follows:1.Isolation and molecular typing of salmonellaAccording to the method of gb4789.4-2016,chicken intestine samples were taken from wuhan vegetable market,swabs were taken from a poultry slaughtering line in jingzhou,and suspected salmonella colonies were isolated and purified,followed by biochemical identification,and 71 salmonella isolations were finally obtained.The isolation rate of salmonella in duck intestine was 55.5%,that of chicken intestine in vegetable market was 29.6%,and that of poultry slaughtering line swab was 18.2%,which was related to the sample source and sampling method.From the original 45 strains in the laboratory,a total of 74 strains out of 29 isolates were selected for molecular typing by means of multi-locus sequence typing,that is,aro C,dna N,hem D,his D,pur E,suc A and thr A butler genes were amplified.After sequencing,the sequences were uploaded to MLST database to obtain the strain sequence type.Among the 74 strains of salmonella isolates,62strains were divided into 11 strains of ST type,among which ST19,ST26,ST226,ST11,ST34 and ST13 were the main sequence types,ST19 was the most(41.9%),and most strains of ST19 were isolates of salmonella of avian origin.The other 12 salmonella isolates were new ST strains.2.Drug resistance spectrum analysis and ESBL detection of salmonella isolates.The susceptibility of 74 salmonella isolates to 8 classes of 18 antibiotics was detected by the paper method.The method of operation and the results were interpreted with reference to CLSI.The results showed that the drug resistance rates of salmonella against erythromycin,tetracycline,ampicillin,amoxicillin,naonidine acid,streptomycin,compound neomycin and chloramphenicol were 71.6%,54.1%,51.4%,51.4%,43.2%,40.5%,35.1%and 29.7%,respectively.The drug resistance rates of the first,second,third and fourth generation cefazolin,cefuroxime sodium,cefotaxime and cefepime were 16.2%,9.5%,10.8%and 5.4%,respectively,and all strains were sensitive to ertapenem and imipenem.The multidrug resistance rate of 74 salmonella isolates was 56.8%,and that of the salmonella isolates of patient origin was 80.0%.The second generation cephalosporin resistant or the third generation cephalosporin resistant salmonella isolates were selected,and the results showed that 7 salmonella isolates,accounting for 9.5%of the total strains,produced ESBLs by two-paper method.Six strains were from patients,and one strain was from chicken intestine samples in the vegetable market.3.Genomic analysis of ESBLs-producing salmonella isolates and discovery of drug-resistant genesIn this experiment,the whole genome of four esbls-producing salmonella isolates resistant to cefepime was sequenced,and the genome sequences were compared with the public database and the drug resistance gene bank(ARDB)by using the bioinformatics method.The results showed that the genome size of salmonella was about 4.9Mbp and the GC base content was about 52%.Bla _CTX-M-55,bla _CTX-M-121,bla _TEM-1,LRA-8,par C,par E,gyr A,gyr B,sul1,sul2,sul3,aad A7,aad A2,aad A3,tet S,tet B(P),tet T,tet M,cmlv resistant genes were detected.Three salmonella isolates were found to have ESBLs resistance gen bla _CTX-M-55,while one salmonella isolate contained ESBLs resistance gene bla _CTX-M-121,which was rarely reported in China.The amino acid sequence encoded by the par C gene of strain H21 was mutated at four sites.Whether it is related to quinolone antibiotic resistance needs to be further studied.