Investigation On The Distribution Of BlaCTX-M,blaTEM,blaSHV In Multi-drug Escherichia Coli

objective:To investigate the clinical distribution and drug-resistant features of Escherichia coli.To detect blaCTX-M,blaTEM,blaSHV and Extended-spectrumβ-lactamases of Escherichia coli.99 strains of Escherichia coli were isolated from the affiliated hospital of Luzhou Medical College(Southwest Medical University)from July 2014 to November2014.Methods:1.Disk diffusion test:Antibiotic susceptibility of the isolated bacteria was performed by the disk diffusion technique on Mueller-Hinton agar plates.The Kirby-Bauer disc diffusion test was recommended by CLSI.Penicillin,aminoglycosides,fluoroquinolones,cephalosporins,carbapenems,sulfonamides,monocyclicβ-lactam were choosen.Quality control was performed as recommended using the E.coli strain ATCC 25922.Resistance patterns were determined by the resistance to cephalosporins,aminoglycosides,fluoroquinolones.2.The Screening and Confirmatory test:Phenotypic detection of ESBLs production was performed by screening and confirmatory test.The results were evaluated according to CLSI guideline 2012.The resistance differences were compared between ESBLs-positive group and ESBLs-negative group by Chi-square test.3.PCR:The plasmid of ESBLs producing strains was extracted.The detection ofβ-lactamase-encoding genes was carried out using PCR with primers that correspond to conserved regions of blaCTX-M,blaTEM and blaSHV-type genes.The amplicons were visualized after electrophoresis on agarose gel stained with GoldView.Electrophoresis results were observed by Ultraviolet detector.The positive gene amplification products were sequenced.Results:1.E.coli were mainly isolated from secretions(34.34%),middle segment urine samples(27.27%).The clinical distribution of E.coli was scattered.2.The results of antimicrobial susceptibility testing:(1)The prevalence of resistance to each antimicrobial agent was:piperacillin 85.86%,piperacillin-tazobactam 7.07%,compound sulfamethoxazole 71.72%,cefazolin 66.67%,cefotaxime 61.62%,ceftazidime32.32%,ceftriaxone 52.53%,cefepime 12.12%,cefoxitin 5.05%,aztreonam27.27%,ciprofloxacin 55.56%,levofloxacin 38.39%,gentamicin 52.53%,amikacin 3.03%,imipenem 1.01%,meropenem 1.01%;(2)The results demonstrate that 34 strains(34.34%)were resistant to three antibiotics and are known as the strains with multidrug resistance(MDR).There were 22(22.22%)double-resistant strains,24(24.24%)one-resistant strains,and19(19.20%)sensitive strains in 99 E.coli strains.The multi-drug resistance patterns were mainly GEN+CTX/CAZ+CIP/LEV,accounting for 91.18%.3.The situation of ESBLs-producing E.coli:(1)The results of antimicrobial susceptibility testing:The resistance rate of ESBLs-positive group was significantly higher than that of ESBLs-negative group for most antibacterial drugs;(2)Multi-drug resistant group was significantly higher than one-resistant group for the prevalence of ESBLs,X~2=24.983,P<0.001;Double-resistant group was higher than one-resistant group for the rate of carrying ESBLs,X~2=9.299,P=0.002,both of the difference was statistically significant;(3)Multi-drug and ESBLs-producing strains were sensitive to imipenem and meropenem.The resistance rate of cefoxitin and piperacillin-tazobactam was low.The strains showed high resistance to cefepime.The strains were seriously resistant to other antimicrobial agents.4.The detection of genes coding for ESBLs:(1)The total detection rate of three genes in 60 ESBLs-producing strains was 85%,including that the detection rate of blaCTX-M was 70.00%,blaTEM was71.67%,blaSHV was 15.00%.(2)Multi-drug resistant strains were mainly composite type of genes coding for ESBLs(60.61%,20/33),among which blaCTX-M+TEM accounted for 80.00%.Double-resistant strains were also mainly composite type of genes coding for ESBLs(66.67%),among which blaCTX-M+TEM accounted for 50.00%.Conclusion:1.The clinical distribution of Escherichia coli was scattered in this local area.The situation of resistant E.coli was serious.ESBLs-producing E.coli was common in this local area.ESBLs mainly existed in multi-drug resistant group and double-resistant group.Multi-drug and ESBLs-producing strains was seriously resistant to antibiotics commonly used,carbapenems was the last line of defense.Genes coding for ESBLs mainly existed in multi-drug resistant strains.Single type of genes coding for ESBLs were mainly blaCTX-M and blaTEM.Composite type of genes coding for ESBLs were mainly blaCTX-M+TEM.