Phenotypic and molecular characterization of extended-spectrum beta-lactamase-producing Escherichia coli in Bangladesh.

Taslima T Lina,Kaisar A Talukder,Mohammad Aminul Islam,Ishrat J Azmi,Atanu Banik,Alejandro Cravioto,Rumana Alim,Armando Navarro,Bijay K Khajanchi,Mahmuda Akter,Gabriel Perez,Belal Mahmood,Ulrich Dobrindt

doi:10.1371/journal.pone.0108735

Abstract

BackgroundResistance to cephalosporins in Enterobacteriaceae is mainly due to the production of extended-spectrum beta-lactamase (ESBL). Little is known about ESBL-producing bacteria in Bangladesh. Therefore, the study presents results of phenotypic and molecular characterization of ESBL-producing Escherichia coli from hospitals in Bangladesh.MethodsA total of 339 E. coli isolated from patients with urinary tract and wound infections attending three different medical hospitals in urban and rural areas of Bangladesh between 2003–2007 were screened for ESBL-production by the double disk diffusion test. Isolates with ESBL-phenotype were further characterized by antibiotic susceptibility testing, PCR and sequencing of different β-lactamase and virulence genes, serotyping, and XbaI-macrorestriction followed by pulsed-field gel electrophoresis (PFGE).ResultsWe identified 40 E. coli with ESBL phenotype. These isolates were resistant to ceftriaxone, ceftazidime, cefotaxime, aztreonam, cefepime, and nalidixic acid but remained susceptible to imipenem. All but one isolate were additionally resistant to ciprofloxacin, and 3 isolates were resistant to cefoxitin. ESBL genes of blaCTX-M-1-group were detected in all isolates; blaTEM-type and blaOXA-1-type genes were detected in 33 (82.5%) and 19 (47.5%) isolates, respectively. Virulence genes that are present in diarrhoeagenic E. coli were not found. Class-1 integron was present in 20 (50%) isolates. All the ESBL-producing E. coli isolates harbored plasmids ranging between 1.1 and 120 MDa. PFGE-typing revealed 26 different pulsotypes, but identical pulsotype showed 6 isolates of serotype O25:H4.ConclusionThe prevalence of multidrug-resistant ESBL-producing E. coli isolates appears to be high and the majority of the isolates were positive for bla CTX-M. Although there was genetic heterogeneity among isolates, presence of a cluster of isolates belonging to serotype O25:H4 indicates dissemination of the pandemic uropathogenic E. coli clone in Bangladesh.

Highlights

In Gram-negative bacteria, production of beta-lactamases is one of the most common mechanisms resulting in resistance to betalactam antibiotics
All E. coli with extended-spectrum beta-lactamase (ESBL) phenotype were serotyped by agglutination assays using 96-well microtitre plates with rabbit serum (SERUNAM) obtained against 187 somatic antigens and 53 flagellar antigens for E. coli, and against 45 somatic antigens for Shigella species described earlier [31]
All E. coli with ESBL phenotype (n = 40) isolates were resistant to 3rd generation cephalosporins

Summary

Introduction

In Gram-negative bacteria, production of beta-lactamases is one of the most common mechanisms resulting in resistance to betalactam antibiotics. Extended-spectrum beta-lactamases (ESBLs) have contributed to the dramatic increase in resistance to new generation beta-lactam agents throughout the world [1,2,3,4]. These enzymes are usually plasmid-encoded and have the capacity to hydrolyze many antibiotics including penicillins, cephalosporins, and aztreonam and are inhibited by clavulanic acid (CA) [2,3]. These phenotypic characteristics facilitate the identification of ESBLs-producing organisms using routine laboratory tests such as double disk diffusion test or E-test.

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