Detection and characterization of extended-spectrum beta-lactamases produced by escherichia coli and klebsiella spp. from clinical specimens of patients with infection in King Chulalongkorn Memorial Hospital

Abstract

Resistance to beta-lactams has been increasing in the treatment of infections caused by Escherichia coli and Klebsiella spp. The production of extended-spectrum beta-lactamases (ESBLs), that hydrolyze extended-spectrum cephalosporins, is the major cause of beta-lactams resistance. In this study, ESBLs were determined by disk diffusion test, double disk synergy test and Etest ESBLs. All ESBLs producing strains were investigated for the presence of blaTEM, blaSHV , blaCTX-M and blaVEB genes by polymerase chain reaction (PCR). Nucleotide sequencing of blaTEM and blaSHV were performed. E.coli and K.pneumoniae were isolated from clinical specimens of patients in Chulalongkorn Memorial Hospital during February to May 2002. Of the 270 isolates, 212 were E.coli and 58 were K.pneumoniae. ESBL production were detected in 17% (36/212) of E.coli and 34.5% (20/58) of K.pneumoniae isolates. Of the 20 K.pneumoniae strains, the beta-lactamases gene were blaSHV (18/20, 90%), blaTEM (10/20, 50%), blaVEB-like (6/20, 30%) and blaCTX-M-like (3/20, 15%). Thirty-six E.coli strains carried blaTEM, blaCTX-M-like and blaVEB-like genes in 72.2% (26/36), 52.8% (19/36) and 16.7% (6/36), respectively. BlaSHV was not detected in ESBL-producing E.coli, whereas it predominated in K.pneumoniae. Of the 56 ESBL producing strains, 30 (53.6%) coharboured at least 2 different bla genes. All TEM identified, were TEM-1B, which is not ESBL. CTX-M ESBLs were the most common in E.coli. In this study, the presence of blaCTX-M and blaVEB in ESBL-producing E.coli and K.pneumoniae indicates the high prevalence of these genes in Thailand.