Molecular study on extended spectrum -lactamase-producing Gram negative bacteria isolated from Ahmadi Hospital in Kuwait

Abstract

During the period from November 2009 to April 2010, 84 out of 560 extended spectrum beta -lactamase (ESBL) producing negative bacteria were isolated from patients in different departments of the Ahmadi Hospital in Kuwait. The isolates were collected from urine catheter, wound, sputum, blood and other different samples. The ESBL infection rate in the in-patients was 62% and part of them (19%) were in the intensive care unit. All the isolated bacteria were identified and tested for antimicrobial susceptibility using an automated system (VITEK 2) and different antibiotic discs (15) by standard disc diffusion. The number of the recorded isolated multi-resistant Gram's negative bacteria was 54 isolates of Escherichia coli, 18 of Klebsiella pneumoniae, 11 of Pseudomonas aeruginosa, six of Proteus mirabilis, five of Enterobacter cloacae, four of Acinetobacter baumanii and one of Enterobacter aerogenes. They were resistant to the third generation of cephalosporins; Ceftazidime, Cefotaxime and Ceftriaxone. Meropenam (MEM) was the highest effective antibiotic against all the isolated bacteria (86%). The production of the ESBL was detected by phenotypic methods using E-test (96.4%), double disk synergy test (95%) and VITEK 2 (84.5%) in all multi-resistant isolates except A. baumanii and P. aeruginosa. All ESBL producing isolates were extracted and subjected to PCR using blaSHV, blaCTX-M and blaTEM primers. The bla-CTX-M (63.1%) was the most predominant ESBL gene that was produced in abundance by 42 isolates of E. coli. The most predominant ESBL isolates producing bla-TEM, bla-CTX-M and bla-SHV genes were successfully identified by 16 S rDNA. The conjugation assay between E. coli HB101 and the most predominant ESBL producing E. coli showed that the bla-CTX-M gene was able to be transferrable suggesting that they were plasmid mediated.