Prevalence of extended -spectrum beta -lactamases in enterobacteriaceae, Pseudomonas and stenotrophomonas as determined by VITEK2 and Etest syptems in Kuwait teaching hospital

To determine the prevalence of extended-spectrum beta-lactamase [ESBL]-producing members of the Enterobacteriaceae using VITEK 2 and E test systems. A total of 3,592 consecutive gram-negative isolates [single isolate per patient] of the family of Enterobacteriaceae and Pseudomonas adjudged to be clinically relevant to the patient's infection were studied for ESBL production over a period of 1 year at Mubarak Al-Kabeer Hospital, Kuwait. Two methods were used: the automated VITEK 2 system and E test ESBL, a manually manipulated plastic strip containing various gradients of beta-lactam antibiotics. These tests and interpretative criteria for the results were performed according to the manufacturer's instructions. Of the 3,592 bacterial isolates, 264 [7.5%] and 185 [5.2%] were positive for ESBL production by the VITEK 2 and E test, respectively. All the ESBL-producing Pseudomonas aeruginosa identified by VITEK 2 gave indeterminate results by E test. Prevalent ESBL producers, identified by the VITEK 2 versus E test, respectively, were: Citrobacter spp. [15 vs. 3.2%], K. pneumoniae [12.2 vs. 11.4%], Enterobacter spp. [12 vs. 3%], E. coli [6.5 vs. 5.6%], P. aeruginosa [6.5 vs. 0%] and Morganella spp. [2 vs. 1%]. The most common infection associated with ESBL-producing pathogens was urinary tract infection [68.2%], followed by wound infection [14.4%] and bloodstream infection [6.1%]. The result of this study showed a relatively high prevalence of clinically significant ESBL producers among the Enterobacteriaceae and Pseudomonas spp. at our teaching hospital. The VITEK 2 identified a higher prevalence of ESBL strains than the E test