Detection of ESBL producing nosocomial gram negative bacteria from a tertiary care hospital in Bangladesh

ABSTRACT

Extended spectrum beta-lactamases [ESBLs] represent a major group of lactamases currently being identified in large number worldwide mostly produced by gram-negative bacteria. The present study was done to see the frequency of ESBLs in gram-negative bacterial isolates causing nosocomial wound infections from a tertiary care hospital in Bangladesh. A total of 125 wound swabs were collected from surgical site infections and burn cases, admitted in Rajshahi Medical College Hospital [RMCH], during January to June, 2008. Swabs were cultured for aerobic bacteria and antimicrobial susceptibility testing was carried out using the Kirby-Bauer agar diffusion method. Gram-negative isolates were tested for ESBLs on Mueller Hinton agar by both modified double disc and phenotypic confirmatory methods. Culture yielded 71 [56.8%] bacterial growths with 60 [84.51%] gram-negative and 11 [15.49%] gram-positive bacteria [Staph aureus]. Gram-negative isolates included 23 [32.39%] E. coli, 19 [26.76%] Klebsiella spp., 16 [22.54%] Pseudomonas spp., and 02 [2.82%] Proteus spp. The number of ESBL producing bacteria in modified double disc and phenotypic confirmatory methods were 28 [46.67%] and 25 [41.66%] respectively. Highest rate of ESBLs was observed in Klebsiella spp. [57.89%] followed by Proteus spp. [50.0%], E. coli [47.83%] and Pseudomonas spp. [31.25%], which showed significantly increasing resistance to 3rd generation cephalosporins, aminoglycoside, quinolone and trimethoprim-sulfamethoxazole. Significant number of nosocomial wound infections is caused by ESBL bacteria; those are not detected by routine antimicrobial susceptibility testing. It is recommended that clinical microbiology laboratory should take urgent measure for ESBLs detection as routine to enhance hospital infection control programme