The prevalence of Extended-Spectrum β-lactamase (ESBLs) producing Klebsiella pneumonia and Eschrrichia coli isolated in Milad hospital of Tehran in 2010

Extended – Spectrum beta – lactamase (ESBLs) are certain enzymes that are produced by Gram- negative bacilli such as K. pneumoniae and E .coli¡ which cause resistance of these organisms to penicillins¡ cephalosporins¡ and monobactams. The aim of this study was to determine prevalence of Extended-Spectrum β-lactamase (ESBL) producing E. coli and K. pneumoniea isolated from urine cultures in Milad hospital of Tehran in 2010.
Material and This study was performed on 735 Gram negative bacilli isolated from urine of patients admitted to Milad hospital of Tehran from March to June 2009 and which included 620 (84.3%) strains of E. coli and 115 (15.7%) strains of K. pneumoniea isolates. From antibacterial susceptibility testing as well as for beta-lactamase production disk diffusion method and combined disk diffusion technique were employed respectively¡ as recommended clinical laboratory standards institutes (CLSI).
ESBLs resistance was detected in 132 (21%) of the E.coli isolates and 18 (12%) of the K. pneumoniae strains. Of the 150 patients which had positive ESBLs isolates¡ 104 of them were outpatients and the other 46 were hospitalized. Resistance of ESBLs producing isolates of K. pneumoniae to carbenicillin¡ ampicillin and amikacin was 99.95%¡ 100% and 78 %¡ respectively. The least percentage of resistance among ESBLs positive isolates were observed against ofloxacin (28%). We observed high rate of resistance among isolates of E.coli to ampicillin (85%)¡ tetracycline (62%)¡ and trimethoprim /sulfamethoxazole (54%). However¡ the least rate of resistance was observed among 3 (0.5%) ESBLs positive isolates of E. coli against nitrofurantoin.
About one fifth of the E. coli and roughly one sixth of the K. pneumoniae isolates were producers of ESBLs. Resistance to other commonly used antibiotics among ESBLs producing isolateswere prevalent.