Prevalence of extended spectrum beta lactamase producing Escherichia coli and Klebsiella pneumoniae urinary isolates in a tertiary care hospital in Kathmandu, Nepal.

BACKGROUND: Escherichia coli and Klebsiella pneumoniae are the major bacterial pathogens being isolated and reported from mid stream urine (MSU) specimens, globally. These uropathogens are mostly implicated as the major extended spectrum beta-lactamase (ESBL) producers, severely limiting the therapeutic management in cases of urinary tract infections. Limited studies had been reported from Nepal investigating the ESBL producers among uropathogens. This study was designed to assess the prevalence of ESBL producing E.coli and K. pneumoniae in urinary isolates at a centrally located major tertiary care hospital in Kathmandu valley, Nepal.

METHODS: Between September 2011 and May 2012, during the nine months period, 6308 MSU specimens were collected aseptically from the same number of clinically suspected patients of urinary tract infections. The samples were cultured on MacConkey agar and blood agar. The isolates with significant bacteriuria (105 CFU / ml) were identified based on standard laboratory procedures. Antimicrobial susceptibility tests were carried out using various antimicrobial discs alongwith ceftriaxone on E.coli and K. pneumoniae isolates by Kirby Bauer disc diffusion method as per the recommendations of CLSI. On initial screening with ceftriaxone (30 μg) disc showing resistance was then confirmed for ESBL production by phenotypic confirmatory disc diffusion test (PCDDT) using ceftazidime (30 ug) and ceftazidime + clavulanic acid (30 μg + 10ug) disc as per guidelines of CLSI (2011).

RESULTS: Out of a total of 6308 MSU specimens investigated for significant bacteriuria, E.coli isolates were 444 (7.04%) and K.pneuminiae were 145 (2.3%) making a total of 589 (9.34%). Initial screening with ceftriaxone disc revealed 155 isolates of E.coli and 70 isolates of K.pneumoniae to be resistant. Further testing by PCDDT method showed 60/444 (=13.51%) of E. coli and 24/145 (=16.55%) of K. pneumoniae isolates to be confirmed ESBL producers. These ESBL - producer uropathogens showed high degree of resistance to ceftriaxone (100.0%), amoxycillin, fluoroquinolones and co-trimoxazole.

CONCLUSION: An emerging and moderately high prevalence of ESBL-producing E. coli and K. pneumoniae was observed and confirmed in the urinary isolates investigated. It is essential to have a regular and routine monitoring of ESBL producing clinical isolates in laboratory practice.