Abstract

Extended spectrum beta lactamase (ESBL) producing members of the family Enterobacteriaceae are a major health problem in the hospitals and community. These enzymes confer bacterial resistance to penicillins, first, second and third generation cephalosporins and aztreonam. The prevalence of ESBLs varies from organism to organism and is increasing day by day. The study was designed to test typhoidal salmonellae for production of ESBL. One hundred and fifty eight (158) isolates of typhoidal salmonellae; Salmonella Typhi (n=126), Salmonella Paratyphi A (n=26) and Salmonella Paratyphi B (n=6) were collected from different hospitals of Lahore and Gujranwala. The isolates were identified morphologically, biochemically (API-20E) and serologically (BD Difco, USA). ESBL production has been tested by three methods; CLSI screening method, double disk diffusion synergistic method and CLSI phenotypic confirmatory method. CLSI screening method detected twenty two (22) strains as ESBL producers. However, when tested by the CLSI confirmatory method and by disk diffusion synergistic method, none proved to be ESBL producer. Based on our study, we concluded that the extended spectrum beta lactamase enzyme does not exist in tested clinical isolates of typhoidal salmonellae, however the isolates suspected to be ESBL by phenotypic methods must be subjected further for molecular analysis.

Key words: ESBL, typhoidal salmonellae, isolate.

Abbreviation

API 20E, Analytical profile index 20 Enterobactericeae; ATCC, American Type Culture Collection; CLSI, Clinical Laboratory Standards Institute; ESBL, extended spectrum beta lastamase; MDR, multi drug resistant.