10.22376/ijpbs.2019.10.1.p1-12 Volume 3 Issue 3 2012 (July - September) Resistance by virtue of production of ESBL in gram negative bacteria is an emerging problem leading to therapeutic failure when β-lactam drugs are used. However, their presence may be missed while using routine disc diffusion methods for antibiotic susceptibility testing. All isolates of lessThan i greaterThan E. coli lessThan /i greaterThan , lessThan i greaterThan K. pneumoniae, K. oxytoca lessThan /i greaterThan and lessThan i greaterThan P. mirabilis lessThan /i greaterThan were studied for ESBL production by CLSI recommended Phenotypic confirmatory test (PCT ) and Double disk approximation test (DDAT). Out of 10,055 clinical samples,1738 study isolates were obtained of which 1196 were lessThan i greaterThan E. coli lessThan /i greaterThan (68.82%), 465 lessThan i greaterThan K. pneumoniae lessThan /i greaterThan (26.75%), 17 lessThan i greaterThan K. oxytoca lessThan /i greaterThan (0.97%) and 60 lessThan i greaterThan P. mirabilis lessThan /i greaterThan (3.46%). 43.10% (749 out of 1738) study isolates were confirmed to be ESBL producers. The best sensitivity was found for Tigecycline (100%) followed by Polymyxin B (91%) and Imipenem (81%). To conclude, we found a very high prevalence of ESBL producers (43.10 %) in our hospital especially from the IPD wards. Ankit Khanduri , Bhaskar Thakuria And Pratima Gupta Extended Spectrum Beta Lactamases, ESBL, Phenotypic confirmatory test, PCT, Double disk approximation test, DDAT 251-260