Susceptibility Pattern of Extended Spectrum β-Lactamase Producing Isolates in Various Clinical Specimens

Objective: To determine the susceptibility pattern of extended spectrum beta-Iactamase (ESBL) producing Gram negative isolates from various clinical specimens. Study Design: Descriptive study. Place and Duration of Study: Microbiology Department, Armed Forces Institue of Pathology, Rawalpindi, from January 2008 to January 2009. Methodology: A total of 308 ESBL producing isolates from various clinical specimens sent to AFIP for culture and sensitivity were identified using standard microbiological techniques and tested for antimicrobial susceptibility. At the same time screening for ESBL production was also done. ESBL production was confirmed by combination disc synergy method. The susceptibility pattern of isolates was then recorded in frequency percentages. Results: Out of the 308 ESBL producing isolates more than 99% were susceptible to carbapenems, 84% to tazobactam/piperacillin, 81% to sulbactam/cefoperazone, 12% to fluoroquinolones, 13% to cotrimoxazole, 59% to amikacin and 18% to gentamicin. Among the urinary isolates 49% were susceptible to Nitrofurontoin and only 5% to Pipemidic acid. Conclusion: Antibiotic choices in case of ESBL producing isolates are limited and at present only carbapenems can be regarded as treatment of choice. As empirical agents, beta-lactam/beta lactamase inhibitor combinations should be used cautiously for serious infections. Fluoroquinolones showed very poor efficacy. Amikacin can be used alternatively in such cases. Nitrofurantoin is still a good oral agent for treating UTI.