Prevalence of extended spectrum beta lactamase producing gram negative bacteria in a tertiary care hospital

Extended spectrum beta lactamase (ESBL) producing Gram negative bacteria are increasingly being associated with hospital infections thereby rendering all beta lactams, except carbapenems ineffective in the treatment of infections related to these organisms. A knowledge about their prevalence is essential to guide the appropriate antibiotic treatment of severe infections in hospitalized patients. The present work was carried out to study the prevalence of ESBL producing Gram negative bacteria in a tertiary care hospital.

A total of 678 Gram negative bacteria were included in the study. They were isolated from various clinical samples obtained from indoor patients admitted to the All India Institute of Medical Sciences, New Delhi during March to June 2001. These isolates were screened for ESBL production by the inhibitor based test recommended by the National Committee for Clinical Laboratory Standards (NCCLS) using Klebsiella pneumoniae ATCC 700603 as positive control and Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853 as negative controls.

Out of the 678 strains tested, 458 (68%) were found to be ESBL producers. Among the bacterial species, ESBL production was most common in Klebsiella spp. (80%). The proportion of ESBL positive isolates was highest from intensive care units (79%), followed by Medical Oncology (75%), Medical (54%) and Surgical wards (50%).

A high prevalence of ESBL positive isolates was found in our hospital. This has important implications as carbapenems remain the only choice of treatment for infections caused by these organisms. The control measures include judicious use of antibiotics and implementation of appropriate infection control measures to control the spread of these strains in the hospital.