Extended spectrum beta lactamase producing gram negative bacilli in a tertiary referral hospital of Assam--experience with two methods.

Extended Spectrum Beta Lactamases (ESBL) are enzymes produced in some gram negative bacilli that mediate resistance to extended spectrum cephalosporins. 683 clinical isolates of Escherisia coli and Klebsiella pneumoniae were studied for their capacity to produce ESBL. Isolates showing resistance to at least two of the third generation cephalosporins were studied for ESBL production by Jarlier technique and combination disc methods. Out of the 457 E. Coli and 226 Klebsiella pneumoniae isolated in Assam Medical College, 29.76% and 53.1% were resistant to two cephalosporins of which 29.41% and 29.16% strains showed production of ESBL. However, 6 (4.41%) and 16 (13.34%) strains additionally showed production of ESBL when tested with combination disc method. Though the Jarlier technique is popular, for detection of ESBL, yet false negative results warrants for alternative method. In the absence of molecular detection methods in routine clinical microbiology laboratory, combination disc method appears to be a better option.