Colistin and Tigecycline susceptibility among carbapenemase producing Enterobacteriaceae at a tertiary care hospital of South India

Abstract

Background: Carbapenem resistance among Enterobacteriaceae is a serious clinical problem and the global spread of such resistant strains has hampered the treatment effort leaving with few choices of antibiotics like tigecycline and colistin. Methods: Therefore, we looked for the susceptibility pattern of tigecycline and colistin among carbapenem-resistant Enterobacteriaceae (CRE) by Epsilometer (E) test at Sri Ramachandra University Hospital, Porur, Chennai, India. This study used the combined disc test with phenylboronic acid and EDTA; and modified Hodge test (MHT) to differentiate the carbapenemases. The minimum inhibitory concentration of tigecycline and colistin susceptibility was determined for CRE isolates by using the E-test strips ranging from 0.016-256 μg /ml. Results: A total of 238 extended spectrum beta lactamase producers from Family Enterobacteriaceae were included in the study. Among those, 37 isolates were MHT positive. On combined disc test, 14 were metallo beta lactamase positive, 4 were Klebseillae pneumoniae carbapenemase positive and only one isolate was found to be positive for both. Out of 51 CRE isolates, the number of tigecycline and colistin resistant were found to be in 30 and 3 respectively according to EUCAST criteria. Conclusion: Tigecycline may be effective but it needs to be monitored routinely. Colistin remains a reliable option for CRE infections. The increasing resistance of CRE to the available antibiotics like tigecycline and colistin is a threat to the therapeutic management of such patients.

Keywords

• carbapenem resistant enterobacteriaceae
• combined disc test
• modified hodge test
• tigecycline
• colistin