Antimicrobial Resistance Pattern of Multidrug Resistant Enterobacteriaceae (MDRE) Isolated from Clinical Samples with Special Reference to Carbapenemase Production and Susceptibility to Tigecycline

Aim: The study was carried out to investigate the prevalence of multidrug resistant Enterobacteriaceae (MDRE), their susceptibility to carbapenems and tigecycline, and subsequently carbapenemase producers among clinical isolates of Enterobacteriaceae.

Study Design: Investigative.

Place and Duration: The study was performed in the Microbiology Department, Institute of Medical Science, associated Sir Sunderlal hospital, Banaras Hindu University Varanasi, during January 2012 to August 2013.

Methods: Samples were collected from patients in accordance with standard practice and Enterobacteriaceae identified by conventional biochemical procedures. Antibiotic susceptibility of isolates and Modified Hodge test were carried out according to the CLSI guide-lines.

Results: A total of 761 isolates belonging to Enterobacteriaceae were obtained from the samples, dominated by 292 E. coli, 236 Klebsiella pneumoniae, 53 Citrobacter freundii, 51 C. koseri, and 36 K. oxytoca. Antibiogram revealed piperacillin-tazobactam as the most effective agent, with 21.9% of the isolates resistant to it, followed by amikacin (22.4%), levofloxacin (22.8%) and minocycline (23.5%). A total of 512 (67.3%) isolates were MDRE, of which 198 (38.7%) were resistant to at least one of the carbapenems, and 3(0.6%) to tigecycline. Of the isolates 322 (62.9%) were carbapenem resistant enterobacteria (CRE). Carbapenemase production was detected in 256 (50.0%) and 105 (20.0%) isolates among the MDRE by disk diffusion and Modified Hodge tests respectively.

Conclusions: High prevalence of MDRE and CRE was observed. Tigecycline showed better in vitro activity over carbapenems indicating an increasing loss of efficacy among these comparators. There was a relatively wide disparity among likely carbapenemase producers identified by Modified Hodge and disk diffusion tests. Findings suggest the need for prudent antimicrobial and infection control policy.