Co-existence of aminoglycosides and β-lactam-resistant Escherichia coli phenotypes in a Tertiary care center of Nepal

Abstract

Introduction: Multidrug-resistant Escherichia coli isolates conferring simultaneous resistance to both aminoglycosides and β-lactam drugs have serious implications for clinicians worldwide. This study was designed to evaluate the co-existence of various β-lactamases in aminoglycoside- resistant Escherichia coli amongst hospitalized subjects in a tertiary care center of Kathmandu, Nepal, between December 2013 and December 2014.

Methods: Standard microbiological techniques were used for isolation and identification of the isolates. The antimicrobial susceptibility of bacterial isolates was determined following Clinical and Laboratory Standard Institute recommended Kirby-Bauer Disc Diffusion method. The defining criterion in this study for an isolate to be MDR, resistance to at least one agent in three or more than three different structural classes was taken.

Results: Among 302 MDR E. coli isolates, 174 (58.0 %) were resistance to gentamicin and 138 (46.0 %) were resistance to amikacin. Maximum aminoglycoside-resistant 9/11(82.0%) strains were isolated from body fluids followed by 7/10 (70.0%) from bile, 6/9 (67.0%) from blood and 2/3 (67.0%) from tissue. Out of 174 aminoglycosides-resistant E. coli isolates, the simultaneous occurrence of Extended-spectrum- b- lactamase (ESBL) and AmpC β–lactamaseswas noted in 13.0 % isolates and Metallo-β-lactamase (MBL) and AmpC β–lactamasesin 8.0 % isolates. None E. coli isolates were positive for all 3 types of β–lactamases in combinations. In amikacin- resistant isolates, ESBL+ AmpC observed in 12% and MBL+AmpC seen in 10% isolates.

Conclusion: Our results show a high frequency of aminoglycoside- resistance phenotypes. Strict application for appropriate use of antimicrobials in medical settings should be essential to minimize the emergence of multidrug-resistance among E. coli in hospitalized patients.