Occurrence of diverse aminoglycoside modifying enzymes with co-existing extended-spectrum-β-lactamases within Enterobacteriaceae isolated in India

Abstract

Objective: The present study describes aminoglycoside modifying enzymes (AMEs) among clinical isolates with coexisting extended spectrum beta-lactamases. Methodology: A total of 227 non duplicate enterobacterial isolates were collected and identified from patients who were admitted to different wards or attended OPD of a tertiary referral hospital of North-East India. Isolates were initially screened for antimicrobial susceptibility testing followed by PCR based screening of aminoglycosides modifying enzymes and co-existing ESBLs and carbapenemases. Horizontal transferability, incompatibility typing and stability of plasmids were also analyzed. Results: Diverse types of AMEs were observed namely; ant(3″)-I, ant(4′)-Ia, aac(3)-IIc, ant(3′)-I, aac(6′)-Ib, ant(2″)-Ia and aac(6′). Majority of the AME positive isolates harboured blaTEM followed by blaCTX-M-15 and a combination of blaTEM and blaCTX-M-15 were also observed. Nine isolates were found to harbour carbapenemases genes. AME genes were found to be located within a self conjugative plasmid of Inc FIA, IncY, IncN, IncFIB and IncA/C incompatibility types. It was observed that most AME genes were stable over 50 days of serial passages whereas aph(3′)-Via and aph(3′)-IIb were completely lost within 50 days. Conclusion: This study underscores the co-existence of AMEs and ESBLs within enterobacteriaceae which emphasize a reassessment of combination therapy in the health settings.

Keywords

• Aminoglycoside modifying enzymes (AME)
• Escherichia coli
• ESBLs