Presence & mobility of antimicrobial resistance in Gram-negative bacteria from environmental samples in coastal Karnataka, India

Abstract

To understand antimicrobial resistance (AMR) patterns and mechanisms of horizontal gene transfer in human-associated environments is essential to AMR surveillance. Gram-negative bacteria (1122 isolates) from food-animal environments were characterized for antimicrobial susceptibility and AMR genes. Seventy five per cent of the isolates (837 of 1122) were resistant to at least one of the antibiotics tested. Resistance to more than three groups of antimicrobials (multidrug resistance) was observed in 43 isolates with most often encountered (12 of 43) resistance to β-lactams, tetracycline, quinolones and nitrofurantoin. The profile of frequently reported plasmid-mediated resistance gene in these isolates was determined. The mobility of these elements as plasmids or phages was examined. The bla_CTX-M gene was present in the plasmid of 61 per cent and packed in induced phage fractions in 72 per cent of the isolates and bla_TEMin 69 per cent phage fractions compared to 15 per cent presence in the plasmid.

Keywords: Antimicrobial resistance; environment; mobile genetic elements; prophage induction.

Figure 1

Resistance profile of Gram-negative bacteria: (A) Resistance pattern observed in different sources; (B) Resistance pattern observed in different genera. AMP, ampicillin; C, chloramphenicol; CIP, ciprofloxacin; COT, co-trimoxazole; CTX, cefotaxime; GEN, gentamicin; IMP, imipenem; MRP, meropenem; NA, nalidixic; NIT, nitrofurantoin; PIT, piperacillin/tazobactam; TET, tetracycline.