Elucidating environmental reservoir of antimicrobial resistance – a phenotypic characterization of gut microbiota from aquatic coleoptera in a low-anthropogenic impact zone

Introduction and Objective. This study investigated the

antibiotic resistance of bacterial isolates obtained from the gut microbiota of

certain insects (Coleoptera: Hydrophilidae and Helophoridae), which were

collected from aquatic areas in Erzurum Province, Türkiye. This area is

characterised by a low level of human impact, thereby providing a unique

opportunity to investigate the baseline microbial diversity and ecological

roles within relatively pristine aquatic environments. Materials and Method.

The antimicrobial susceptibility of the isolates was assessed using disc

diffusion and minimum inhibitory concentration (MIC) methods. The analysis

encompassed 30 Gram-negative bacteria belonging to the genera Aeromonas,

Acinetobacter, Vibrio, Pseudomonas, Escherichia and Yersinia. Results. The

results indicated that the most resistant bacteria were Aeromonas, Pseudomonas

and Acinetobacter, while enteric bacteria demonstrated greater sensitivity. It

is noteworthy that nitrofurantoin, a commonly used antibiotic for treating

urinary tract infections, exhibited the highest level of resistance among the

antibiotics tested by disc diffusion, followed by cephalosporins and

penicillins. Conclusion. The MIC testing with DKGM and NF kits demonstrated

high resistance to cephalosporins, sulfonamides, polymyxins and monobactams.

Furthermore, two multidrug-resistant (MDR) isolates exhibited resistance to at

least two antibiotic classes. These findings underscore the necessity for

expanded antimicrobial resistance surveillance beyond clinical settings,

extending into environmental samples, and contributing to ongoing research on

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