Elucidating Environmental Reservoir of Antimicrobial Resistance: A Phenotypic Characterization of Gut Microbiota from Aquatic Coleoptera in a Low-Anthropogenic Impact Zone

Introduction and objective

The present study concentrated on reviving bacterial isolates from the gut microbiota of particular

insects (Coleoptera: Hydrophilidae and Helophoridae) collected in water bodies in the vicinity of

Erzurum, Turkey. 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.

Material and methods

The antimicrobial susceptibility of the isolates was then 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.

Conclusions

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 resistance mechanisms.