Environmental baseline assessment of antibiotic resistance in urban freshwater systems with public health relevance in Vadodara, India

Abstract

Urban freshwater ecosystems are increasingly recognized as reservoirs of antimicrobial resistance (AMR), yet baseline data from Indian lake systems remain limited. This study assessed the distribution of phenotypic antibiotic resistance among culturable bacterial isolates in two urban lakes in Vadodara—Danteshwar and Gotri—using a culture-based approach. A total of 53 isolates were recovered and tested against Streptomycin, Azithromycin, Ciprofloxacin, and Meropenem using the Kirby–Bauer disc diffusion method. Resistance was most frequent to Streptomycin (24.5%) and Azithromycin (22.6%), moderate to Ciprofloxacin (13.2%), and rare to Meropenem (1.9%). One multidrug-resistant isolate was identified as Pseudomonas straminea using 16S rRNA gene sequencing. The Antibiotic Resistance Index (ARI) values were 0.167 for Danteshwar and 0.148 for Gotri, providing baseline information on resistance occurrence within the cultured bacterial communities. Although pollutant-specific parameters were not measured, the detection of antibiotic-resistant bacteria in freshwater lakes suggests environmental influences associated with wastewater exposure or urban runoff may influence resistance persistence in natural systems. These findings underscore the need to include freshwater bodies in environmental AMR surveillance frameworks. Future studies employing metagenomics, expanded antibiotic panels, pollutant quantification, and seasonal sampling are recommended to better resolve the ecological and anthropogenic drivers of AMR in freshwater ecosystems.