Swimming pools as emerging environmental reservoirs of antimicrobial-resistant bacteria in two cities of southwestern Colombia: Cali and Jamundí

Antimicrobial-resistant microorganisms are considered emerging environmental contaminants, and chlorination could exacerbate this issue. The main objective of this study was to characterize the antibiotic resistance profile of bacteria isolated from swimming pools in Cali and Jamundí, two cities in the southwest of Colombia. A total of 16 swimming pool water samples were microbiologically analyzed to determine bacterial diversity and assess antibiotic susceptibility to ten broad-spectrum antibiotics using the disk diffusion method. Bacterial isolates showing resistance were identified through 16S rRNA gene sequencing and selective differential growth media. A total of 69% of swimming pool samples did not comply with Colombian microbiological regulations. Among the bacterial isolates, 92% exhibited resistance to at least one antibiotic, with no significant differences between Gram-positive and Gram-negative species. Clinically relevant multidrug-resistant strains were identified, including Escherichia coli, Pseudomonas otitidis, Staphylococcus warneri, Proteus mirabilis, and Bacillus cereus, some of which showed simultaneous resistance to critical antibiotics such as tetracycline, ceftriaxone, vancomycin, and kanamycin. These results confirm that swimming pools provide a favorable environment for the presence of bacterial resistance. From a One Health perspective, these results emphasize the interconnectedness of human, animal, and environmental health, reinforcing the need for stricter monitoring and control of recreational waters to mitigate the spread of antibiotic resistance. Keywords: one health, recreational water, waterborne pathogens.