Combatting Waterborne Threats: Evaluating Antibiotic Effectiveness against Environmental Isolates of Aeromonas hydrophila

Ferolin Jessina, G.; Arasi, R.; Prakash, N.S.; Soumiya, S.; Surya, K.; Mary, S.J.A.J., and Petchimuthu, M., 2025. Combatting waterborne threats: Evaluating antibiotic effectiveness against environmental isolates of Aeromonas hydrophila. Journal of Coastal Research, 41(2), 247–254. Charlotte (North Carolina), ISSN 0749-0208. The emergence of antibiotic-resistant strains of Aeromonas hydrophila highlights the urgency of understanding the efficacy of conventional antibiotics against environmental isolates. This study investigated the time-kill kinetics of selected antibiotics against A. hydrophila strains isolated from the water of shrimp culture ponds along the Vedaranyam Canal region, Tamil Nadu, India. Identification and characterization of the strains were done through microbiological and molecular techniques. The antibiotics selected for the study included commonly used agents such as ciprofloxacin, gentamicin, ampicillin, oxytetracycline, erythromycin, furazolidone, nitrofurantoin, streptomycin, and tetracycline. The minimum inhibitory concentration (MIC) of antibiotics was determined by the broth macrodilution method. Antibiogram study revealed that the isolates were sensitive to a few antibiotics and showed intermediate resistance to others. The MIC of the antibiotics sensitive against A. hydrophila were obtained. Following the MIC determination, a time-kill kinetic assay was performed at 1× MIC, 2× MIC, and 4× MIC to find the bacteriostatic/bactericidal nature of the test compounds. The results of the study showed a strong bacteriostatic effect of the antibiotics tested against the isolated strains of A. hydrophila. This study provides basic first-line data about the pharmacological activity of the antibiotics. Results indicated that the effectiveness of antibiotics against A. hydrophila isolates varied both in terms of concentration and exposure time. This study contributes valuable insights into the temporal dynamics of antibiotic efficacy against environmental isolates of A. hydrophila.