The Occurrence and Antibacterial Susceptibility of Salmonella spp. & Shigella spp. along the Southern Coastal Belt of Sri Lanka, from Galleface to Mirissa

Abstract

Salmonella spp. and Shigella spp. are widespread pathogenic bacteria that cause Salmonellosis and Shigellosis, respectively. The resistance of these bacteria to commonly used antibiotics is a critical global challenge. The present study focuses on the prevalence of Salmonella spp. and Shigella spp. along the Galle face to Mirissa coastal belt in Sri Lanka and to assess their antibiotic resistance to Amoxicillin (AMX), Ciprofloxacin (CPX), Augmentin (AUG), Tetracycline (TET), Cloxacillin (CLOX), and Erythromycin (ERM). Water samples were collected in triplicate from nineteen selected beach sites that are famous for tourism-related recreational activities. Salmonella spp. and Shigella spp. were identified following standard microbiological procedures and confirmed through biochemical tests. Antibacterial susceptibility and Multiple Antibiotic Resistance (MAR) were evaluated based on the Clinical and Laboratory Standards Institute (CLSI) guidelines. Water quality analysis was carried out according to APHA standard methods. The results showed that Salmonella spp. was present in 18 sites out of 19 selected beach sites, while Shigella spp. was detected in 17 out of the 19. Notably, 94.4% of Salmonella spp. isolates resisted AMX at 60 µg/mL, and 66.7% were resistant to AMX at 360 µg/mL. Additionally, 88.9% of Shigella spp. isolates were resistant to AMX at 60 µg/mL, and 82.35% were resistant at 360 µg/mL. However, all bacteria were susceptible to CPX, TET, and ERM at 60 µg/mL. Resistance rates for AUG, ERM, and CLOX were 4.7%, 3.15%, and 38.94%, respectively. The MAR of the isolated bacteria ranged from 0.166 to 0.5. These findings underscore the urgent need for responsible antibiotic usage.