Multi-Drug Resistant Bacteria from Sewage Treatment Plants in Johor: Isolation and Characterization

In this study, we revealed multi-drug resistant (MDR) bacteria isolated from three sewage treatment plants (STPs) against ciprofloxacin, chloramphenicol, gentamicin, tetracycline, and sulfamethoxazole. The antibiotic susceptibility test (AST) result shows that these isolates are distinctly highly resistant to sulfamethoxazole for influent (100%) and effluent (80-100%) samples for the first sampling (S1), while the lowest resistance (0%), resistant to chloramphenicol in some locations, in the second sampling (S2). Among the culturable isolates, multi-resistant bacteria were screened through AST, and these species were identified through 16S rRNA gene sequencing. From the cumulative multi-resistant isolates, 45.45% are known opportunistic bacteria species from the Enterobacteriaceae family (Citrobacter sp., Serratia sp., Enterococcus sp., and Escherichia sp.), while 27.27% are Aeromonadaceae and Pseudomonadaceae, respectively. This study reveals the prevalence of culturable multi-resistant opportunistic bacteria in influent and effluents of the three selected STPs for both sampling times.