Yara Haddad, “Characterizing Antimicrobial Susceptibility Profiles among Aeromonas Isolates throughout the Wastewater Process”
Mentor: Troy Skwor, Biomedical Sciences, Biomedical Sciences & Health Care Administration (School of)
Poster #24
Antibiotic resistance (AMR) is a growing global health challenge, and wastewater serves as a critical environment for the growth and spread of resistant bacteria. This study aimed to assess the prevalence of antibiotic susceptibility and their corresponding resistance genes throughout the wastewater treatment process: influent, pre-chlorinated, and final post-chlorinated effluents. Presumptive Aeromonas bacterial isolates were identified from filtered sewage water by yellow colonies on ampicillin dextrin agar with vancomycin. Bacterial isolates underwent testing for antimicrobial susceptibility using the Kirby Bauer disk diffusion assay. Alkaline lysis was used to acquire DNA, and PCR targeted resistance genes, including OXA-1, TEM-1, qnrS, qnrB, qnrA, CTX-M subgroup 1,2 and 9, sul1 and 2, tetA, tetB, tetC, tetD, tetE, int-1, and gyrB as a control gene. Throughout the wastewater process, resistance to the carbapenem drug meropenem was 8% in influent, 0% in treated effluent, and 2% in post-chlorinated effluent. The beta-lactamase TEM-1 was detected amongst a few of these isolates, but most cases of resistance were unexplained on a molecular level. Tetracycline resistance remained stable throughout the treatment process between 7 – 10%. This was primarily attributed to the presence of tetE in 84.6% of isolates and tetA only in a fraction of them (7.7%). Resistance to trimethoprim/sulfamethoxazole was highest in influent (22%), though still present in treated (15%) and final post-chlorinated (18%) effluents. Amongst these populations, over 90% encoded sul1 and/or sul2 and over 65% encoded the class 1 integron integrase (int1). Lastly, less than 5% of wastewater isolates exhibited resistance to fluoroquinolone ciprofloxacin, although the highest resistance was evident to first generation quinolone nalidixic acid (>30%). QnrS gene was encoded by many of the nalidixic acid-resistant isolates. These findings demonstrate the persistence of antibiotic resistance in wastewater, even after final disinfection suggesting a need for alternative mitigation strategies to combat these resistant populations.