Abundance of Antibiotic Resistant Enterococci in Relation to Two Wastewater Treatment Plants in Mobile, Alabam

Antibiotic resistant bacteria are frequently detected in surface waters and pose environmental, health, and economic threats. In this study, water samples were collected upstream and downstream the Clifton C. Williams and Wright Smith Jr. WWTPs which both discharge into the Mobile River. Samples were filtered and placed on petri plates containing mEI Agar. Colonies were counted. Randomly selected Enterococcus colonies were screened using antibiotic disc diffusion, and each colony was classified as resistant, intermediate, or susceptible.;After 3 sampling dates, the average enterococci abundances were 6.1, 439.1, and 1.6 CFU/100 mL, and there were significantly more bacteria downstream than upstream of the WWTPs. Apart from a site on 10/10/16 in which enterococci abundances were over 2500 CFU, all sampling sites were below US EPA recreational water criteria. The enterococci colonies were 19.1% resistant, 16.2% intermediate, and 64.9% susceptible to at least 1 of the 8 antibiotics tested. While resistance to ciprofloxacin, erythromycin, and streptomycin was common, only 1 instance of vancomycin resistance was detected. In conclusion, this study found that neither WWTP increased the abundance of enterococci in the Mobile River or the prevalence of antibiotic resistant enterococci.