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Assessment and characterization of antibiotic resistant enterococci at subtropical marine beaches (ASM 2024)
Citation:
Pemberton, A., J. Kelleher, B. McMinn, AND A. Korajkic. Assessment and characterization of antibiotic resistant enterococci at subtropical marine beaches (ASM 2024). ASM Microbe 2024, Atlanta, GA, June 13 - 17, 2024.
Impact/Purpose:
The prevalence of antibiotic resistant bacteria, including enterococci, in recreational waters is an emerging public health treat. Documenting their occurrence through environmental surveillance programs will allow for more accurate risk assessment regarding the exposure of bathers to surface waters contaminated with antibiotic resistant bacteria.
Description:
Background: Enterococci are ubiquitous in wastewater, which can contaminate surface waters, including recreational water, via many pathways, providing a route of exposure for humans Antibiotic resistant Enterococcus spp. are among the leading causes of nosocomial infections worldwide and specifically vancomycin resistant enterococci (VRE) have been identified by the Centers for Diseases Control and Prevention as a serious threat to public health. The environmental surveillance of recreational waters, characterization of the occurrence of antibiotic resistant enterococci, and understanding prevalence of multidrug resistance (MDR) will allow for more accurate risk assessment regarding the exposure of bathers to waters contaminated with antibiotic resistant bacteria. Methods: A total of 169 water samples were collected from three Gulf of Mexico beaches, including: Sylvan Beach, TX (SB; n=57), East Courthouse Beach, MS (EC; n=52) and Picnic Island, FL (PI; n=60). Enterococci were enumerated using standard membrane filtration technique followed by incubation on mEI agar. We also performed antibiotic resistance testing to eight clinically relevant antibiotics using Kirby Bauer disk diffusion method on nearly 2000 individual isolates. Results: Enterococci were detected in all samples, in concentrations ranging from 0.18 to 3.28 log10 colony forming units 100 mL A recommended single sample maximum enterococci criteria (104 CFU/100 mL) was exceeded in 32% of samples and more frequently at EC (42%) and PI (40%) sites than SB (14%). The VRE were rarely detected (~1% of isolates) and only at EC and SB sites. The MDR (defined as complete resistance to three or more antibiotics) also occurred infrequently (0-3% of isolates), but it was significantly higher (p < 0.0001) at the SB site compared to EC and PI. The MDR most frequently occurred to a combination of resistance to ampicillin, erythromycin, quinupristin/dalfopristin, meropenem and tetracycline.Conclusions: Our results indicate that even though VRE and MDR enterococci are a small proportion of the total enterococci population, they still occur and as the fully resistant phenotype which carries the most public health implications. Interestingly, the beach (i.e., SB) with the least exceedances had the most VRE and MDR isolates, suggesting that there are different sources and/or reservoirs of these strains in the environment, but this assertion warrants additional research.