Abstract

Antibiotic-resistant Staphylococcus aureus isolated from homes impacted by sewage and flooding events in Maryland, USA

Claire Barlow, MPH¹, Kathryn Dixon, ScM², Nick An, MPH³, Hana Fisaha, MSc³, Priscila Alves, PhD³, Brienna Anderson-Coughlin, PhD³, Marccus Hendricks, PhD³ and Rachel Rosenberg Goldstein, PhD³
(1)University of Maryland, College Park, MD, (2)College Park, MD, (3)University of Maryland, College Park, College Park, MD

APHA 2025 Annual Meeting and Expo

Infections due to antibiotic-resistant bacteria (ARB) are on the rise and becoming increasingly challenging to treat. Specifically, exposure to methicillin-resistant Staphylococcus aureus (MRSA) can cause life-threatening illnesses including bacteremia and soft tissue infections. Although historically studied in health-care settings, wastewater can be an environmental source of ARB, including S. aureus. In several urban areas in Maryland, Sanitary Sewer Overflows (SSOs) result in raw, untreated wastewater entering waterways and homes due to extreme precipitation, failing infrastructure, and clogged or damaged sewer lines. SSOs present a critical public health challenge. To evaluate the public health risk associated with SSOs in Maryland, we conducted household surveys, visual inspections, and collected surface samples (n=97) from residences (n=76) across Baltimore, Montgomery, and Prince George’s counties that experienced a sewage backup or flooding event from August 2023 - February 2025. Fisher’s exact tests were used to compare S. aureus and ARB presence by time since sewage event, classified as ≤6 months or >6 months, as previous research has shown that S. aureus can persist on surfaces for up to 7 months. Twenty-one sampled homes had an event ≤6 months prior to sampling, 55 >6 months prior to sampling. We identified ARB, including MRSA (3/76, 4%) and methicillin-resistant coagulase-negative Staphylococci (CoNS) (25/76, 33%) in impacted homes. We also identified methicillin-susceptible S. aureus (14/76, 18%) and CoNS (74/76, 97%) in impacted homes. S. aureus and ARB detection did not differ significantly based on time since the sewage event (p=0.53, p=0.43). Next steps involve antimicrobial susceptibility testing and whole-genome sequencing to identify antibiotic-resistance genes and virulence factors for the S. aureus and resistant isolates. Further research is necessary to better understand pathogen persistence and the risk of exposure to ARB among residents experiencing SSOs.

Environmental health sciences Protection of the public in relation to communicable diseases including prevention or control Public health biology