MARYLAND — A study presented at ASM Microbe 2026 in Washington, D.C. found that over one-third of Maryland homes with sewage overflows contained antibiotic-resistant Enterococci bacteria. Nick An is the corresponding study author and a doctoral candidate at the University of Maryland School of Public Health.
Researchers collected 107 environmental samples from 86 Maryland homes between October 2023 and June 2025. These samples were analyzed for Enterococci bacteria, which are used as indicators of fecal contamination. Laboratory analysis detected Enterococci bacteria in 46% of the tested homes.
The study identified the species E. faecalis in 21% of sampled residences and E. faecium in 27% of sampled residences. Both E. faecalis and E. faecium bacterial strains can cause infections in individuals with compromised immune systems. Homes reporting sewage or water incidents within 30 days before sampling showed higher rates of Enterococci detection compared to residences without recent incidents.
Multidrug resistant Enterococci, defined as bacterial strains resistant to three or more distinct antibiotic classes, were present in more than 10% of the sampled homes. Residences with recent sewage or water events contained three times the concentration of multidrug resistant bacteria compared to those without recent events; however, researchers noted this variation could be attributed to chance given the sample size.
Nick An said, "Our research underscores an urgent need to invest in upgrading water and sewer infrastructure to protect public health from this growing threat." The research team will continue environmental sample collection from flood and sewage-impacted residences over the upcoming summer months. An said, "We also plan to share our findings at community events in neighborhoods we have worked in and more broadly in Maryland communities impacted by sewage overflows." The study received financial support from a University of Maryland Grand Challenges grant and the National Institute on Minority Health and Health Disparities within the National Institutes of Health under award identification DP2MD019355.