New research presented last week at the annual conference of the American Society for Microbiology (ASM)—known as ASM Microbe 2026—suggests that pathogenic, drug-resistant bacteria could pose a threat to people living in homes with sewage overflows.
The research, conducted by scientists from the University of Maryland (UMD), found that Enterococcus bacteria were present in nearly half (46%) of 86 Maryland homes that had sewage backups from clogged, broken, or overwhelmed pipes from October 2023 to June 2025. Analysis of sewage water samples found that multidrug-resistant (MDR) enterococci were present in 12% of the homes with backups.
Enterococcus bacteria are found in soil and plants but also in the intestinal tracts of people, animals, and birds. Their presence in water is an indicator of fecal contamination, which is common in untreated sewage water.
While many species of the more than 60 recognized enterococci species don’t pose a threat to people, two species—Enterococcus faecium and Enterococcus faecalis—have become leading causes of healthcare-related infections, with intrinsic resistance to some antibiotics and acquired resistance to others.
Of the 39 homes with enterococci present, 21% had E faecalis and 27% had E faecium present. The presence of enterococci bacteria was significantly higher (62%) in homes with recent sewage or water events (within the past month), and homes with more recent sewage overflows were three times as likely to have MDR enterococci present, though the researchers said this could have been by chance.
Extreme weather could exacerbate the problem
While sewage backups are a concern for homeowners everywhere, the authors say they’re concerned that more people could be exposed to potentially pathogenic bacteria as extreme weather events, like floods, become more common and sewer systems continue to age.
“Our research underscores an urgent need to invest in upgrading water and sewer infrastructure to protect public health from this growing threat,” corresponding study author Nick An, a PhD candidate in the UMD School of Public Health, said in an ASM press release.
An and his colleagues say they plan to continue collecting samples from homes with sewage overflows over the summer and will share their findings with community groups.
Our research underscores an urgent need to invest in upgrading water and sewer infrastructure to protect public health from this growing threat.