Antibiotic-resistant bacteria detected in homes impacted by sewage

Antibiotic-resistant (AR) bacterial infections are disproportionately experienced by Black communities in the U.S. Exposure to AR bacteria could occur when untreated sewage enters homes through sanitary sewer overflows (SSOs) or basement sewage backups (“backups”). Through a community-engaged pilot study in Baltimore, Maryland, which has a large Black population where many live below the poverty line, we evaluated the presence of methicillin-resistant Staphylococcus aureus (MRSA), methicillin-susceptible S. aureus (MSSA), coagulase-negative staphylococci (CoNS), methicillin-resistant CoNS (MR-CoNS), and E. coli in homes experiencing sewage events. We collected surface (n = 41) and standing water (n = 6) samples from 40 homes in neighborhoods where SSOs or backups frequently occur. Samples were processed using modified standard membrane filtration. A subset of isolates underwent whole genome sequencing (WGS). Among participants, 95% (38/40) identified as Black and 95% (38/40) self-reported having an SSO or backup. Over 72% (29/40) of participants had a sewage event within six months of sampling, and 42.5% (17/40) had an event less than one month prior. Nearly 17% (1/6) of water samples were positive for MRSA and MR-CoNS and 66.7% (4/6) positive for CoNS and E. coli. No MRSA was found on sampled surfaces, but multidrug-resistant (MDR) MSSA, MR-CoNS, CoNS and E. coli were detected on 2.4% (1/41), 12.2% (5/41), 80.5% (33/41), and 26.8% (11/41) of surfaces, respectively. Detection of target bacteria differed significantly between homes with events that occurred less than one month compared to those where events occurred more than one month prior to sample collection (p = 0.046). Five of six isolates analyzed by WGS for ARGs were MDR and 85 distinct virulence genes were identified among isolates analyzed for VFGs (n = 3). Our results suggest that SSOs or backups could be a source of AR bacteria exposure in underserved communities, and therefore a critical research area for public health and urban planning.