Vancomycin-Resistant Enterococci and Bacterial Community Structure following a Sewage Spill into an Aquatic Environment

Abstract

Sewage spills can release antibiotic-resistant bacteria into surface waters, contributing to environmental reservoirs and potentially impacting human health. Vancomycin-resistant enterococci (VRE) are nosocomial pathogens that have been detected in environmental habitats, including soil, water, and beach sands, as well as wildlife feces. However, VRE harboring vanA genes that confer high-level resistance have infrequently been found outside clinical settings in the United States. This study found culturable Enterococcus faecium harboring the vanA gene in water and sediment for up to 3 days after a sewage spill, and the quantitative PCR (qPCR) signal for vanA persisted for an additional week. Culturable levels of enterococci in water exceeded recreational water guidelines for 2 weeks following the spill, declining about five orders of magnitude in sediments and two orders of magnitude in the water column over 6 weeks. Analysis of bacterial taxa via 16S rRNA gene sequencing showed changes in community structure through time following the sewage spill in sediment and water. The spread of opportunistic pathogens harboring high-level vancomycin resistance genes beyond hospitals and into the broader community and associated habitats is a potential threat to public health, requiring further studies that examine the persistence, occurrence, and survival of VRE in different environmental matrices. IMPORTANCEVancomycin-resistant enterococci (VRE) are harmful bacteria that are resistant to the powerful antibiotic vancomycin, which is used as a last resort against many infections. This study followed the release of VRE in a major sewage spill and their persistence over time. Such events can act as a means of spreading vancomycin-resistant bacteria in the environment, which can eventually impact human health.A ntibiotic-resistant bacteria (ARB) are a growing public health threat and an economic burden globally. The Centers for Disease Control and Prevention (CDC) in the United States has placed a high priority on addressing antibiotic resistance because of rising rates of ARB infection and associated disease burden and health care costs (1, 2). Most infections caused by ARB are nosocomial transmissions (i.e., originating in a hospital), but the role of environmental reservoirs in spreading ARB outside clinical settings is poorly understood. Studies have emphasized the role of environmental reservoirs in the spread of antibiotic resistance for decades, but more field and laboratory studies are necessary to address the specific mechanisms and conditions under which ARB survive and antibiotic resistance genes (ARGs) persist or can be transferred (3-5). Wastewater treatment plants (WWTPs) are sources of ARB, ARGs, and antimicrobial compounds through both treated effluent and the unplanned release of raw sewage to surface waters (6-9). ARB, ARGs, and antibiotics can be released into aquatic environments through human and agricultural waste, establishing routes of human exposure and threats to ecosystem health.Vancomycin i...

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