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Biological Health Hazard – Antibiotic resistance bacteria (VRSA), [environmental contamination – sewage]: Florida


Published Date: 2016-07-28 15:40:52
Subject: PRO/AH/EDR> Vancomycin resistance – USA: (FL) E. faecium, sewage spill, envir. contam., 2014
Archive Number: 20160728.4376123

Date: Friday, 15 July 2016
Source: Applied and Environmental Microbiology [edited]

Citation: Young S, Nayak B, Sun S, Badgley B, Rohr J, Harwood VJ: Vancomycin resistant enterococci and bacterial community structure following a sewage spill into an aquatic environment. Appl Environ Microbiol. 2016; pii: AEM.01927-16. [Epub ahead of print]. DOI: 10.1128/AEM.01927-16

Sewage spills can release antibiotic resistant bacteria to 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, beach sands and wildlife feces. However, VRE harboring _vanA_ genes that confer high-level resistance have infrequently been found outside of clinical settings in the U.S. This study found culturable _Enterococcus faecium_ harboring the _vanA_ gene in water and sediment up to 3 days after a sewage spill, and the qPCR signal for _vanA_ persisted for an additional week. Culturable enterococci levels in water exceeded recreational water guidelines for 2 weeks following the spill, declining about 5 orders of magnitude in sediments and 2 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 both 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 examining the persistence, occurrence and survival of VRE in different environmental matrices.

Significance of the study: vancomycin-resistant enterococci (VRE) are harmful bacteria that are resistant to the powerful antibiotic vancomycin, 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.

Communicated by:
Philip Henika
USDA, Agricultural Research Service, retired

[Enterococci are Gram-positive cocci that normally inhabit the lower gastrointestinal tract of animals, including humans. They commonly cause both community-acquired and nosocomial infections, which include urinary tract infection, biliary sepsis, and other intra-abdominal infections, wound infections, bacteremia, and endocarditis. The most common enterococcal pathogens are _Enterococcus faecalis_ and _Enterococcus faecium_.

Vancomycin is a glycopeptide antibiotic that has been used to treat infections caused by antibiotic-resistant Gram-positive bacteria, including enterococci. However, vancomycin-resistant enterococci (VRE) have become increasingly common worldwide since they were 1st reported in 1988 in the UK and France. Although _E. faecalis_ is more common overall among clinical isolates, _E. faecium_ is more common than _E. faecalis_ among VRE.

Of the several genotypes of vancomycin resistance, _vanA_ and _vanB_ are most common as they are located on mobile genetic elements that can readily move between enterococci. _VanA_ strains have high MICs (minimum inhibitory concentrations) to both vancomycin and another related antibiotic teicoplanin; _vanB_ strains have moderate to high MICs to vancomycin and are susceptible to teicoplanin.

Avoparcin, a member of the class of antibiotics (glycopeptides) to which vancomycin belongs, had been used in some countries in animal feed as a growth promoter. Because avoparcin confers cross-resistance to vancomycin, the use of avoparcin can select for VRE. VRE, i.e. vancomycin-resistant _E. faecium_ carrying the _vanA_ genotype, was more common in the intestinal tract of farm animals and humans with no exposure to hospitals and in sewage in European countries that used avoparcin in animal feed for growth promotion than in European countries, Canada and the USA that never used avoparcin in animal husbandry.

In the USA, where use of glycopeptides had been restricted to use in hospitals, VRE has been much more common in hospitals, detected in fecal colonization or infections in people with hospital exposure and hospital sewage, and rarely found in humans in the community with no hospital exposure or in food animals ( Once the use of avoparcin was discontinued in European countries, the prevalence of VRE among farm animals decreased ( In China, where glycopeptides, including avoparcin, are banned in animal husbandry, VRE reportedly has been rarely found on farms (

In the field study reported in the abstract above, culturable VRE and/or _vanA_ genes were transiently detected in sediment and water samples after a 3-day sewage spill released more than 500 000 gallons of untreated sewage in a residential neighborhood in 2014. The spill in this study was not in close proximity to any hospital; and sewage from the nearest hospital flowed away from the break site. The source of the VRE in this study was not explained. – Mod.ML

A HealthMap/ProMED-mail map can be accessed at:]

See Also

Staphylococcus aureus, MRSA – Brazil: (SP) vancomycin resistant (VRSA) update 20140422.2420131

Antibiotic resistance – USA (03): vancomycin, comment 20131125.2073470
Antibiotic resistance – USA (02): vancomycin, comment 20131118.2061191
Antibiotic resistance – USA: vancomycin, crow 20131111.2048866
Vancomycin resistant enterococci – China: (HK) E. faecium ST6/CC5 20130801.1858689
Staphylococcus aureus, MRSA – Brazil: (SP) vancomycin resistant (VRSA) 20130630.1800166

Vancomycin resistant enterococci – Sweden 20100727.2515

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