Enterococci in the Environment

Abstract

SUMMARYEnterococci are common, commensal members of gut communities in mammals and birds, yet they are also opportunistic pathogens that cause millions of human and animal infections annually. Because they are shed in human and animal feces, are readily culturable, and predict human health risks from exposure to polluted recreational waters, they are used as surrogates for waterborne pathogens and as fecal indicator bacteria (FIB) in research and in water quality testing throughout the world. Evidence from several decades of research demonstrates, however, that enterococci may be present in high densities in the absence of obvious fecal sources and that environmental reservoirs of these FIB are important sources and sinks, with the potential to impact water quality. This review focuses on the distribution and microbial ecology of enterococci in environmental (secondary) habitats, including the effect of environmental stressors; an outline of their known and apparent sources, sinks, and fluxes; and an overview of the use of enterococci as FIB. Finally, the significance of emerging methodologies, such as microbial source tracking (MST) and empirical predictive models, as tools in water quality monitoring is addressed. The mounting evidence for widespread extraenteric sources and reservoirs of enterococci demonstrates the versatility of the genusEnterococcusand argues for the necessity of a better understanding of their ecology in natural environments, as well as their roles as opportunistic pathogens and indicators of human pathogens.

Fate and transport of tylosin-resistant bacteria and macrolide resistance genes in artificially drained agricultural fields receiving swine manure

“…Additionally, ermB was only detected in one interband sample in the first year of the crop rotation, while Garder et al (2014) detected ermB and ermF at quantifiable levels in every interband sample in the two previous years (fall 2010-spring 2012). The drought conditions in the summer of 2012 in Northeast Iowa may have caused additional stress to bacteria hosting the resistance genes and therefore hastened the return of overall concentrations to those found in no-manure control plot soils (Cools et al, 2001;Byappanahalli et al, 2012). The reduction in ermB and ermF genes in soil over winter are similar to those reported previously (Garder et al, 2014;Fahrenfeld et al, 2014).…”

Assessment of the microbiological quality of recreational waters: indicators and methods

“…In 1984, enterococci were given formal genus status, after genetic (DNA-DNA and DNA-RNA hybridization) studies demonstrated a more distant relationship with the streptococci. The Enterococcus was proposed as a unique genus, separate from Streptococcus (Byappanahalli et al 2012). According to ISO 7899-2, intestinal enterococci are able to reduce 2,3,5-triphenyltetrazolium chloride to formazan and to hydrolyse esculin at 44°C on the selective media, Slanetz and Bartley agar, containing sodium azide, which inhibits the growth of Gram-negative and staphylococci.…”

Antimicrobial resistance in Enterococcus strains isolated from healthy domestic dogs

“…Enterococcus species are Gram-positive bacteria belonging to the gastrointestinal microbiota of humans and animals, mammals and birds, and are widely distributed in the environment such as terrestrial and water habitats [1]. Some 42 ± 1°C for 18-24 h. From plates with growth of colonies typical for enterococci, at least one colony was subcultured on KAAA.…”