25-Enterococci in the Environment

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3510518/

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ABSTRACT

Summary: Enterococci 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 genus Enterococcus 

Microbiol Mol Biol Rev. 2012 Dec; 76(4): 685–706.

doi: 10.1128/MMBR.00023-12

PMCID: PMC3510518

PMID: 23204362

Enterococci in the Environment

Muruleedhara N. Byappanahalli,^a,* Meredith B. Nevers,^a,* Asja Korajkic,^b,* Zachery R. Staley,^c,* and Valerie J. Harwood^c,*

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ABSTRACT

Summary: Enterococci 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 genus Enterococcus and 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.

Table 1

Species of the genus Enterococcus and their currently known habitats

Group	Species	Known habitat(s)	Human pathogen	Reference(s)
E. faecalis	E. faecalis	Human, animal (multiple), plant, insect	Yes	70, 203, 235, 283
	E. haemoperoxidus	Surface water		320
	E. moraviensis	Surface water		320
	E. silesiacus	Drinking water		323
	E. termitis	Animal (termite)		323
	E. caccae	Human		54
E. faecium	E. faecium	Human, animal (multiple), plant, insect	Yes	70, 192, 203, 235, 283
	E. durans	Human, animal (multiple), insect	Yes	67, 70, 203
	E. hirae	Animal (multiple), plant		101, 203, 235
	E. mundtii	Soil, plant	Yes	66
	E. villorum	Animal (hog)		339
	E. canis	Animal (dog)		82
	E. ratti	Animal (rat)		324
	E. asini	Animal (donkey)		86
	E. phoeniculicola	Animal (bird)		202
	E. canintestini	Animal (dog)		243
	E. thailandicus	Human, animal (cattle)		55, 295, 316
E. avium	E. avium	Human, animal (multiple)	Yes	67, 121, 203, 257
	E. pseudoavium	Human		65
	E. malodoratus	Animal (cattle)		67
	E. raffinosus	Human	Yes	65, 241
	E. gilvus	Human		330

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