Enterococci as probiotics and their implications in food safety

Abstract

Enterococci belong to the lactic acid bacteria (LAB) and they are of importance in foods due to their involvement in food spoilage and fermentations, as well as their utilisation as probiotics in humans and slaughter animals. However, they are also important nosocomial pathogens that cause bacteraemia, endocarditis and other infections. Some strains are resistant to many antibiotics and possess virulence factors such as adhesins, invasins, pili and haemolysin. The role of enterococci in disease has raised questions on their safety for use in foods or as probiotics. Studies on the incidence of virulence traits among enterococcal strains isolated from food showed that some can harbour virulence traits, but it is also thought that virulence is not the result of the presence of specific virulence determinants alone, but is rather a more intricate process. Specific genetic lineages of hospital-adapted strains have emerged, such as E. faecium clonal complex (CC) 17 and E. faecalis CC2, CC9, CC28 and CC40, which are high risk enterococcal clonal complexes. These are characterised by the presence of antibiotic resistance determinants and/or virulence factors, often located on pathogenicity islands or plasmids. Mobile genetic elements thus are considered to play a major role in the establishment of problematic lineages. Although enterococci occur in high numbers in certain types of fermented cheeses and sausages, they are not deliberately added as starter cultures. Some E. faecium and E. faecalis strains are used as probiotics and are ingested in high numbers, generally in the form of pharmaceutical preparations. Such probiotics are administered to treat diarrhoea, antibiotic-associated diarrhoea or irritable bowel syndrome, to lower cholesterol levels or to improve host immunity. In animals, enterococcal probiotics are mainly used to treat or prevent diarrhoea, for immune stimulation or to improve growth. From a food microbiological point of view, the safety of the bacteria used as probiotics must be assured, and data on the major strains in use so far indicate that they are safe. The advantage of use of probiotics in slaughter animals, from a food microbiological point of view, lies in the reduction of zoonotic pathogens in the gastrointestinal tract of animals which prevents the transmission of these pathogens via food. The use of enterococcal probiotics should, in view of the development of problematic lineages and the potential for gene transfer in the gastrointestinal tract of both humans and animals, be carefully monitored, and the advantages of using these and new strains should be considered in a well contemplated risk/benefit analysis.

Probiotic attributes, antioxidant, anti-inflammatory and neuromodulatory effects of Enterococcus faecium CFR 3003: in vitro and in vivo evidence

“…The use of enterococci as probiotics is still a controversial issue because the multiple antibiotic traits of some strains may contribute to their pathogenicity (Lei et al, 2014) and any probiotic bacterium resistant to most antibiotics may have negative consequences for human health (Dixit et al, 2013). Specifically, vancomycin-resistant enterococci are causing problems in hospitals on a global scale (Franz et al, 2011). In the present study, E. faecium showed no evidence of resistance to the clinically relevant antibiotics vancomycin, penicillin G, rifamycin and tetracycline.…”

“…in different hosts, such as mice, piglets and humans, to treat various gastrointestinal disorders have been well studied (Szabó et al, 2009). E. faecium NCIMB 10415 is widely used as a feed additive for animals (Franz et al, 2011), and evidence has corroborated the probiotic benefits of such strains. Furthermore, oral administration of E. faecium was shown to affect the intestinal microflora and modulate the immune function of mice and dogs (Benyacoub et al, 2003;Sun et al, 2010).…”

Country-specific antibiotic use practices impact the human gut resistome

“…The higher transmission of resistance genes for antibiotics used in food-producing animals in Mediterranean countries might Cold Spring Harbor Laboratory Press on May 9, 2018 -Published by genome.cshlp.org Downloaded from also be linked to diet as it has been reported that raw or cured food products, common in southern Europe (aged cheeses, cured sausages, olive fermentations), can carry high bacterial loads (Franz et al 2011). Indeed, we find that resistance was detected in fermented food products (see Supplemental Information) for some of the antibiotics where the resistance potential also differs most between countries.…”

Isolation and characterization of bacterial strains with a hydrolytic profile with potential use in bioconversion of agroindustial by-products and waste

“…has been reported for many researchers to be a source of lipolytic enzymes intestine of warm-blooded animals (MARTÍN-PLATERO et al, 2009;FRANZ et al, 2011). However, due to its aptitude to resist or grow in hostile environments such as extreme pH, temperatures, and salinity, Enterococcus can be found in many foods such as milk, cheese, fermented sausage, and fermented olives (GIRAFFA, 2003;MARTÍN-PLATERO et al, 2009).…”