Definition
Enterococcaceae is a family of Gram‑positive, non‑spore‑forming bacteria within the order Lactobacillales (formerly lactic acid bacteria) and the phylum Firmicutes. Members of this family are characterized by their coccoid shape and facultative anaerobic metabolism.
Overview
The family Enterococcaceae comprises several genera, the most prominent being Enterococcus and Vagococcus. Species of Enterococcus are widely distributed in nature, inhabiting the gastrointestinal tracts of humans and animals, as well as soil, water, and food products. Some members are opportunistic pathogens, notably Enterococcus faecalis and Enterococcus faecium, which are implicated in urinary tract infections, wound infections, bacteremia, and endocarditis. The family is of particular interest in clinical microbiology because of the intrinsic and acquired resistance of many Enterococcus species to multiple antibiotics, including vancomycin.
Etymology / Origin
The family name derives from the genus Enterococcus (from Greek enteron “intestine” and coccus “berry”), reflecting the typical intestinal habitat of its members, combined with the standard bacterial family suffix “‑aceae”.
Characteristics
- Cellular morphology: Small, spherical (cocci) cells that frequently occur in pairs (diplococci) or short chains.
- Cell wall composition: Thick peptidoglycan layer characteristic of Gram‑positive bacteria; contains teichoic acids.
- Metabolism: Facultatively anaerobic; capable of fermenting a variety of carbohydrates to produce lactic acid, but many species also ferment other substrates such as amino acids.
- Genomic features: 16S rRNA gene sequencing places Enterococcaceae within the Lactobacillales clade. Whole‑genome analyses reveal a high degree of genetic plasticity, including mobile genetic elements that contribute to antibiotic resistance and virulence.
- Growth conditions: Grow on standard laboratory media (e.g., blood agar, bile‑esculin agar) at temperatures ranging from 20 °C to 45 °C; many species tolerate high salt concentrations and alkaline pH.
- Clinical relevance: Enterococcus spp. are notable for their ability to acquire resistance determinants such as vanA and vanB, leading to vancomycin‑resistant enterococci (VRE). They also possess virulence factors including aggregation substance, gelatinase, and cytolysin.
Related Topics
- Enterococcus – the principal genus of the family, encompassing both commensal and pathogenic species.
- Lactobacillales – the order of lactic acid bacteria to which Enterococcaceae belongs.
- Vagococcus – another genus within the family, primarily associated with animal sources.
- Antibiotic resistance – especially mechanisms underlying vancomycin resistance in enterococci.
- Nosocomial infections – hospital‑acquired infections where Enterococcaceae members are common etiological agents.
- Phylogeny of Firmicutes – broader bacterial classification context including related families such as Streptococcaceae and Lactobacillaceae.