Enterococcus species

Enterococcus species

Organism

Gram-positive cocci typically in pairs and short chains.
Facultative anaerobe (def).
Most commonly isolated species are Enterococcus faecalis and Enterococcus faecium.

Habitat

Normal flora of the intestinal tract in humans and animals.

Source

Usually the patient's own fecal flora; some transmission is patient-to-patient.

Clinical Disease

Responsible for about 10% of all nosocomial infections (def).
Most common infections are urinary tract infections (UTIs) and bacteremia (def).
Other infections include endocarditis (def) as a complication of bacteremia and wound infections; infections within the peritoneal cavity including intra-abdominal abcesses (usually polymicrobial (def)) especially following penetrating trauma such as gunshot wounds, knife wounds, and surgical wounds; kidney infections as a complication of UTIs, prostate infections, and infections of damaged or compromised skin, such as diabetic or decubitus ulcers, burns, and surgical wounds (often polymicrobial (def)).
The enterococci have become the second most common bacterium isolated from nosocomial urinary and wound infections, and the third most common cause of nosocomial bacteremia. Each year in the U.S., in fact, enterococci account for approximately 110,000 urinary tract infections, 40,000 wound infections, 25,000 cases of nosocomial bacteremia, and 1100 cases of endocarditis.
Predisposing factors include:
- urinary (def) and intravascular (def) catheters.
- long-term hospitalization while receiving broad-spectrum antibiotics.

Pathogenesis

Fimbriae-like proteins originating in the cytoplasmic membrane that promote attachment to epithelial cells as well as plasmid (def) exchange.
Various cell wall adhesins (def) that promote attachment to cells of the intestinal tract.
Secreted cytolysin that inhibits growth of other intestinal gram-positive bacteria to facilitate enterococcal colonization; also induces local tissue damage.
Secreted pheromone that is a chemoattractant for neutrophils and subsequently promote inflammatory reactions.
Secreted gelatinase that hydrolizes collagen and hemoglobin.
Inherently resistant to many beta-lactam antibiotics; acquires resistance genes to aminoglycosides and vancomycin (VRE or vancomycin-resistant enterococci.) See antibiotic table. The enterococci are among the most antibiotic resistant of all bacteria, with some isolates resistant to all known antibiotics.

Treatment

aminoglycosides plus vancomycin; linezolid; streptogramin; selected fluoroquinolones* (see antibiotic table).

*Drugs may change with time.

For a more detailed article on Enterococcus infection in females, see Enterococcal Infections, by Curtis J Donskey, MD, Chairman of Infection Control, Instructor, Department of Internal Medicine, Section of Infectious Diseases, Stokes Cleveland VA Medical Center, Case Western Reserve University and Robert A Salata, MD, Chief and Clinical Program Director of Division of Infectious Diseases, Vice Chair for International Affairs, Professor, Department of Medicine, Case Western Reserve University School of Medicine