Enterococcus

Enterococci are facultative anaerobic organisms, i.e., they are capable of cellular respiration in both oxygen-rich and oxygen-poor environments.[5] Though they are not capable of forming spores, enterococci are tolerant of a wide range of environmental conditions: extreme temperature (10–45 °C), pH (4.6–9.9), and high sodium chloride concentrations.[6]

Enterococci typically exhibit gamma-hemolysis on sheep's blood agar.

This genus appears to have evolved 425 million years ago to 500 million years ago.[8]

Important clinical infections caused by Enterococcus include urinary tract infections (see Enterococcus faecalis), bacteremia, bacterial endocarditis, diverticulitis, meningitis, and spontaneous bacterial peritonitis.[6][9][10] Sensitive strains of these bacteria can be treated with ampicillin, penicillin and vancomycin.[11] Urinary tract infections can be treated specifically with nitrofurantoin, even in cases of vancomycin resistance.[12]

Example of a workup algorithm of possible bacterial infection in cases with no specifically requested targets (non-bacteria, mycobacteria etc.), with most common situations and agents seen in a New England community hospital setting. Enterococcus is included near bottom-center.

From a medical standpoint, an important feature of this genus is the high level of intrinsic antibiotic resistance. Some enterococci are intrinsically resistant to β-lactam-based antibiotics (penicillins, cephalosporins, carbapenems), as well as many aminoglycosides.[9] In the last two decades, particularly virulent strains of Enterococcus that are resistant to vancomycin (vancomycin-resistant Enterococcus, or VRE) have emerged in nosocomial infections of hospitalized patients, especially in the US.[6] Other developed countries, such as the UK, have been spared this epidemic, and, in 2005, Singapore managed to halt an epidemic of VRE.[15] Although quinupristin/dalfopristin (Synercid) was previously indicated for treatment of VRE in the USA, the FDA approval for this indication has since been retracted.[16] The rationale for the retraction of Synercid's indication for VRE was based upon poor efficacy in E. faecalis, which is implicated in the vast majority of VRE cases.[17][18] Tigecycline has also been shown to have antienterococcal activity, as has rifampicin.[19]

In bodies of water, the acceptable level of contamination is very low; for example in the state of Hawaii, and most of the United States, the limit for water off its beaches is a five-week geometric mean of 35 colony-forming units per 100 ml of water, above which the state may post warnings to stay out of the ocean.[20] In 2004, measurement of enterococci took the place of fecal coliforms as the new USA federal standard for water quality at public saltwater beaches and alongside Escherichia coli at freshwater beaches.[21] It is believed to provide a higher correlation than fecal coliform with many of the human pathogens often found in city sewage.[22]