The genus Enterococcus is characterized by single, paired, or short-chain gram-positive catalase-negative cocci(Teixeira et al., 2007).
In humans, as well as in other mammals and birds, these microbes are mainly found in the gastrointestinal tract as commensals but may become opportunistic pathogens in individuals with serious diseases whose immune systems are compromised and in patients who have been hospitalized for prolonged periods or received broad-spectrum antimicrobial therapy (Arias et al., 2010).
Enterococci have emerged as important nosocomial pathogen, they are recognized as the second-most common cause of urinary tract infections and the third-most common cause of nosocomial bacteremia (Lindenstrau et al., 2011).
Although many species can be recovered from human infections, Enterococcus faecalis (E.faecalis) is the most frequently recovered, representing more than 90% of clinical isolates, followed by Enterococcus faecium (E.faecium) (Dahlén et al., 2012).
Enterococcus transmission occurs endogenously (from the gut to the bloodstream) and exogenously (in the hospital environment, e.g., via inanimate objects and the hands of health care workers and visitors) or through the consumption of contaminated food and water, the latter being the most common route of transmission, especially in developing countries (Iversen et al., 2004; Silva et al., 2005).
Classically, E. faecalis has been linked to increased virulence, whereas E. faecium commonly exhibits multiresistance characteristics (Sharifi et al., 2012).
In a study on enterococcal UTI , VRE isolates possessed significantly fewer virulence factors than the susceptible isolates( Tiwari et al.,2015).
Several virulence factors have been described in enterococci, for instance, gelatinase, cytolysin, and hyaluronidase. The first two virulence factors are found in E.faecalis, while the 3rd virulence factor is specific for E.Faecium( Vankerckhoven et al., 2004).
The production of cytolysin has also been shown to significantly worsen the severity of endocarditis and endophthalmitis in animal models as well as to contribute to the severity of enterococcal disease in humans. Cytolysin genes are carried on a plasmid or are integrated into the bacterial chromosome (Vankerckhov et al., 2004) and Gelatinase is a zinc metalloprotease, encoded by gelE, with hydrolytic capacity (Lindenstrau et al., 2011).
Formerly, another virulence factor, hyaluronidase, was described in E. faecium (Rice et al., 2003). The E. faecium hyaluronidase, encoded bythe chromosomal hyl, shows homology to the hyaluronidases previously described in Streptococcus pyogenes, Staphylococcus aureus, and Streptococcus pneumonia( Hynes et al.,2000), which are believed to contribute to invasion of the nasopharynx and pneumococcal pneumonia (Berry et al.,2000).
Multiplex PCR is a rapid and convenient assay that allows simultaneous amplification of more than one locus in the same reaction and is used in both clinical and research laboratories (Henegariu et al., 1997).
Enterococci with high level aminoglycoside resistance (HLAR), B-lactamase production and glycopeptides resistance including vancomycin resistant enterococci (VRE) have emerged, thus posing a therapeutic challenge to physicians (Sood et al.,2008 ).
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