Toxin Antitoxin System in Enterococcus : mazEF-higBA-Virulence Factors

TOxin Antitoxin (TA) system is a regulatory system where two set of genes encode the toxin and the corresponding antitoxin. TA systems were first described in the mid 80's. The TA system could be harbored by chromosome or plasmid. In all the TA systems, antitoxin is unstable and toxin is stable. In TA systems that contain plasmid, the results would be daughter cells that inherit the plasmid. The daughter cells that are unable to inherit the plasmid harboring TA systems are killed. Due to the degradation of antitoxin, the stable toxin kills the cell. This is called post segregation killing. Enterococcus is Gram-positive cocci, facultative anaerobic and belong to lactic acid bacteria of the phylum Firmicutes. Enterococcus is able to resist the wide range of hostile conditions such as different pH, high concentration of NaCl and the extended temperature between 5C to 65C. E. faecalis and E. faecium are two of the most important commensal species in human intestine. The major infections caused by Enterococcus are urinary tract infections, biliary tract infections, meningitis, endocarditis, diverticulitis and bacteremia.