Antimicrobial Resistance in Enterococci

Enterococci show intrinsic low resistance to a large number of antibiotics (β-lactams, lincosamines, aminoglycosides and trimetoprim-sulfametoxazol). In addition, Enterococci can acquire new resistance to antimicrobial agents. This can happen by mutation or acquisition of extrachromosomal DNA, as plasmids or transposons. Resistance to erythromycin, aminoglycosides and tetracycline are common. Resistance to glycopeptide antibiotics and to newer antimicrobial substances may turn opportunistic enterococcal infections into high-risk infections, specially for immunocompromised patients. Enterococci isolated at different steps in the food chain also show a remarkable incidence of antimicrobial resistance. Heavy metal resistance and biocide tolerance could be factors in the co-selection of antibiotic resistance in the absence of antibiotic selective pressure, such as at certain steps of the food chain.