ENTEROCOCCUS RESISTANCE TO BETA-LACTAM ANTIBIOTICS IMPLICATION ON SYNERGY BETWEEN BETA-LACTAMS AND OTHER ANTIBIOTICS

Enterococci are naturally more resistant to beta-lactam antibiotics than streptococci. Among these E. faecalis can become more resistant to beta-lactams when it acquires a beta-lactamase gene. E. faecium and E. raffinosus can become more resistant by expressing high quantities of a low molecular weight PBP. Enterococci are generally tolerant towards beta-lactams. The presence of a synergy between beta-lactams and aminoglycosides depends of the absence or the presence of a modifying enzyme and the level of beta-lactam resistance. Glycopeptide-beta-lactam synergy is also dependant of the level of resistance to beta-lactams. When the synergy exists, it can be explained by the substitution, as an essential PBP, of the low molecular weight PBP5 for a high molecular weight PBP very sensitive to inhibition by beta-lactams.