ANTIBIOTIC-RESISTANCE IN BACTERIA

Selective antibiotic pressure due to the increased use of glycopeptide antibiotics for the control of infections caused by gram-positive bacteria has resulted in the emergence of resistance in enterococci and coagulase-negative staphylococci. It is of particular concern that resistance is mediated in some enterococcal strains by self-transferable plasmids with a wide hose range; such a situation may lead to the transfer of this type of glycopeptide resistance to other gram-positive pathogens. Although glycopeptide antibiotics have been used for 30 years, cases of resistance have been slow to emerge. This is probably due to the unique interaction between a compact and relatively rigid antibiotic molecule and its target, which is, unusually, a substrate for peptidoglycan synthesis rather than an enzyme involved in catalysis. For this reason, any mechanism of resistance is likely to be unusual: diminished accessibility of glycopeptides to their target sites is the most likely possibility in both enterococci and coagulase-negative staphylococci but whether this results from target protection or modification has not yet been demonstrated convincingly.