Resistance to β-Lactam Antibiotics in Bacteroides Spp.

Bacteroides spp., particularly B. fragilis, are well-recognised bacterial pathogens. Production of the typical β-lactamases of Bacteroides restricts the therapeutic use of β-lactam agents mainly to the β-lactamase inhibitor combinations and carbapenems. These compounds have the advantage of broad-spectrum activity and the ability to combat polymicrobial infections. Resistance of Bacteroides spp. to β-lactam antibiotics appears to be increasing, largely because of an overall increase in β-lactamase activity. There has been a rise in the prevalence of isolates showing high-level production of typical Bacteroides β-lactamases and an increase in reports other potent β-lactamase types. In the case of B. fragilis, metallo-enzymes are a particular threat to current therapeutic practice, as they are not inhibited by common β-lactamase inhibitors and are able to hydrolyse carbapenems. The presence of permeability barriers may confer low-level β-lactam resistance and supplement the effect of β-lactamase activity. There are also sporadic reports of loss of β-lactam activity because of reduced affinity of the penicillin-binding proteins.