An overview of the response of bacteria to beta-lactam antibiotics.

A great variety exists in the ways bacteria respond to beta-lactam antibiotics. The responses of gram-positive cocci and gram-negative bacilli are fundamentally different, and beta-lactam antibiotics vary widely in their ability to penetrate to the target proteins, to bind to those proteins, and to withstand hydrolysis by enzymes that the organism may possess. Continuous turbidimetric monitoring offers a simple means by which the response of bacterial cultures can be followed in undisturbed test conditions. Microscopy of the cultures permits the turbidimetric record to be related to morphologic changes elicited by the antibiotic. Such studies reveal that cephalosporins can often evoke a transient response in bacteria that are completely unaffected by penicillins; beta-lactamase inhibitors appear to be more effective when they build on such a partial response.