The comparative performance of beta-lactam antibiotics against ampicillin sensitive Escherichia coli in conditions simulating those of the infected urinary bladder.

The response of an ampicillin sensitive strain of Escherichia coli to 6 beta-lactam antibiotics was compared in a mechanical model which simulates the hydrokinetic features of the urinary bladder. The performance of the antibiotics was found to differ in a way that could not be predicted by more conventional in vitro techniques. For example, benzylpenicillin was found to be at least as effective as any cephalosporin. Possible reasons for these findings and the relevance of the results to therapeutic practice are discussed.