In vitro activity of cefpirome against selected clinical enterobacterial isolates with beta-lactamase-mediated resistance.

Previous studies have shown that there is a high incidence of resistance to cephalosporins among enterobacteria isolated in Greek hospitals. This resistance is mainly due to either the derepression of chromosomal cephalosporinases or the acquisition of plasmids coding for SHV-5 type beta-lactamase. In the present study the activity of cefpirome against a number of enterobacteria (Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Enterobacter aerogenes and Serratia marcescens) possessing the mechanisms mentioned above was examined. Cefpirome was found active against all the strains characterized by stable derepression of chromosomal class-C enzymes. The antibiotic was less potent against strains expressing SHV-5 type beta-lactamase due to its hydrolysis by the enzyme. Also cefpirome exhibited good activity against E. aerogenes strains with reduced susceptibility to imipenem. These in vitro data suggest that cefpirome might be useful in treating infections caused by these resistant microorganisms that are frequently encountered in Greek hospitals.