| epidemiology of conjugative plasmid-mediated ampc beta-lactamases in the united states. | a sample of 752 resistant klebsiella pneumoniae, klebsiella oxytoca, and escherichia coli strains from 70 sites in 25 u.s. states and the district of columbia was examined for transmissibility of resistance to ceftazidime and the nature of the plasmid-mediated beta-lactamase involved. fifty-nine percent of the k. pneumoniae, 24% of the k. oxytoca, and 44% of the e. coli isolates transferred resistance to ceftazidime. plasmids encoding ampc-type beta-lactamase were found in 8.5% of the k. pneumon ... | 2004 | 14742206 |