| epidemiology of rob beta-lactamase among ampicillin-resistant haemophilus influenzae isolates in the united states. | we surveyed 161 clinical isolates of ampicillin-resistant, beta-lactamase-producing isolates of haemophilus influenzae obtained between 1975 and 1985 to determine whether they produced tem-1 or rob beta-lactamase. plasmid dna was obtained from a rob-producing isolate, f990, and a plasmid (pbr322) known to encode tem-1. both plasmids were labeled with 32p and hybridized to whole cell dna obtained from the clinical isolates. all 161 isolates hybridized with one of the plasmid probes and could be c ... | 1988 | 3257784 |