title: Activity of beta-lactamase inhibitor sulbactam plus ampicillin against animal isolates of Pasteurella, Haemophilus, and Staphylococcus.
abstract: Antibiotic susceptibilities of Pasteurella sp, Haemophilus pleuropneumoniae, and Staphylococcus aureus isolates were determined. The combination of sodium sulbactam, a beta-lactamase inhibitor, and ampicillin had a synergistic effect against all ampicillin-resistant pathogens, rendering them susceptible to ampicillin. Studies of cell-free beta-lactamase from Pasteurella and Haemophilus isolates confirmed the presence of a constitutive penicillinase. Inhibitory concentrations of sulbactam-ampicillin were bactericidal, as demonstrated by killing curves. Ampicillin-resistant Pasteurella and Haemophilus isolates did not develop resistance to sulbactam-ampicillin when passed as many as 8 times in the presence of sublethal concentrations of sulbactam-ampicillin. The in vitro synergistic activity of sulbactam-penicillin also was seen in an in vivo synergistic response in mice challenge exposed to an ampicillin-resistant P haemolytica.
mesh_terms: D000667:Ampicillin / Q000494:pharmacology*; D000668:Ampicillin Resistance; D000818:Animals; D002417:Cattle; D002514:Cephapirin / Q000494:pharmacology; D004338:Drug Combinations; D004352:Drug Resistance, Microbial; D006190:Haemophilus / Q000187:drug effects* / Q000302:isolation & purification; D010325:Pasteurella / Q000187:drug effects* / Q000302:isolation & purification; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000302:isolation & purification; D013407:Sulbactam / Q000494:pharmacology*; D013552:Swine; D065093:beta-Lactamase Inhibitors
chemical_list: D004338:Drug Combinations; D065093:beta-Lactamase Inhibitors; D000667:Ampicillin; D002514:Cephapirin; D013407:Sulbactam