Susceptibility of Haemophilus influenzae type b to ampicillin-sulbactam.
Seventy-five strains of Haemophilus influenzae type b, including 45 beta-lactamase-positive strains, were tested by MIC and time kill studies for susceptibility to ampicillin-sulbactam at various ratios. beta-Lactamase-negative strains were inhibited by lower concentrations of ampicillin-sulbactam than beta-lactamase-positive organisms. beta-Lactamase-negative strains showed a decrease in CFU per milliliter by a factor of 10(4) after a 24-h incubation with ampicillin-sulbactam. beta-Lactamase-positive isolates showed an initial decrease by a factor of up to 10(2) CFU per milliliter, but by the end of incubation these isolates grew to approximately the same cell density as the antibiotic-free control regardless of ampicillin-sulbactam ratios. Caution should be exercised in the use of this combination in treatment of meningitis, in which a high bacterial density is commonly encountered.
Azimi
P H
PH
Division of Infectious Diseases, Children's Hospital Oakland, California.
Dunphy
M G
MG
D000667:Ampicillin / Q000494:pharmacology*; D002675:Child, Preschool; D004359:Drug Therapy, Combination / Q000494:pharmacology; D006192:Haemophilus Infections / Q000382:microbiology; D006193:Haemophilus influenzae / Q000187:drug effects*; D006801:Humans; D008826:Microbial Sensitivity Tests; D013407:Sulbactam / Q000494:pharmacology*
D000667:Ampicillin; D013407:Sulbactam