beta-Lactamase inhibitory activity of iodopenicillanate and bromopenicillanate

Iodopenicillanate and bromopenicillanate were shown to be effective inhibitors of a variety of beta-lactamases. Staphylococcus aureus isolates were synergistically inhibited by iodopenicillanate and bromopenicillanate combined with ampicillin. Methicillin-resistant S. aureus was not synergistically inhibited. Escherichia coli which possessed TEM beta-lactamase activity had a reduction in ampicillin minimal inhibitory concentration, but an E. coli isolate which had chromosomal beta-lactamase and a low ampicillin minimal inhibitory concentration showed no reduction in ampicillin minimal inhibitory concentration with either iodopenicillanate or bromopenicillanate. Of the Klebsiella isolates tested, 80% were synergistically inhibited by both iodopenicillanate and bromopenicillanate. Most Morganella isolates were synergistically inhibited by either iodopenicillanate or bromopenicillanate combined with ampicillin, as were many Salmonella, Shigella, Citrobacter diversus, and Citrobacter freundii isolates. No Pseudomonas aeruginosa isolates were synergistically inhibited by iodopenicillanate or bromopenicillanate. Preincubation did not improve the inhibitory activity of iodopenicillanate or bromopenicillanate.