In vitro antimicrobial activity of some cyclic hydroxamic acids and related lactams

Against Enterobacter aerogenes 13048, Serratia marcescens 13880, Klebsiella pneumoniae 10031, Pseudomonas aeruginosa 10145, Escherichia coli 9723, Lactobacillus casei 7469, Lactobacillus plantarum 8014, Leuconostoc dextranicum 8086, and Streptococcus faecalis 8043, the mean minimal inhibitory concentrations of three cyclic hydroxamic acids, 3-amino-3,4-dihydro-1-hydroxycarbostyril, the 6-chloro analog, and the 7-chloro analog, were 0.6, 0.6, and 0.2 micrograms/ml, and those of the corresponding lactams, 3-amino-3,4-dihydrocarbostyril, the 6-chloro analog, and the 7-chloro analog, were 60, 60, and 6 micrograms/ml, respectively. Under the same assay conditions the mean minimal inhibitory concentrations of chloramphenicol and kanamycin were both 2 micrograms/ml. In addition, the cyclic hydroxamic acids but not the lactams inhibited the growth of Candida albicans at minimal inhibitory concentrations ranging from 20 to 200 micrograms/ml, at pH 7, as compared with that of amphotericin B, at 2 micrograms/ml.