Two cyclic homopentapeptides, CP-101, 680 and CP-163, 234 [6a-(3', 4'-dichlorophenylamino) analogs of viomycin and capreomycin, respectively], were identified as novel antibacterial agents for the treatment of animal disease, especially for livestock respiratory disease. The
in vitro microbiological characterization of both CP-101, 680 and CP-163, 234 was carried out using their parent compounds, viomycin and capreomycin, as controls. This characterization included antibacterial spectrum, influence of media, inoculum size, pH, EDTA, polymixin B nonapeptide (PMBN), serum, cell-free protein synthesis inhibition, and time-kill kinetics. Our results indicated that the capreomycin analog, CP-163, 234, showed slightly improved
in vitro potency over the viomycin analog, CP-101, 680. Both analogs showed very potent cell-free protein synthesis inhibition activity and were bactericidal against
Pasteurella haemolytica,
P. multocida and
Actinobacillus pleuropneumoniae at the level of 4 times and 8 times MICs. CP-163, 234 was bactericidal at the level of 4× and 8× MIC against
E. coli, but re-growth was observed after 24 hours incubation at both concentrations of CP-101, 680.
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