title: Potency of marbofloxacin for pig pneumonia pathogens Actinobacillus pleuropneumoniae and Pasteurella multocida: Comparison of growth media.
abstract: Pharmacodynamic properties of marbofloxacin were established for six isolates each of the pig respiratory tract pathogens, Actinobacillus pleuropneumoniae and Pasteurella multocida. Three in vitro indices of potency were determined; Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC) and Mutant Prevention Concentration (MPC). For MIC determination Clinical Laboratory Standards Institute guidelines were modified in three respects: (1) comparison was made between two growth media, an artificial broth and pig serum; (2) a high inoculum count was used to simulate heavy clinical bacteriological loads; and (3) five overlapping sets of two-fold dilutions were used to improve accuracy of determinations. Similar methods were used for MBC and MPC estimations. MIC and MPC serum:broth ratios for A. pleuropneumoniae were 0.79:1 and 0.99:1, respectively, and corresponding values for P. multocida were 1.12:1 and 1.32:1. Serum protein binding of marbofloxacin was 49%, so that fraction unbound (fu) serum MIC values were significantly lower than those predicted by correction for protein binding; fu serum:broth MIC ratios were 0.40:1 (A. pleuropneumoniae) and 0.50:1 (P. multocida). For broth, MPC:MIC ratios were 13.7:1 (A. pleuropneumoniae) and 14.2:1 (P. multocida). Corresponding ratios for serum were similar, 17.2:1 and 18.8:1, respectively. It is suggested that, for dose prediction purposes, serum data might be preferable to potency indices measured in broths.
authors.affiliation: The Royal Veterinary College, Department of Comparative Biological Sciences, Hatfield, Herts, United Kingdom. Electronic address: ldorey@rvc.ac.uk.
authors.forename: L
authors.initials: L
authors.lastname: Dorey
authors.affiliation: Norbrook Laboratories Ltd., Newry, Co. Down, Northern Ireland, United Kingdom.
authors.forename: S
authors.initials: S
authors.lastname: Hobson
authors.affiliation: The Royal Veterinary College, Department of Comparative Biological Sciences, Hatfield, Herts, United Kingdom.
authors.forename: P
authors.initials: P
authors.lastname: Lees
mesh_terms: D016977:Actinobacillus pleuropneumoniae / Q000187:drug effects*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D019540:Area Under Curve; D003470:Culture Media; D024841:Fluoroquinolones / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D016979:Pasteurella multocida / Q000187:drug effects*; D011001:Pleuropneumonia / Q000382:microbiology / Q000662:veterinary*; D013552:Swine; D013553:Swine Diseases / Q000188:drug therapy / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents; D003470:Culture Media; D024841:Fluoroquinolones; C080260:marbofloxacin
keywords: Actinobacillus pleuropneumoniae; Marbofloxacin; Minimum Bactericidal Concentration; Minimum Inhibitory Concentration; Mutant Prevention Concentration; Pasteurella multocida