title: Factors influencing the potency of marbofloxacin for pig pneumonia pathogens Actinobacillus pleuropneumoniae and Pasteurella multocida.
abstract: For the pig respiratory tract pathogens, Actinobacillus pleuropneumoniae and Pasteurella multocida, Minimum Inhibitory Concentration (MIC) of marbofloxacin was determined in recommended broths and pig serum at three inoculum strengths. MICs in both growth matrices increased progressively from low, through medium to high starting inoculum counts, 104, 106and 108CFU/mL, respectively. P. multocida MIC ratios for high:low inocula were 14:4:1 for broth and 28.2:1 for serum. Corresponding MIC ratios for A. pleuropneumoniae were lower, 4.1:1 (broth) and 9.2:1 (serum). MIC high:low ratios were therefore both growth matrix and bacterial species dependent. The effect of alterations to the chemical composition of broths and serum on MIC were also investigated. Neither adjusting broth or serum pH in six increments over the range 7.0 to 8.0 nor increasing calcium and magnesium concentrations of broth in seven incremental steps significantly affected MICs for either organism. In time-kill studies, the killing action of marbofloxacin had the characteristics of concentration dependency against both organisms in both growth matrices. It is concluded that MIC and time-kill data for marbofloxacin, generated in serum, might be preferable to broth data, for predicting dosages of marbofloxacin for clinical use.
authors.affiliation: The Royal Veterinary College, Department of Comparative Biological Sciences, Hawkshead Campus, Hatfield, Herts AL9 7TA, 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, BT35 6QQ, Northern Ireland, United Kingdom.
authors.forename: S
authors.initials: S
authors.lastname: Hobson
authors.affiliation: The Royal Veterinary College, Department of Comparative Biological Sciences, Hawkshead Campus, Hatfield, Herts AL9 7TA, United Kingdom.
authors.forename: P
authors.initials: P
authors.lastname: Lees
mesh_terms: D000189:Actinobacillus Infections / Q000382:microbiology / Q000517:prevention & control / Q000662:veterinary*; D016977:Actinobacillus pleuropneumoniae / Q000187:drug effects*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D024841:Fluoroquinolones / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D008826:Microbial Sensitivity Tests; D010326:Pasteurella Infections / Q000382:microbiology / Q000517:prevention & control / Q000662:veterinary*; D016979:Pasteurella multocida / Q000187:drug effects*; D011014:Pneumonia / Q000382:microbiology / Q000517:prevention & control / Q000662:veterinary; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology / Q000517:prevention & control*
chemical_list: D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; C080260:marbofloxacin
keywords: Actinobacillus pleuropneumoniae; Marbofloxacin; Minimum inhibitory concentration; Pasteurella multocida; Time-kill