Determination of the Duration of Antibacterial Efficacy following Administration of Gamithromycin Using a Bovine Mannheimia haemolytica Challenge Model

Abstract

The antibacterial efficacy of gamithromycin administered once 1, 5, or 10 days prior to a challenge infection with Mannheimia haemolytica serotype A1 was evaluated. Forty calves were randomly allocated on day ؊11, restricted by body weight, to one of three treatment groups given gamithromycin at 6 mg/kg of body weight 10, 5, or 1 days before challenge or to an untreated control group. M. haemolytica A1 challenge infections were induced on day 0 by depositing 7.4 ؋ 10 7 CFU at the bifurcation of the main bronchus using a bronchoscope. Clinical observations were made daily from the day of allocation to day 10, when necropsy was scheduled; three calves died or were euthanized in extremis on welfare grounds prior to scheduled necropsy. At necropsy the lungs were removed, pneumonic lesions were scored, and samples of lung tissue were cultured for M. haemolytica. The three groups of animals treated with gamithromycin before challenge had significantly lower lung M. haemolytica counts and fewer clinical signs of respiratory disease than did the saline-treated group. For most of the clinical parameters, the pattern of responses differed significantly (P < 0.05) between the gamithromycin-treated groups and the control group. There were no statistically significant differences between groups in the mean lung lesion scores, partly as a result of high individual variability, particularly within the control group. The administration of gamithromycin 1, 5, and 10 days prior to M. haemolytica A1 challenge resulted in a reduction in bacterial isolation from the lungs and a reduction in the severity of clinical disease.

Infection-stage adjusted dose of beta-lactams for parsimonious and efficient antibiotic treatments: A Pasteurella multocida experimental pneumonia in mice

“…Although this “late” approach limits antibiotic consumption and exposure, it can also lead to extensive pulmonary damage in affected animals and to spread of the disease within the herd [ 16 , 17 ]. Metaphylaxis, the second approach, is therefore more frequently adopted as an early BRD treatment and consists of treating the entire cohort of animals when only a few express clinical signs of BRD [ 18 , 19 ]. This approach has the advantages of ensuring both a good survival rate of the cohort and ease of use [ 18 ] but, compared to the first individual approach, has the disadvantage of exposing animals to antibiotic consumption even when this is not required.…”

Pharmacokinetic and pharmacodynamic testing of marbofloxacin administered as a single injection for the treatment of bovine respiratory disease

“…, 2006; Zhao & Drlica, 2008). The scientific rationale for the use of fluoroquinolones as a SISAAB for the treatment of bovine respiratory disease (BRD) clearly differentiate from the simple convenience of commonly used single‐injection long‐acting antibiotics such as macrolide derivatives for the treatment and prevention of BRD (Forbes et al. , 2011; Grandemange, E., Fournel, S., Giboin, H. & Woehrle, F., personnel communication).…”

“…To date, this approach has been primarily developed and applied to fluoroquinolones used in human medicine such as ciprofloxacin, gatifloxacin, levofloxacin or moxifloxacin (Croisier et al, 2004;Cui et al, 2006;Zhao & Drlica, 2008). The scientific rationale for the use of fluoroquinolones as a SISAAB for the treatment of bovine respiratory disease (BRD) clearly differentiate from the simple convenience of commonly used single-injection long-acting antibiotics such as macrolide derivatives for the treatment and prevention of BRD (Forbes et al, 2011;Grandemange, E., Fournel, S., Giboin, H. & Woehrle, F., personnel communication).…”

Impact of Timing and Dosage of a Fluoroquinolone Treatment on the Microbiological, Pathological, and Clinical Outcomes of Calves Challenged with Mannheimia haemolytica

“…Two therapeutic strategies are commonly implemented by veterinarians and farmers. Metaphylaxis represents a current practice of early BRD treatment, that consists in treating the entire cohort of animals, in which only a few express clinical signs of BRD (Nickell and White, 2010 ; Forbes et al, 2011 ). The advantages of this approach are good survival rate in the cohort and ease of use (Nickell and White, 2010 ); it also has the disadvantage of exposing to antibiotics a potentially large proportion of animals intended for human consumption even when not required.…”