ceftiofur and danofloxacin

Although 90% of BRD relapses are reported to receive retreatment with a different class of antimicrobial, studies examining the impact of antimicrobial selection (i.e. bactericidal or bacteriostatic) on retreatment outcomes and the emergence of antimicrobial resistance (AMR) are deficient in the published literature. This survey was conducted to determine the association between antimicrobial class selection for treatment and retreatment of BRD relapses on antimicrobial susceptibility of Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni. Pathogens were isolated from samples submitted to the Iowa State University Veterinary Diagnostic Laboratory from January 2013 to December 2015. A total of 781 isolates with corresponding animal case histories, including treatment protocols, were included in the analysis. Original susceptibility testing of these isolates for ceftiofur, danofloxacin, enrofloxacin, florfenicol, oxytetracycline, spectinomycin, tilmicosin, and tulathromycin was performed using Clinical and Laboratory Standards Institute guidelines. Data were analyzed using a Bayesian approach to evaluate whether retreatment with antimicrobials of different mechanistic classes (bactericidal or bacteriostatic) increased the probability of resistant BRD pathogen isolation in calves. The posterior distribution we calculated suggests that an increased number of treatments is associated with a greater probability of isolates resistant to at least one antimicrobial. Furthermore, the frequency of resistant BRD bacterial isolates was greater with retreatment using antimicrobials of different mechanistic classes than retreatment with the same class. Specifically, treatment protocols using a bacteriostatic drug first followed by retreatment with a bactericidal drug were associated with a higher frequency of resistant BRD pathogen isolation. In particular, first treatment with tulathromycin (bacteriostatic) followed by ceftiofur (bactericidal) was associated with the highest probability of resistant M. haemolytica among all antimicrobial combinations. These observations suggest that consideration should be given to antimicrobial pharmacodynamics when selecting drugs for retreatment of BRD. However, prospective studies are needed to determine the clinical relevance to antimicrobial stewardship programs in livestock production systems.

Topics: Animals; Anti-Bacterial Agents; Anti-Infective Agents; Bovine Respiratory Disease Complex; Cattle; Cephalosporins; Disaccharides; Drug Resistance, Microbial; Fluoroquinolones; Heterocyclic Compounds; Mannheimia haemolytica; Microbial Sensitivity Tests; Pasteurella multocida; Pasteurellaceae; Prospective Studies; Recurrence; Respiratory Tract Diseases; Serogroup; Tylosin

The in vitro susceptibilities of 76 isolates of Actinobacillus pleuropneumoniae collected from pigs with pleuropneumonia were tested with 12 commonly used antimicrobial drugs by an agar dilution minimal inhibitory concentration procedure according to National Committee for Clinical Laboratory Standards (NCCLS) guidelines. Field isolates had low MICs for ceftiofur, danofloxacin and penicillin. No correlation of antimicrobial resistance was related to serotype.

Topics: Actinobacillus Infections; Actinobacillus pleuropneumoniae; Animals; Anti-Infective Agents; Cephalosporins; Drug Resistance, Microbial; Fluoroquinolones; Korea; Microbial Sensitivity Tests; Penicillins; Pleuropneumonia; Swine; Swine Diseases

SPF pigs aged 10 weeks were infected intranasally with Actinobacillus pleuropneumoniae serotype 2. After the onset of clinical symptoms of respiratory disease, which occurred 20 h post-infection, parenteral treatment with ceftiofur, danofloxacin, enrofloxacin, penicillin or tiamulin was initiated (n = 8 per group). Untreated groups, of which one was infected, served as controls. The uninfected control group did not show any signs of disease, while the infected control group was severely affected by the infection and also expressed a decreased weight gain following the challenge. Based on clinical signs, the magnitude of pathological lesions in the respiratory tract found at necropsy performed 17 days post-infection and the number of reisolates of A. pleuropneumoniae made at necropsy, treatments with the quinolones (danofloxacin and enrofloxacin) and the cephalosporine (ceftiofur) were superior to those with penicillin and tiamulin. The latter groups also developed antibodies to A. pleuropneumoniae to a larger extent. Some of the pigs treated with ceftiofur and danofloxacin developed antibodies to A. pleuropneumoniae, and the microbe was reisolated from approximately 50% of these animals. In contrast, pigs treated with enrofloxacin did not develop antibodies to A. pleuropneumoniae, and the challenge strain was not found at necropsy. The performance with respect to daily weight gain and feed conversion corresponded well with the clinical signs developed and the findings made at necropsy. The decreased growth recorded during the acute phase of the disease was, to a large extent, caused by a reduced feed intake.

Topics: Actinobacillus Infections; Actinobacillus pleuropneumoniae; Animals; Anti-Bacterial Agents; Anti-Infective Agents; Body Weight; Cephalosporins; Diterpenes; Enrofloxacin; Fluoroquinolones; Lung; Lung Diseases; Penicillins; Quinolones; Swine; Swine Diseases; Weight Gain