Cpharm.vetmed.vt.edu

Minimum Inhibitory Concentration (MIC) Breakpoints for Veterinary Pathogens

Breakpoints are for categorizing bacterial isolates as susceptible, intermediately susceptible or
resistant. Shaded rows are breakpoints extrapolated from human medicine.
MIC Breakpoint (µg/ml)
Antimicrobial Agent
Staphylococcus spp. Streptococcus spp. E. coli Pasteurella multocida *Amoxicillin-clavulanate breakpoints were determined from an examination of MIC distribution of isolates, efficacy data, and PK-PD analysis of amoxicillin in dogs. The dosage regimen used for PK-PD analysis of amoxicillin was 11 mg/kg administered every 12 hours orally. **Amoxicillin-clavulanate breakpoints were determined from an examination of MIC distribution of isolates, efficacy data, and PK-PD analysis of amoxicillin in cats at a dosage of 12.5 mg/kg (amoxicillin) administered every 12 hours orally. Ampicillin Actinobacillus pleuropneumoniae Pasteurella multocida Streptococcus suis Bordetella bronchiseptica * Systemic breakpoint derived from microbiological, pharmacokinetic, and pharmacodynamic data. For dogs, the dose of amoxicillin modeled was 22 mg/kg every 12 hours orally. ** A breakpoint of ≤8 should be used for urinary tract infections. This breakpoint was derived from published literature in which orally administered ampicillin 25.6 mg/kg, and amoxicillin 11 mg/kg was administered to healthy dogs at 8-hour intervals for five consecutive doses and produced urine concentrations in dogs >300 g/mL. *** Breakpoint derived from microbiological, pharmacokinetic data (using accepted clinical doses), and pharmacodynamic data. For horses, the dose of ampicillin sodium modeled was 22 mg/kg IM q12. † Breakpoint derived from microbiological data using ampicillin, pharmacokinetic data from a dose of 15 mg/kg IM of amoxicillin once daily, and pharmacodynamic data. Cefazolin urinary/genital) Staphylococcus aureus Staphylococcus pseudintermedius Pasteurella multocida Streptococci-beta-hemolytic group E. coli Cefazolin breakpoints were determined from an examination of MIC distribution of isolates and PK-PD analysis of cefazolin. The dosage regimen used for PK-PD analysis of cefazolin was 25 mg/kg administered every six hours intravenously in horses and dogs. Ceftiofur Streptococcus uberis E. coli Cefpodoxime Streptococcus canis (Group G, b hemolytic) E. coli Pasteurella multocida Proteus mirabilis Cephalothin Staphylococcus aureus Staphylococcus pseudintermedius Streptococci beta-hemolytic group E. coli Cephalothin breakpoints were determined from an examination of MIC distribution of isolates, efficacy data, and PK-PD analysis of cephalexin. The dosage regimen used for PK-PD analysis of cephalexin was 25 mg/kg administered every 12 hours orally. Cephalothin is only used to predict results for all first-generation cephalosporins except cefazolin. Cefazolin should be tested separately with Enterobacteriaceae. Chloramphenicol Streptococci (not S. pneumoniae) MIC distributions of canine isolates support these breakpoints for use in canine skin and soft tissue infection; however, efficacy data and PK-PD targets were unavailable. Clindamycin Mannheimia haemolytica Pasteurella multocida Difloxacin Enterobacteriaceae Staphylococcus spp. Other organisms Enrofloxacin Enterobacteriaceae Pseudomonas aeruginosa Actinobacillus spp. Marbofloxacin Enterobacteriaceae Staphylococcus spp. Other organisms Orbifloxacin Enterobacteriaceae Staphylococcus spp. Other susceptible organisms Oxacillin Staphylococcus pseudintermedius Penicillin G Histophilus somni *Breakpoint derived from microbiological, pharmacokinetic data (using accepted clinical, but extra-label doses), and pharmacodynamic data. The dose of procaine penicillin G modeled was 22 000 U/kg, IM, q24h. **Breakpoint derived from microbiological, pharmacokinetic data (using accepted clinical, but extra-label doses), and pharmacodynamic data. The dose of procaine penicillin G modeled was 22 000 U/kg, IM, q24h. Penicillin-novobiocin Staphylococcus aureus Streptococcus agalactiae Streptococcus dysgalactiae Streptococcus uberis Pirlimycin Streptococcus agalactiae Streptococcus dysgalactiae Streptococcus uberis Rifampin Bovine Respiratory Disease Mannheimia haemolytica Pasteurella multocida Histophilus somni Sulfisoxazole Actinobacillus pleuropneumoniae Pasteurella multocida Streptococcus suis *Breakpoint derived from pharmacokinetic data of oxytetracycline at 20 mg/kg IM, once, and pharmacodynamic data. These interpretive criteria are applicable only for the injectable formulations. Tetracycline is the class representative. **Breakpoint derived from pharmacokinetic data of oxytetracycline at 20 mg/kg IM, once, and pharmacodynamic data. These interpretive criteria are applicable only for the injectable formulations. Tetracycline is the class representative. Tiamulin Actinobacillus pleuropneumoniae Ticarcillin Pasteurella multocida Actinobacillus pleuropneumoniae Trimethoprim-sulfamethoxazole

Source: http://cpharm.vetmed.vt.edu/VM8784/antimicrobials/principles/CSLI%20Breakpoints%202013.pdf