In-vitro activity of ceftiofur against Australian isolates of the family Pasteurellaceae associated with respiratory disease in cattle and pigs

Abstract

The in vitro antibacterial activity of ceftiofur against isolates of Pasteurella multocida and Pasteurella haemolytica (19 and 34 respectively) obtained from Australian cattle and isolates of P. multocida and Actinobacillus pleuropneumoniae (30 and 50 respectively) from Australian pigs was investigated. A reference strain of Escherichia coli was used as a control strain. The minimum inhibitory concentration (MIC) of ceftiofur for the isolates was determined using a modified agar dilution method. The agar plates contained a final concentration of ceftiofur that varied from 50 mg/ml to 0.20 mg/ml. The MIC for the reference strain of E. coli was always 0.78 mg/ml. The MICs for all the P. multocida, P. haemolytica and A. pleuropneumoniae isolates were less than or equal to 0.2 mg/ml. It is concluded that all the isolates were susceptible to ceftiofur.