Antimicrobial Resistance in Members of the FamilyPasteurellaceae

This chapter focuses mainly on the genera Pasteurella, Mannheimia, Actinobacillus, Haemophilus, and Histophilus, for which sufficient data on antimicrobial susceptibility and the detection of resistance genes are currently available. A study in Germany, investigating the susceptibility of bovine isolates of P. multocida and M. haemolytica collected in 1999 to spectinomycin and comparator agents, showed that none of the 302 isolates tested were resistant to florfenicol, cefquinome, or ceftiofur, and only 6.5% of the P. multocida and 1.4% of the M. haemolytica isolates were classified as resistant to spectinomycin. The chapter provides an overview of the current knowledge of resistance genes and resistance mediating mutations so far detected in bacteria of the genera Pasteurella, Mannheimia, Actinobacillus, and Haemophilus. Molecular analysis of isolates of Pasteurella, Mannheimia and Actinobacillus revealed that antimicrobial resistance genes were associated with plasmids in many cases. The examples given in the chapter illustrate that Pasteurella, Mannheimia, Actinobacillus, and Haemophilus have obviously acquired a number of resistance genes from other gram-negative or maybe even gram-positive bacteria. Knowledge of the location and colocation of the resistance genes on mobile genetic elements as well as the conditions for their coselection and persistence will be valuable for veterinarians and will assist them in selecting the most efficacious antimicrobial agents for the control of isolates of the family Pasteurellaceae.