Some aspects of the occurrence of resistant bacteria in the normal animal flora.

The paper outlines some of the problems encountered in assessing the occurrence of antibiotic resistance in the normal flora of animals, using Escherichia coli as an example. Additional information is provided on the occurrence and mechanisms of resistance in Clostridium perfringens, Pasteurella haemolytica and Staphylococcus aureus, and some of the factors which may affect this resistance. The paper concludes with general considerations about the choice of organism, the sample size and the desirability of designing standard protocols.