Identification and antibiotic susceptibility of bacterial isolates from dogs with otitis externa in Australia

Objective To identify and quantify the five most frequently isolated significant bacterial microorganisms, and their antibiotic susceptibility, from bacterial cultures of samples taken from the ears of dogs with otitis externa. Methods Bacterial culture and susceptibility testing data for ear swabs from dogs with presumed otitis externa were collated and evaluated. Results The five most frequently isolated microorganisms were: Pseudomonas aeruginosa, Staphylococcus pseudintermedius, Proteus sp., beta-haemolytic streptococci and Escherichia coli. Susceptibility to gentamicin was very high for most isolates, whereas for polymyxin B, high levels of resistance were seen. Beta-haemolytic streptococci had high levels of resistance to all of the antibiotics tested. Conclusions This study provides veterinarians with Australian data to assist in cytological interpretation and initial empirical therapy of canine otitis externa.