Antimicrobial susceptibilities of Staphylococcus aureus isolated from commercial broilers in northeastern Georgia

Staphylococcus aureus is an important opportunist that can cause superficial to life-threatening illnesses in a variety of animal species. In poultry, this organism has been implicated in osteomyelitis, synovitis, and cellulitis. Whereas most infections can be treated with antibiotics, because of the organism's propensity to acquire antimicrobial resistance, it is important to continually monitor antibiotic susceptibilities of clinical isolates. We surveyed 77 clinical poultry S. aureus isolates, collected from 1998 to 2000, for susceptibilities to a panel of 18 antimicrobial agents. Thirty-six percent of isolates were susceptible to all antibiotics. Forty-three and 16% of avian S. aureus were resistant to one and two antibiotics respectively. Staphylococcus aureus isolates were commonly resistant to tetracycline (40%; minimal inhibitory concentration [MIC]90 > 32 microg/ml), lincomycin (19%; MIC90 > 32 microg/ml), erythromycin (12%; MIC90 > 8 microg/ml), and kanamycin (8%; MIC90 < 128 microg/ml). All S. aureus isolates were susceptible to chloramphenicol, gentamicin, streptomycin, nitrofurantion, linezolid, quinupristin/dalfopristin, vancomycin, and the production antimicrobials virginiamycin, salinomycin, and flavomycin. A periodic assessment of antimicrobial susceptibilities of important avian pathogens like S. aureus will be important in helping the clinician's choice of antibiotic to control infection.