Reproducibility of antibiogram of bovine mammary gland staphylococci under conditions of repeated subculturing.
The reproducibility of antibiogram profiles of 10 staphylococcal isolates of bovine mammary gland origin was tested under conditions of repeated subculturing. Prototype (original or index) antibiogram profiles were determined by subculturing these isolates from stock cultures stored at -70 degrees C. The isolates were then subcultured four times on blood agar and antibiogram profiles determined at each subculture on Mueller-Hinton agar. The antibiogram profiles of each isolate at each subculture were compared with the prototype profiles of that isolate. At repeat antibiogram determinations, deviations of < or = 5 mm in the individual zones of inhibition of penicillin, ampicillin and streptomycin from the prototype antibiogram profiles, resulted in a shift of only three isolates from the resistant to intermediate and one isolate from intermediate to resistant status of antibiotic susceptibility classification. It is suggested that in the interpretation of antibiogram, susceptibility classification (resistant, intermediate, or susceptible) variations accruing from a few millimetres differences in the diameter of the zones of inhibition should probably be disregarded.
Muhammad
G
G
Department of Veterinary Preventive Medicine, Ohio State University Columbus 43210, USA.
Hoblet
K H
KH
Bech-Nielsen
S
S
Jackwood
D L
DL
Smith
K L
KL
D000667:Ampicillin / Q000494:pharmacology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002417:Cattle; D004352:Drug Resistance, Microbial; D005260:Female; D008321:Mammary Glands, Animal / Q000382:microbiology*; D010406:Penicillins / Q000494:pharmacology; D015203:Reproducibility of Results; D013210:Staphylococcus / Q000145:classification / Q000187:drug effects*; D013307:Streptomycin / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D010406:Penicillins; D000667:Ampicillin; D013307:Streptomycin