Susceptibilities of bovine summer mastitis bacteria to antimicrobial agents.
The susceptibility to 9 antimicrobial agents of 32 aerobic bacterial isolates and to 10 antimicrobial agents of 37 anaerobic bacterial isolates from 23 cases of bovine summer mastitis (16 Actinomyces pyogenes isolates, 8 Streptococcus dysgalactiae isolates, 3 S. uberis isolates, 3 S. acidominimus isolates, 2 Streptococcus spp., 15 Peptostreptococcus indolicus isolates, 10 Fusobacterium necrophorum isolates, and 12 isolates of anaerobic gram-negative rods) was determined by the agar dilution method. All isolates except one Bacteroides fragilis isolate (beta-lactamase producer) were susceptible to penicillin G, amoxicillin, amoxicillin-clavulanate, cefoxitin, clindamycin, and chloramphenicol (the B. fragilis strain was susceptible to the last four), which had MICs at which 90% of isolates were inhibited (MIC90s) of < or = 0.06, < or = 0.06, < or = 0.06 0.25, < or = 0.06, and 4.0 micrograms/ml, respectively. Spiramycin was active against the gram-positive aerobes (MIC90, 1.0 microgram/ml) but not against the anaerobes (MIC90, 16.0 micrograms/ml). Similar trends were noted for susceptibilities of aerobic and anaerobic bacteria to ofloxacin (MIC90s, 2.0 and 8 micrograms/ml, respectively). Occasional strains of aerobic streptococci were resistant to oxytetracycline, but all anaerobes were susceptible. Tinidazole was active against all anaerobes (MIC90, 2.0 micrograms/ml). beta-Lactamase was produced only by the B. fragilis isolate.
Jousimies-Somer
H
H
Anaerobe Reference Laboratory, National Public Health Institute, Helsinki, Finland. Hannele.Somer@ktl.fi
Pyörälä
S
S
Kanervo
A
A
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001420:Bacteria, Aerobic / Q000187:drug effects* / Q000302:isolation & purification; D001421:Bacteria, Anaerobic / Q000187:drug effects* / Q000302:isolation & purification; D002417:Cattle; D004352:Drug Resistance, Microbial; D005260:Female; D008414:Mastitis, Bovine / Q000188:drug therapy / Q000382:microbiology*; D008826:Microbial Sensitivity Tests
D000900:Anti-Bacterial Agents