Pharmacokinetics of tinidazole in cows--a preliminary study

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.

Penicillin G and penicillin G-tinidazole treatment of experimentally induced summer mastitis--effect on elimination rates of bacteria and outcome of the disease

Two udder hind quarters of ten pregnant heifers were inoculated experimentally with a combination of Actinomyces pyogenes, Peptostreptococcus indolicus and Fusobacterium necrophorum at a dose of 9 x 10(8) colony forming units (CFU) of each species of bacteria. The development of aerobic-anaerobic mastitis was followed-up clinically and through analysis of udder secretion samples. All heifers developed acute clinical mastitis. Thick, purulent secretions with foul odour were already present 24 h after infusion. At 32 h post inoculation, 19 of 20 quarters harboured all infused bacteria, the viable counts of bacteria varying from 10(4) to 10(5) CFU/ml. No bacteria were isolated from blood samples taken simultaneously. NAGase values of udder secretions, indicating tissue damage, were high. The heifers were treated systemically with penicillin G alone, or in combination with tinidazole. Treatment started 32 h after inoculation and was continued for three days. The anaerobic bacteria (F. necrophorum and P. indolicus) were usually eliminated within four days, while A. pyogenes infections often persisted in the quarters. Penicillin G with tinidazole was not more effective than penicillin G alone: of the four heifers which recovered from infection, two were treated with penicillin G alone and two with the drug combination. The most important factor affecting the recovery seemed to be the host response of individual heifers. The six heifers which did not recover from the infection were continuously infected after calving, harbouring A. pyogenes in ten quarters, and P. indolicus and F. necrophorum each in three quarters.

Clinical, bacteriological and therapeutic aspects of bovine mastitis caused by aerobic and anaerobic pathogens

Twenty cows and three heifers with summer mastitis-like signs were included in the study. Forty aerobic and 38 anaerobic bacterial isolates representing 23 different species were isolated from udder secretions, the mean number of species being 3.4/sample. Pathogens most often were recovered in quantities exceeding 10(5) CFU/ml. Growth of pathogenic bacteria in the blood was found in only one case. Most cases occurred in housed animals and had often been preceded by teat injury. No anaerobic growth was found in milk samples of a control group consisting of 29 cows with ordinary acute mastitis. Values of indicators of inflammation in milk (NAGase and plasmin activity) were high, mean values being 914.1 and 1.3 units. The animals with aerobic/anaerobic mastitis were treated using various antimicrobial agents. All but three quarters were lost to milk production. Two animals with complete recovery were given a combination of penicillin G and tinidazole.