Prepartum antibiotic therapy with a cephapirin dry-cow product against naturally occurring intramammary infections in heifers.

Intramammary infusion of a dry-cow antibiotic preparation containing 300 mg of cephapirin benzathine into 18 Jersey heifers, 10-12 weeks prepartum, resulted in cure rates of existing intramammary infection (IMI) of 96% (24/25), 100% (4/4), and 90% (28/31) for Staphylococcus aureus, Streptococcus species, and Staphylococcus species, respectively. Cure rates of IMI that had been treated with a lactating-cow therapy containing 200 mg cephapirin benzathine at parturition were 62.5% (15/24), 100% (22/22), and 100% (3/3) for Staphylococcus aureus, Streptococcus species, and Staphylococcus species, respectively. Initial somatic cell counts (SCC) of secretions from infected quarters were greater than from uninfected quarters. At 2 months postpartum, the SCC of milk from treated and cured quarters were reduced in comparison with quarters that remained infected. Cephapirin benzathine was present at detectable concentrations in 94, 80, 68, and 61% of treated quarters at 1, 2, 3, and 4 weeks after infusion of the cephapirin dry-cow product, respectively. At parturition, 24% of treated quarters were positive for antibiotic, however, no quarters remained positive for antibiotic at 5 days postpartum. An additional 40 heifers from a commercial herd were sampled and infused in all quarters with the cephapirin dry-cow product at 16-20 weeks prepartum. Cure rates for the commercial herd were 94% (29/31), 94% (16/17), 100% (44/44), and 100% (3/3), respectively, for quarters infected by S. aureus, Streptococcus species, Staphylococcus species, and coliforms.

The postantibiotic effect of selected antibiotics on Staphylococcus aureus Newbould 305 from bovine intramammary infection.

The postantibiotic effect (PAE) was determined for selected antibiotics against Staphylococcus aureus Newbould 305 originating in vivo from mastitic milk and compared with the PAE for the same S. aureus strain cultured in vitro. The PAE was measured at 2 and 4 times the MIC for 1 and 2 h of exposure. The PAE of penicillin, pirlimycin, and tilmicosin were reduced against S. aureus 305 originating in vivo compared with S. aureus 305 grown in vitro. The PAE of cephapirin was increased against S. aureus originating in vivo. Minimal effect on PAE was noted for novobiocin. The PAE for rifampicin extended beyond the limits of the test parameters (> 180 min) for all antibiotic concentrations, media, and exposure times tested, except at 2 times the MIC and at 1 h exposure when the PAE was reduced to 60 min for S. aureus 305 originating in vivo. The PAE of an antibiotic may be an important consideration in determining therapy intervals and antibiotic concentrations for treatment of bovine mastitis.

Effect of selected antibiotics on Staphylococcus aureus present in milk from infected mammary glands.

Milk from a mammary gland infected with Staphylococcus aureus Newbould 305 was collected and dispensed into sterile tubes. Selected antibiotics were added at 2, 4, or 32 times the MIC, and the percentage survival of S. aureus at various times through 24 h after addition of each antibiotic was determined. Percentage survival of the same S. aureus strain grown in vitro and added to 1) Mueller-Hinton broth and 2) ultrahigh temperature pasteurized milk with the same concentration of antibiotics was also determined. Percentage survival observed after 24 h in milk from the infected quarter at 2, 4, and 32 times MIC, respectively, were: penicillin: 12, 9.4, and 13%; cephapirin 43, 50, and 30%; erythromycin: 120, 95, and 82%; pirlimycin: > 1000, 148, and 38%; tilmicosin: > 1000, > 1000, and 9%; ciprofloxacin: 458, 6, and 3%; norfloxacin: 40, 10, and < 1%; rifampicin: < 1, < 1, and < 1%; and novobiocin: 20, 41, and 5%. By comparison, percentage survival observed after 24 h for in vitro grown S. aureus tested in Mueller-Hinton broth at 2, 4, and 32 times MIC, respectively, were < 1% for penicillin, cephapirin, pirlimycin, ciprofloxacin, norfloxacin, and rifampicin, and < 10% for erythromycin, novobiocin, and tilmicosin. UHT milk had minimal effect on percentage survival compared to Mueller-Hinton broth for S. aureus 305 when tested against penicillin or cephapirin. Increased survival was noted in UHT milk for erythromycin, pirlimycin, and tilmicosin at all antibiotic concentrations and for ciprofloxacin, norfloxacin, rifampicin, and novobiocin at 2 times the MIC.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of a milk-derived factor on the inflammatory response to Staphylococcus aureus intramammary infection.

Daily injections of an anti-inflammatory milk-derived factor (MDF) into mice increased resistance to Staphylococcus aureus challenge, and reduced leukocyte infiltration. Intraperitoneal injection of MDF into lactating mice prior to S. aureus intramammary challenge resulted in greater milk secretory activity and less inflammation compared with untreated controls, but had little effect on the number of S. aureus recovered from mammary tissue. Infusion of MDF directly into mouse mammary glands prior to challenge reduced S. aureus recovered after challenge. Incubation of bovine mammary macrophages in medium supplemented with MDF enhanced phagocytosis of opsonized S. aureus. In addition, infusion of 5 mg MDF into uninfected bovine mammary glands 24 h prior to S. aureus challenge resulted in fewer infections (five of ten) than in control quarters (seven of nine). Repeated daily injections of 5 mg MDF into S. aureus-infected quarters increased the percent of mammary neutrophils and decreased the recovery of S. aureus, but did not eliminate infections. Intravenous injection of 8 g MDF into cows resulted in pronounced leukopenia while the accompanying effect on mammary leukocytes was less marked but followed a similar course. Results suggest that the use of MDF in mice enhanced resistance to experimental infection and was beneficial in maintaining mammary secretory activity and reducing inflammation after bacterial challenge. In the cow, MDF promoted phagocytosis in vitro and was effective against challenge when infused intramammarily.

Efficacy of a cephapirin dry cow product for treatment of experimentally induced Staphylococcus aureus mastitis in heifers.

A dry cow product containing 300 mg of cephapirin benzathine was evaluated in pregnant and nonpregnant Jersey heifers for its effect on experimentally induced Staphylococcus aureus mastitis. Cephapirin was detectable in mammary secretion of nonpregnant heifers for up to 5 wk and in tissue for 1 wk after intramammary infusion. Staphylococcus aureus was not detectable in tissue and secretion of treated quarters at 1 and 3 wk but was not eliminated from two quarters of one heifer tested at 6 wk posttreatment. Histologic evaluation of mammary tissue from nonpregnant heifers revealed significant differences in leukocytosis between uninfected and S. aureus-infected quarters but no differences in epithelium, lumen, and stroma, indicating no difference in secretion potential or glandular development. Twenty-five pregnant Jersey heifers were experimentally infected in two quarters with S. aureus 12 to 14 wk prepartum. After 1 to 3 wk, 13 heifers were infused in 21 S. aureus-infected quarters with a commercial cephapirin dry cow product. Nine infected quarters were left untreated. All treated quarters were bacteriologically negative both at calving and through 2 mo after calving. Of the 9 infected quarters not treated prepartum, 1 spontaneously cured and 2 became non-functional. The remaining quarters were treated at calving with a commercial cephapirin lactating cow product. Of these, 3 cured and 3 failed to resolve.

Histological response of the bovine mammary gland to intramammary devices.

Histologic response of the bovine mammary gland to presence of three intramammary device models (abraded, star, or grooved) was studied in 12 lactating cows. Uninfected quarters fitted with devices exhibited greater leukocyte infiltration into teat and gland cistem linings as well as into mammary parenchyma adjacent to the gland cistem compared with unfitted control quarters. Cytologic alterations to cistem linings in device-fitted quarters ranged from degeneration and sloughing of surface cells of the double-layered epithelium to hyperplasia, stratification, and keratin formation. In uninfected quarters, quantification of mammary parenchymal components showed no differences among models for percentages of epithelium, but percentage of lumen was lowest and stroma highest for the star intramammary device model, suggesting reduced secretory activity or mammary involution in response to these intramammary devices. Presence of bacterial infection amplified the histologic responses to all devices. Leukocyte infiltration remained greater in device-fitted quarters compared with controls but was elevated over uninfected quarters for all treatments. Likewise, hyperplasia, stratification, and keratin formation of the cistem epithelial lining were more frequently observed in infected quarters. Among models in infected quarters, percentage of lumen was lowest and stroma highest in quarters fitted with abraded devices. In most cases, presence of infection masked any effect of devices on mammary parenchymal components. Plaque formation was observed on all models and tended to be thicker on those retrieved from infected quarters. Electron microscopic examination showed that plaque was composed of leukocytes, cell debris, keratin, and amorphous material. Results demonstrated that most intramammary device models were successful in stimulating leukocytosis into the gland, and tissues from fitted quarters displayed alterations to cisternal linings; however, quarters fitted with these devices exhibited reduced secretory activity.

A convenient method for differentiation of coagulase-negative staphylococci isolated from bovine mammary glands.

The utility of trehalose-mannitol broth and arabinose-cellobiose broth for identification of Staphylococcus epidermidis and novobiocin-resistant staphylococci was determined using 236 coagulase-negative staphylococci isolated from bovine mammary glands. None of the 49 S. epidermidis strains was positive in trehalose-mannitol broth; whereas, all strains of Staphylococcus hyicus, Staphylococcus chromogenes, Staphylococcus haemolyticus, Staphylococcus hominis, Staphylococcus warneri, and Staphylococcus simulans were positive. Of the novobiocin-resistant staphylococcal species, only Staphylococcus saprophyticus was negative in arabinose-cellobiose broth. Except for one strain of Staphylococcus sciuri and one strain of Staphylococcus kloosii, all remaining strains of novobiocin-resistant staphylococcal species were positive in arabinose-cellobiose broth. Results indicate that trehalose-mannitol broth is an acceptable method for identification of S. epidermidis isolated from bovine mammary glands. Furthermore, arabinose-cellobiose broth is a useful method of screening for novobiocin-resistant staphylococci.

Evaluation of the Staph-Zym system with staphylococci isolated from bovine intramammary infections.

A total of 148 staphylococci isolated from bovine intramammary infections were used to evaluate the Staph-Zym system (ROSCO, Taastrup, Denmark). The overall accuracy of the system was 91.9%. The system correctly identified all strains of Staphylococcus aureus, Staphylococcus simulans, and Staphylococcus xylosus and 95% of Staphylococcus intermedius strains. Of 33 Staphylococcus hyicus strains, 31 (93.9%) were classified correctly by the Staph-Zym system, as well as 8 (80%) of 10 Staphylococcus chromogenes strains. All 11 Staphylococcus epidermidis strains and the 1 Staphylococcus haemolyticus strain included in the study were identified, but the Staph-Zym system had difficulty distinguishing strains of Staphylococcus warneri and Staphylococcus hominis from other species in the S. epidermidis group. The Staph-Zym system correctly identified all six S. xylosus strains and two of three Staphyloccus sciuri strains. The Staph-Zym system was considered an acceptable alternative to conventional methods for identification of bovine mammary gland isolates.