Germicidal activities of representatives of five different teat dip classes against three bovine mycoplasma species using a modified excised teat model.

Six representative teat dips from five different teat dip classes were tested for germicidal activity against challenge exposure to Mycoplasma bovis, Mycoplasma californicum, and Mycoplasma bovigenitalium using a modified excised teat model. All teat dip formulations tested were efficacious against all of the Mycoplasma species, providing bacterial logarithmic reductions above 4. The germicides performed best against M. bovigenitalium with an average log reduction (LR) of 6.29. Average LR were 5.41 and 5.70 against M. bovis and M. californicum, respectively. The iodine and chlorhexidine products performed best against M. bovis and M. californicum, respectively, with complete kill of all organisms. The chlorhexidine and the barrier chlorine product also had complete kill of M. bovigenitalium organisms.

Prevalence of mastitis in dairy heifers and effectiveness of antibiotic therapy.

Dairy heifers were treated 0 to 90 d, 90 to 180 d, or 180 to 270 d prepartum with one of five different antibiotic products to determine the best time and with which product they should be treated prior to calving. Two hundred thirty-three heifers were included in the study. At the initial sampling, 56.5% of quarters were infected with some type of organism and 15.4% of quarters were infected with Staphylococcus aureus. Treatments included a cephapirin dry cow product, a penicillin-novobiocin dry cow product, a penicillin-streptomycin dry cow product, an experimental dry cow product containing tilmicosin, and a cephalonium dry cow product not available in the United States. Cure rates for the five antibiotic products indicated that all were equally effective against Staph. aureus and all were significantly more effective than the spontaneous cure rate observed in untreated control quarters. No differences in efficacy were observed due to the different treatment times prepartum. However, fewer new Staph. aureus infections occurred after treatment in the group treated at 180 to 270 d prepartum, indicating that treatment in the third trimester will reduce the chances of new intramammary infections occurring after treatment and persisting to calving.

A comparison of two commercially available Escherichia coli J5 vaccines against E. coli intramammary challenge.

The efficacy of two commercially available Escherichia coli J5 bacterins was investigated. Jersey cows were randomly assigned to one of three treatment groups: 1) unvaccinated controls, 2) vaccinated with J.VAC (Merial Limited, Athens, GA), and 3) vaccinated with J5 bacterin. All cows were vaccinated at drying off and at 2 wk before anticipated calving. Cows that were vaccinated with the J5 bacterin also received a third immunization at calving. One quarter of each cow was challenged with approximately 64 cfu of E. coli at 14 to 30 d postcalving. Immunization by either vaccine did not influence the severity of coliform mastitis; however, the mean number of colony-forming units of E. coli recovered from challenged quarters was significantly lower for immunized cows than for control cows at 144 h postchallenge. Serum and mammary secretion immunoglobulin (Ig)G, IgG1, and IgG2 titers against E. coli J5 whole-cell antigens were enhanced in vaccinated cows. Serum and mammary secretion IgM were not different among treatment groups. Somatic cell counts in milk from challenged quarters, rectal temperatures, and the clinical status of cows following intramammary challenge were not different among treatment groups.

Efficacy of parenterally or intramammarily administered tilmicosin or ceftiofur against Staphylococcus aureus mastitis during lactation.

Two antibiotic preparations, tilmicosin and ceftiofur, were tested intramammarily and parenterally against Staphylococcus aureus mastitis in lactating cows. Neither product was effective as a lactating cow treatment at the doses and durations of treatment tested. Injection or infusion of tilmicosin and infusion of ceftiofur resulted in reductions of bacteria present in milk; however, only one quarter treated with infusion of tilmicosin was cured, and no cures were observed for the other treatments. Somatic cell counts were transiently reduced by infusion of ceftiofur and by infusion and injection of tilmicosin; however, they returned to pretreatment values by 28 d posttreatment.

Role of horn flies (Haematobia irritans) in Staphylococcus aureus-induced mastitis in dairy heifers.

OBJECTIVE: To determine whether Staphylococcus aureus can colonize in horn flies and whether colonization is sufficiently persistent for transmission of the organism to cows by flies. ANIMALS: 2 Jersey heifers exposed to infected horn flies. PROCEDURE: Staphylococcus aureus was allowed to colonize in horn flies, and duration of colonization was determined. Flies with colonized S aureus were allowed to feed on teats of uninfected heifers to determine whether intramammary infection could be transmitted from fly to heifer. Scab material from naturally infected heifers was submitted for bacteriologic culture to determine whether S aureus was present and whether scabs could serve as a possible source of S aureus for flies. RESULTS: Staphylococcus aureus colonized in horn flies and remained for up to 96 hours after exposure. Exposure of teats of uninfected heifers to horn flies colonized with S aureus resulted in intramammary infection in 3 of 4 exposed teats. Culture of scab material from teats of naturally infected heifers revealed high concentration of S aureus (> 107 colony-forming units/mg), and flies without previously colonized S aureus were allowed to feed on scabs; S aureus colonized in them just as readily as it did in flies that had fed on experimentally infected blood. CONCLUSIONS: Horn flies are capable of transmitting S aureus-induced intramammary infection to heifers, and scabs on teats are a potential source of S aureus. Fly control on dairy cows in herds with known S aureus problems is recommended as a method to help prevent these infections.

Comparison of success of antibiotic therapy during lactation and results of antimicrobial susceptibility tests for bovine mastitis.

Antimicrobial susceptibility testing was conducted on a variety of mastitis pathogens. The infected quarters were subsequently treated during lactation with a commercially available product containing penicillin and novobiocin that was designed for lactating cows. Cows were treated as per the recommendations of the product manufacturer, and cures were determined by the absence of bacteria in both sets of duplicate quarter milk samples that were collected at 28 d posttreatment. Comparisons were made between the susceptibility of the bacteria and the therapeutic success or failure. All isolates tested were considered to be susceptible to the penicillin and novobiocin combination. Bacteriologic cure rates for newly acquired Staphylococcus aureus intramammary infection (IMI) (< 2 wk in duration) at 28 d posttreatment were 70%. Cure rates for chronic Staph. aureus IMI (> 4 wk duration) were much lower (35%), reaffirming previous reports of the intractable nature of chronic Staph. aureus IMI. Cure rates for subclinical IMI caused by other organisms were 90% for Streptococcus agalactiae, 91% for Streptococcus uberis, 90% for Streptococcus dysgalactiae, 77% for other Streptococcus spp., and 71% for Staphylococcus spp. other than Staph. aureus. In vitro testing was considered to be a predictor of therapy outcome for IMI caused by Staphylococcus spp., newly acquired Staph. aureus, Strep. uberis, Strep. dysgalactiae, and Strep. agalactiae, but was not considered to be a useful predictor of efficacy for chronic IMI caused by Staph. aureus.

Therapeutic and prophylactic effect of prepartum antibiotic infusion in heifers.

Prepartum bacteriologic examination of secretions from 42 dairy heifers 12-14 weeks prepartum revealed a total of 24 Staphylococcus aureus infected quarters, 53 Staphylococcus species infected quarters, and 20 Streptococcus species infected quarters. Prepartum intramammary therapy of primigravid dairy heifers with two commercially available dry cow antibiotics (penicillin-novobiocin or cephapirin) resulted in cure rates of 94%, 97%, and 100% for S. aureus, Staphylococcus species, and Streptococcus species intramammary infections (IMI), respectively. No protective effect was observed for dry cow treatment of uninfected quarters of heifers for any of the antibiotic preparations. No antibiotic was detectable in heifer secretions collected at parturition indicating that antibiotic concentrations may have fallen below protective levels prior to parturition.

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)

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.

Effects of a 1.94% sulfonic acid teat dip and a 1% iodophor teat dip on teat canal infections in lactating dairy cows.

Sixty-three cows were used in a natural exposure trial for 1 yr to determine the effects of a 1.94% linear dodecyl benzene sulfonic acid and a 1% iodophor teat dip on teat canal and intramammary infections. Overall, total teat canal infections increased 28.9% and total intramammary infections increased 30% in quarters dipped with the linear dodecyl benzene sulfonic acid compared with a 14.3% increase in teat canal infections and a 17.4% decrease in intramammary infections for the iodophor group. Higher frequencies were observed for teat canal and intramammary infections caused by Staphylococcus epidermidis in the linear dodecyl benzene sulfonic acid group. Staphylococcus hyicus was the predominant organism isolated from teat canal and intramammary infections in the iodophor group. No difference was observed between the two teat dips in the persistence of Staphylococcus aureus teat canal infections. A greater number of S. hyicus teat canal infections persisted in the iodophor group, whereas teat canal infections produced by S. epidermidis and Staphylococcus xylosus persisted longer in the sulfonic acid group. Results of this study indicated that use of a linear dodecyl benzene sulfonic acid teat dip for 1 yr was not associated with increased S. aureus teat canal infections and intramammary infections. However, linear dodecyl benzene sulfonic acid appeared to affect the distribution of coagulase-negative staphylococci isolated from teat canal infections and intramammary infections.

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.

Determination of milk and mammary tissue concentrations of ceftiofur after intramammary and intramuscular therapy.

Twenty-five Staphylococcus aureus strains isolated from bovine mastitis were tested for their susceptibility to ceftiofur. Zone diameter for 30 micrograms disks averaged 39 mm, and minimum inhibitory concentrations ranged from .5 to 1 microgram/ml. Tissue and milk concentrations were determined from biopsy and quarter milk samples collected from eight cows treated with either intramammary infusion of 100 or 200 mg of ceftiofur, one or two intramuscular injections of 500 mg of ceftiofur, or combination therapy of intramammary infusion coupled with intramuscular injection. Three additional cows received two intramammary infusions of 200 mg of cephapirin at 24-h intervals. Intramuscular injections of ceftiofur resulted in tissue and milk concentrations below detectable limits. Staphylococcus aureus was not eliminated from infected mammary glands by infusion of 100 mg of ceftiofur or by injection of 500 mg of ceftiofur by 48 h after treatment. Combination therapy of 100 mg of ceftiofur infused and 500 mg injected reduced S. aureus numbers in milk and tissue markedly, as did infusion of 200 mg of ceftiofur. Cows receiving intramammary infusion of 200 mg of ceftiofur (two doses at 24-h intervals) had highest concentrations in milk (450 micrograms/ml at 4 and 6 h) and in tissue (.08 microgram/mg at 30 h). These concentrations are similar to those obtained with two 200-mg doses of cephapirin at 24-h intervals. Histologic analysis of mammary parenchymal tissues showed that combination therapy resulted in higher percentages of alveolar luminal area and lower percentages of interalveolar stroma compared with infusion or injection alone. Histology of quarters receiving combination therapy was not different from that of quarters receiving cephapirin infusion alone.

Minimum inhibitory concentrations and disk diffusion zone diameter for selected antibiotics against streptococci isolated from bovine intramammary infections.

The antimicrobial susceptibility to 11 antibiotics was determined of 358 streptococcal isolates representing six species was determined. All isolates were from milk samples obtained from clinical or subclinical cases of bovine mastitis. Agar disk diffusion zone diameters and minimum inhibitory concentrations were obtained for all isolates. Of the antibiotics tested that are available for mastitis therapy, cephalothin, penicillin, ampicillin, novobiocin, and erythromycin demonstrated acceptable activity against nonenterococcal streptococci, but only penicillin and ampicillin demonstrated moderate activity against Enterococcus faecalis. Enterococcus faecalis demonstrated substantial resistance to cephalothin, erythromycin, gentamicin, streptomycin, and tetracycline, while the nonenterococcal streptococci demonstrated substantial resistance to gentamicin, streptomycin, and tetracycline. Streptococcus uberis demonstrated greater antibiotic resistance than did Streptococcus dysgalactiae, while Aerococcus viridans demonstrated the greatest overall resistance of the nonenterococcal species.

Effect of postmilking teat antisepsis on teat canal infections in lactating dairy cows.

Effects of a .18% iodophor teat dip and a fatty acid plus lactic acid teat dip on teat canal infections were studied in two separate trials under experimental challenge procedures using Staphylococcus aureus and Streptococcus agalactiae. The iodophor teat dip was 90% effective in preventing new S. aureus teat canal infections and 95.6% effective in reducing progression of S. aureus teat canal infections to intramammary infections. The dip also reduced persistence of S. aureus teat canal colonizations from week to week by 94.4%. The fatty acid plus lactic acid dip had no effect on preventing S. aureus teat canal infections but reduced progression of S. aureus teat canal infections to intramammary infections by 43.8%. The fatty acid plus lactic acid dip also reduced the persistence of S. aureus teat canal infections by 39%. An insufficient number of Strep. agalactiae teat canal infections was detected in both trials for valid analyses. Neither dip had any effect on prevalence of naturally occurring, coagulase-negative staphylococcal teat canal infections or on teat canal infections by other organisms.