Progress 10/01/02 to 09/30/04
Outputs
Two studies were undertaken to evaluate the ability of Lysigin (BIVI Inc., St. Joseph, MO) to potentiate extended intramammary pirlimycin therapy. Study 1: Twelve lactating Holstein-Friesian cows with chronic S. aureus intramammary infection (IMI) were studied. Animals were randomly assigned to 1 of 2 treatment groups: 1) extended pirlimycin therapy (n=7 cows, 10 quarters) and 2) extended pirlimycin therapy in conjunction with Lysigin (n=5 cows, 6 quarters). Extended pirlimycin therapy consisted of 3 consecutive cycles of intramammary pirlimycin as per label directions. Group 2 cattle were immunized (days -14, -2 & 7) with 5 ml Lysigin subcutaneously in the neck. Mammary quarter foremilk samples for culture and linear score somatic cell count (SCS) were collected (days -14, -2, 0, 3, 5, 8, 15, 22, 29 & 36). Samples were collected prior to vaccination (days -14 & -2) and prior to intramammary antibiotic administration (days 0, 3, & 5). Staphylococcus aureus isolates were
typed using pulsed-field gel electrophoresis before (all cows) and after treatment (cows not cured). Cow and mammary quarter cure rates were 43% and 50% for group 1 and 60% and 66% for group 2 with no differences between groups (P>0.633). Pulsed-field gel electrophoresis revealed 8 strains of S. aureus among 12 cattle. We had insufficient data to evaluate the effect of S. aureus strain-type on treatment outcome due to the diversity of S. aureus strains isolated. There were no significant difference between groups with regard to SCS (P=0.224). However, SCSs were significantly higher before pirlimycin therapy than afterwards regardless of group (P<0.001). Study 2: Eighty-five cattle with 144 S. aureus infected mammary quarters were studied. Animals were assigned to one of two treatment groups based on ear tag number. Even-numbered cattle received extended pirlimycin therapy with vaccination (n=43 cattle, 71 S. aureus infected mammary quarters) and odd-numbered cattle received extended
pirlimycin therapy alone (n=42 cattle, 73 quarters). All cattle received 50 mg pirlimycin HCl in S. aureus infected mammary quarters once daily for eight consecutive days. In addition, even-numbered cattle were vaccinated with Lysigin as above. Mammary quarter foremilk samples for bacterial culture and SCS were collected immediately prior to first vaccination, immediately prior to treatment and 4 days, 2, 4 and 6 weeks following treatment. Four days after treatment, vaccinated cattle had significantly more S. aureus culture negative quarters than those receiving pirlimycin alone (90% and 74%, respectively; P=0.021). However, many of the quarters in both groups subsequently became culture positive for S. aureus resulting in no difference in overall cure rate between groups (15% and 14%, respectively; P=0.945). Mean infected quarter SCC was not significantly different between groups (P=0.158). The mean mammary quarter SCC in study animals remained above 1,000,000 cells/ml post-treatment
in both groups as did the mean mammary quarter SCC in quarters which cured their S. aureus IMI.
Impacts
Results of these 2 studies show that Lysigin fails to potentiate extended pirlimycin therapy of S. aureus intramammary infection (IMI) when cattle are followed over an extended follow-up period. The efficacy of extended pirlimycin therapy for curing S. aureus IMI regardless of vaccination seems to be herd dependent. In light of these data caution should be exercised when prescribing extended pirlimycin therapy to clear S. aureus IMIs in dairy cattle.
Publications
- Luby CD, Middleton JR, Davis A, Bader R, Butcher M. 2004. Efficacy of a commercially available Staphylococcus aureus bacterin in the potentiation of treatment of Staphylococcus aureus mastitis in dairy cattle. Proceedings of the 43rd Annnual Meeting of the NMC. Charlotte, NC. February 1-4. Pages 339-340.
- Luby CD, Middleton JR, Corbett RB, Bader GR. 2005. Comparison of the Efficacy of Extended Pirlimycin Therapy Alone or in Combination with Lysigin in the Treatment of Staphylococcus aureus Mastitis on a Large Commercial Dairy. Proceedings of the 44th Annual Meeting of the National Mastitis Council. Orlando, FL. January 16-19. Pages 251-252.
- Luby CD, Middleton JR. 2005. Efficacy of vaccination and antibiotic therapy for Staphylococcus aureus mastitis. Vet Rec. In Press.
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Progress 01/01/03 to 12/31/03
Outputs
Introduction - The hypothesis tested was that a commercially available Staphylococcus aureus bacterin would enhance the efficacy of extended pirlimycin HCl (Pirsue, Pfizer) intramammary therapy of S. aureus intramammary infection (IMI). Materials and Methods - To date 12 Holstein-Friesian dairy cattle have been studied. Cattle were randomly divided into two groups (Group 1 = extended pirlimycin HCl therapy (n = 7); Group 2 = vaccinated and treated with extended pirlimycin HCl therapy (n = 5)). Group 1 and 2 cattle were treated with three cycles of pirlimycin HCl intramammary therapy according to label directions; each cycle separated by the 36-hour label milk withdrawal. In addition, group 2 cattle were vaccinated with Lysigin (Boehringer Ingelheim Vetmedica, Inc.) on days -14, -2, and 7 relative to initiation of pirlimycin HCl therapy. Mammary quarter foremilk samples for cultures and somatic cell counts were collected on -12, -7, -4, -2, 0, 3, 5, 8, 15, 22, 29 and
36 days relative to the initiation of pirlimycin HCl therapy (day 0). Quantitative milk cultures were performed according to National Mastitis Council guidelines. Somatic cell counts were determined by a commercial laboratory using an automated counter (Mid-South Dairy Records, Springfield, MO). Staphylococcus aureus strain-types were determined using pulsed-field gel electrophoresis (PFGE) as described by Middleton et al. (2002). Cure rates were defined as: 1) cures (animals no longer infected with the original strain of S. aureus post-treatment) and 2) Staphylococcus aureus IMI unaffected. Cure rates between groups were compared using the Fisher's exact test (alpha < 0.05; Sigma Stat). Changes in somatic cell count score (SCS) were analyzed using a general linear model analysis of variance for repeated measures (alpha < 0.05; NCSS). Results - Group 1 cow and mammary quarter cure rates were 43 and 56%, respectively. Group 2 cow and mammary quarter cure rates were 60 and 71%,
respectively. There were no significant differences between groups with regard to cow and mammary quarter cure rates (P > 0.60, respectively; Power < 0.10). There were no significant differences between groups with regard to SCS (P = 0.09; Power = 0.08). However, all post-treatment SCSs were lower than pre-treatment SCSs (P = 0.00). Conclusion - While there was an increased cure rate in animals which were vaccinated and treated with extended pirlimycin HCl intramammary therapy, but the difference was not statistically significant (P > 0.60). Cure rates in cattle treated with extended pirlimycin therapy alone were much higher in the present study than those reported by others (Sears et al., 1999; Timms et al., 2000) and the observed differences in cure rate may be dependent upon herd and/or S. aureus strain differences in the respective study populations. Regardless of treatment group SCSs were reduced following treatment. Hence, while there was not a great advantage of using a vaccine
to enhance intramammary antibiotic therapy in the herd studied here, greater differences may be seen in a different herd. This study will be repeated with a larger number of cattle to increase statistical power.
Impacts
Results to date show equivalence of Lysigin to autogenous S. aureus bacterins in the enhancement of cure rates with extended pirlimycin HCl intramammary therapy. Therefore, the time and effort needed to produce an autogenous bacterin can be negated by using Lysigin, a commercially available S. aureus vaccine, while improving the outcome of S. aureus mastitis therapy.
Publications
- Luby CD, Middleton JR, Davis A, Bader R, Butcher M. 2004. Efficacy of a commercially available Staphylococcus aureus bacterin in the potentiation of treatment of Staphylococcus aureus mastitis in dairy cattle. Proc. Natl. Mastitis Counc. 43:339-340.
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