Efficacy of vaccination and antibiotic therapy against Staphylococcus aureus mastitis in dairy cattle

Autor: C. D. Luby, J. R. Middleton
Rok vydání: 2005
Předmět:
Zdroj: Veterinary Record. 157:89-90
ISSN: 0042-4900
DOI: 10.1136/vr.157.3.89
Popis: PREVIOUS work has shown that the administration of either an autogenous or an experimental Staphylococcus aureus bacterin, in conjunction with extended pirlimycin (Pirsue; Pfizer) therapy, can increase S aureus intramammary infection cure rates when compared with extended pirlimycin therapy alone (Sears and Belschner 1999, Timms and others 2000). In those studies, the mammary quarter cure rates in cows that were vaccinated 14 and two days before, and six or seven days after, the start of extended intramammary pirlimycin therapy ranged from 33 to 79 per cent, compared with a mammary quarter cure rate of 14 to 18 per cent among cattle treated with extended pirlimycin therapy alone. The studies suggest that vaccination with a S aureus bacterin around the time of intramammary antibiotic therapy may enhance the efficacy of treatment for S aureus mastitis. However, the success rates were herd dependent (Sears and Belschner 1999). One possible explanation for this may be due to differences in the susceptibility of different strains of S aureus to treatment (Middleton and others 2001). There is a polyvalent S aureus bacterin (Lysigin; Boehringer Ingelheim Vetmedica) marketed for the vaccination of dairy cattle in the USA. No studies have evaluated the ability of this product to potentiate extended intramammary pirlimycin therapy of S aureus infections. This short communication describes a study to evaluate the ability of the polyvalent bacterin to potentiate extended intramammary pirlimycin therapy, and the use of pulsed-field gel electrophoresis (PFGE) to strain-type S aureus isolates from infected mammary quarters to determine whether the outcome of treatment was strain dependent. Twelve lactating Holstein-Friesian cows with chronic S aureus intramammary infections, based on sequential milk cultures, were studied. The animals were randomly assigned to one of two treatment groups, regardless of their stage of lactation and parity: seven cows (10 quarters) were assigned to receive extended pirlimycin therapy (group 1) and five cows (six quarters) were assigned to receive extended pirlimycin therapy in conjunction with the polyvalent bacterin (group 2). The extended pirlimycin therapy consisted of three cycles of intramammary pirlimycin treatment, with each treated quarter receiving two 50 mg doses of pirlimycin, 24 hours apart, followed by the manufacturer’s 36-hour milk withhold, such that the treatments were administered starting on day 0 and 24, 60, 84, 120 and 144 hours later. The vaccinated cattle were immunised 14 days and two days before the start of pirlimycin therapy and seven days after, with 5 ml of the polyvalent bacterin administered subcutaneously into the neck. Mammary quarter foremilk samples for culture and somatic cell count (SCC) were collected on days –14, –2, 0, 3, 5, 8, 15, 22, 29 and 36. Samples were collected before vaccination on days –14 and –2 and before the intramammary antibiotic administration on days 0, 3 and 5. Milk cultures were performed according to established guidelines (Hogan and others 1999), with the exception that a 0·05 ml culture medium inoculum was used. All coagulase-positive staphylococci were further speciated using a commercial test kit (apiStaph; bioMerieux). Milk SCC determinations were performed by a commercial laboratory and the results were reported as raw SCC and linear score SCC (SCS) (Mid-South Dairy Records). S aureus strain types were determined using PFGE as described by Middleton and others (2002). The PFGE gel was run in 0·5 x TBE buffer on a CHEF DRII PFGE machine (Bio-Rad) with a 5 to 50 second pulse time at 200 V for 24 hours at 14°C. Cures were defined as animals or mammary quarters no longer infected with the original strain of S aureus after treatment. The cure rates were compared between groups using Fisher’s exact test (α=0·05). Changes in SCS during the study period were analysed using analysis of variance for repeated measures (α=0·05). The cow and mammary quarter cure rates were 43 per cent and 50 per cent, respectively, for cows in group 1, and 60 per cent and 66 per cent, respectively, for those in group 2; there were no significant differences between the groups (P>0·633). PFGE revealed eight strains of S aureus (Fig 1); the strains were well distributed between the groups (Table 1). Four Veterinary Record (2005) 157, 89-90
Databáze: OpenAIRE
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