Comparison of the effects of tylosin and tilmicosin as a systemic treatment of dry Holstein cows.

The aim of the present study was to evaluate the efficacy of macrolides to eliminate intramammary infection (IMI) caused by Staphylococcus aureus (S. aureus) and Streptoccus spp. 3 weeks before calving time. Eighty Holstein dairy cows with subclinical mastitis pathogens were divided into three groups. Three weeks before expected parturition time, cows in group 1 received tilmicosin (n = 29), cows in group 2 received tylosin (n = 30) and cows in group 3 were left as negative control (n = 21). Milk samples were obtained on 3 and 7 days after calving. Randomly amplified polymorphic DNA (RAPD) method was determined for all of the S. aureus isolates that had the same isolates before and after parturition. The total cure rate was 63.33, 75.86 and 66.66% for tylosin, tilmicosin and control groups, respectively. Furthermore, cure rates were not significant, when each type of mastitis causing pathogens were considered separately. The incidence of clinical mastitis during 60 days after calving for tylosin, tilmicosin and Control groups was 23.33, 27.58 and 38.09%, respectively. Only four S. aureus isolated before drying-off were similar to post-calving isolate, according to RAPD-PCR method. In conclusion, antibiotic therapy before calving improved the cure rate numerically, however, it was not significant.

Comparison of virulence factors and capsular types of Streptococcus agalactiae isolated from human and bovine infections.

Streptococcus agalactiae is a leading cause of human and bovine infections. A total of 194 S. agalactiae isolates, 55 isolates from bovines and 139 from humans, were analyzed for capsular types, virulence genes (scpB, hly, rib, bca and bac) and mobile genetic elements (IS1548 and GBSi1) using polymerase chain reaction (PCR) and multiplex PCR. Capsular type III was predominant (61%), followed by types V, II, Ib, and IV. The scpB, hly, bca and bac virulence genes were only found among human isolates. Twelve and 2 distinct virulence gene profiles were identified among human and bovine isolates respectively. The virulence gene profiles scpB- hly- IS1548- rib-bca (51%) and scpB- hly- IS1548- bca (19%) were only predominant among human isolates. The rib gene was the most common virulence gene in both human and bovine isolates. The study showed a high prevalence of virulence genes in S. agalactiae strains isolated from human infections, these result can support the idea that S. agalactiae isolated from humans and bovines are generally unrelated and probably belonged to separate populations.