Pathogenesis and inflammatory response in experimental caprine mastitis due to Staphylococcus chromogenes.

Coagulase-negative staphylococci (CNS) are the most frequently isolated bacteria in cases of subclinical mastitis in dairy cows. CNS species may differ in their pathogenicity, but very little is known about their virulence factors or their immune response in intramammary infections. To our knowledge, no experimental studies into the mastitis pathogenesis caused by CNS have been described in lactating goats. The aim of this study was to induce an experimentally Staphylococcus chromogenes mastitis in lactating goats aimed at verifying if the model can be used to evaluate the inflammatory response, the dynamics of infection and the pathological findings within the first hours of intramammary inoculation. Six Saanen goats in mid-lactation were inoculated with 1 × 107 colony forming units of S. chromogenes. Bacterial growth peaked in milk from the challenged right halves of the mammary glands (RMG) at 4 h post inoculation (PI). Shedding of viable bacteria showed a marked decrease at 12 h PI. An increase in mean somatic cell counts was observed in the milk samples from 8 h PI onwards. Mild clinical signs were evoked by intramammary inoculation. Staphylococcus chromogenes could be isolated in tissue from all RMG. Histological examination of specimens of the RMG and lymph nodes of the goats showed an increased inflammatory response throughout the experiment with respect to control halves. In conclusion, the experimental inoculation of S. chromogenes in lactating goats is capable of eliciting an inflammatory response and capable of causing pathological changes. This research represents a preliminary study for a better knowledge of the mastitis pathogenesis caused by S. chromogenes.

Gliotoxinogenic Aspergillus fumigatus in the dairy herd environment.

The potential association between hygienic conditions in the environment of lactating cows and the presence of gliotoxinogenic Aspergillus fumigatus strains was studied. Milk samples (individual cow's milk [ICM], bulk tank milk [BTM]) from 44 dairy farms were sampled. In ICM samples, eight different species of Aspergillus were identified. A. flavus and A. fumigatus were predominant, with 37.8% and 26.1% relative densities, respectively. A. fumigatus strains were isolated from 61.4% of the BTM samples, and 34% of these strains were able to produce gliotoxin. Principal component analysis was used to associate the presence of A. fumigatus with some hygienic and sanitary practices. A significant and positive correlation was observed between dry cow therapy and forestripping. The presence of A. fumigatus gliotoxin producers in milk was associated with high somatic cells count (SCC) samples. Good hygienic and sanitary practices were associated with absence of A. fumigatus and relatively low SCCs of <250,000 cells/ml. In general, a high percentage of dairy farms were positive for A. fumigatus in BTM samples. This is the first work that indicates the positive effects of adequate hygienic and sanitary practices in dairy herds on the control of A. fumigatus and related species. By reducing the frequency of Aspergillus spp. in the dairy environment, the risk of farm handlers' exposure and the risk of intramammary fungal infections would also be reduced.