Mammary Gland Pathology Subsequent to Acute Infection with Strong versus Weak Biofilm Forming Staphylococcus aureus Bovine Mastitis Isolates: A Pilot Study Using Non-Invasive Mouse Mastitis Model

BACKGROUND: Biofilm formation by Staphylococcus aureus is an important virulence attribute because of its potential to induce persistent antibiotic resistance, retard phagocytosis and either attenuate or promote inflammation, depending upon the disease syndrome, in vivo. This study was undertaken to evaluate the potential significance of strength of biofilm formation by clinical bovine mastitis-associated S. aureus in mammary tissue damage by using a mouse mastitis model. METHODS: Two S. aureus strains of the same capsular phenotype with different biofilm forming strengths were used to non-invasively infect mammary glands of lactating mice. Biofilm forming potential of these strains were determined by tissue culture plate method, ica typing and virulence gene profile per detection by PCR. Delivery of the infectious dose of S. aureus was directly through the teat lactiferous duct without invasive scraping of the teat surface. Both bacteriological and histological methods were used for analysis of mammary gland pathology of mice post-infection. RESULTS: Histopathological analysis of the infected mammary glands revealed that mice inoculated with the strong biofilm forming S. aureus strain produced marked acute mastitic lesions, showing profuse infiltration predominantly with neutrophils, with evidence of necrosis in the affected mammary glands. In contrast, the damage was significantly less severe in mammary glands of mice infected with the weak biofilm-forming S. aureus strain. Although both IL-1ß and TNF-a inflammatory biomarkers were produced in infected mice, level of TNF-a produced was significantly higher (p<0.05) in mice inoculated with strong biofilm forming S. aureus than the weak biofilm forming strain. CONCLUSION: This finding suggests an important role of TNF-a in mammary gland pathology post-infection with strong biofilm-forming S. aureus in the acute mouse mastitis model, and offers an opportunity for the development of novel strategies for reduction of mammary tissue damage, with or without use of antimicrobials and/or anti-inflammatory compounds for the treatment of bovine mastitis

Long-term performance deterioration models for semi-rigid asphalt pavement in cold region

As the demand for the semi-rigid asphalt pavement reconstruction and maintenance technologies is increasing in the seasonal cold regions, the pavement performance deterioration models are essential for the success of the reconstruction and maintenance projects. This study is carried out to develop the deterioration models based on the preliminary investigation results of typical successful maintenances. All critical technical indexes concerning the asphalt pavement maintenance were studied. By combining the engineering practices, a long-term performance database of the semi-rigid asphalt pavement was established through a large amount of survey data, and the related environmental parameters. Based on the database achieved, the deterioration models of the semi-rigid asphalt pavement performances were built via the statistical regression method. It is concluded that the proposed deterioration models were useful and practical for the establishment of the maintenance decision of the semi-rigid asphalt pavements