Transcriptomic analysis of milk somatic cells in mastitis resistant and susceptible sheep upon challenge with Staphylococcus epidermidis and Staphylococcus aureus

<p>Abstract</p> <p>Background</p> <p>The existence of a genetic basis for host responses to bacterial intramammary infections has been widely documented, but the underlying mechanisms and the genes are still largely unknown. Previously, two divergent lines of sheep selected for high/low milk somatic cell scores have been shown to be respectively susceptible and resistant to intramammary infections by <it>Staphylococcus spp</it>. Transcriptional profiling with an 15K ovine-specific microarray of the milk somatic cells of susceptible and resistant sheep infected successively by <it>S. epidermidis </it>and <it>S. aureus </it>was performed in order to enhance our understanding of the molecular and cellular events associated with mastitis resistance.</p> <p>Results</p> <p>The bacteriological titre was lower in the resistant than in the susceptible animals in the 48 hours following inoculation, although milk somatic cell concentration was similar. Gene expression was analysed in milk somatic cells, mainly represented by neutrophils, collected 12 hours post-challenge. A high number of differentially expressed genes between the two challenges indicated that more T cells are recruited upon inoculation by <it>S. aureus </it>than <it>S. epidermidis</it>. A total of 52 genes were significantly differentially expressed between the resistant and susceptible animals. Further Gene Ontology analysis indicated that differentially expressed genes were associated with immune and inflammatory responses, leukocyte adhesion, cell migration, and signal transduction. Close biological relationships could be established between most genes using gene network analysis. Furthermore, gene expression suggests that the cell turn-over, as a consequence of apoptosis/granulopoiesis, may be enhanced in the resistant line when compared to the susceptible line.</p> <p>Conclusions</p> <p>Gene profiling in resistant and susceptible lines has provided good candidates for mapping the biological pathways and genes underlying genetically determined resistance and susceptibility towards <it>Staphylococcus </it>infections, and opens new fields for further investigation.</p

Changing trends in mastitis

<p>Abstract</p> <p>The global dairy industry, the predominant pathogens causing mastitis, our understanding of mastitis pathogens and the host response to intramammary infection are changing rapidly. This paper aims to discuss changes in each of these aspects. Globalisation, energy demands, human population growth and climate change all affect the dairy industry. In many western countries, control programs for contagious mastitis have been in place for decades, resulting in a decrease in occurrence of <it>Streptococcus agalactiae </it>and <it>Staphylococcus aureus </it>mastitis and an increase in the relative impact of <it>Streptococcus uberis </it>and <it>Escherichia coli </it>mastitis. In some countries, <it>Klebsiella </it>spp. or <it>Streptococcus dysgalactiae </it>are appearing as important causes of mastitis. Differences between countries in legislation, veterinary and laboratory services and farmers' management practices affect the distribution and impact of mastitis pathogens. For pathogens that have traditionally been categorised as contagious, strain adaptation to human and bovine hosts has been recognised. For pathogens that are often categorised as environmental, strains causing transient and chronic infections are distinguished. The genetic basis underlying host adaptation and mechanisms of infection is being unravelled. Genomic information on pathogens and their hosts and improved knowledge of the host's innate and acquired immune responses to intramammary infections provide opportunities to expand our understanding of bovine mastitis. These developments will undoubtedly contribute to novel approaches to mastitis diagnostics and control.</p

Factors affecting mechanical nociceptive thresholds in healthy sows

Objective: To describe anatomical and methodological factors influencing mechanical nociceptive thresholds (MNTs) and intra-site variability in healthy sows. Study design: Prospective, randomized validation. Animals: Eight pregnant, healthy, mixed-parity sows (176-269kg). Methods: Repeated MNT measurements were taken: 1) with a hand-held probe and a limb-mounted actuator connected to a digital algometer; 2) at nine landmarks on the limbs and tail; and 3) at 1 and 3minute intervals. Data were analysed using linear mixed regression models. Results: The MNTs (SEM) of the limbs were lower with the probe (14.7 +/- 1.2N) than with the actuator (21.3 +/- 1.2N; p<0.001), in the pelvic versus the thoracic limbs (16.7 +/- 1.2 versus 19.2 +/- 1.2N; p<0.001), and in the lateral versus the dorsal metatarsi and metacarpi (17.6 +/- 1.2 versus 18.4 +/- 1.2N; p=0.002). MNTs were higher in all subsequent measurements compared with the first (p<0.001) and in the morning compared with the afternoon (p=0.04). We found no evidence of MNT differences based on interval between consecutive measurements (1 versus 3minutes). Variability was lower in the thoracic limbs [mean back-transformed log(10) coefficient of variation (CV)+/- SE=25.5 +/- 1.5% versus 30.6 +/- 1.5% in the pelvic limbs; p<0.001], with the actuator (22.7 +/- 1.5% versus 33.4 +/- 1.5% with the probe; p<0.001), and on the left (CV=26.9 +/- 1.5% versus 29.3 +/- 1.5% on the right; p=0.01). Tail data (probe only) were analysed separately: mean MNT (+/- SE) was 11.7 (+/- 1.8); MNT increased in days 3-6 of testing compared with day 1 (p< 0.001). The mean CV (+/- SE) was 38.9% (+/- 1.1%). Conclusions and clinical relevance: MNTs and intra-site variability in healthy sows were affected by several factors, indicating that this methodology requires considerable attention to detail