Staphylococcus aureus (S. aureus) is problematic for lactating mammals and public health. Understanding of mechanisms by which the hosts respond to severe invasion of S. aureus remains elusive. In this study, the genome-wide expression of mRNAs and miRNAs in bovine mammary gland cells were interrogated at 24 h after intra-mammary infection (IMI) with high or low concentrations of S. aureus. Compared to the negative control quarters, 194 highly-confident responsive genes were identified in the quarters with high concentration (109 cfu/mL) of S. aureus, which were predominantly implicated in pathways and biological processes pertaining to innate immune system, such as cytokine-cytokine receptor interaction and inflammatory response. In contrast, only 21 highly-confident genes were significantly differentially expressed in face of low concentration (106 cfu/mL) of S. aureus, which slightly perturbed the cell signaling and invoked corresponding responses like vasoconstriction, indicating limited perturbations and immunological evading. Additionally, the significant up-regulations of bta-mir-223 and bta-mir-21-3p were observed in the quarters infected by high concentration of S. aureus. Network analysis suggested that the two miRNAs' pivotal roles in defending hosts against bacterial infection probably through inhibiting CXCL14 and KIT. The significant down-regulation of CXCL14 was also observed in bovine mammary epithelial cells at 24 h post-infection of S. aureus (108 cfu/mL) in vitro. Integrated analysis with QTL database further suggested 28 genes (e.g., CXCL14, KIT, and SLC4A11) as candidates of bovine mastitis. This study first systematically revealed transcriptional and post-transcriptional responses of bovine mammary gland cells to invading S. aureus in a dosage-dependent pattern, and highlighted a complicated responsive mechanism in a network of miRNA-gene-pathway interplay.

Clinical mastitis cows normally produce clotted milk, thus the much higher somatic cells in milk are unable to be counted by routine FOSS machine. The proteins coded by CD4 and LAG-3 genes can bind to MHC class II molecules and play important roles in inflammatory diseases. The present study was designed to investigate the effects of single nucleotide polymorphisms (SNPs) in bovine CD4 and LAG-3 genes on the somatic cell counts (SCCs) of clinical mastitis Holstein cows. For the first time, we detected SCCs in the clinical mastitis cows' milk by Newman's staining combined with microscope assays. Our association results showed that two novel SNPs (T104010752C and C104028410T) identified in bovine CD4 and LAG-3 genes respectively were significantly associated with SCCs of clinical mastitis cows (P<0.05). In addition, the combined genotypic effect of both the SNPs was also significant on SCCs (P<0.05). The results imply that the novel SNPs in CD4 and LAG-3 genes could be significant candidate markers against Clinical mastitis in Holstein cattle.

BackgroundBovine mastitis is the most common and costly disease of lactating cattle worldwide. Apart from milk somatic cell count (SCC) and somatic cell score (SCS), serum cytokines such as interleukin-17 (IL-17) and interleukin-4 (IL-4) may also be potential indicators for bovine mastitis. The present study was designed to investigate the effects of single nucleotide polymorphisms (SNPs) in bovine IL-17F and IL-17A genes on SCC, SCS and serum cytokines in Chinese Holstein and Inner-Mongolia Sanhe cattle, and to compare the mRNA expression variations of the cows with different genotypes.ResultsA total of 464 lactating cows (337 Holstein and 127 Inner-Mongolia Sanhe cattle) were screened for SNPs identification and the data were analyzed using fixed effects of herd, parity, season and year of calving by general linear model procedure. The results revealed that SNP g.24392436C > T in IL-17F and SNP g.24345410A > G in IL-17A showed significant effects on SCC and IL-4 in Holstein (n = 337) and on IL-17 and IL-4 in Sanhe cattle (n = 127). The homozygous GG genotype of SNP g.24345410A > G had significantly higher mRNA expression compared with the heterozygous AG genotype.ConclusionsThe results indicate that IL-17F and IL-17A could be powerful candidate genes of mastitis resistance and the significant SNPs might be useful genetic markers against mastitis in both dairy and dual purpose cattle.Electronic supplementary materialThe online version of this article (doi:10.1186/s40104-016-0137-1) contains supplementary material, which is available to authorized users.

Background: Drug-resistance and immunological escape of Staphylococcus aureus and its “superbug”, methicillin-resistant S. aureus (MRSA), have become one of main causes of bacterial infection in both human and animals. In dairy cattle, elimination of bovine mastitis induced by S. aureus is of importance because S. aureus-infected cows normally are culled passively. Methods: Here, we investigated the beneficial effects of bovine trafficking protein particle complex 9 (TRAPPC9) gene and folic acid supplementation in the control of mastitis induced by S. aureus or MRSA by a series of in vivo and in vitro experiments. Results: The data showed that the genetic mutations and DNA methylation of TRAPPC9 were highly linked with the mastitis resistance of dairy cows. Additionally, knockdown of bovine TRAPPC9 was significantly involved in the mRNA expression levels of interleukin’s genes (increased IL-1β and IL-6), and down-regulated the protein level of NF-κB-P65 in the mastitis cell model induced by MRSA. Meanwhile, dose-dependent folic acid addition can inhibit the invasion of MRSA into Mac-T cells and improve TRAPPC9 expression in dairy cows. Conclusions: Altogether, our data suggest that an appropriate dose of folic acid can significantly reduce the inflammation caused by MRSA partially through TRAPPC9 mediated NF-κB pathway. These findings provide new insights to control the drug-resistant pathogens and to restrict the overuse of antibiotics through combined effects of the intrinsic host gene and extrinsic nutrient.