Pathology of udder lesions in sows

Classification, bacteriological findings, and analysis of sex hormone receptors and cytokine expression in mammary lesions of abattoir sows

Mammary lesions in sows can prevent suckling piglets from consuming colostrum that provides fundamental nutrients and protective immunity. Although mammary gross lesions are frequently found in sows at farms or slaughterhouses, with the exception of mastitis, they have received little research attention. In this study, we investigated mammary lesions observed in South Korean sows between 2015 and 2016. Mammary tissue samples of 82 sows showing gross lesions during meat inspection were histologically classified and immunohistochemical analysis was conducted to assess the expression of estrogen receptor (ER)-α, ER-β, and progesterone receptor (PR) for mammary hyperplastic lesions as well as that of cluster of differentiation (CD) 3, CD79a, interleukin (IL)-1α, IL-1β, IL-6, and IL-8 for mastitis. Furthermore, 20 swab samples were cultured, and the isolated bacteria were identified using polymerase chain reactions for 16S ribosomal RNA genes. The lesions were classified as hyperplasia, mastitis, or hyperplasia with mastitis. Immunohistochemistry results revealed that there was neither expression of ER-α nor of ER-β, but all examined hyperplastic samples expressed PR. In addition, there was a significant correlation between CD3 and IL-1β expressions, as well as between IL-1β and IL-6 expressions. Regarding the identity of the isolated bacteria, Pseudomonas spp. were most frequently detected. The results of this study have revealed the incidence and characteristics of porcine mammary lesions.

Comparative host specificity of human- and pig- associated Staphylococcus aureus clonal lineages

Bacterial adhesion is a crucial step in colonization of the skin. In this study, we investigated the differential adherence to human and pig corneocytes of six Staphylococcus aureus strains belonging to three human-associated [ST8 (CC8), ST22 (CC22) and ST36(CC30)] and two pig-associated [ST398 (CC398) and ST433(CC30)] clonal lineages, and their colonization potential in the pig host was assessed by in vivo competition experiments. Corneocytes were collected from 11 humans and 21 pigs using D-squame® adhesive discs, and bacterial adherence to corneocytes was quantified by a standardized light microscopy assay. A previously described porcine colonization model was used to assess the potential of the six strains to colonize the pig host. Three pregnant, S. aureus-free sows were inoculated intravaginally shortly before farrowing with different strain mixes [mix 1) human and porcine ST398; mix 2) human ST36 and porcine ST433; and mix 3) human ST8, ST22, ST36 and porcine ST398] and the ability of individual strains to colonize the nasal cavity of newborn piglets was evaluated for 28 days after birth by strain-specific antibiotic selective culture. In the corneocyte assay, the pig-associated ST433 strain and the human-associated ST22 and ST36 strains showed significantly greater adhesion to porcine and human corneocytes, respectively (p<0.0001). In contrast, ST8 and ST398 did not display preferential host binding patterns. In the in vivo competition experiment, ST8 was a better colonizer compared to ST22, ST36, and ST433 prevailed over ST36 in colonizing the newborn piglets. These results are partly in agreement with previous genetic and epidemiological studies indicating the host specificity of ST22, ST36 and ST433 and the broad-host range of ST398. However, our in vitro and in vivo experiments revealed an unexpected ability of ST8 to adhere to porcine corneocytes and persist in the nasal cavity of pigs.