Unique features of bovine lymphocytes exposed to a staphylococcal enterotoxin

We previously demonstrated that stimulation of bovine peripheral blood mononuclear cells (PBMCs) with staphylococcal enterotoxin C (SEC), led to an inversion of the CD4(+):CD8(+) T cell ratio and generation of an atypical CD8(+) T cell subpopulation expressing CD26. In the present study, we examined T cell apoptosis and proliferation profiles of PBMC subpopulations in cultures stimulated with SEC. Unlike when stimulated with concanavalin A, nucleic acid synthesis in bovine PBMC cultures stimulated with SEC was low during the first four days but increased greatly on day 5. In contrast, nucleic acid synthesis in human PBMC cultures stimulated with SEC increased continuously. To investigate the mechanism of delayed bovine T cell proliferation, various cell phenotypes were monitored. The inversion of the bovine CD4(+):CD8(+) T cell ratio in PBMC cultures stimulated by SEC was associated with higher proliferation and lower apoptosis of CD8(+) T cells compared to CD4(+) T cells. The mRNA levels for interleukin (IL)-4 and IL-13 were sustained over 4 days but IL-12 mRNA levels dropped to background on day 2. These data suggest that SEC induces a prolonged Th-2- biased microenvironment, and together with the inversion of the bovine CD4(+):CD8(+) T cell ratios in bovine PBMC cultures with SEC, may in part explain the inability of the mammary immune system to establish an effective response to Staphylococcus aureus infections.

Immunosuppression by T regulatory cells in cows infected with Staphylococcal superantigen

Our recent study has provided that the in vitro SEC-induced proliferation of bovine T cells is preceded by a period of a non-proliferative immunoregulation of T cells that may be associated with cytokine production regulated by type 1 or type 2 T cells. Inversion of CD4+:CD8+ T cell ratio and induction of CD8+T cells with immunoregulatory activity could increase the probability of intracellular survival of Staphylococcus aureus (S. aureus). The increase of activated CD8+(ACT2+ BoCD8+) T cells in cows with mastitis caused by S. aureus may be associated with immune-regulatory function in the bovine mammary gland. The difference and similarity between bovine activated CD8+ T cells (CD8+ CD26+)and well-established human CD4+ CD25+ T regulatory (Tr)cells may help to reveal their unique immune regulatory system in the host infected with S. aureus.

Multidrug-resistant Salmonella typhimurium and Salmonella enteritidis identified by multiplex PCR from animals

Antibiotic resistance in Salmonella enteritidis and S. typhimurium, one of most frequent etiologic pathogens of food-borne bacterial gastroenteritidis in humans, is a serious health problem worldwide. Fifteen and 22 each of S. enteritidis and S. typhimurium were isolated from animals from 1983 to 1999 in Korea and tested for their antibiotic resistance patterns and phage types. S. enteritides isolates were highly resistant to sulfonamides (86.7%) and four of them (26.6%) showed multiple antibiotic resistance. The most frequent phage type (PT) of S. enteritids was PT1 (33.3%) even though none of them had multiple antibiotic resistance. S. typhimurium isolates were highly resistant to streptomycin, sulfonamides, and tetracycline, 100%, 95.5%, and 86.4% respectively. The incidence of multiple antibiotic resistance of S. typhimurium isolates was extremely high (100%) comparing to S. enteritidis isolates (26.7%). Two of the five ACSSuT type S. typhimurium isolates, resistant to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline, were phage type DT104. All S. typhimurium isolates were sensitive to florfenicol. For the rapid detection of multiple antibiotic resistant S. enteritidis and S. typhimurium isolates, particularly ACSSuT type S. typhimurium DT104, antibiotic resistance genes, cmlA/tetR, PSE-1, and TEM, and Salmonella spp. Specific gene, SipB/C, were amplified using four pairs of primers in hot-started multiplex polymerase chain reaction. Two Korean isolates of S. typhimurium DT104 showed TEM amplicons instead of PSE-1 for the ampicillin resistance. The multiplex PCR used in this study was useful in rapid detection of ACSSuT type S. typhimurium and identification of b-lactamase gene distribution among Salmonella isolates.

Multidrug-resistant Salmonella typhimurium and Salmonella enteritidis Identified by Multiplex PCR in Korea

No Abstract Available.