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박영경,Lawrence K. Fox,Dale D. Hancock,Wade McMahan,Yong Ho Park 대한수의학회 2012 JOURNAL OF VETERINARY SCIENCE Vol.13 No.1
Changes in udder health and antibiotic resistance of mastitis pathogens isolated from dairies upon conversion from conventional to organic management over a 3-year period was studied. Coagulase-negative staphylococci (CNS) were the most prevalent mastitis pathogens isolated. CNS were significantly less resistant to b-lactam antibiotics when isolated from milk after the herd transitioned to organic management. Cessation of the use of antimicrobial therapies in dairies in combination with organic management could lead to a reduction in the antimicrobial resistance of mastitis pathogens.
박영경,백영환,윤장원,Lawrence K. Fox,황선영,박용호 대한수의학회 2013 Journal of Veterinary Science Vol.14 No.3
The sequences of the ccrAB genes from bovine-, canine- and chicken-originating methicillin-resistant Staphylococcus (S.)epidermidis (MRSE) and bovine methicillin-resistant Staphylococcus (S.) aureus (MRSA) were compared to investigate the frequency of intra-species horizontal transfer of the staphylococcal cassette chromosome mec (SCCmec)complex. Nineteen MRSE strains were isolated from bovine milk, chickens, and dogs, and their genetic characteristics were investigated by multilocus sequence typing and SCCmec typing. Among the animal MRSE strains, the most frequent SCCmec type was type IV, which consisted of the type B mec complex and ccrAB type 2. The ccrA2 and ccrB2 genes were sequenced from the bovine, chicken and canine MRSE strains and compared with those of the bovine MRSA strains. The sequences generally clustered as MRSA and MRSE groups, regardless of the animal source. Additionally, no bovine MRSE sequence was associated with the bovine MRSA groups. Although most of the bovine MRSE and MRSA isolates possessed SCCmec type IV sequences, our results suggest that the intra-species gene transfer of the SCCmec complex between bovine S. aureus and bovine S. epidermidis strains is not a frequent event.
Suppression of bovine T lymphocytes responses by the superantigen staphylococcal enterotoxin C
Witold A. Ferens,Gregory A. Bohach,William C. Davis,Lawrence K. Fox,이상운(Sang Un Lee),박용호(Yong Ho Park) 한국예방수의학회 1998 예방수의학회지 Vol.22 No.3
Staphylococcus aureus에 의한 유방염은 주로 만성으로 경과되며 항생제 치료에 대한 저항성을 나타낸다. 기존의 보고에 의하면, 이 질병은 동일항원 혹은 다른 종류의 항원에 대한 면역반응의 억제와 관련된다고 알려져 있으나, 이러한 효과와 관련된 특이적인 인자는 아직 밝혀지지 않고 있다. 본 실험은 superantigen으로 알려진 포도상구균 장독소가 유방염의 숙주방어기전에 간섭하리라는 가능성을 제시하였다. 본 실험에서 포도상구균 장독소 C형 (SEC)은 in vitro상에서 세포증식의 억제와 CD8⁺T 림프구 표면의 ACT3 marker의 과다 발현에 의해 특징지어지는 소 T 림프구의 일탈된 활성을 유도하였다. SEC에 의한 소 T 림프구의 증식반응은 일시적이었으며, 배양 4일 후에는 ACT1, ACT16 및 IL-2Rα 등 활성세포 표면인자의 증가와 연관되어 왕성한 증식을 나타내었다. 비록 CD4⁺T 림프구와 CD8⁺T림프구는 배양 후 4일과 7일 사이에 증식을 나타내었지만, 상대적으로 CD8⁺T 림프구 아집단의 증식이 더 왕성하였으며 이로 인해 CD4:CD8 비율이 반전되는 결과를 가져왔다.
Unique features of bovine lymphocytes exposed to a staphylococcal enterotoxin
박용호,Sang Un Lee,Witold A. Ferens,Sparrow Samuels,William C. Davis,Lawrence K. Fox,Jong Sam Ahn,Keun Seok Seo,Byoung Sun Chang,황선영,Gregory A. Bohach 대한수의학회 2006 Journal of Veterinary Science Vol.7 No.3
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
박용호,Byoung Sun Chang,Gregory A.Bohach,Sang-Un Lee,William C.Davis,Lawrence K.Fox,Witold A.Ferens,Keun Seok Seo,Hye Cheong Koo,Nam Hoon Kwon 대한수의학회 2005 Journal of Veterinary Science Vol.6 No.3
Our recent study has provided that the in vitro SECinduced 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.