Olson Michael A, Cullimore Caz, Hutchison Weston D, Grimsrud Aleksander, Nobrega Diego, De Buck Jeroen, Barkema Herman W, Wilson Eric, Pickett Brett E, Erickson David L
Department of Microbiology and Molecular Biology, Brigham Young University, Provo, UT, United States.
Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada.
Front Microbiol. 2024 Aug 29;15:1452007. doi: 10.3389/fmicb.2024.1452007. eCollection 2024.
Bovine mastitis caused by compromises animal health and inflicts substantial product losses in dairy farming. It may manifest as subclinical through severe acute disease and can be transient or persistent in nature. Little is known about bacterial factors that impact clinical outcomes or allow some strains to outcompete others in the mammary gland (MG) environment. Mastitis-associated (MAEC) may have distinctive characteristics which may contribute to the varied nature of the disease. Given their high levels of intraspecies genetic variability, virulence factors of commonly used MAEC model strains may not be relevant to all members of this group.
In this study, we sequenced the genomes of 96 MAEC strains isolated from cattle with clinical mastitis (CM). We utilized clinical severity data to perform genome-wide association studies to identify accessory genes associated with strains isolated from mild or severe CM, or with high or low competitive fitness during competition assays. Genes associated with mastitis pathogens or commensal strains isolated from bovine sources were also identified.
A type-2 secretion system (T2SS) and a chitinase (ChiA) exported by this system were strongly associated with pathogenic isolates compared with commensal strains. Deletion of from MAEC isolates decreased their adherence to cultured bovine mammary epithelial cells.
The increased fitness associated with strains possessing this gene may be due to better attachment in the MG. Overall, these results provide a much richer understanding of MAEC and suggest bacterial processes that may underlie the clinical diversity associated with mastitis and their adaptation to this unique environment.
由[病原体名称未给出]引起的牛乳腺炎损害动物健康，并给奶牛养殖造成重大产品损失。它可能表现为从亚临床到严重急性疾病，并且在性质上可以是短暂的或持续的。关于影响临床结果或使某些菌株在乳腺（MG）环境中比其他菌株更具竞争力的细菌因素知之甚少。乳腺炎相关大肠杆菌（MAEC）可能具有独特特征，这可能导致该疾病的多样性。鉴于它们种内遗传变异性高，常用MAEC模型菌株的毒力因子可能与该组的所有成员无关。
在本研究中，我们对从临床乳腺炎（CM）牛分离的96株MAEC菌株进行了基因组测序。我们利用临床严重程度数据进行全基因组关联研究，以鉴定与从轻度或重度CM分离的菌株相关的辅助基因，或在竞争试验中具有高或低竞争适应性的菌株相关的辅助基因。还鉴定了与从牛源分离的乳腺炎病原体或共生菌株相关的基因。
与共生菌株相比，一种2型分泌系统（T2SS）和由该系统输出的一种几丁质酶（ChiA）与致病分离株密切相关。从MAEC分离株中删除[基因名称未给出]会降低它们对培养的牛乳腺上皮细胞的粘附。
与具有该基因的菌株相关的适应性增加可能是由于在MG中更好的附着。总体而言，这些结果提供了对MAEC更丰富的理解，并表明了可能是乳腺炎相关临床多样性及其对这种独特环境适应基础的细菌过程。
