Laboratory of Microbiology and Infectious Diseases, Faculty of Veterinary Medicine, School of Health Science, Aristotle University of Thessaloniki, University Campus, 54124, Thessaloniki, Greece.
Laboratory of Animal Husbandry, Faculty of Veterinary Medicine, School of Health Science, Aristotle University of Thessaloniki, University Campus, 54124, Thessaloniki, Greece.
BMC Vet Res. 2022 Jan 11;18(1):29. doi: 10.1186/s12917-021-03128-w.
Mycoplasma agalactiae, causing agent of contagious agalactia, infects domestic small ruminants such as sheep and goats but also wild Caprinae. M. agalactiae is highly contagious and transmitted through oral, respiratory, and mammary routes spreading rapidly in an infected herd.
In an outbreak of contagious agalactia in a mixed herd of sheep and goats, 80% of the goats were affected displaying swollen udders and loss of milk production but no other symptom such as kerato-conjunctivitis, arthritis or pulmonary distress commonly associated to contagious agalactia. Surprisingly, none of the sheep grazing on a common pasture and belonging to the same farm as the goats were affected. Whole genome sequencing and analysis of M. agalactiae strain GrTh01 isolated from the outbreak, revealed a previously unknown sequence type, ST35, and a particularly small, genome size of 841'635 bp when compared to others available in public databases. Overall, GrTh01 displayed a reduced accessory genome, with repertoires of gene families encoding variable surface proteins involved in host-adhesion and variable antigenicity being scaled down. GrTh01 was also deprived of Integrative Conjugative Element or prophage, and had a single IS element, suggesting that GrTh01 has a limited capacity to adapt and evolve.
The lack of most of the variable antigens and the Integrative Conjugative Element, both major virulence- and host specificity factors of a M. agalactiae strain isolated from an outbreak affecting particularly goats, indicates the implication of these factors in host specificity. Whole genome sequencing and full assembly of bacterial pathogens provides a most valuable tool for epidemiological and virulence studies of M. agalactiae without experimental infections.
导致接触性传染性乳腺炎的病原体无乳支原体感染绵羊和山羊等家养小反刍动物，也感染野生小反刍动物。无乳支原体高度传染性，通过口腔、呼吸道和乳腺途径传播，在感染的畜群中迅速传播。
在绵羊和山羊混合畜群的接触性传染性乳腺炎暴发中，80%的山羊受到影响，表现为乳房肿胀和产奶量下降，但没有其他症状，如角结膜炎、关节炎或肺部窘迫，这些症状通常与接触性传染性乳腺炎有关。令人惊讶的是，在同一牧场放牧的、与山羊同属一个农场的绵羊没有受到影响。对从暴发中分离出的无乳支原体菌株 GrTh01 进行全基因组测序和分析，揭示了一种以前未知的序列型 ST35，其基因组大小特别小，为 841'635 bp，与公共数据库中其他已有的序列相比。总体而言，GrTh01 显示出一个减少的辅助基因组，涉及宿主粘附和可变抗原性的可变表面蛋白的基因家族的 repertoire 被缩小。GrTh01 还缺乏整合共轭元件或噬菌体，并且只有一个 IS 元件，这表明 GrTh01 适应和进化的能力有限。
从特别影响山羊的暴发中分离出的无乳支原体菌株缺乏大多数可变抗原和整合共轭元件，这两个都是无乳支原体菌株的主要毒力和宿主特异性因素，这表明这些因素在宿主特异性中起作用。全基因组测序和细菌病原体的完整组装为无乳支原体的流行病学和毒力研究提供了最有价值的工具，而无需进行实验感染。
