Streptococcus agalactiae (Group B Streptococcus, (GBS)) is the leading cause of mastitis (inflammation of the mammary gland) among dairy camels in Sub-Saharan Africa, with negative implications for milk production and quality and animal welfare. Camel milk is often consumed raw and presence of GBS in milk may pose a public health threat. Little is known about the population structure or virulence factors of camel GBS. We investigated the molecular epidemiology of camel GBS and its implications for mastitis control and public health. Using whole genome sequencing, we analysed 65 camel milk GBS isolates from 19 herds in Isiolo, Kenya. Six sequence types (STs) were identified, mostly belonging to previously described camel-specific STs. One isolate belonged to ST1, a predominantly human-associated lineage, possibly as a result of interspecies transmission. Most (54/65) isolates belonged to ST616, indicative of contagious transmission. Phylogenetic analysis of GBS core genomes showed similar levels of heterogeneity within- and between herds, suggesting ongoing between-herd transmission. The lactose operon, a marker of GBS adaptation to the mammary niche, was found in 75 % of the isolates, and tetracycline resistance gene tet(M) in all but two isolates. Only the ST1 isolate harboured virulence genes scpB and lmb, which are associated with human host adaptation. GBS in milk from Kenyan camel herds largely belongs to ST616 and shows signatures of adaptation to the udder. The finding of similar levels of within- and between herd heterogeneity of GBS in camel herds, as well as potential human-camel transmission highlights the need for improved internal as well as external biosecurity to curb disease transmission and increase milk production.

中文翻译：

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牛奶中 B 族链球菌的基因组分析表明需要改善生物安全：对肯尼亚牧民骆驼的横断面研究

无乳链球菌（B 族链球菌，(GBS)）是撒哈拉以南非洲地区奶骆驼乳腺炎（乳腺炎症）的主要原因，对牛奶产量、质量和动物福利产生负面影响。骆驼奶通常是生吃的，牛奶中 GBS 的存在可能会对公共健康构成威胁。关于骆驼 GBS 的种群结构或毒力因子知之甚少。我们研究了骆驼 GBS 的分子流行病学及其对乳腺炎控制和公共卫生的影响。我们利用全基因组测序，分析了来自肯尼亚伊西奥洛 19 个畜群的 65 株骆驼奶 GBS 分离株。鉴定出六种序列类型（ST），大部分属于先前描述的骆驼特异性 ST。一种分离株属于 ST1，这是一种主要与人类相关的谱系，可能是种间传播的结果。大多数（54/65）分离株属于 ST616，表明具有传染性传播。GBS 核心基因组的系统发育分析显示群体内部和群体之间的异质性水平相似，表明群体之间正在持续传播。在 75% 的分离株中发现了乳糖操纵子（GBS 适应乳腺生态位的标志物），并且在除两个分离株之外的所有分离株中发现了四环素抗性基因 tet(M)。只有 ST1 分离株含有毒力基因 scpB 和 lmb，它们与人类宿主适应有关。肯尼亚骆驼群牛奶中的 GBS 主要属于 ST616，并显示出适应乳房的特征。骆驼群内和群间 GBS 异质性水平相似，以及潜在的人骆驼传播，突出表明需要改善内部和外部生物安全，以遏制疾病传播并增加牛奶产量。