M-team and Mastitis and Milk Quality Research Unit, Department of Internal Medicine, Reproduction and Population Medicine, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820, Merelbeke, Belgium.
Flanders Research Institute for Agriculture, Fisheries and Food (ILVO), Technology and Food Science, Burgemeester Van Gansberghelaan 115 bus 1, 9820, Merelbeke, Belgium.
Vet Res. 2021 Oct 28;52(1):137. doi: 10.1186/s13567-021-01007-8.
Although extensive research has been performed on bovine non-aureus staphylococci (NAS), several aspects such as bacteria-host interaction remain largely unstudied. Moreover, only a few mastitis pathogen challenge studies in cows have been conducted in the dry period, an important period that allows intramammary infection (IMI) to cure and new IMI to occur. We challenged 16 quarters of 4 Holstein Friesian cows at dry off with 100; 100 000 or 10 000 000 CFU of the udder-adapted S. chromogenes IM strain. Four quarters from one cow served as negative controls. Internally sealed quarters remained untouched, whereas non-sealed quarters were sampled 3 times during the dry period. After parturition, colostrum and daily milk samples were taken during the first week of lactation of all quarters. In total, 8 quarters appeared to be colonized, since S. chromogenes IM was recovered at least once during the experiment, as substantiated using Multilocus Sequence Typing. S. chromogenes IM shedding was highest in dry quarters inoculated with 10 000 000 CFU. Colonized quarters had the highest quarter somatic cell count (qSCC) in early lactation. Inoculated quarters (both colonized and non-colonized) had lower IL-6 and IL-10 concentrations in the dry period, whilst IFN-γ levels tended to be higher in colonized quarters compared to non-inoculated quarters. Also, IgG2 levels were higher in inoculated compared to non-inoculated quarters and the IgG2/IgG1 ratio was on average above 1. To conclude, we showed that dry quarters can be colonized with S. chromogenes IM, resulting in a shift towards a Th1 response in late gestation and early lactation characterised by an increased IgG2 concentration. However, further research is needed to confirm our findings.
尽管已经对牛非金黄色葡萄球菌（NAS）进行了广泛的研究，但细菌-宿主相互作用的几个方面仍在很大程度上未被研究。此外，在干奶期仅进行了少数牛乳腺炎病原体挑战研究，而干奶期是允许乳腺内感染（IMI）治愈和发生新的 IMI 的重要时期。我们用 100、100000 或 10000000CFU 乳腺适应的 S. chromogenes IM 菌株对 4 头荷斯坦弗里生奶牛的 16 个乳区进行干奶期挑战。一头牛的 4 个乳区作为阴性对照。内部密封的乳区未被触及，而非密封的乳区在干奶期内被采样 3 次。分娩后，在所有乳区泌乳的第一周内采集初乳和每日奶样。总共有 8 个乳区似乎被定植，因为在实验过程中至少有一次回收了 S. chromogenes IM，这通过多位点序列分型得到了证实。用 10000000CFU 接种的干乳区的 S. chromogenes IM 脱落量最高。定植的乳区在泌乳早期的乳区体细胞计数（qSCC）最高。接种的乳区（定植和非定植）在干奶期的 IL-6 和 IL-10 浓度较低，而 IFN-γ 水平在定植乳区与非接种乳区相比往往较高。此外，与非接种乳区相比，接种乳区的 IgG2 水平较高，IgG2/IgG1 比值平均高于 1。总之，我们表明，干乳区可以被 S. chromogenes IM 定植，导致在妊娠晚期和泌乳早期向 Th1 反应转变，其特征是 IgG2 浓度增加。然而，需要进一步的研究来证实我们的发现。
