Non-S. aureus staphylococci (NAS) are the most frequently isolated pathogens from bovine milk and can cause intramammary infections (IMI). They can also be found in teat canals, on bovine skin and in cows' environment, which may lead to unnoticed contamination of milk samples. The aim of this study was to investigate the role of NAS species as mastitis-causing pathogens or contaminants, and to identify possible differences between NAS species. A longitudinal study was conducted with consecutive milk sampling in five German dairy herds. Species identification was performed using matrix-assisted laser desorption ionization-time of flight mass spectrometry. Infections were distinguished from contaminations using two different definitions based on the repeated detection of an NAS species. Of 15 NAS species found, eight and ten, respectively, were associated with an IMI. Staphylococcus simulans and S. chromogenes were associated with IMI in more than 90 % of the findings. S. warneri, S. xylosus, S. microti, S. haemolyticus, and S. succinus seem to be frequent causes of IMI as well as contaminants. If a species-differentiation is available after cultivating NAS, the findings should be interpreted in consideration of the observations made in this study, whether it is more likely a question of a contaminant or a cause of intramammary infection. The bacteria shedding intensity of the NAS species with a more substantially adverse effect on udder health seems to be higher than that of the less important NAS pathogens.

中文翻译：

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非S。牛奶样品中的金黄色葡萄球菌（NAS）：感染或污染？

非S。金黄色葡萄球菌（NAS）是从牛乳中最常见的病原体，可引起乳内感染（IMI）。它们还可以在乳头渠，牛皮肤和奶牛的环境中发现，这可能导致牛奶样品被无意污染。这项研究的目的是调查NAS物种作为引起乳腺炎的病原体或污染物的作用，并确定NAS物种之间的可能差异。进行了一项纵向研究，对五个德国奶牛场进行了连续的牛奶采样。使用基质辅助激光解吸电离飞行时间质谱进行物种鉴定。根据对NAS物种的重复检测，使用两种不同的定义将感染与污染区分开来。在发现的15种NAS物种中，分别有8种和10种，与IMI相关联。在超过90％的发现中，葡萄球菌模拟物和发色链球菌与IMI相关。Warneri，S。xylosus，S。microti，S。haemolyticus和S. succinus似乎是IMI和污染物的常见原因。如果在培养NAS后可以进行物种分化，则应考虑本研究中的观察结果来解释研究结果，是否更可能是污染物问题或乳房内感染的原因。NAS物种的细菌散发强度对乳房健康产生更大的负面影响，似乎比不太重要的NAS病原体更高。溶血性葡萄球菌和琥珀酵母似乎是IMI和污染物的常见原因。如果在培养NAS后可以进行物种分化，则应考虑本研究中的观察结果来解释研究结果，是否更可能是污染物问题或乳房内感染的原因。NAS物种的细菌散发强度对乳房健康产生更大的负面影响，似乎比不太重要的NAS病原体更高。溶血性葡萄球菌和琥珀酵母似乎是IMI和污染物的常见原因。如果在培养NAS后可以进行物种分化，则应考虑本研究中的观察结果来解释研究结果，是否更可能是污染物问题或乳房内感染的原因。NAS物种的细菌散发强度对乳房健康产生更大的负面影响，似乎比不太重要的NAS病原体更高。