Wörmann Mirka E, Bhatte Ashwini, Wichmann-Schauer Heidi, Tenhagen Bernd-Alois, Lienen Tobias
Department of Biological Safety, German Federal Institute for Risk Assessment, 10589 Berlin, Germany.
Animals (Basel). 2023 Nov 17;13(22):3549. doi: 10.3390/ani13223549.
Methicillin-resistant (MRSA) may cause difficult-to-treat infections in dairy cattle. One possible route of MRSA transmission into calves is via the feeding of contaminated waste milk. We tested the heat resistance of 17 MRSA strains isolated from German dairy farms in colostrum and raw milk in a laboratory approach. Heating colostrum or raw milk at 60 °C for 30 min eliminated all viable MRSA in the milk, provided the MRSA inoculation rate is low (10 cfu mL). In contrast, raw milk highly inoculated with MRSA (10 cfu mL) required a holding time of at least 30 min at 70 °C to fully eliminate MRSA from it. However, quantitative analysis showed that a heat treatment for 10 min at 60 °C already significantly reduced the number of viable MRSA in highly inoculated raw milk. Heating colostrum and raw milk above 60 °C may destroy immunoglobulins which are crucial for the calf's health. Therefore, we suggest that colostrum and raw milk that is to be fed to calves on MRSA-positive dairy farms is heated at 60 °C for at least 10 min to reduce the likelihood of transmitting MRSA. In addition, the 60 °C heat-treated colostrum/raw milk should be fed to the calves as soon as possible to avoid re-growth of viable MRSA.
耐甲氧西林金黄色葡萄球菌（MRSA）可能会在奶牛中引发难以治疗的感染。MRSA传播到犊牛体内的一种可能途径是通过喂食受污染的废乳。我们采用实验室方法测试了从德国奶牛场分离出的17株MRSA菌株在初乳和生乳中的耐热性。如果MRSA接种率较低（10 cfu/mL），将初乳或生乳在60℃加热30分钟可消除乳中的所有存活MRSA。相比之下，接种了高浓度MRSA（10⁶ cfu/mL）的生乳需要在70℃保持至少30分钟才能完全消除其中的MRSA。然而，定量分析表明，在60℃进行10分钟的热处理已能显著减少高接种量生乳中存活的MRSA数量。将初乳和生乳加热到60℃以上可能会破坏对犊牛健康至关重要的免疫球蛋白。因此，我们建议，在MRSA呈阳性的奶牛场，要喂给犊牛的初乳和生乳应在60℃加热至少10分钟，以降低传播MRSA的可能性。此外，经60℃热处理的初乳/生乳应尽快喂给犊牛，以避免存活的MRSA再次生长。
