Mehrzad J, Duchateau L, Burvenich C
Ghent University, Faculty of Veterinary Medicine, Department of Physiology, Biochemistry and Biometrics, Salisburylaan 133, B-9820 Merelbeke, Belgium.
J Dairy Sci. 2004 Dec;87(12):4150-62. doi: 10.3168/jds.S0022-0302(04)73558-4.
To study the host-pathogen interactions during Escherichia coli mastitis, we first determined whether E. coli infection would change blood and milk polymorphonuclear neutrophil (PMN) chemiluminescence (CL) and viability. We then hypothesized that when E. coli invade the mammary gland, the viable PMN in milk would efficiently phagocytose and destroy E. coli before establishment of infection. We observed that the phagocytosis-dependent and independent CL were closely linked to PMN viability and were crucial to the outcome of mastitis. Maximal PMN influx and colony-forming units in infected quarters appeared at postinfection hours (PIH) 6 to 24. This further boosted PMN recruitment through bone marrow-blood barrier as well as blood-milk barrier. The survival of recruited PMN in the E. coli-infected quarters was much higher than that of noninfected quarters. Chemiluminescence activity of PMN from the infected quarters significantly increased following E. coli infection, even exceeding that of blood at PIH 6, 12, and 18 to 24; no such increase was observed in noninfected quarters, suggesting that the various responses of milk PMN to stimuli resulted largely from PMN viability. The highest CL intensity and durability was observed in milk PMN from infected quarters at PIH 12. Whereas an increased viability of PMN in the noninfected quarters was only significant at PIH 6, the viability of PMN in infected quarters was long lasting and significantly higher at PIH 6 to 72. Importantly, higher preinfection milk PMN viability correlated with bacterial clearance, which was accompanied by faster recovery. Our study strongly supports the hypothesis that boosting milk PMN viability could be a strategy with which to prevent or reduce the severity of coliform mastitis in dairy cows. This strategy might be achieved through strengthening bone marrow functionality.
为了研究大肠杆菌性乳腺炎期间的宿主-病原体相互作用，我们首先确定大肠杆菌感染是否会改变血液和乳汁中的多形核中性粒细胞（PMN）的化学发光（CL）及活力。然后我们推测，当大肠杆菌侵入乳腺时，乳汁中存活的PMN会在感染确立之前有效地吞噬并破坏大肠杆菌。我们观察到，依赖吞噬作用和不依赖吞噬作用的CL都与PMN活力密切相关，并且对乳腺炎的结局至关重要。感染乳腺中PMN的最大流入量和菌落形成单位出现在感染后6至24小时。这进一步促进了PMN通过骨髓-血液屏障以及血液-乳汁屏障的募集。募集到的PMN在大肠杆菌感染乳腺中的存活率远高于未感染的乳腺。大肠杆菌感染后，感染乳腺中PMN的化学发光活性显著增加，甚至在感染后6、12以及18至24小时超过了血液中的化学发光活性；在未感染的乳腺中未观察到这种增加，这表明乳汁中PMN对刺激的各种反应很大程度上源于PMN的活力。在感染后12小时，感染乳腺的乳汁中PMN观察到最高的CL强度和持续性。未感染乳腺中PMN活力的增加仅在感染后6小时显著，而感染乳腺中PMN的活力持续时间长，在感染后6至72小时显著更高。重要的是，感染前较高的乳汁PMN活力与细菌清除相关，同时恢复更快。我们的研究有力地支持了这一假说，即提高乳汁中PMN的活力可能是预防或减轻奶牛大肠埃希菌性乳腺炎严重程度的一种策略。这一策略可能通过增强骨髓功能来实现。
