Infections of the udder by Escherichia coli very often elicit acute inflammation, while Staphylococcus aureus infections tend to cause mild, subclinical inflammation and persistent infections. The molecular causes underlying the different disease patterns are poorly understood. We therefore profiled the kinetics and extents of global changes in the transcriptome of primary bovine mammary epithelial cells (MEC) after challenging them with heat-inactivated preparations of E. coli or S. aureus pathogens. E. coli swiftly and strongly induced an expression of cytokines and bactericidal factors. S. aureus elicited a retarded response and failed to quickly induce an expression of bactericidal factors. Both pathogens induced similar patterns of chemokines for cell recruitment into the udder, but E. coli stimulated their synthesis much faster and stronger. The genes that are exclusively and most strongly upregulated by E. coli may be clustered into a regulatory network with tumor necrosis factor alpha (TNF-␣) and interleukin-1 (IL-1) in a central position. In contrast, the expression of these master cytokines is barely regulated by S. aureus. Both pathogens quickly trigger an enhanced expression of IL-6. This is still possible after completely abrogating MyD88-dependent Toll-like receptor (TLR) signaling in MEC. The E. coli-specific strong induction of TNF-␣ and IL-1 expression may be causative for the severe inflammatory symptoms of animals suffering from E. coli mastitis, while the avoidance to quickly induce the synthesis of bactericidal factors may support the persistent survival of S. aureus within the udder. We suggest that S. aureus subverts the MyD88-dependent activation of immune gene expression in MEC.

BackgroundColiform bacteria are the most common etiologic agents in severe mastitis of cows. Escherichia coli infections are mostly restricted to a single udder quarter whereas neighboring quarters stay clinically inapparent, implicating the presence of a systemic defense reaction. To address its underlying mechanism, we performed a transcriptome study of mammary tissue from udder quarters inoculated with E. coli (6 h and 24 h post infection), from neighboring quarters of the same animals, and from untreated control animals.ResultsAfter 6 h 13 probe sets of differentially expressed genes (DEG) were detected in infected quarters versus control animals. Eighteen hours later 2154 and 476 DEG were found in infected and in neighboring quarters vs. control animals. Cluster analysis revealed DEG found only in infected quarters (local response) and DEG detected in both infected and neighboring quarters (systemic response). The first group includes genes mainly involved in immune response and inflammation, while the systemic reaction comprises antigen processing and presentation, cytokines, protein degradation and apoptosis. Enhanced expression of antimicrobial genes (S100A8, S100A9, S100A12, CXCL2, GNLY), acute phase genes (LBP, SAA3, CP, BF, C6, C4BPA, IF), and indicators of oxidative stress (GPX3, MT1A, MT2A, SOD2) point to an active defense reaction in infected and neighboring healthy quarters. Its early onset is indicated by increased transcription of NFIL3 at 6 h. NFIL3 is a predicted regulator of many genes of the systemic response at 24 h. The significance of our transcriptome study was evidenced by some recent findings with candidate gene based approaches.ConclusionsThe discovery and holistic analysis of an extensive systemic reaction in the mammary gland significantly expands the knowledge of host-pathogen interactions in mastitis which may be relevant for the development of novel therapies and for genetic selection towards mastitis resistance.

Zusammenfassung Gegenstand und Ziel Darstellung der Untersuchungsergebnisse von 150 Abortfällen beim Rind aus dem Jahr 2018 (Januar–September). Material und Methoden Je nach Einsendematerial und Anforderung erfolgten serologische, bakteriologische und/oder molekularbiologische Untersuchungen zum Nachweis von in Österreich anzeigepflichtigen und nicht anzeigepflichtigen Aborterregern. Ergebnisse Neben rein tierpathogenen Infektionserregern konnten bei je 1 Tier Brucella melitensis, Salmonella Dublin und bei 2 Feten Coxiella burnetii nachgewiesen werden. Schlussfolgerung Die Ergebnisse zeigen, dass im Zusammenhang mit Aborten immer eine besondere Sorgfaltspflicht hinsichtlich Schutz der exponierten Person (Landwirt, Tierarzt, Laborpersonal) erforderlich ist. Auch mit dem Wiederauftreten von lange nicht mehr aufgetretenen Tierseuchen ist jederzeit zu rechnen, wie aus dem aktuellen Brucella-Nachweis ersichtlich wird. Klinische Relevanz Wichtigste Voraussetzung für eine hohe Aufklärungsrate bei infektiös bedingten Aborten stellt die Wahl des geeigneten Probenmaterials dar, nämlich Fetus mit Plazenta und maternale Blutproben. Aufgrund des großen Erregerspektrums ist die Abortdiagnostik umfangreich und aufwendig.