Host–pathogen gene expression profiles during infection of primary bovine mammary epithelial cells with Escherichia coli strains associated with acute or persistent bovine mastitis

Escherichia coli intramammary infection (IMI) is often acute with local and systemic clinical manifestations that clear within 7 days. However, if not diagnosed early and treated, E. coli IMI could result in generalized systemic reaction and death. Persistent E. coli IMI is characterized by mild clinical manifestations followed by acute episodes of clinical mastitis during lactation. Factors responsible for pathogenesis of E. coli IMI and variation in clinical manifestations are not known. There are studies indicating that the outcome of E. coli IMI is mainly determined by cow factors. However, recent research demonstrated that virulence attributes of E. coli strains have significant impact on the outcome of E. coli IMI. The aims of this study were; (a) to compare gene expression profiles of PBMEC cocultured with strains of E. coli associated with acute or persistent IMI and; (b) to identify genes of E. coli induced during bacterial interaction with PBMEC. Utilizing cDNA we analyzed gene expression patterns of PBMEC cocultured with strains of E. coli using non-treated PBMEC as negative control. We evaluated also expression patterns of virulence associated genes of E. coli after co-culture with PBMEC using qRT-PCR. Our results showed that infection by both strains induced increased expression of pro-inflammatory cytokines, chemokines and innate immune response and apoptosis related genes. Our qRT-PCR results showed significant up-regulation of ler, eae, flic and iutA genes mainly in the strains of E. coli associated with persistent IMI. The pathogenesis and clinical severity of E. coli IMI may be determined by combined effects of host–pathogen factors.