Abstract
Mastitis remains a major infection of dairy cows and an important issue for dairy farmers and the dairy industry, in particular infections due to Escherichia coli strains. So far, properties specific to E. coli causing mastitis remain ill defined. In an attempt to better understand the properties required for E. coli to trigger mastitis, we used a range of in vitro assays to phenotypically characterize four E. coli strains, including the prototypical E. coli mastitis strain P4, possessing different relative abilities to cause mastitis in a mouse model. Our results indicate that a certain level of serum resistance might be required for colonization of the mammary gland. Resistance to neutrophil killing is also likely to contribute to a slower clearance of bacteria and higher chances to colonize the udder. In addition, we show that the four different strains do induce a pro-inflammatory response by mammary epithelial cells but with different intensities. Interestingly, the prototypical mastitis strain P4 actually induces the less intense response while it is responsible for the most severe infections in vivo. Altogether, our results suggest that different strategies can be used by E. coli strains to colonize the mammary gland and cause mastitis.
Highlights
IntroductionClinical forms of mastitis are characterized by the inflammation of the udder, impairing mammary cell functions
In dairy cattle worldwide, mastitis remains a major issue
Lesions were scored as 0 to 4
Summary
Clinical forms of mastitis are characterized by the inflammation of the udder, impairing mammary cell functions. As a consequence, it constitutes a threat for the health of cows. Considering on the one hand the treatment costs to cure the disease, and on the other hand a shortfall in milk production, mastitis is a major source of financial losses for the dairy farmers. Mastitis results in most cases from the invasion of the udder by bacteria. E. coli reduces milk production yields, at most it can cause severe dysfunction of the udder and can sometimes lead to the death of the animal [1]
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