Experimental challenge of bovine mammary glands with Enterococcus faecium during early and late lactation

Abstract

Mammary glands of early and late lactation cows were challenged with Enterococcus faecium of bovine origin to determine in vivo pathogenicity and milk somatic cell count (SCC) responses. A total of 20 early lactation and 18 late lactation mammary glands were challenged. Two isolates highly adaptive and 2 isolates poorly adaptive for in vitro growth in mammary secretion were used as challenge strains of bacteria. Challenged quarters of early lactation cows were more susceptible to intramammary infection caused by E. faecium than those of late lactation cows. Intramammary challenge with isolates poorly adaptive for in vitro growth in mammary secretions resulted in 94.7% of quarters infected compared with 36.8% of the quarters infused with the isolates highly adaptive for in vitro growth in mammary secretions. Milk from quarters infused with the isolates poorly adaptive for in vitro growth had higher SCC and bacterial counts compared with quarters challenged with the isolates highly adaptive for in vitro growth. A stage of lactation effect within treatment groups was measured when milk SCC were compared between early and late lactation cows. Milk SCC in uninfused (negative control) quarters were lower in early lactation cows compared with late lactation cows. Conversely, in quarters infused with isolates poorly adaptive for in vitro growth, SCC were higher in early lactation cows compared with late lactation cows on d 2, 3, 4, 15, 16, and 17 postchallenge. In quarters infused with isolates highly adaptive for in vitro growth, SCC response did not differ between early and late lactation cows. In vitro growth of E. faecium in mammary secretion was inversely related to in vivo pathogenicity in the mammary glands of early and late lactation cows.

An update on environmental mastitis: Challenging perceptions

“…There is, however, no obvious association between outcome of infection and gene content (Hossain et al., ). Strain‐specific virulence has also been documented for E. faecium (Petersson‐Wolfe et al., ). Potential virulence genes underpinning such differences have not been studied in enterococci, but the genomic tools that have been developed to study virulence factors of S. uberis mastitis could provide insight into the functional genomics of other GPCN species (Blanchard et al., ).…”

“…Both misnomers cover streptococci, enterococci and lactococci, among others. The major streptococci are S. uberis and Streptococcus dysgalactiae , the major enterococci are Enterococcus faecium and Enterococcus faecalis , and the main lactococci are Lactococcus lactis and Lactococcus garvieae (Cameron et al., ; Petersson‐Wolfe, Wolf, & Hogan, ). The role of enterococci as causative agents of mastitis has long been recognized whereas Lactococcus spp., previously studied as potential tools in mastitis prevention or treatment, have only recently been recognized as mastitis pathogens in their own right (Plumed‐Ferrer et al., ; Rodrigues et al., ).…”

“…Potential virulence genes underpinning such differences have not been studied in enterococci, but the genomic tools that have been developed to study virulence factors of S. uberis mastitis could provide insight into the functional genomics of other GPCN species (Blanchard et al., ). As for coliforms, host characteristics affect the outcome of GPCN infections: cows in early lactation responded differently to E. faecium challenge than those in late lactation, and a S. uberis strain that largely failed to cause infection in mid‐lactation animals had been isolated from CM at parturition (Petersson‐Wolfe et al., ; Tassi et al., ). In vitro, macrophages from dry cow secretion are more active against S. uberis than those from mid‐lactation cows, even though S. uberis infections commonly occur in the dry period (Denis et al., ).…”

A Critical Appraisal of Probiotics for Mastitis Control

“…Thus, the absence of an MEC response to LAB, as established in vitro in a screening test for harmless bacteria, may not predict an absence of a response in vivo . In fact, S. uberis, Enterococcus spp., and Lactococcus lactis are MG pathogens that are able to induce clinical mastitis when inoculated ( 20 , 54 , 59 ).…”

Characterization of an Enterococcus faecium strain in a murine mastitis model

“…To the best of our knowledge, there is limited information available on E. faecium as mastitis agent (Petersson‐Wolfe et al ). Furthermore, different studies have been assayed using murine models.…”