Colonization and local host response following intramammary Staphylococcus chromogenes challenge in dry cows

Abstract

Although extensive research has been performed on bovine non-aureus staphylococci (NAS), several aspects such as bacteria-host interaction remain largely unstudied. Moreover, only a few mastitis pathogen challenge studies in cows have been conducted in the dry period, an important period that allows intramammary infection (IMI) to cure and new IMI to occur. We challenged 16 quarters of 4 Holstein Friesian cows at dry off with 100; 100 000 or 10 000 000 CFU of the udder-adapted S. chromogenes IM strain. Four quarters from one cow served as negative controls. Internally sealed quarters remained untouched, whereas non-sealed quarters were sampled 3 times during the dry period. After parturition, colostrum and daily milk samples were taken during the first week of lactation of all quarters. In total, 8 quarters appeared to be colonized, since S. chromogenes IM was recovered at least once during the experiment, as substantiated using Multilocus Sequence Typing. S. chromogenes IM shedding was highest in dry quarters inoculated with 10 000 000 CFU. Colonized quarters had the highest quarter somatic cell count (qSCC) in early lactation. Inoculated quarters (both colonized and non-colonized) had lower IL-6 and IL-10 concentrations in the dry period, whilst IFN-γ levels tended to be higher in colonized quarters compared to non-inoculated quarters. Also, IgG2 levels were higher in inoculated compared to non-inoculated quarters and the IgG2/IgG1 ratio was on average above 1. To conclude, we showed that dry quarters can be colonized with S. chromogenes IM, resulting in a shift towards a Th1 response in late gestation and early lactation characterised by an increased IgG2 concentration. However, further research is needed to confirm our findings.

Priming of the murine mammary gland with Staphylococcus chromogenes IM reduces bacterial growth of Streptococcus uberis: a proof-of-concept study

“…On the other hand, our research also revealed the limits of S. chromogenes IM as a potential priming agent against S. uberis mastitis. Likewise observed in dairy cows [ 13 ], S. chromogenes IM induces mastitis in the murine mammary gland. Indeed, the observed influx of polymorphonuclear immune cells and significantly increased levels of proinflammatory mediators IL-8 and LCN2 support this latter statement.…”

“…These effects have been related to bacterial secreted mediators such as bacteriocins and other potentially beneficial mechanisms such as priming of the immune system [ 9 , 11 ]. We previously showed that S. chromogenes IM, a bovine-derived mastitis strain, is able to (i) inhibit the in vitro growth of major mastitis pathogens including S. uberis and (ii) colonize the bovine mammary gland in vivo [ 12 , 13 ]. To better understand whether priming the mammary gland with S. chromogenes IM inhibits the growth of S. uberis , mouse experiments were hereafter conducted in which S. chromogenes IM-primed murine mammary glands were challenged with S. uberis .…”

“…As expected, no bacteria were isolated from the sham-sham inoculated group. Confirmation of the retrieved bacterial species after plating serial dilutions of the mammary gland homogenates on Columbia blood agar (5% defibrinated sheep blood) was done by MALDI-ToF MS as described by our group (data not shown) [ 13 ]. Plating on this agar allowed to distinguish S. uberis from S. chromogenes based on colony morphology.…”

“…In the specific case of bovine mastitis, recent insights are suggesting the use of bovine NAS to prime the mammary gland and prevent infection by major mastitis pathogens [ 8 , 9 , 11 ]. In this proof-of-concept study, priming of the mammary gland with S. chromogenes IM, a NAS strain previously characterized and used by our groups in multiple in vitro and in vivo studies [ 5 – 7 , 12 , 13 , 19 ], was investigated to counteract mastitis caused by the major mastitis pathogen S. uberis in a mouse mastitis model [ 14 , 15 ]. First, the inoculum dose and priming potential of the murine mammary gland by this specific NAS strain were studied.…”

Novel Quantitative Assay to Describe In Vitro Bovine Mastitis Bacterial Pathogen Inhibition by Non-aureus Staphylococci

“…In that respect, NAS might provide protection against intramammary infection (IMI) with major mastitis bacterial pathogens [13,14]. Over the years, our research group has reported multiple findings substantiating, to some extent, the latter concept [15][16][17][18][19][20].…”