Interaction between milk composition and bacterial growth

Topic 1. Faster identification of bacteria in milk by using headspace-GC/MS.

Mastitis is an inflammation of the mammary gland. Although mastitis can have different origins, it is most often associated with bacterial infections. Mastitis is the most costly disease of dairy cows. In The Netherlands, the average costs of a clinical mastitis case are estimated between €168 and €277 depending mainly on stage of lactation (Hogeveen, 2005). A range of more than 140 microorganisms may cause mastitis in cows. However, a limited group of 5 bacteria (Staphylococcus aureus, coagulasenegative staphylococci, Streptococcus uberis, Streptococcus dysgalactiae, and Escherichia coli) is responsible for approximately 80% of the Dutch mastitis cases in which bacteria could be cultured from the milk (Barkema et al., 1998; Sampimon et al., 2008).
Milk from cows with mastitis is often analyzed using bacteriological culturing to detect the pathogens causing the mastitis. Determination of mastitis causing pathogens is of great interest, both for choice of treatment of the cow as well as for possible measures that have to be taken on the farm to prevent the spread of mastitis. Bacteriological culturing, however, has the disadvantage of being time-consuming. A faster and more accurate method of pathogen identification is thus advantageous, because farmers are earlier able to choose an optimal treatment at the cow and the herd level.
Within the Dairy Science and Technology research group within the Food Quality and Design chair, several approaches for better identification of mastitis pathogens are tested, mainly using advanced GC/MS- or NMR-based metabolomic approaches. These methods may facilitate faster diagnosis of cows with mastitis, which should lead to more optimized antibiotic treatments of these cows, and in the end also the reduction of antibiotics use.

Aim

Several research questions may be suitable for thesis students within the above described framework:

• What is the effect of the presence of multiple pathogens in one sample on fast diagnostic methods?
• Can we add components to increase the rate of metabolite formation to further speed up the method?
• Potential to detect other (non-mastitis related) bacteria in milk with the previously developed methods?

For more information on this topic please contact Kasper Hettinga.