Growth of methicillin-resistant Staphylococcus aureus during raw milk soft cheese-production and the inhibitory effect of starter cultures

• Published in: Food microbiology Vol. 119; p. 104451
• Main Authors: Wörmann, M.E., Pech, J., Reich, F., Tenhagen, B.-A., Wichmann-Schauer, H., Lienen, T.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.05.2024
• Subjects: Agar; Animals; Cheese - analysis; Cheese-production; Food Microbiology; Lactococcus lactis - physiology; Methicillin-Resistant Staphylococcus aureus; Milk; MRSA; Raw milk; Staphylococcus aureus; Starter culture; Raw milk; Starter culture; Cheese-production; MRSA
• ISSN: 0740-0020; 1095-9998
• DOI: 10.1016/j.fm.2023.104451

The consumption of raw milk or raw milk products might be a potential risk factor for the transmission of methicillin-resistant Staphylococcus aureus (MRSA). Therefore, we studied MRSA growth during raw milk soft cheese-production. Furthermore, we investigated the inhibitory effect of four starter cultures (Lactococcus lactis, Lacticaseibacillus rhamnosus, Lactiplantibacillus plantarum, Lactobacillus helveticus) on the growth of MRSA in a spot-agar-assay and in raw milk co-culture following a cheesemaking temperature profile. During the initial phases of raw milk cheese-production, MRSA counts increased by 2 log units. In the ripening phase, MRSA counts only dropped slightly and remained high up to the end of the storage. Comparable MRSA counts were found in the rind and core and strain-specific differences in survival were observed. In the spot-agar-assay, all four starter cultures showed strong or intermediate inhibition of MRSA growth. In contrast, in raw milk, only Lactococcus lactis strongly inhibited MRSA, whereas all other starter cultures only had minor inhibitory effects on MRSA growth. Our results indicate that MRSA follow a similar growth pattern as described for other S. aureus during raw milk soft cheese-production and illustrate the potential use of appropriate starter cultures to inhibit MRSA growth during the production of raw milk cheese. •MRSA counts increased 2 log units after 22 h of cheesemaking.•MRSA growth in raw milk cheese was strain-dependent.•Four starter cultures inhibited MRSA growth in laboratory media.•One starter culture had a strong inhibitory effect against MRSA in raw milk.