Impact of probiotic culture combinations on the survival and population dynamics of Clostridioides difficile in white cheese during manufacture and ripening.

چکیده اصلی

White brined cheeses can provide a suitable environment for the persistence of spore-forming bacteria such as Clostridioides difficile. This study examined the behaviour of C. difficile during the controlled manufacture and 90-day ripening of laboratory-scale white brined cheeses and assessed the inhibitory effects of two probiotic combinations. After pasteurization, C. difficile spores were inoculated into designated batches, while two formulations previously shown to suppress the pathogen in vitro (commercial probiotic + isolate 43; YF-L901 + isolate 33) were added to separate groups. Physicochemical and microbiological parameters were monitored throughout ripening. Six experimental white-brined cheese groups were produced, consisting of rennet-only control cheeses with and without Clostridioides difficile inoculation, as well as probiotic-containing cheeses prepared with two different culture combinations under both inoculated and non-inoculated conditions. In the rennet-only batch containing C. difficile, counts decreased from 6.54 to 5.00 log CFU/g by day 90. C. difficile counts declined from 5.61 to 4.20 log CFU/g in cheeses containing the commercial probiotic + isolate 43, and from 5.54 to 4.38 log CFU/g in those with YF-L901 + isolate 33. Probiotic-supplemented cheeses also showed stronger lactic acid bacteria development, confirming successful colonisation of the cheese matrix. Although typical ripening changes in pH, moisture and salt were observed, these factors alone did not account for the reductions in C. difficile. Overall, probiotic-containing cheeses exhibited a more pronounced decline in C. difficile than the non-probiotic control. These results indicate that inhibition may be influenced not only by acidification but also by broader microbial interactions associated with the added cultures.

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