Inhibition ofListeria monocytogenesby a formulation of selected dairy starter cultures and probiotics in anin vitromodel

Abstract

Three strains of lactic acid bacteria (LAB) and a commercial probiotic were selected to evaluate their in vitro activity towards Listeria monocytogenes. The strains Lactococcus lactis ssp. lactis, strain 340, L. lactis ssp. lactis, strain 16; Lactobacillus casei ssp. casei, strain 208 and Enterococcus faecium UBEF-41 were inoculated into skim milk and brain heart infusion broth (BHI) to get an initial Lactococcus: Lactobacillus: E. faecium UBEF-41 ratio of 2:1:1 and a concentration of approximately 7 log cfu mL À1 until challenge vs. pathogen. L. monocytogenes ATCC 7644 was also inoculated in same media to get approximately 4 log cfu mL À1 . Growth curves in skim milk and BHI at 4, 10 and 30 C, respectively were studied for: (i) LAB formulation; (ii) L. monocytogenes and (iii) LAB vs. L. monocytogenes. When challenged with LAB, at 30 C in milk, L. monocytogenes was not detectable after day-3 and in BHI it decreased below log cfu mL À1 after day-5. At 10 and 4 C, in both media, L. monocytogenes counts were always significantly lower (p < .001) than the counts of L. monocytogenes alone from day-2 for milk at 4 C and BHI at 10 C and from day-7 for BHI at 4C and milk at 10 C. In conclusion, the proposed formulation was able to limit L. monocytogenes in vitro growth, even at refrigeration temperature. ARTICLE HISTORY

Quality of traditionally produced Istrian sausage and identification of autochthonous lactic acid bacteria strains as potential functional starter cultures

“…1). In fact, all strains were able to inhibit Listeria cells due to acid production (data not shown) which is in line with findings of Iulietto et al [53]. As the presence of E. coli was recorded on ripening day 21 in sample A, the strong inhibitory effect of the strains on E. coli 3014, with the percentage of survival lower than 20%, should be highlighted.…”

“…The nondissociated form of lactic acid induces intracellular pH decrease, thus causing collapse of the proton electrochemical gradient in susceptible bacteria, resulting in its bacteriostatic or bactericidal action. In addition, antimicrobial peptides bacteriocins are also commonly produced among Lactobacillus species with the antagonistic activity, mostly against phylogenetically related bacteria [11,[53][54][55][56]. Casaburi et al [57] isolated the bacteriocin-producing L. curvatus 54M16 strain considered to be an appropriate starter culture during fermented sausage ripening to improve the quality and safety of traditional fermented sausages prepared without the addition of antimicrobials.…”

Searching potential candidates for development of protective cultures: Evaluation of two Lactobacillus strains to reduce Listeria monocytogenes in artificially contaminated milk

“…These results demonstrated that the minimum lactobacilli concentration required to reduce listerial growth in whole milk was 10 6 CFU ml −1 . Although the antilisterial activity of Lactobacillus strains has been previously reported in milk and other dairy products (Ehsani et al, ; Iulietto et al, ), the determination of the minimum concentration of lactobacilli required to reduce listerial growth in milk has not been previously studied. Our findings partially agreed with a previous report carried out by Pujato et al (), where the antilisterial effect of another LAB strain was evaluated.…”

“…Currently, there is very scarce information on the antilisterial activity produced by Lactobacillus spp. specifically tested in milk (Iulietto et al, ; Millette, Luquet, & Lacroix, ). In those few reports, lactobacilli strains, originally isolated from milk and dairy products, were conveniently evaluated in milk with low fat content to test their in situ antilisterial activity.…”

Behavior of Listeria monocytogenes during the Shelf-life of Fresh Refrigerated Pesto Sauce, According to Regulation (EU) 2073/2005 and Subsequent Amendments

“…However, the growth dynamics of the pathogen, highlighted in the study, indicate that the sauce does not represent a favourable substrate for the development of the microorganism during the shelf-life at the tested storage temperatures (δ <0.5 log CFU/g) [10]. It could be supposed a competitive action against L. monocytogenes from the naturally present microbiota consisting of lactic acid bacteria and yeasts which can grow in the product during its shelf-life, as reported by numerous scientific studies [21][22][23][24].…”