Effect of Lactococcus sp. on the growth of Listeria sp. in the model UHT milk system

Abstract

Abstract:The work was aimed at the growth suppression of cultured listerias strains by cultured lactococci strains or commercial mesophilic cheese cultures during common cultivations in the model UHT milk system (0.5% w/w of milk fat content) at 30°C during 18 h aerobically. Milk was primarily fermented by lactococci at the level of 10 8 CFU/ml and secondarily contaminated by listerias at the level of 10 3 CFU/ml. The most intensive growth suppressions of both Listeria innocua (CCM 5884 or Ln-03) strains were caused by Lactococcus lactis subsp. lactis (LCC 416 or CHCC 2281) strains or DELVO-ADD ® 100-X DSF cheese culture; the listerias growth reductions was from the level of 10 3 CFU/ml to 10 0 CFU/ml. Obtained results should be applied to dairy industry provided that HACCP, GHP and GMP systems must be observed. Bacteria of Listeria genus attract an attention because of the health safety of final products, especially secondarily ripening cheeses, in the dairy industry of the Czech Republic and the European Union (EU). The majority of listerias species are harmless. L. monocytogenes (LM) species is pathogenic for human with 20% of death on listeriosis (Macela et al. 2006). L. ivanovii species is pathogenic just for sheep (Batt 2000). LM represents a facultative intracellular pathogen, which infects hosts by alimentary way (Schech 1983). Raw milk produced in milk farms represents a danger source of LM contamination as long as it is obtained during milking under GMP non-performance. In dairies raw milk is treated by heat with a guarantee LM inactivation. Final products can be secondarily contaminated by LM under conditions of sanitation regimes defaults or production control errors with the assistance of HACCP system. Listerias are able to reproduce at low storage temperatures and because of long incubation period of listeriosis it is difficult to prove whether a final product was contaminated at a producer or at a consumer only. For that reason naturally ways of listerias elimination are found. For example lactic acid bacteria can reduce or inhibit listerias and show rich biochemical activities. KeywordsThere are various products with antilisterial effect on the market of the Czech Republic and the EU. Listex TM P100 is a well-known and described commercial product that contains a virulent strictly lytic phage of P100 type, which shows a high specificity against LM (Carlton 2005).The aim of this work was to check a biochemical potential of lactococci for the reduction of listerias' growth in the model UHT milk system. Cultivation conditions of used strains. Lactococci and cheese cultures were cultivated in M17 broth with lactose (0.5% w/w) (LM17 broth) at 30°C for 18 h aerobically. Listerias were cultivated in BHI broth at 30°C for 18 h aerobically. All strains were also cultivated in UHT milk (0.5% w/w of milk fat content) with/ or without addition of yeast extract (YE) (0.5% w/w) at 30°C for 18 h aerobically. For work were used 1% (v/w) inocula. MATEriAlS And METHodS StrainsEstimation of lactococci and listerias...

Antilisterial activity of lactic acid bacteria against Listeria monocytogenes strains originating from different sources

“…mundtii CCM 1282) were chosen for this study because of their significant potential for the application in fermented dairy technology as biopreservative agents. The antilisterial activity of these strains against non-pathogenic L. innocua, commonly used as indicator strain, was previously confirmed (Kučerová et al 2009;Šviráková et al 2009 (Liu & Hansen 1990) and known as thermostable (Hurst 1981), was not confirmed as the main antilisterial agent for CCDM 416, as was primarily assumed. Probably, the production of another unspecified thermolabile compound is expected.…”

Determination of antilisterial effect of some microbial isolates from traditional zlatar cheese during the fermentation of soft white cheese

“…The antilisterial effect ( L. monocytogenes reductions of 3–4 log10 units in cheese) of the added bacteriocinogenic of L. lactis spp. lactis provides an important biological control potential in cheese production, as evidenced by numerous authors (Šviráková et al ., 2009). The results suggested the potential of using lactococci in cheese production, as part of the mesophilic starter cultures contributing to the biological system of effective control of L. monocytogenes growth.…”