Population dynamics of two antilisterial cheese surface consortia revealed by temporal temperature gradient gel electrophoresis

Abstract

BackgroundSurface contamination of smear cheese by Listeria spp. is of major concern for the industry. Complex smear ecosystems have been shown to harbor antilisterial potential but the microorganisms and mechanisms involved in the inhibition mostly remain unclear, and are likely related to complex interactions than to production of single antimicrobial compounds. Bacterial biodiversity and population dynamics of complex smear ecosystems exhibiting antilisterial properties in situ were investigated by Temporal temperature gradient gel electrophoresis (TTGE), a culture independent technique, for two microbial consortia isolated from commercial Raclette type cheeses inoculated with defined commercial ripening cultures (F) or produced with an old-young smearing process (M).ResultsTTGE revealed nine bacterial species common to both F and M consortia, but consortium F exhibited a higher diversity than consortium M, with thirteen and ten species, respectively. Population dynamics were studied after application of the consortia on fresh-produced Raclette cheeses. TTGE analyses revealed a similar sequential development of the nine species common to both consortia. Beside common cheese surface bacteria (Staphylococcus equorum, Corynebacterium spp., Brevibacterium linens, Microbacterium gubbeenense, Agrococcus casei), the two consortia contained marine lactic acid bacteria (Alkalibacterium kapii, Marinilactibacillus psychrotolerans) that developed early in ripening (day 14 to 20), shortly after the growth of staphylococci (day 7). A decrease of Listeria counts was observed on cheese surface inoculated at day 7 with 0.1-1 × 102 CFU cm-2, when cheeses were smeared with consortium F or M. Listeria counts went below the detection limit of the method between day 14 and 28 and no subsequent regrowth was detected over 60 to 80 ripening days. In contrast, Listeria grew to high counts (105 CFU cm-2) on cheeses smeared with a defined surface culture.ConclusionsThis work reports the first population dynamics study of complex smear ecosystems exhibiting in situ antilisterial activity. TTGE revealed the presence of marine lactic acid bacteria that are likely related to the strong Listeria inhibition, as their early development in the smear occurred simultaneously with a decrease in Listeria cell count.

Ripening conditions: A tool for the control of Listeria monocytogenes in uncooked pressed type cheese

“…Such inhibition by a complex consortium has also been observed in raw milk versus pasteurised (Gay & Amgar, 2005), in the cores of PDO Saint-Nectaire cheeses (Millet et al, 2006;Saubusse et al, 2007) and also in their rinds (Retureau et al, 2010) and in the rinds of smear cheeses (Maoz et al, 2003;Mayr et al, 2004;Roth et al, 2010).…”

“…An extensive literature is available on the antiListeria activities of individual strains (Garcia, Depaz, Gaya, Edna, & Nunez, 1997;O'Sullivan, Connor, Ross, & Hill, 2006;Motta & Brandelli, 2008) and complex microbial consortia in cheese core (Millet, Saubusse, Didienne, Tessier, & Montel, 2006;Saubusse, Millet, Delbes, Callon, & Montel, 2007) or rind (Gay & Amgar, 2005;Maoz, Mayr, & Sherer, 2003;Retureau, Callon, Didienne, Buchin, & Montel, 2010;Roth, Miesher Schwenninger, Hasler, Eugster-Meier, & Lacroix, 2010). Cheese ripening conditions -temperature, relative humidity and air velocity in the ripening chamber -greatly influence microbial growth and consequently the biochemical and sensorial characteristics of the cheese (Leclerq Perlat, Oumer, Bergere, Spinnler, & Corrieu, 1999;Picque et al 2009;Sihufe et al 2010).…”

Microbial composition of defect smear – A problem evolving during foil-prepacked storage of red-smear cheeses

“…The cell numbers were found to be higher on agar media containing higher concentrations of NaCl than for TGYA plates typically used for the determination of total plate counts (Roth et al, 2010). This might be explained by the adaptation of the respective microorganisms to the salty cheese environment (Roth et al, 2010).…”

“…and Marinilactibacilllus spp. known as facultative anaerobic halophilic and alkaliphilic bacteria (FAHA) have been detected on cheese surface (Feurer, Irlinger, Spinnler, Glaser, & Vallaeys, 2004;Ishikawa et al, 2007;Roth, Schwenninger, Eugster-Meier, & Lacroix, 2011;Roth et al, 2010). Gram-positive bacteria belonging to the genus Arthrobacter, Brachybacterium, Brevibacterium, Corynebacterium, Microbacterium, Micrococcus and Staphylococcus represent desired smear microorganisms, whereas enterococci that are frequently found in cheese smear are assumed to represent hygiene indicators (Brennan et al, 2004).…”

“…The cheese smear is a complex microbial ecosystem evolved through a dynamic process started by de-acidification of the cheese surface through yeast growth and metabolism, followed by the colonization with bacterial populations, mainly coagulase-negative staphylococci and coryneform bacteria including Micrococcaceae, Brevibacteriaceae and Corynebacteriaceae (Brennan et al, 2004;Roth, Schwenninger, Hasler, Eugster-Meier, & Lacroix, 2010). Also marine bacteria like Facklamia spp.…”