e. when yeasts on cheese BIIB057 manufacturer surface had reached high counts of 6.5 ± 0.2 × 106 CFU cm-2. From the amount added to the smear brine (5 × 103 CFU ml-1), Listeria counts of 1.4 ± 0.9 × 101 CFU cm-2 (first trial) and of 1.0 ± 0.6 × 102 CFU cm-2 (repetition) were recovered from the surface immediately after contamination. Listeria development was strongly affected by the surface flora applied for ripening. A decrease of Listeria counts below the detection limit of the method (< 3 CFU cm-2) was observed
for cheeses treated with complex consortia F or M supplemented with Debaryomyces hansenii selleck chemicals llc FAM14334 (Figure 4). Listeria could be recovered from cheese surface (~2000 cm2) with an enrichment procedure at the end of ripening (60 to 80 days), for both consortia. In contrast,
Listeria counts on control cheeses treated with the commercial culture OMK 704 increased to ca. 105 CFU cm-2 after one month (Figure 4). Figure 4 In situ inhibition of Listeria on cheese surface by complex consortia. Cheese surfaces were treated with smear brines (3.3% (w/v) NaCl), inoculated with either consortium F, consortium M or the defined commercial culture OMK 704 (control cheese). Two independent experiments were carried out for each treatment. Different symbols indicate different commercial cheese production. Smear brines were inoculated with Listeria innocua on day 7 and 8, at 5 × 103 CFU ml-1. Stars indicate times where Listeria counts were below the detection limit of the enumeration method (< 3 CFU cm-2;
dashed line). Discussion AZD9291 clinical trial To our knowledge, this work describes the first dynamic study of naturally developing anti-listerial cheese surface consortia. The monitoring of two complex consortia obtained from industrial productions was carried out with TTGE, a culture independent fingerprinting technique which enabled species-level detection of high-GC and low-GC bacteria in separate runs. Previous studies reported a broad range of biodiversity in smear consortia, with 2 to 15 bacterial species detected [2, 5, 22, 23]. High bacterial diversity was observed in consortium F, with 13 species detected at dominant level by culture independent analysis. The cultivation approach detected only 9 of the 13 species present at dominant level in consortium F, but enabled detection of 6 additional species present CYTH4 at subdominant level. TTGE is a semiquantitative approach with limited sensitivity compared to the cultivation approach. However, as fingerprinting technique, TTGE enabled to overcome the arbitrary selection exercised on the flora by the cultivation step, giving a more complete view of biodiversity at dominant level. The combined use of both approaches led to a detailed knowledge of biodiversity in cheese smear flora, as already observed by Feurer et al. and Mounier et al. [5, 24]. The identification strategy used in the present study for the cultivation approach, i.e.