Characterization of microflora in Latin-style cheeses by next-generation sequencing technology

Authors

Tina S. Lusk, Oak Ridge Institute for Science and Education, Oak Ridge, TN
Andrea R. Ottesen, US Food and Drug Administration, College Park, MD
James R. White, University of Maryland
Marc W. Allard, US Food and Drug Administration, College Park, MD
Eric W. Brown, US Food and Drug Administration, College Park, MDFollow
Julie A. Kase, George Washington University

Document Type

Journal Article

Publication Date

11-7-2012

Journal

BMC Microbiology

Volume

Volume 12, Issue 254

Keywords

Biodiversity; Cheese--microbiology; High-Throughput Nucleotide Sequencing--methods; Metagenomics--methods

Abstract

Background

Cheese contamination can occur at numerous stages in the manufacturing process including the use of improperly pasteurized or raw milk. Of concern is the potential contamination by Listeria monocytogenes and other pathogenic bacteria that find the high moisture levels and moderate pH of popular Latin-style cheeses like queso fresco a hospitable environment. In the investigation of a foodborne outbreak, samples typically undergo enrichment in broth for 24 hours followed by selective agar plating to isolate bacterial colonies for confirmatory testing. The broth enrichment step may also enable background microflora to proliferate, which can confound subsequent analysis if not inhibited by effective broth or agar additives. We used 16S rRNA gene sequencing to provide a preliminary survey of bacterial species associated with three brands of Latin-style cheeses after 24-hour broth enrichment.

Results

Brand A showed a greater diversity than the other two cheese brands (Brands B and C) at nearly every taxonomic level except phylum. Brand B showed the least diversity and was dominated by a single bacterial taxon, Exiguobacterium, not previously reported in cheese. This genus was also found in Brand C, although Lactococcus was prominent, an expected finding since this bacteria belongs to the group of lactic acid bacteria (LAB) commonly found in fermented foods.

Conclusions

The contrasting diversity observed in Latin-style cheese was surprising, demonstrating that despite similarity of cheese type, raw materials and cheese making conditions appear to play a critical role in the microflora composition of the final product. The high bacterial diversity associated with Brand A suggests it may have been prepared with raw materials of high bacterial diversity or influenced by the ecology of the processing environment. Additionally, the presence ofExiguobacterium in high proportions (96%) in Brand B and, to a lesser extent, Brand C (46%), may have been influenced by the enrichment process. This study is the first to define Latin-style cheese microflora using Next-Generation Sequencing. These valuable preliminary data will direct selective tailoring of agar formulations to improve culture-based detection of pathogens in Latin-style cheese.

Comments

Reproduced with permission of BioMedCentral Microbiology

Creative Commons License

This work is licensed under a Creative Commons Attribution 3.0 License.

APA Citation

Lusk, T.S., Ottesen, A.R., White, J.R., Allard, M.W., Brown, E.W. & Kase, J.A. (2012). Characterization of microflora in Latin-style cheeses by next-generation sequencing technology. BMC Microbiology; 12(254).

Peer Reviewed

1

Open Access

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