title: The microbial content of raw and pasteurized cow milk as determined by molecular approaches.
abstract: The microbial composition of raw and pasteurized milk is assessed on a daily basis. However, many such tests are culture-dependent, and, thus, bacteria that are present at subdominant levels, or that cannot be easily grown in the laboratory, may be overlooked. To address this potential bias, we have used several culture-independent techniques, including flow cytometry, real-time quantitative PCR, and high-throughput DNA sequencing, to assess the microbial population of milk from a selection of commercial milk producers, pre- and postpasteurization. The combination of techniques employed reveals the presence of a previously unrecognized and diverse bacterial population in unpasteurized cow milk. Most notably, the use of high-throughput DNA sequencing resulted in several bacterial genera being identified in milk samples for the first time. These included Bacteroides, Faecalibacterium, Prevotella, and Catenibacterium. Our culture-independent analyses also indicate that the bacterial population of pasteurized milk is more diverse than previously appreciated, and that nonthermoduric bacteria within these populations are likely to be in a damaged, nonculturable form. It is thus apparent that the application of state-of-the-art approaches can provide a detailed insight into the bacterial composition of milk and could potentially be employed in the future to investigate the factors that influence the composition of these populations.
authors.affiliation: Teagasc Food Research Centre, Moorepark, Fermoy, Cork, Ireland.
authors.forename: Lisa
authors.initials: L
authors.lastname: Quigley
authors.forename: Robert
authors.initials: R
authors.lastname: McCarthy
authors.forename: Orla
authors.initials: O
authors.lastname: O'Sullivan
authors.forename: Tom P
authors.initials: TP
authors.lastname: Beresford
authors.forename: Gerald F
authors.initials: GF
authors.lastname: Fitzgerald
authors.forename: R Paul
authors.initials: RP
authors.lastname: Ross
authors.forename: Catherine
authors.initials: C
authors.lastname: Stanton
authors.forename: Paul D
authors.initials: PD
authors.lastname: Cotter
mesh_terms: D000818:Animals; D002417:Cattle; D005434:Flow Cytometry / Q000379:methods; D059014:High-Throughput Nucleotide Sequencing / Q000379:methods; D008892:Milk / Q000737:chemistry / Q000382:microbiology*; D061352:Pasteurization / Q000592:standards*; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods
keywords: flow cytometry; high-throughput DNA sequencing; quantitative PCR