A standard bacterial isolate set for research on contemporary dairy spoilage

Trmčić, Aljoša; Martin, N.H.; Boor, Kathryn J.; Wiedmann, Martin

doi:10.3168/jds.2015-9490

Cited by 53 publications

(37 citation statements)

References 41 publications

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“…High endospore counts caused by this genus can lead to rejection of milk powder due to presumed poor hygiene (27). Thermophiles such as Anoxybacillus in general can cause product spoilage (29)(30)(31). Like Thermus, Anoxybacillus seems to be relatively well controlled as the relative abundance of this genus was at Ͻ0.8% by 16:00 in all concentration steps, after CIP occurred.…”

Section: Discussionmentioning

confidence: 99%

Viable and Total Bacterial Populations Undergo Equipment- and Time-Dependent Shifts during Milk Processing

Kable

Srisengfa

Xue

et al. 2019

Appl Environ Microbiol

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We set out to identify the viable and total bacterial content in milk as it passes through a large-scale, dairy product manufacturing plant for pasteurization, concentration, separation, blending, and storage prior to cheese manufacture. A total of 142 milk samples were collected from up to 10 pieces of equipment for a period spanning 21 h on two collection dates in the spring and late summer of 2014. Bacterial composition in the milk was determined by 16S rRNA marker gene, highthroughput DNA sequencing. Milk samples from the late summer were paired such that half were treated with propidium monoazide (PMA) to enrich for viable cells prior to quantification by PCR and identification by DNA sequence analysis. Streptococcus had the highest median relative abundance across all sampling sites within the facility on both sampling dates. The proportions of Anoxybacillus, Thermus, Lactococcus, Lactobacillus, Micrococcaceae, and Pseudomonas were also elevated in some samples. Viable cells detected by PMA treatment showed that Turicibacter was enriched after high-temperature short-time pasteurization, whereas proportions of Staphylococcus were significantly reduced. Using clean-in-place (CIP) times as a reference point, Bacillus, Pseudomonas, and Anoxybacillus were found in high relative proportions in several recently cleaned silos (Ͻ19 h since CIP). At later times (Ͼ19 h after CIP), 10 of 11 silos containing elevated viable cell numbers were enriched in Acinetobacter and/or Lactococcus. These results show the tremendous point-to-point and sample-dependent variations in bacterial composition in milk during processing. IMPORTANCE Milk undergoes sustained contact with the built environment during processing into finished dairy products. This contact has the potential to influence the introduction, viability, and growth of microorganisms within the milk. Currently, the population dynamics of bacteria in milk undergoing processing are not well understood. Therefore, we measured for total and viable bacterial composition and cell numbers in milk over time and at different processing points in a cheese manufacturing facility in California. Our results provide new perspectives on the dramatic variations in microbial populations in milk during processing even over short amounts of time. Although some of the changes in the milk microbiota were predictable (e.g., reduced viable cell numbers after pasteurization), other findings could not be easily foreseen based on knowledge of bacteria contained in raw milk or when the equipment was last cleaned. This information is important for predicting and controlling microbial spoilage contaminants in dairy products.

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Section: Discussionmentioning

confidence: 99%

Viable and Total Bacterial Populations Undergo Equipment- and Time-Dependent Shifts during Milk Processing

Kable

Srisengfa

Xue

et al. 2019

Appl Environ Microbiol

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“…Among Rahnella isolates, we also identified a newly classified environmental species, Rahnella inusitata (Brady et al, 2014). This species was previously isolated from a sample of pasteurized milk and was included in our standard bacterial isolate set of dairy spoilage (Trmčić et al, 2015). The strain included in the collection is able to cause a ropy defect in fluid milk most likely through the production of exopolysaccharides.…”

Section: Coliforms Identified In Cheese Include Genera That Benefit Cmentioning

confidence: 99%

Coliform detection in cheese is associated with specific cheese characteristics, but no association was found with pathogen detection

Trmčić

Chauhan

Kent

et al. 2016

Journal of Dairy Science

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Coliform detection in finished products, including cheese, has traditionally been used to indicate whether a given product has been manufactured under unsanitary conditions. As our understanding of the diversity of coliforms has improved, it is necessary to assess whether coliforms are a good indicator organism and whether coliform detection in cheese is associated with the presence of pathogens. The objective of this study was (1) to evaluate cheese available on the market for presence of coliforms and key pathogens, and (2) to characterize the coliforms present to assess their likely sources and public health relevance. A total of 273 cheese samples were tested for presence of coliforms and for Salmonella, Staphylococcus aureus, Shiga toxin-producing Escherichia coli, Listeria monocytogenes, and other Listeria species. Among all tested cheese samples, 27% (75/273) tested positive for coliforms in concentrations >10cfu/g. Pasteurization, pH, water activity, milk type, and rind type were factors significantly associated with detection of coliforms in cheese; for example, a higher coliform prevalence was detected in raw milk cheeses (42% with >10cfu/g) compared with pasteurized milk cheese (21%). For cheese samples contaminated with coliforms, only water activity was significantly associated with coliform concentration. Coliforms isolated from cheese samples were classified into 13 different genera, including the environmental coliform genera Hafnia, Raoultella, and Serratia, which represent the 3 genera most frequently isolated across all cheeses. Escherichia, Hafnia, and Enterobacter were significantly more common among raw milk cheeses. Based on sequencing of the housekeeping gene clpX, most Escherichia isolates were confirmed as members of fecal commensal clades of E. coli. All cheese samples tested negative for Salmonella, Staph. aureus, and Shiga toxin-producing E. coli. Listeria spp. were found in 12 cheese samples, including 5 samples positive for L. monocytogenes. Although no association was found between coliform and Listeria spp. detection, Listeria spp. were significantly more likely to be detected in cheese with the washed type of rind. Our data provide information on specific risk factors for pathogen detection in cheese, which will facilitate development of risk-based strategies to control microbial food safety hazards in cheese, and suggest that generic coliform testing cannot be used to assess the safety of natural cheese.

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“…Paenibacillus represents more than 95% of bacteria in raw milk after 10 days of refrigerated shelf life [173], while spoilage of pasteurized milk due to Paenibacillus is delayed by the germination process of spores and usually occurs after 17–21 days [174]. Strains that are able to grow at low temperature (6 °C) share numerous genetic features including genes that encode peptidases with cold-adapted features and cold-adaptation related proteins [175].…”

Section: Dairy Spoilagementioning

confidence: 99%

“…However, not all dairy-isolated strains produce these activities [174]. Paenibacillus species isolated from dairy products include P. amylolyticus , P. lactis , P. lentimorbus , P. lucanolyticus , P. odorifer , P. peoriae , and P. stellifer [173, 174, 176]. …”

Section: Dairy Spoilagementioning

confidence: 99%

Current knowledge and perspectives of Paenibacillus: a review

et al. 2016

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Isolated from a wide range of sources, the genus Paenibacillus comprises bacterial species relevant to humans, animals, plants, and the environment. Many Paenibacillus species can promote crop growth directly via biological nitrogen fixation, phosphate solubilization, production of the phytohormone indole-3-acetic acid (IAA), and release of siderophores that enable iron acquisition. They can also offer protection against insect herbivores and phytopathogens, including bacteria, fungi, nematodes, and viruses. This is accomplished by the production of a variety of antimicrobials and insecticides, and by triggering a hypersensitive defensive response of the plant, known as induced systemic resistance (ISR). Paenibacillus-derived antimicrobials also have applications in medicine, including polymyxins and fusaricidins, which are nonribosomal lipopeptides first isolated from strains of Paenibacillus polymyxa. Other useful molecules include exo-polysaccharides (EPS) and enzymes such as amylases, cellulases, hemicellulases, lipases, pectinases, oxygenases, dehydrogenases, lignin-modifying enzymes, and mutanases, which may have applications for detergents, food and feed, textiles, paper, biofuel, and healthcare. On the negative side, Paenibacillus larvae is the causative agent of American Foulbrood, a lethal disease of honeybees, while a variety of species are opportunistic infectors of humans, and others cause spoilage of pasteurized dairy products. This broad review summarizes the major positive and negative impacts of Paenibacillus: its realised and prospective contributions to agriculture, medicine, process manufacturing, and bioremediation, as well as its impacts due to pathogenicity and food spoilage. This review also includes detailed information in Additional files 1, 2, 3 for major known Paenibacillus species with their locations of isolation, genome sequencing projects, patents, and industrially significant compounds and enzymes. Paenibacillus will, over time, play increasingly important roles in sustainable agriculture and industrial biotechnology.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-016-0603-7) contains supplementary material, which is available to authorized users.

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A standard bacterial isolate set for research on contemporary dairy spoilage

Cited by 53 publications

References 41 publications

Viable and Total Bacterial Populations Undergo Equipment- and Time-Dependent Shifts during Milk Processing

Viable and Total Bacterial Populations Undergo Equipment- and Time-Dependent Shifts during Milk Processing

Coliform detection in cheese is associated with specific cheese characteristics, but no association was found with pathogen detection

Current knowledge and perspectives of Paenibacillus: a review

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