Predominant microflora of downgraded Danish bulk tank milk.
The microflora of downgraded Danish bulk tank milk was examined to identify the main causes of increased microbial counts. Seventy-five representative samples with a microbial count exceeding 3.0 x 10(4) cfu/mL were selected for a more detailed microbial examination. A total of 1237 isolates from these samples were identified. Gram-negative, oxidase-positive bacteria were found in 72% of the samples. Coliforms were found in 20% of the samples, and non-coliforms were found in 49% of the samples. Coryneforms, other gram-positive rods, Lactococcus spp., Micrococcus spp., and coagulase-negative Staphylococcus spp. were found in 28 to 53% of the samples. Bacillus spp., Enterococcus spp., Staphylococcus aureus, Streptococcus dysgalactiae, Streptococcus uberis, and yeasts were found in <25% of the samples. Additionally, the isolates were divided into 3 groups, based on the main cause of an elevated microbial count. Microorganisms primarily associated with poor hygiene dominated the microflora in 64% of the samples; bacteria also related to poor hygiene, but in addition associated with growth at low temperatures (psychrotrophic bacteria) dominated the microflora in 28% of the samples; and bacteria mainly associated with mastitis dominated the microflora in 8% of the samples. A bulk tank milk storage period of 48 h instead of 24 h did not affect the proportion of downgraded milk samples and could not be associated with a specific group of microorganisms. Further, no relationship was found between somatic cell counts and the presence of mastitis bacteria.
Holm
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Danish Dairy Board, Department of Veterinary and Milk Quality, Frederiks Allé, Arhus C, Denmark.
Jepsen
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Larsen
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Jespersen
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D000192:Actinomycetales / Q000302:isolation & purification; D000818:Animals; D015169:Colony Count, Microbial; D003718:Denmark; D004755:Enterobacteriaceae / Q000302:isolation & purification; D006090:Gram-Negative Bacteria / Q000302:isolation & purification; D017045:Lactococcus / Q000302:isolation & purification; D008837:Micrococcus / Q000302:isolation & purification; D008892:Milk / Q000382:microbiology*; D013210:Staphylococcus / Q000302:isolation & purification; D013291:Streptococcus / Q000302:isolation & purification; D015003:Yeasts / Q000302:isolation & purification