flow cytometry method for rapid detection and enumeration of total bacteria in milk

• Published in: Applied and Environmental Microbiology Vol. 66; no. 3; pp. 1228 - 1232
• Main Authors: Gunasekera, T.S, Attfield, P.V, Veal, D.A
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for Microbiology 01.03.2000
• Subjects: Animals; Bacteria; Bacteria - isolation & purification; bacterial counting; Biological and medical sciences; Colony Count, Microbial; Flow Cytometry - methods; food contamination; Food industries; Food Microbiology; Fundamental and applied biological sciences. Psychology; Lipids; Methods; microbial contamination; Microbiology; Milk; Milk - microbiology; Milk and cheese industries. Ice creams; Proteins; Flow cytometry; Bacteria; Rapid technique; Microbiological testing; Enumeration(counting); Milk
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/aem.66.3.1228-1232.2000

Application of flow cytometry (FCM) to microbial analysis of milk is hampered by the presence of milk proteins and lipid particles. Here we report on the development of a rapid (< or = 1-h) FCM assay based on enzymatic clearing of milk to determine total bacteria in milk. When bacteria were added to ultra-heat-treated milk, a good correlation (r > or = 0.98) between the FCM assay and the more conventional methods of plating and direct microscopic counting was achieved. Raw milk data showed a significant correlation (P < 0.01) and a good agreement (r = 0.91) between FCM and standard plate count methods. The detection limit of the FCM assay was < or = 10(4) bacteria ml of milk(-1). This limit is below the level of detection required to satisfy legislation in many countries and states.