Method for flow cytometric detection of Listeria monocytogenes in milk

Abstract

This report describes a method for the detection of Listeria monocytogenes in raw milk by flow cytometric analysis of fluorescently labeled bacterial populations. The use of immunofluorescence in combination with measures of DNA content by propidium iodide labeling and size by light scattering enabled specific identification of L. monocytogenes from Streptococcus faecalis, Streptococcus agalactiae, Streptococcus uberis, Staphylococcus epidermidis, and Staphylococcus hyicus. Additional specific resolution of L. monocytogenes populations was achieved through selective enrichment of raw milk in Listeria enrichment broth. These procedures should permit the rapid screening of milk and other food samples for L. monocytogenes and eliminate many of the shortcomings associated with conventional fluorescent-antibody procedures.

Improved detection of bacteria by flow cytometry using a combination of antibody and viability markers

“…Medical applications include bacterial responses to antibiotics (Gant et al 1993 ;Mason et al 1995), analysis of blood (Mansour et al 1985) and other clinical samples (Humphreys et al 1994 ;van der Waaij et al 1994). Interest in food analysis has centred around pathogenic bacteria and spoilage organisms (Donnelly and Baigent 1986 ;Patchett et al 1991 ;Laplace-Builhé et al 1993).…”

Detection of low levels of specific Salmonella species by fluorescent antibodies and flow cytometry

“…Unlike the study of lymphocytes, little work has been done on combining FCM and monoclonal antibodies for the detection of bacteria (Tyndall et al 1985;Phillips and Martin 1988;Nelson et al 1991) and even less using the two for detection in foods (Donnelly and Baigent 1986).…”

Rapid enumeration of bacteria grown on surimi-based products by flow cytometry

“…10 There are several methods available for the enumeration and detection of microbial cells in milks and soft drinks. [11][12][13][14][15] However, these methods cannot be applied to determining the number of cells firmly adhered to the surface of solid food such as surimibased products. Because the sample for FCM must be prepared as a cell suspension, it is necessary to remove the bacterial cells from the surface of food products as the first step in sample preparation for FCM assay.…”