Methods for the isolation and identification ofListeriaspp. andListeria monocytogenes: a review

Abstract

Listeria monocytogenes is an important food-borne pathogen and is widely tested for in food, environmental and clinical samples. Identification traditionally involved culture methods based on selective enrichment and plating followed by the characterization of Listeria spp. based on colony morphology, sugar fermentation and haemolytic properties. These methods are the gold standard; but they are lengthy and may not be suitable for testing of foods with short shelf lives. As a result more rapid tests were developed based on antibodies (ELISA) or molecular techniques (PCR or DNA hybridization). While these tests possess equal sensitivity, they are rapid and allow testing to be completed within 48 h. More recently, molecular methods were developed that target RNA rather than DNA, such as RT-PCR, real time PCR or nucleic acid based sequence amplification (NASBA). These tests not only provide a measure of cell viability but they can also be used for quantitative analysis. In addition, a variety of tests are available for sub-species characterization, which are particularly useful in epidemiological investigations. Early typing methods differentiated isolates based on phenotypic markers, such as multilocus enzyme electrophoresis, phage typing and serotyping. These phenotypic typing methods are being replaced by molecular tests, which reflect genetic relationships between isolates and are more accurate. These new methods are currently mainly used in research but their considerable potential for routine testing in the future cannot be overlooked.

Detection and enumeration of viable Listeria monocytogenes cells from ready-to-eat and processed vegetable foods by culture and DVC-FISH

“…In our work, counts were below <100 cfu / g for the eight positive The detection of L. monocytogenes by PCR was only possible by including an enrichment step, which could be due to an increase in viable cells (Lee & McClain, 1986) or to the dilution of potential inhibitors present in the sample (Gasanov, Hughes & Hansbro, 2005). The most common inhibitors are organic and phenolic compounds, glycogen, lipids, humic compounds and heavy metals (Wilson, 1997), some of them present in the soil for cultivation (fertilizer) and in the crop.…”

Development of a nucleic acid lateral flow immunoassay for simultaneous detection of Listeria spp. and Listeria monocytogenes in food

“…They are based on either chromogenic media [14][15][16], antibodies [17][18][19], or nucleic acid-based techniques [20,21]. Identification of Listeria spp.…”

Antimicrobial susceptibilities of Listeria monocytogenes human strains isolated from 1970 to 2008 in Brazil

“…Among the 13 serotypes of L. monocytogenes in the literature, serovar 4b is primarily responsible for most of the outbreaks in humans 5,13 while the serovar 1/2a prevails in food and in some regions of the world where it is more common in human cases [14][15][16] .…”