An insight into the isolation, enumeration, and molecular detection of Listeria monocytogenes in food.

Jodi Woan-Fei Law,Kok-Gan Chan,Learn-Han Lee,Nurul-Syakima Ab Mutalib

doi:10.3389/fmicb.2015.01227

Abstract

Listeria monocytogenes, a foodborne pathogen that can cause listeriosis through the consumption of food contaminated with this pathogen. The ability of L. monocytogenes to survive in extreme conditions and cause food contaminations have become a major concern. Hence, routine microbiological food testing is necessary to prevent food contamination and outbreaks of foodborne illness. This review provides insight into the methods for cultural detection, enumeration, and molecular identification of L. monocytogenes in various food samples. There are a number of enrichment and plating media that can be used for the isolation of L. monocytogenes from food samples. Enrichment media such as buffered Listeria enrichment broth, Fraser broth, and University of Vermont Medium (UVM) Listeria enrichment broth are recommended by regulatory agencies such as Food and Drug Administration-bacteriological and analytical method (FDA-BAM), US Department of Agriculture-Food and Safety (USDA-FSIS), and International Organization for Standardization (ISO). Many plating media are available for the isolation of L. monocytogenes, for instance, polymyxin acriflavin lithium-chloride ceftazidime aesculin mannitol, Oxford, and other chromogenic media. Besides, reference methods like FDA-BAM, ISO 11290 method, and USDA-FSIS method are usually applied for the cultural detection or enumeration of L. monocytogenes. most probable number technique is applied for the enumeration of L. monocytogenes in the case of low level contamination. Molecular methods including polymerase chain reaction, multiplex polymerase chain reaction, real-time/quantitative polymerase chain reaction, nucleic acid sequence-based amplification, loop-mediated isothermal amplification, DNA microarray, and next generation sequencing technology for the detection and identification of L. monocytogenes are discussed in this review. Overall, molecular methods are rapid, sensitive, specific, time- and labor-saving. In future, there are chances for the development of new techniques for the detection and identification of foodborne with improved features.

Highlights

Listeria monocytogenes has become an important foodborne pathogen and it can be found in a variety of foods which include raw foods and processed foods (Gasanov et al, 2005; Janzten et al, 2006; Liu, 2006; Jeyaletchumi et al, 2010a; Välimaa et al, 2015)
The results indicated that loop-mediated isothermal amplification (LAMP) assay was 100 times more sensitive than the conventional polymerase chain reaction (PCR) assay
The results of this study showed that double LAMP (dLAMP) assay was more sensitive and less time consuming as compared to normal LAMP assay

Summary

INTRODUCTION

Listeria monocytogenes has become an important foodborne pathogen and it can be found in a variety of foods which include raw foods and processed foods (Gasanov et al, 2005; Janzten et al, 2006; Liu, 2006; Jeyaletchumi et al, 2010a; Välimaa et al, 2015). ALOA detects PI-PLC that is present in L. monocytogenes and in some strains of L. ivanovii through the hydrolysis of L-α-phosphatidylinositol in the medium by PI-PLC This results in the production of water insoluble fatty acids and the formation of an opaque halo around the colonies. Additional variations of ALOA and commercially available media include Biosynth Chromogenic Medium (BCM) L. monocytogenes detection system (Biosynth), Compass L. mono (Biokar Diagnostics), BrillianceTM Listeria Agar (Oxoid) and chromID Ottaviani Agosti Agar (bioMérieux; Janzten et al, 2006; Zunabovic et al, 2011). The culture methods involve a twostage enrichment process followed by plating on a selective differential agar (Beumer and Hazeleger, 2003; Janzten et al, 2006).

Summary of method

Molecular methods Simple PCR

Limitations

CONCLUSION