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

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 (BLEB), Fraser broth and University of Vermont Medium (UVM) Listeria enrichment broth are recommended by regulatory agencies such as FDA-BAM, USDA-FSIS and ISO. Many plating media are available for the isolation of L. monocytogenes, for instance, PALCAM, 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. MPN technique is applied for the enumeration of L. monocytogenes in the case of low level contamination. Molecular methods including polymerase chain reaction (PCR), multiplex polymerase chain reaction (mPCR), real-time/quantitative polymerase chain reaction (qPCR), nucleic acid sequence-based amplification (NASBA), loop-mediated isothermal amplification (LAMP), DNA microarray and Next Generation Sequencing (NGS) technology for the detection and identification of L. monocytogenes are discussed in this review. Overall, molecular methods are rapid, sensitive, specific, time- and labour-saving. In future, there are chances for the development of new techniques for the detection and identification of foodborne with improved features

Rapid Methods for the Detection of Foodborne Bacterial Pathogens: Principles, Applications, Advantages and Limitations

The incidence of foodborne diseases has increased over the years and resulted in major public health problem globally. Foodborne pathogens can be found in various foods and it is important to detect foodborne pathogens to provide safe food supply and to prevent foodborne diseases. The conventional methods used to detect foodborne pathogen are time consuming and laborious. Hence, a variety of methods have been developed for rapid detection of foodborne pathogens as it is required in many food analyses. Rapid detection methods can be categorized into nucleic acid-based, biosensor-based and immunological-based methods. This review emphasizes on the principles and application of recent rapid methods for the detection of foodborne bacterial pathogens. Detection methods included are simple polymerase chain reaction (PCR), multiplex PCR, real-time PCR, nucleic acid sequence-based amplification (NASBA), loop-mediated isothermal amplification (LAMP) and oligonucleotide DNA microarray which classified as nucleic acid-based methods; optical, electrochemical and mass-based biosensors which classified as biosensor-based methods; enzyme-linked immunosorbent assay (ELISA) and lateral flow immunoassay which classified as immunological-based methods. In general, rapid detection methods are generally time-efficient, sensitive, specific and labor-saving. The developments of rapid detection methods are vital in prevention and treatment of foodborne diseases

Evaluation of antioxidative and cytotoxic activities of Streptomyces pluripotens MUSC 137 isolated from mangrove soil in Malaysia

A well characterized strain, Streptomyces pluripotens MUSC 137 was isolated from mangrove soil at Tanjung Lumpur, Malaysia. The biological activities of this particular strain of Streptomyces were then explored. For experimentation, the extract of fermentation was prepared by using solvent extraction method. The antioxidant activity was examined by using DPPH assay. The cytotoxicity activity of extract was assessed against selected human cancer cell lines, namely colon cancer cells (HCT-116, Caco-2, SW480 & HT-29), breast cancer cell (MCF-7), lung cancer cell (A549), prostate cancer cell (DU145) and cervical cancer cell (Ca Ski). The results showed MUSC 137 extract possessed significant antioxidant activity and cytotoxic effect against some of the tested cancer cell lines. Lowest IC50 was recorded in MCF-7 cells (61.33 ± 17.10 µg/mL), followed by HCT-116 and A549. Subsequently, the extract was subjected to chemical analysis using GC-MS, which led to the identification of chemical constituents present in the extract of MUSC 137. The analysis resulted in the identification of chemical constituents including deferoxamine and pyrrolizidines related-compounds which may responsible for antioxidant and cytotoxic activities observed. The result of the present investigation is the first report on the potential antioxidative and cytotoxic activities of Streptomyces pluripotens MUSC 137