PCR-based methodologies for detection and characterization of Listeria monocytogenes and Listeria ivanovii in foods and environmental sources

Listeria monocytogenes is an important foodborne pathogen responsible for listeriosis,a fatal disease.It is widely distributed in various foods and environmental sources.In this review,we focused on addressing PCR-based technologies,including conventional PCR,qPCR and droplet digital PCR(ddPCR).Specifically,we described(a)conventional PCR and mono-,duplex-and multiplex-qPCR methodologies;(b)development and applications of gene HlyA-,Iap-,PrfA–and SsrA-based conventional and qPCR assays as well as PCR assays targeting newly identified gene targets for specific detection of L.monocytogenes;differentiation of viable from dead L.monocytogenes by qPCR in conjugation with propidium monoazide pretreatment;PCR-based serotype identification of L.monocytogenes isolates;PCR-based detection of L.ivanovii,infecting ruminants,differentiation of L.monocytogenes from other Listeria species;and sigB-gene based PCR identification of Listeria spp;(c)applications of ddPCR in detection of L.monocytogenes;and(d)application of qPCR assays in detection and subtyping of L.monocytogenes in milk and dairy products;meats,meat products and meat-processing environment;and seafood,seafood products and processing environment.Our goal was to provide a relatively comprehensive overview of PCR-based methodologies available in detection,characterization and subtyping of various strains of L.monocytogenes in foods and environmental sources.

Prevalence and methodologies for detection,characterization and subtyping of Listeria monocytogenes and L.ivanovii in foods and environmental sources

Listeria monocytogenes,one of the most important foodborne pathogens,can cause listeriosis,a lethal disease for humans.L.ivanovii,which is closely related to L.monocytogenes,is also widely distributed in nature and infects mainly warm-blooded ruminants,causing economic loss.Thus,there are high priority needs for methodologies for rapid,specific,cost-effective and accurate detection,characterization and subtyping of L.monocytogenes and L.ivanovii in foods and environmental sources.In this review,we(A)described L.monocytogenes and L.ivanovii,world-wide incidence of listeriosis,and prevalence of various L.monocytogenes strains in food and environmental sources;(B)comprehensively reviewed different types of traditional and newly developed methodologies,including culture-based,antigen/antibody-based,LOOP-mediated isothermal amplification,matrix-assisted laser desorption ionization-time of flight-mass spectrometry,DNA microarray,and genomic sequencing for detection and characterization of L.monocytogenes in foods and environmental sources;(C)comprehensively summarized different subtyping methodologies,including pulsed-field gel electrophoresis,multi-locus sequence typing,ribotyping,and phage-typing,and whole genomic sequencing etc.for subtyping of L.monocytogenes strains from food and environmental sources;and(D)described the applications of these methodologies in detection and subtyping of L.monocytogenes in foods and food processing facilities.

Investigation of potential Shiga toxin producing Escherichia coli(STEC)associated with a local foodborne outbreak using multidisciplinary approaches

Shiga toxin producing Escherichia coli(STEC)outbreak is a public health concern as it can potentially cause a variety of clinical manifestations including diarrhea,hemorrhagic colitis and hemolytic uremic syndrome(HUS).However E.coli are generally innocuous commensal organisms,and there is a need to discriminate pathogenic from non-pathogenic isolates rapidly and accurately.In this study,we have used standard culture based methods and advanced molecular approaches to characterize E.coli in food in a local outbreak investigation.We show that the application of DNA based detection methods including real-time PCR and DNA microarray along with a traditional culture method can identify the organism implicated in an outbreak at the strain level for pathogenic potential.

Isodicentric Ychromosome: Case Study

Isodicentric chromosomes are a frequently appearing abnormality in the human Y chromosome. Making predictions regarding the phenotypic outcomes of a variety of duplications/deletions in the dicentric Y chromosome generally depends on the breakpoint location and also the level of mosaicism (45, X cell lines);in certain instances, these may not be detected and result in variations running between male, abnormal female, or ambiguity in individual genitalia. A referral was received from a urology clinic concerning two patients, one aged 34 and one aged 35, with a request to investigate reasons for infertility: G-banded karyotyping and fluorescence in situ hybridization (FISH) revealed the presence of an isodicentric Y chromosome.