Abstract
The goal of this study was to develop the Listeria species-specific PCR assays based on a house-keeping gene (lmo1634) encoding alcohol acetaldehyde dehydrogenase (Aad), previously designated as Listeria adhesion protein (LAP), and compare results with a label-free light scattering sensor, BARDOT (bacterial rapid detection using optical scattering technology). PCR primer sets targeting the lap genes from the species of Listeria sensu stricto were designed and tested with 47 Listeria and 8 non-Listeria strains. The resulting PCR primer sets detected either all species of Listeria sensu stricto or individual L. innocua, L. ivanovii and L. seeligeri, L. welshimeri, and L. marthii without producing any amplified products from other bacteria tested. The PCR assays with Listeria sensu stricto-specific primers also successfully detected all species of Listeria sensu stricto and/or Listeria innocua from mixed culture-inoculated food samples, and each bacterium in food was verified by using the light scattering sensor that generated unique scatter signature for each species of Listeria tested. The PCR assays based on the house-keeping gene aad (lap) can be used for detection of either all species of Listeria sensu stricto or certain individual Listeria species in a mixture from food with a detection limit of about 104 CFU/mL.
Highlights
Listeria monocytogenes, a foodborne pathogen, causes fatal systemic infection in immunocompromised hosts including the elderly, infants, pregnant women and their fetuses, HIV infected patients, and patients with malignancy receiving chemotherapy
The acetaldehyde dehydrogenase (Aad) (Lmo1634) is known as Listeria adhesion protein (LAP) and its homolog is present in all species of Listeria sensu stricto known as archetypal Listeria species (L. monocytogenes, L. ivanovii, L. seeligeri, L. welshimeri, L. innocua, and L. marthii) [1,7,8]
L. floridensis, L. aquatic, L. cornellensis, L. riparia, L. grandensis, L. booriae, L. rocourtiae, L. newyorkensis, L. weihenstephanensis, L. fleischmannii and L. grayi [8,9] are considered atypical and these group are phylogenetically divergent from the species of Listeria sensu stricto [9,10,11,12]
Summary
A foodborne pathogen, causes fatal systemic infection in immunocompromised hosts including the elderly, infants, pregnant women and their fetuses, HIV infected patients, and patients with malignancy receiving chemotherapy. Alcohol acetaldehyde dehydrogenase (Aad) in L. monocytogenes is a house-keeping enzyme and is involved in bacterial adhesion and paracellular translocation through epithelial barrier during intestinal phase of listeriosis [1,2,3,4]. Such a housekeeping enzyme with moonlighting function in prokaryotes plays an important role in pathogenesis [5,6]. L. monocytogenes is pathogenic to humans and is responsible for fatal outbreaks involving ready-to-eat meat, dairy, fish, fruits, and vegetables [13]. The case-fatality rate for listeriosis is 20%–30% [19]
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