Project description:Background:Listeria is a Gram-positive, non-spore forming, facultative anaerobic intracellular bacterium. The most important pathogens in mammals include Listeria monocytogenes and Listeria ivanovii. The former generally causes disease and death in both humans and animals while the latter performs sporadically and primarily causes illness in ruminants. Aims:The aim of this project was to use conventional and molecular techniques to determine whether the provided samples were L. monocytogenes, and whether they were genetically similar or different. Methods:The provided presumptive Listeria cultures isolated from industrial processed food are conventionally assumed to be L. monocytogenes. All samples were cultured on brain heart infusion agar and broth first and then on blood agar. Later, hly gene amplification was applied. Results:The provided culture phenotypically resembled L. monocytogenes as it caused haemolysis on blood agar plates; however, the absence of the hly gene revealed that they were genotypically different. 16S rRNA confirmed three species of Listeria species including L. grayi, L. welshimeri and L. ivanovii. The results from 16S rRNA sequencing confirmed the results obtained from hly gene amplification. Conclusion:Enterobacterial repetitive intergenic consensus polymerase chain reaction (ERIC PCR) confirmed that all bacterial cultures were isolated from different sources depending on their ERIC PCR profile variation.
Project description:The objective of this study was to produce phage display-derived binders with the ability to distinguish Listeria monocytogenes from other Listeria spp., which may have potential utility to enhance detection of Listeria monocytogenes. To obtain binders with the desired binding specificity a series of surface and solution phage-display biopannings were performed. Initially, three rounds of surface biopanning against gamma-irradiated L. monocytogenes serovar 4b cells were performed followed by an additional surface biopanning round against L. monocytogenes 4b which included prior subtraction biopanning against gamma-irradiated L. innocua cells. In an attempt to further enhance binder specificity for L. monocytogenes 4b two rounds of solution biopanning were performed, both rounds included initial subtraction solution biopanning against L. innocua. Subsequent evaluations were performed on the phage clones by phage binding ELISA. All phage clones tested from the second round of solution biopanning had higher specificity for L. monocytogenes 4b than for L. innocua and three other foodborne pathogens (Salmonella spp., Escherichia coli and Campylobacter jejuni). Further evaluation with five other Listeria spp. revealed that one phage clone in particular, expressing peptide GRIADLPPLKPN, was highly specific for L. monocytogenes with at least 43-fold more binding capability to L. monocytogenes 4b than to any other Listeria sp. This proof-of-principle study demonstrates how a combination of surface, solution and subtractive biopanning was used to maximise binder specificity. L. monocytogenes-specific binders were obtained which could have potential application in novel detection tests for L. monocytogenes, benefiting both the food and medical industries.
Project description:Listeria monocytogenes strain 10403S has been studied extensively for stress response activity toward multiple stressors (acid, osmotic, cold, high temperature, etc.) as well as multiple stress regulons (SigB, CtsR, HrcA, etc.). Here we aimed to determine the transcriptional response of Listeria monocytogenes in early log phase towards the strong oxidative stress imposed by ClO2. The elucidation of such a response allows for further a more completel understanding of the mechanism of inactivation by sanitizers, specifically ClO2. Independent RNA isolations were performed for strain 10403S with and without exposure to ClO2 from cells grown to early log phase. Four biological replicates were used in competitive whole-genome microarray experiments. For each set of hybridizations, RNA from a control sample of Listeria monocytogenes was hybridized with RNA from a culture of L. monocytogenes following exposure to ClO2. Dye swapping was performed for the four replicates to mitigate any concerns of dye bias.
Project description:These studies were designed to examine the acute Listeria monocytogenes transcriptional response to mammalian (porcine) bile. Triplicate WT Listeria monocytogenes (strain 10403S) were grown to mid-log in BHI at 37 °C. Samples were divided, and either treated or not treated by addition of porcine bile (Sigma, to 1% final) for 30 minutes.
Project description:Tumbling motility is one of the useful characteristics of Listeria monocytogenes. This can be helpful to identify the causative pathogen along with Gram staining before the confirmatory microbiological examination.
Project description:These studies were designed to examine the transcription of Listeria monocytogenes strains 10403S and LO28 during intracellular replication in mammalian macrophages. Duplicate WT Listeria monocytogenes (strains 10403S and LO28) were used to infect mouse bone marrow-derived macrophages (BMMs). Bacterial RNA was harvested at 4 hours post-infection.