introduction: this study was intended to determine the presence and distribution of listeria monocytogenes in various meat and dairy products from qazvin province by culture followed by biochemical and morphological assays. the identity of the isolates was further obtained by amplification of prfa gene in bacteria isolates. this gene is a transcriptional activator of virulence gene expression w...

Introduction: This study was intended to determine the presence and distribution of Listeria monocytogenes in various meat and dairy products from Qazvin Province by culture followed by biochemical and morphological assays. The identity of the isolates was further obtained by amplification of prfA gene in bacteria isolates. This gene is a transcriptional activator of virulence gene ex...

We have isolated, by molecular cloning and genetic complementation of a listeriolysin-negative mutant, a gene required for the expression of this virulence factor in Listeria monocytogenes. The mutant strain SLCC53, which was nonhemolytic and avirulent, harbored a deletion of 450 base pairs located approximately 1500 base pairs upstream of the listeriolysin gene. No transcripts corresponding to...

Pathogens have developed intricate strategies to overcome the host’s innate immune responses. In this paper we use live-cell microscopy with a single bacterium resolution follow in real time interactions between food-borne pathogen L. monocytogenes and host macrophages, key event controlling infection vivo . We demonstrate that results heterogeneous outcomes, only subset of bacteria able establ...

The droplet digital polymerase chain reaction (ddPCR) determines DNA amounts based upon the pattern of positive and negative droplets, according to Poisson distribution, without the use of external standards. However, division into positive and negative droplets is often not clear because a part of the droplets has intermediate fluorescence values, appearing as "rain" in the plot. Despite the d...

The degU (lmo2515) gene encodes a putative response regulator in the food-borne pathogen Listeria monocytogenes. It has 63% amino acid identity to the DegU response regulator of Bacillus subtilis. We have characterized the degU gene product in L. monocytogenes EGD by generation of a deletion mutant. The DeltadegU mutant was found to be non-motile in motility plate assay and no flagellin was det...

We have identified a Crp/Fnr-like transcriptional regulator of Streptococcus pyogenes that when inactivated attenuates virulence. The gene, named srv for streptococcal regulator of virulence, encodes a 240-amino-acid protein with 53% amino acid similarity to PrfA, a transcriptional activator of virulence in Listeria monocytogenes.

The role of sigma(B) in Listeria monocytogenes infection of human intestinal epithelial cells was investigated. Invasion defects associated with loss of sigma(B) paralleled those of a DeltainlA strain independently of the sigma(B)-dependent P2(prfA) promoter. Concomitantly, amounts of inlA transcript and InlA protein were significantly decreased in the DeltasigB strain.

Group A Streptococcus (GAS) possesses a complex regulatory system enabling the organism to colonize a range of physiologically distinct host sites. Within this network of regulators is the streptococcal regulator of virulence (Srv). Srv is a member of the CRP/FNR family of transcriptional regulators and is most similar to pleiotropic regulatory factor A (PrfA), a positive regulator of virulence...