Cholesterol-dependent cytolysins (CDCs)* are produced by a large number of pathogenic gram-positive bacteria. A member of this family, listeriolysin O (LLO), is produced by the intracellular pathogen Listeria monocytogenes. A unique feature of LLO is its low optimal pH activity (approximately 6) which permits escape of the bacterium from the phagosome into the host cell cytosol without damaging...

Successful infection by Listeria monocytogenes is dependent upon a range of bacterial extracellular proteins including a cytolysin termed listeriolysin O and phosphatidylcholine-specific phospholipase C. Five plant essential oils--bay, clove, cinnamon, nutmeg and thyme--significantly reduced the production of listeriolysin O by L. monocytogenes. The greatest change was observed after culture wi...

The introduction into Brucella suis 1330 of a plasmid allowing the heterologous expression of a hybrid cytolysin containing listeriolysin from Listeria monocytogenes, and its export via the Escherichia coli hemolysin secretion pathway, resulted in secretion of active listeriolysin monitored by erythrocyte lysis. In contrast to observations with the nonhemolytic control strain, the phagosomes of...

The aim of the study was to determine the occurrence of Listeria sp. in poultry meat and poultry meat products and estimate the prevalence of L. monocytogenes strains producing listeriolysin O. No listeria strain was detected in any of 50 examined heat-treated products. These bacteria were present in 43 out of 70 samples of raw poultry meat and 6 of Listeria strains were defined as L. monocytog...

Three genome-wide RNA interference screens were performed in Drosophila S2 cells to dissect the contribution of host processes to Listeria monocytogenes entry, vacuolar escape, and intracellular growth. Among the 116 genes identified, several host pathways previously unrecognized as playing a role in listerial pathogenesis were identified: knockdowns affecting vacuolar trafficking to and from t...

Listeriolysin is a 60-kDa protein which allows the growth of Listeria monocytogenes in macrophages and other cells and has been shown to be a virulence factor in Listeria infections of adult mice. However, the neonate and fetoplacental unit are major populations susceptible to listeriosis. Recent data indicate that macrophage and T-cell functions are markedly inhibited in these young mice, and ...

Listeria monocytogenes is a food-borne pathogen, which is able to induce diarrhea when residing in the intestine. We studied the effect of listeriolysin O (LLO), an extracellular virulence factor of L. monocytogenes, on intestinal transport and barrier function in monolayers of HT-29/B6 human colon cells using the Ussing technique to understand the pathomechanisms involved. Mucosal addition of ...

An attenuated strain of S. typhimurium has been used as a vehicle for oral genetic immunization. Eukaryotic expression vectors containing truncated genes of ActA and listeriolysin--two virulence factors of Listeria monocytogenes--have been used to transform S. typhimurium aroA. Multiple or even single oral immunizations with such transformants induced excellent cellular and humoral responses. I...

Type I IFNs (IFN-alpha/beta) modulate innate immune responses. Here we show activation of transcription factor IFN regulatory factor 3, the synthesis of large amounts of IFN-beta mRNA, and type I IFN signal transduction in macrophages infected with Listeria monocytogenes. Expression of the bacterial virulence protein listeriolysin O was necessary, but not sufficient, for efficient IFN-beta prod...

Bacterial pathogens can interfere during infection with host cell organelles, such as mitochondria, the endoplasmic reticulum-Golgi system or nuclei. As important cellular functions are often compartmentalized in these organelles, their targeting allows pathogens to manipulate key host functions during infection. Here, we identify lysosomes as a new class of organelles targeted by the pathogeni...