The vacuole is quickly lysed by the pore-forming toxin listeriolysin O (LLO), encoded by the hly gene, and the two phospholipases C phosphatidylinositol phospholipase C (PI-PLC) and phosphatidylcholine phospholipase C (PC-PLC), encoded by the plcA and plcB genes, respectively ( 5, 26, 44). monocytogenes into the host cell, where it lies in a phagocytic vacuole. In addition, several bacterial factors, including two proteins of the internalin family, InlA (or internalin) and InlB ( 12), facilitate entry of L. The first step in infection is adhesion to the eukaryotic cells via bacterial surface factors such as adhesins ( 14) and the Ami protein ( 29). These results demonstrate a relationship between the phenotypic classification and the genotypic modifications for at least group I and III strains and suggest a common evolution of these strains within a group. Group IV strains poorly colonized spleens of mice and were practically indistinguishable from fully virulent strains on the basis of the above-mentioned in vitro criteria. Several substitutions were observed for five out of six group III strains in the plcA gene and for one out of three group II strains in the plcB gene. Group II strains had low phosphatidylcholine phospholipase C activity, whereas group III strains had low phosphatidylinositol phospholipase C activity. Group II and III strains entered cells but did not form plaques. These genetic modifications could explain the low virulence of group I strains, since mutated PrfA proteins were inactive. These strains exhibited a mutated PrfA eight strains had a single amino acid substitution, PrfAK220T, and the other three had a truncated PrfA, PrfAΔ174-237. Group I included 11 strains that did not enter cells and had no phospholipase activity. Using the results of cell infection assays and phospholipase activities, the low-virulence strains were assigned to one of four groups by cluster analysis and then virulence-related genes were sequenced. monocytogenes strains were shown to be of low virulence in a plaque-forming assay and in a subcutaneous inoculation test in mice. It does not store any personal data.Several models have shown that virulence varies from one strain of Listeria monocytogenes to another, but little is known about the cause of low virulence. The cookie is set by the GDPR Cookie Consent plugin and is used to store whether or not user has consented to the use of cookies. The cookie is used to store the user consent for the cookies in the category "Performance". This cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category "Other. The cookies is used to store the user consent for the cookies in the category "Necessary". The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional". The cookie is used to store the user consent for the cookies in the category "Analytics". These cookies ensure basic functionalities and security features of the website, anonymously. Necessary cookies are absolutely essential for the website to function properly.
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