LISTERIA

·         Gram +ve cocco-bacilli in chains

·         Peritrichous flagella (optimally produced at 20°-30°C)

·         Slow tumbling motility at 25°C (characteristic)

·         Non-motile at higher temperatures (37°C)

·         Most common serotypes for human disease- ½a, ½b, 4b

·         Human diseases occur in pregnancy/immunosuppression

·         Pathogenesis-

o   Most important determinant of pathogenesis of L.M. – Listeriolysin O (type of β-Hemolysin)

o   Iron is a virulence factor as Listeria produce siderphores which utilize iron from transferring.

o   Immunity against Listeria is Cell mediated (Cytotoxic CD8+ T-cells)- eliminate infection

o   IFN-γ & TNF control infection

·         Killed vaccine does not provide immunity.