It is caused by L. monocytogens that are gram positive rods, aerobic, catalase positive, beta hemolytic and motile with peritrichous flagella. These organisms can be found in the soil, sewage and surface water. There are 11 serotypes based on cell wall and flagella antigens. Infection can occur through contaminated food, and organisms can grow at refrigerator temperatures. Newborns and adults with debilitating and immunosuppressive conditions are the most susceptible.
Immunity is by cell mediated activity.
Treatment - Penicillin G, ampicillin, erythromycin and gentamicin.