INTRACELLULAR MULTIPLICATION AND TOXIC DESTRUCTION OF CULTURED MACROPHAGES BY CAPNOCYTOPHAGA-CANIMORSUS

Capnocytophaga canimorsus is a gram-negative rod that causes opportuni stic infections resulting in bacteremia, septicemia, meningitis, and d eath in immunocompromised, splenectomized, and alcoholic individuals. Infections caused by a related species, Capnocytophaga cynodegmi, rema in localized at the site of the wound where the organism is introduced . Both organisms are part of the normal canine oral flora and are intr oduced through puncture wounds via dog bites, We found that both C, ca nimorsus and C. cynodegmi attach, are phagocytized, and multiply intra cellularly in J774 mouse macrophage cells, After 48 h of infection by C. canimorsus, large sections of the macrophage cell layer were observ ed to detach and lyse, while the monolayer infected with C. cynodegmi demonstrated no cytotoxic effects, Tissue culture supernatants from th e C. canimorsus-infected J774 cells filtered through a 0.22-mu m-pore membrane produced a similar effect on fresh monolayers, while filtrate s from C, cynodegmi and uninfected controls produced no effect, No end otoxin release was observed in these supernatants. We conclude that th e cytotoxic phenotype of C. canimorsus is the likely result of a toxin produced by this organism.