Persistence of associated gram-negative bacteria in experimental actinomycotic lesions in mice

Abstract

Mixed actinomycotic infections were established in a susceptible weanling mouse model by using combinations of Actinomyces israelii and Eikenella corrodens or A. israelii and Actinobacillus actinomycetemcomitans. Acute lesions caused by either of the gram-negative organisms alone were resolved within a few weeks; however, these organisms persisted up to 3 months in chronic lesions in combination with A. israelii.

Enhancement of experimental actinomycosis in mice by Eikenella corrodens

“…Thus, it appears safe to conclude that the mixed A. viscosus-E. corrodens infection would not have persisted into the chronic stage. A similar result in which an infection caused by smooth A. israelii 12597 was confined to the acute stage even when E. corrodens was present was described previously (12).…”

“…Internal organs were examined for the presence and location of actinomycotic abscesses. Sham-inoculated controls were not included in the present experiments, as this procedure has consistently yielded negative results in the past (2,12).…”

“…Recent studies on mixed actinomycotic infections in the mouse model have provided experimental evidence of mutualism between the different types of pathogens in the lesion. The gram-negative organisms E. corrodens and A. actinomycetemcomitans were found to persist in chronic actinomycotic lesions in association with A. israelii even though they were unable to survive in acute lesions by themselves (12). The mechanism of this apparent protective effect is not known, but histological evidence indicates that polymorphonuclear leukocytes do not penetrate and invade the developing central bacterial granule of A. israelii lesions (1).…”

“…Actinomycotic infections that resemble natural actinomycosis can be produced experimentally in a susceptibleweanling-mouse model with pure cultures of Actinomyces israelii, A. naeslundii, and A. viscosus (2,4,7,8). Mixed actinomycotic infections have been produced in this model with A. israelii in combination with Eikenella corrodens or A. actinomycetemcomitans (12). The gram-negative bacteria persisted in the chronic experimental lesions in association with A. israelii but were unable to survive alone in pureculture lesions in the same animal model.…”

Thoracic and abdominal wall swellings in dogs caused by foreign bodies

“…According to Holm (1950Holm ( , 1951, human actinomycosis appears to be a cooperative disease of Actinomyces species and a mixed flora of other anaerobic bacteria. Furthermore, Actinomyces species alone seldom succeed in producing disease, as confirmed by laboratory tests Kelly 1983, Jordan andothers 1984). Perhaps the pathogenic significance of Actinomyces species, in lesions referred to as actinomycosis, is overestimated because of the conspicuous macroscopic and microscopic features (granules and branching filaments) of the microorganism in tissues and exudate compared with other bacteria recovered from infections of this kind.…”