Enhancement of experimental actinomycosis in mice by Eikenella corrodens.

The infectivity of Actinomyces israelii in a susceptible-weanling-mouse was increased by the presence of Eikenella corrodens in the inoculum. A minimal infecting dose of 1.7 X 10(7) CFU of A. israelii was required to establish chronic lesions after an intraperitoneal injection. When E. corrodens (3.8 X 10(7) CFU) was included in the inoculum, chronic lesions were established with a dose of 8.5 X 10(4) CFU of A. israelii. E. corrodens alone did not produce persistent lesions. Viable E. corrodens could be recovered from chronic mixed actinomycotic lesions in numbers that often equaled or exceeded the populations of A. israelii in the lesions. The duration of acute actinomycotic infections caused by A. viscosus was temporarily extended by the presence of E. corrodens. The cellular inflammatory response and overall morphology of mixed experimental lesions containing A. israelii and E. corrodens did not appear to be significantly different from those of pure-culture lesions containing A. israelii alone. E. corrodens cells could not be readily discerned in stained histological sections of mixed experimental lesions.