INFECTIVITY OF FUSO-SPIROCHETAL EXUDATES FOR GUINEA PIGS, HAMSTERS, MICE AND CHICK EMBRYOS BY SEVERAL ROUTES OF INOCULATION

¹ Department of Bacteriology, College of Physicians and Surgeons, and School of Dental and Oral Surgery, Columbia University, New York, N. Y.

Fusospirochetal exudates were derived from a case of chronic suppurative periodontoclasia, passed through guinea pigs at least 14 times, and stored when necessary by freezing in CO₂ ice. Such frozen exudates, when thawed rapidly after storage for as long as 13 months, were found to contain typical microorganisms with apparently unimpaired motility, and to yield characteristic infection with dosages similar to those required with fresh exudates.

The following hosts were found susceptible to infection by the routes noted: guinea pig, subcutaneous or intraperitoneal; hamster, subcutaneous; and mouse, intraperitoneal or intracerebral.

Infectivity, as determined by successive dilution, is uniformly low, about the equivalent of 0.01 ml. of undiluted exudate being required for a minimal response. There was considerable variation in individual response, for example, the equivalent of 0.1 or 0.2 ml. of undiluted exudate was frequently a fatal dose, but in some instances failed to infect. No marked differences in infectivity were correlated with species or route of inoculation among the adult hosts.

Differences in pattern of response among the hosts and routes employed tend to favor subcutaneous inoculation in the guinea pig both for passage and for titration of infectivity.

The intracerebral route in mice, and all routes of inoculation tested in chick embryos, seemed less suitable than other methods, apparently because of excessive sensitivity to infection with microorganisms other than spirochetes. Typical fusospirochetal infection occurred in only 2 of 54 intracerebrally injected mice, and could be obtained irregularly in chick embryos only by injecting agar with the inoculum into the amniotic sac. Such infection in chick embryos could not be passed to fresh embryos.

Mice that survived intracerebral inoculation seemed as susceptible as previously uninoculated mice to subsequent intraperitoneal infection.