HOST-PARASITE RELATIONSHIPS WITH BRUCELLA NEOTOMAE.

Gibby, Irvin W. (Cornell University Medical College, New York, N.Y.), and Anna M. Gibby. Host-parasite relationships with Brucella neotomae. J. Bacteriol. 89:9-16. 1965.-An investigation was undertaken to ascertain whether a vigorous parasitic state could be evolved by transfer procedures in the host-parasite system, Brucella neotomae versus the white mouse. Visible disease was not maintained and initial high doses were abruptly decreased if the parasite was serially transferred through host animals without the use of an adjuvant. Of several adjuvants tested, 5% mucin was the most effective in enhancing Brucella infections in the white mouse, and with this adjuvant a vigorous lethal disease was maintained in serial transfer. In one transfer series, bacterial colonies of a form different from B. neotomae were obtained. Substrains of the altered bacterial form were agglutinated by Brucella antiserum and exhibited other properties consistent with the genus, Brucella. Cultures and selected clones of this organism in low doses caused rapidly lethal disease in the white mouse in the absence of mucin. Also, the disease could be maintained in serial transfer as an acute lethal process without mucin. It is concluded that the host-parasite interaction was drastically altered with the emergence of a highly virulent parasite in an infectious state that had previously been relatively benign. Various related aspects of parasitism are discussed.