In 1938, Sabin(1,Z) and Findlay et aE(3) almost simultaneously reported the recovery of pleuropneumonia-like organisms ( PPLO) from brains of mice undergoing intracerebral passage of toxoplasma and lymphocytic choriomeningi t is virus, respectively . The isolated PPLO, when passed intracerebrally in mice, induced a characteristic turning on the long axis of the body which led to the term "rolling disease"( 3 ) . The American strain was called type A by Sabin while the British strain was designated L: in Klieneberger's series. Sabin and co-workers (4-6) subsequently recovered type A and 4 other serologically distinct strains of PPLO, types B, C, D and E, from the brain, nose, conjunctival sac, and respiratory tract of normal mice. All 5 types produced arthritis in mice following intravenous inoculation of fluid cultures. In addition, the type A strain was also shown to elaborate, in vitro, a potent neurotropic exotoxin for mice. When 0.5-ml amounts of a 24-48 hour fluid culture of type A were introduced intravenously into 3-week-old mice, the rolling syndrome was observed after 1-2 hours and death usually occurred shortly thereafter. The mice that survived with persistent neurological signs showed neurolytic lesions in the cerebellum after 18 hours. The L5 organism was found to be serologically identical to the type A strain but differed in being less virulent for mice and in not forming exotoxin in vitro (3,6). Following these reports, other PPLO isolations from mice were recorded( 7-1 1).The original neurotoxic type A strain, as well as the other 4 American types, were apparently lost and have not been available for serological comparisons with more recent isolates from mice( 11). The original L3 strain was also lost but a strain with similar properties was subsequently recovered ( 3 ) and, although it lost its virulence after pro-longed subcultivation, sufficient biochemical and serological characteristics were determined to establish this strain in current classification schemes( 10,12,13). This strain (PG-28) is now the prototype of L5 and type A strains recovered earlier and is known as Mycoplasma neurolyticum ( 1 2 ) .We recently secured cultures of Sabin's type A and C strains that were lyophilized in February 1943. This report describes the recovery of mycoplasma from these cultures and the results of virulence and serological tests.Materials and methods. Mycoplasma isolation. The 2 vials of lyophilized mycoplasma were wiped with gauze soaked in 5% phenol and allowed to air dry. Upon opening the vials, 0.5 ml of sterile brain heart-infusion broth was injected into each with separate sterile needles and syringes. Approximately 0.1 ml from each vial was transferred to agar plates (60 X 15 mm) and liquid cultures ( 5 ml) of the following media; (A) brain heart-infusion broth (BBL) plus 1 % peptone (Parke-Davis) and adjusted to pH 8.0. After sterilization, sterile, fresh 2. 570 yeast extract (14) and sterile horse serum (Cappel) were added to give 10% and 2070 concentrations, respectively; (B) PPLO broth (D...

Heretofore all attempts to demonstrate protective antibody in antitularense serums have failed whenever animals were challenged with a strain of high virulence. Previous test animals have been the mouse, guinea pig, hamster, and rabbit. Sources of immune or hyperimmune serums were goats, horses, sheep, rabbits, and man: Our considerable unpublished experience with these animals and serums is in good agreement with the reports of Francis and Felton (1) and Bell and Kahn (2). If injected with serum before challenge these animals will usually exhibit significant prolongations of the survival time beyond that of control animals, but no actual survivals against as little as 1 to 10 M.L.D. of a virulent challenge strain.The inability to demonstrate serum protection in these highly susceptible animals has contributed to a widespread but unfounded belief that immune and hyperimmune serums are ineffective therapeutic agents in human tularemia. Although reports by Foshay (3, 4) on the results of serum therapy in individual patients, as well as analyses of accumulated data derived from the independent observations of more than 600 clinical observers, have continued to demonstrate significant reductions in mortality and highly significant reductions in morbidity in comparison with comparable data from untreated patients, universal acceptance of the value of serum therapy has been impeded by a lack of suitable means to demonstrate protective antibody and to establish quantitative criteria for potency. The work here reported was undertaken to supply these deficiencies.The inability of the highly susceptible mouse, guinea pig, hamster, and rabbit to react with any useful degree of resistance before death occurs. following infection with a single virulent unit of Bacterium tularense makes these animals unsuitable test hosts for serum protection experiments.The reasons for this inability, obviously inoperative for many other infectious agents under similar conditions of testing, are unknown at present. The reactions of these animals to invasion are quite unlike that of man, for whom there is ample evidence that the great majority rapidly develop a high degree of resistance, resulting-in a disease that is characterized clinically by a low mortality and, pathologically, by tissue reactions that soon exhibit subacuteness and chronicity.During the course of the initial investigations on this disease, McCoy (5) Challenge strain. The strain of Bacterium tularense used was the highly virulent strain SCHU, which had been studied extensively and had been maintained frequently in animal passage since its isolation in 1941. Its subcutaneous LDIs titers for mice, guinea pigs, and rabbits varied from 9.1 to 9.7/0.5 ml. The LD50 titers were determined by the method of Reed and Muench (6). They are expressed as the logarithms of the dilutions, disregarding the minus sign.Challenge suspensions. Challenge suspensions were prepared from the second of 2 consecutive 16-hour subcultures on glucose glycerol cystine human blood agar. The growth was p...

No abstract