Treatment of tularemia, including pulmonary tularemia, with gentamicin.

An alternative to streptomycin for treatment of possible tularemia would be useful on occasions when a patient develops a perplexing pneumonia that does not respond to initial treatment. In geographic areas where tularemia is endemic, an antimicrobial drug that is bactericidal for Francisella tularensis and is also effective against a spectrum of common pulmonary pathogens, including the Enterobacteriaceae and most strains of Pseudomonas aeruginosa, would be desirable. The purposes of this report are (1) to describe observations regarding the in vitro susceptibility of Francisella tularensis to streptomycin, kanamycin, and gentamicin; (2) to describe in vivo efficacy of these drugs in mouse tularemia; (3) to describe the results in 10 patients with tularemia treated with gentamicin. Gentamicin was bactericidal for Francisella tularensis in vitro, was effective in mouse tularemia when given in large doses, and was effective in humans when given in the standard recommended dose.

Murine model for study of cell-mediated immunity: protection against death from fully virulent Francisella tularensis infection.

To assess cell-mediated immunity in terms of host protection, an experimental model was developed in which passively transferred spleen cells from immunized AKR/J mice enabled nonimmume syngeneic recipients to survive an otherwise fatal infection with fully virulent Francisella tularensis. Donor immunization was achieved by administering live attenuted tularemia vaccine and, subsequently, the virulent streptomycin-sensitive SCHU S4 strain of F. tularensis. At selected intervals after immunization, donor spleen cells were transferred to streptomycin-treated recipients challenged subcutaneously, intravenously, or intraperitoneally with 25 to 50 minimal lethal doses of virulent streptomycin-resistant F. tularensis SCHU S5. The protection afforded by immune spleen cells was maximal (essentially 100%) 12 days after the SCHU S4 secondary immunization.

Biochemical and immunological properties of ribonucleic acid-rich extracts from Francisella tularensis.

Ribonucleic acid (RNA)-rich extracts derived from the attenuated strain of Francisella tularensis (strain LVS) protected Swiss mice against lethal challenge with F. tularensis strain 425 but not against strain SCHU S4. No killed preparation, including an RNA-rich extract from SCHU S4 itself, offered protection against strain SCHU S4 in contrast to the high level of protection offered against this strain by vaccination with live strain LVS. The protective activity observed against strain 425 was sensitive to ribonuclease but not to Pronase. Protective activity is not a general property of bacterial RNA, since RNA-rich extracts from Staphylococcus aureus offered no protection against tularemia, although disc gel electrophoresis showed similar kinds and amounts of RNA in preparations form F. tularensis and S. aureus. Furthermore, inability to localize activity to a specific region in sucrose gradients suggests a structural rather than an informational role for the RNA in such extracts. RNA-rich extracts from F. tularensis but not from S. aureus were efficient inducers of F. tularensis opsonins in mouse serum, suggesting one mechanism by which such extracts confer protection.

Pathogenesis of tularemia in monkeys aerogenically exposed to Francisella tularensis 425.

The pathogenesis of tularemia was studied in groups of rhesus monkeys (Macaca mulatta) that inhaled graded 10-fold doses ranging from 10 through 10(6) organisms of Francisella tularensis 425, a strain highly virulent for the white mouse but of reduced virulence for the domestic rabbit. Mean incubation periods ranged from 3 to 6 days followed by acute illness lasting 5 to 11 days with subsequent recovery of most animals. The higher inhaled doses resulted in shorter incubation periods, longer and more severe acute illnesses, and 18% mortality at the highest dose. Strain 425 multiplied in the lungs, disseminated to the regional lymph nodes, and became systemic. Maximal bacterial populations in tissues were reached by the 7th day after exposure of the animals regardless of the number of organisms inhaled. F. tularensis was no longer recoverable from any of six tissues examined 2 months after exposure. The most significant tissue changes occurred in the lungs; these consisted of foci of liquefaction necrosis, lobular consolidation, and pleural effusion and adhesions. The data indicate that the inhaled dose of strain 425 determined the maximal growth of the organism in the lungs which in turn influenced the severity of the usually self-limiting pneumonia and systemic infection. Although the monkey is less resistant to tularemia than is man, this laboratory animal when infected with F. tularensis 425 provides a useful model for the self-limiting type of human pulmonary tularemia usually observed in Europe and Asia but to a lesser extent in North America.

Isolation and Properties of a Deuterium-Tolerant Mutant of Pasteurella tularensis.

A spontaneously occurring stable deuterium-tolerant mutant was selected from highly virulent Pasteurella tularensis strain SCHU S4; the frequency of mutants in the cell populations was between 10(-3) and 10(-4). Upon cultivation of parent strain SCHU S4 in media containing D(2)O in lieu of H(2)O, inhibitory effects became manifest at 18% D(2)O and increased significantly beyond 54% D(2)O; mutant strain SCHU DT was not inhibited by media containing as much as 98% D(2)O. When cultivated in media containing D(2)O, mutant SCHU DT, in comparison with parent strain SCHU S4, showed a significant reduction in dermal and respiratory virulence for laboratory animals. Its immunogenic properties were comparable to viable P. tularensis vaccine strain LVS. Data on the comparative growth of various P. tularensis strains on media containing D(2)O suggested that "Old World" strains might be more tolerant to isotopic substitution of deuterium for protium than North American strains. Because of the residual virulence of SCHU DT for experimental animals it is believed to have limited value as a potential live vaccine strain.

Effect of aerosol age on the infectivity of airborne Pasteurella tularensis for Macaca mulatta and man.

Sawyer, William D. (U.S. Army Medical Unit, Fort Detrick, Frederick, Md.), Joseph V. Jemski, Arthur L. Hogge, Jr., Henry T. Eigelsbach, Elwood K. Wolfe, Harry G. Dangerfield, William S. Gochenour, Jr., and Dan Crozier. Effect of aerosol age on the infectivity of airborne Pasteurella tularensis for Macaca mulatta and man. J. Bacteriol. 91:2180-2184. 1966.-In aging aerosols of Pasteurella tularensis SCHU-S4, the respiratory infectivity for man and Macaca mulatta decreased more rapidly than the viability of the organisms. Infectivity was diminished after 120 min, and was reduced 10-fold after 180 min. These findings confirmed previous observations made in mice and guinea pigs, and also revealed that smaller losses of infectivity were detectable in the primate hosts.