DEUTERIUM-TOLERANT PASTEURELLA TULARENSIS
VICKERS-ARMSTRONGS (AIRCRAFT) LTD WEYBRIDGE (UNITED KINGDOM)
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Substitution of deuterium oxide for water in liquid medium has been shown to affect the growth and viability of Pasteurella tularensis SCHU S4 adversely as the D2O concentration is increased. Prolonged lag phase, cell enlargement, chain formation, and clumping were observed. This report concerns the selection and characterization of a deuterium-tolerant mutant SCHU DT, variation between strains with regard to growth on solid medium containing D2O, and properties of organisms grown in the presence of deuterium. SCHU DT was capable of multiplication on solid medium containing 98 D2O and showed no reversion when serially transferred more than 20 times on medium without D2O it possessed aerosol properties similar to parent SCHU S4, but was of significantly lower virulence for the mouse, guinea pig, and rabbit. The majority of guinea pigs surviving a respiratory exposure of 10,000 SCHU DT were at least as resistant to challenge with SCHU S4 as animals administered live vaccine strain LVS. Several Eastern European and Asiatic strains were able to multiply in medium containing 98 per cent D2 O whereas strain SCHU S4 and several SCHU S4 colony-type mutants of lowered virulence were inhibited. Deuterated LVS cells, although less virulent than normal cells, were comparable in immunogenicity for the mouse.