Send to

Choose Destination
J Infect Dis. 1994 Oct;170(4):841-7.

Reduced virulence of rifampicin-resistant mutants of Francisella tularensis.

Author information

Department of Cellular Immunology, Walter Reed Army Institute of Research, Washington, D.C.


Rifampicin-resistant mutants of a live vaccine strain (LVS) of Francisella tularensis were produced and screened for virulence in mice; 4 avirulent clones with intraperitoneal (ip) LD50s > 10(6) cfu, compared with 10(2) cfu for LVS, were characterized. Growth characteristics at 37 degrees C, surface envelope proteins, and lipopolysaccharide profiles of resistant mutants were identical to those of LVS. Polymerase activity of the mutants was more resistant than the enzyme from LVS to the inhibitory action of rifampicin. Growth rates for mutants and LVS were similar during the first 5 h at 42 degrees C, but viability of the mutants decreased to < 0.01% at 24 h. LVS and mutants differed in their ability to grow in vitro in host macrophages: LVS increased 580-fold over 72 h; mutants increased 33-fold. After ip inoculation of the organisms into mice, increasing numbers of LVS from peritoneal cells were isolated; mutants decreased over 4 days.

[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for Silverchair Information Systems
Loading ...
Support Center