The Journal of Medical Microbiology, Vol 11, Issue 2 145-154, Copyright © 1978 by Society for General Microbiology
Experimental infections with protease-deficient mutants of Pseudomonas aeruginosa in mice
B. Wretlind and T. Kronevi
The virulence of a protease-producing strain of Psuedomonas aeruginosa was
compared with that of mutants that had lost the ability to produce
proteases and other extracellular enzymes. Lethal infections were produced
by inoculating mice intraperitoneally with bacteria in mucin, or by
inoculating mice intraperitoneally or intravenously with bacteria 4 days
after treatment with cyclophosphamide, 200 mg per kg body weight. No
significant difference in virulence between the wild-type parent strain and
some of its protease-deficient mutants was found. Histopatholoical
examination of different organs in the cyclophosphamide-treated and
infected mice showed striking fatty infiltration and focal necrosis of
liver, multiple necrotic foci in the spleen and haemorrhagic cystitis with
necorsis. The cystitis was produced by cyclophosphamide alone but was
aggravated by the infection. In conclusion, no correlation between the
production of protease in broth culture and the ability to produce lethal
septicaemia in mice was found, and extracellular proteases probably didnot
contribute to the virulence of P. aeruginosa. However, the
histopathological changes in the liver suggested a role for exotoxin A
insystemic infections.
