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Infect Immun, April 1998, p. 1726-1734, Vol. 66, No. 4
Department of Bacteriology, School of
Medicine, Nara Medical University, Nara 634, Japan
Received 17 November 1997/Returned for modification 22 December
1997/Accepted 16 January 1998
Infection with Shiga toxin (Stx)-producing enterohemorrhagic
Escherichia coli is increasing among children. In this
study, 5-week-old C57BL/6 mice with protein calorie malnutrition (PCM) that had been fed a 5% protein diet for 2 weeks since ablactation were
inoculated intragastrically with 2 × 106 CFU of
Stx-producing E. coli O157:H7. More than 75% of infected mice with PCM died by 10 days postinfection. Infected mice with PCM
developed neurologic symptoms 5 days after infection, while well-nourished control mice receiving a 25% protein diet did not. In
the intestinal tracts of infected mice with PCM, inoculated E. coli O157:H7 multiplied between days 2 and 4 of infection, with a
peak of growth at day 4. Although the pathogens were not culturable
from the stool after day 7, O157 lipopolysaccharide was detectable in
the stool by enzyme-linked immunosorbent assay even after day 8. Stx
was detectable in the stool after day 2 of infection and increased in
proportion to the growth of inoculated organisms. The maximal
production of Stx occurred at 4 days postchallenge, and Stx was
detectable in the blood on days 3 to 5. In contrast, well-nourished
control mice survived the infection, and all of them remained well even
after 3 weeks of infection. In these control mice, inoculated E. coli O157:H7 disappeared from the stool before day 3. Stx was not
detectable in the stool and blood of infected control mice at any time
from day 1 through day 8. Histologically, cerebral hemorrhages seemed
to be the cause of acute death of infected mice with PCM.
Immunocytochemical staining demonstrated the positive immunoreaction to
Stx at the alveus and stratum pyramidale of the hippocampus and in
renal tubules of infected malnourished mice. Such immunoreactions were
not found in tissues from infected control mice. Histological study of
the intestinal epithelium before infection showed that PCM severely
affected the development of intestinal epithelia. These findings
strongly indicate that PCM-induced nondevelopment of intestinal
physical barrier is one of the predisposing factors for infection with
Stx-producing E. coli O157:H7 in mice and suggest that our
mouse model may explain the high incidence of infection with
Stx-producing E. coli O157:H7 in the children whose
intestinal epithelia have not yet completely developed.
0019-9567/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Enhancement of Susceptibility to Shiga
Toxin-Producing Escherichia coli O157:H7 by Protein
Calorie Malnutrition in Mice
*
Corresponding author. Mailing address: Department of
Bacteriology, School of Medicine, Nara Medical University, 840, Shijyocho, Kashihara, Nara 634, Japan. Phone: 81-744-29-8839. Fax:
81-744-29-7375. E-mail: eijikita{at}naramed-u.ac.jp.
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