Pathogenic E. coli (page 2)
(This chapter has 4 pages)
© Kenneth Todar, PhD
Escherichia coli in the
The commensal E. coli strains that inhabit the large
intestine of all humans and warm-blooded animals comprise no more than
the total bacterial biomass.
The E. coli flora is apparently in
constant flux. One study on the distribution of different E. coli
strains colonizing the large intestine of women during a one year
period (in a hospital setting) showed that 52.1% yielded one serotype,
34.9% yielded two, 4.4% yielded three, and 0.6% yielded four. The
most likely source of new serotypes of E. coli is acquisition
by the oral route.
To study oral acquisition, the carriage rate of E.
coli carrying antibiotic-resistance plasmids (R factors) was
among vegetarians, babies, and nonvegetarians. It was assumed that
nonvegetarians might carry more E. coli with R factors due to
their presumed high incidence in animals treated with growth-promoting
antimicrobial agents. However, omnivores had no higher an incidence of
R-factor-containing E. coli than vegetarians, and babies had
more resistant E. coli in their feces than nonvegetarians. No
suitable explanation could be offered for these findings.
Besides, investigation of the microbial flora of the uninhabited
Krakatoa archipelago has shown the presence of antibiotic-resistant E.
coli associated with plants.
The bottom line seems to be that most of us have more than one
of E. coli in our gut, and
intestinal strains tend to displace one another about three or four
times a year.
Pathogenesis of E. coli