E. Coli and sickness

Peter Herman x5495 rpeter at nmsu.edu
Fri Feb 5 17:23:16 EST 1993


In article <1993Feb1.152222.14078 at gserv1.dl.ac.uk> BAKERK at FRIR.AFRC.AC.UK (Ken Baker) writes:
>>E. coli is indeed an organism which is part of the normal bacterial
>>flora of the human gut, though in very low numbers compared to other
>                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>bacteria.  The outbreak that is in the news is due to ingestion of a
> ^^^^^^^^
>>strain that is found in cattle gut and produces a toxin like the one
>
>Sorry, not true. E.coli is far and away the most common bacteria in the
>human gut.
>
>
>Cheers,
>
>
>Ken.

At risk of starting a flame war, I would sure like to know Ken's
source on this.  E. coli represents much less than 1% of
normal adult human gut flora.  Far and away the largest component of
the flora is the obligate anaerobe Bacteriodes fragilis 
(~ 6x10E10/ml feces).  Next in line come genera such as Eubacterium, 
Peptostreptococcus, and Fusobacterium.  A plethora of other
genera come next.  A long way down the list of normal flora you come to 
E. coli with about 1X10E8 cells/ml. That is less than 1% of
Bacteriodes, never mind the total normal gut flora.
My particular source on this is Stanier's Microbial World (5th ed)
Tbl 29.2.  The text I use in teaching General Micro (Prescott,
Harley & Kline, Microbiology, 1st ed, WH Brown 1990) says
"Even the most abundant of the latter, (refering to facultative
anaerobes) Escherichia coli, constitutes only about 0.1% of the
total population" (p 563).  Similar information can be found in any
general or medical micro text.

So let me repeat
"E. coli is indeed an organism which is part of the normal bacterial
flora of the human gut, though in very low numbers compared to other
bacteria."



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