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Major Pathogenic Bacteria
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The major bacterial
pathogens are presented in
Table 14-1 and described in
Chapters 15-26.
So that the reader may
concentrate on the important
pathogens, the bacteria that
are less medically important
are described in a separate
chapter (see Chapter 27).
The readily stained
organisms fall into four
categories: gram-positive
cocci, gram-negative cocci,
grampositive rods, and
gram-negative rods.
For ease of understanding,
the organisms associated
with the enteric tract are
further subdivided into
three groups: (1) pathogens
both inside and outside the
enteric tract, (2) pathogens
inside the enteric tract,
and (3) pathogens outside
the enteric tract.
Chlamydia, Rickettsia
example, Campylobacter
causes enteric tract disease
but frequently has an
animal.
The organisms that are not
readily Gram-stained fall
into six major categories:
Mycobacterhtm species, which
are acid-fast rods;
Mycoplasma species, which
have no cell wall and so do
not stain with Gram stain;
Treponema and leptospira
species, which are
spirochetes too thin to be
seen when stained with
GrarrTstam; and Chlamydia
and Rickettsia species,
which stain well with Giemsa
stain or other special
stains but poorly with Gram
stain.
Table 14---2 presents the 10
most common "notifiable"
bacterial diseases in the
United States for 1997 as
compiled by the Centers for
Disease Control and
Prevention.
Important Properties
Anaerobes are characterized
by their ability to grow
only in an atmosphere
containing less than 20%
oxygen; ie, they grow poorly
if at all in room air.
Facultative anaerobes such
as Escherichia coli can grow
well under either
circumstance.
Aerotolerant organisms such
as Clostridium histolytictim
can grow to some extent in
air but multiply much more
rapidly in a lower oxygen
concentration.
The precise reason why the
growth of anaerobes is
inhibited by oxygen is not
understood, but several
factors are probably
involved (see Chapter 3).
Clinical Infections Many of
the medically important
anaerobes are part of the
normal human flora.
Veillonella ample, such
specimens as blood, pleural
fluid, pus, and
transtracheal aspirates are
appropriate, but sputum and
feces are not.
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