good response of the bone marrow. The primary
bacteria-destroying cells (known as phagocytes)
are the neutrophils, and the bone marrow should
supply large numbers of these to combat the
infection. The greater the shift to the left
(increase in immature neutrophils), the more
severe the infection.
The appearance of
numerous juvenile cells (metamyelocytes)
indicates irritation of the bone marrow with
regeneration. If the infection continues and the
patients resistance declines, the shift advances
further to the left. If improvement ensues, the
shift declines and recedes to normal.
A falling white cell count with the number and
maturity of neutrophils progressing toward
normal indicates recovery.
A continued shift to the left with a falling total
white cell count indicates a breakdown of the
bodys defense mechanism and is a poor
The percentage of eosinophils, lymphocytes,
and monocytes generally decreases in acute
In tuberculosis, an increase in monocytes
(monocytosis) indicates activity in the infected
area. An increase in lymphocytes (lympho-
cytosis) indicates healing.
Eosinophils increase in parasitic infections and
bacteria classifications, common bacteria,
and procedural steps for making smears,
Gram staining, and reading and reporting
Bacteriology is the study of bacteria. Of primary
interest to Hospital Corpsman is medical bacteriology,
which deals with the bacteria that cause disease in man.
Bacteria are prokaryotic microorganisms of the
kingdom Protista. They reproduce asexually by
transverse binary fission in which the cell divides into
two new cells. Bacteria are found almost everywhere,
and the human body harbors vast numbers. Many
bacteria are beneficial and essential to human life; only
a few are harmful to man.
Since there are thousands of types of bacteria, a
method of classification is essential. Bacteria are
classified according to their respective
toxins produced, and
Grams stain reaction.
The disease-producing ability of bacteria is
referred to as either pathogenic or nonpathogenic.
Pathogens are bacteria that cause diseases, and
nonpathogens are harmless bacteria. Bacteria that are
essential to our body are, in their proper environment,
called common or normal flora. For example, alpha
streptococcus in the throat is common flora, but when
it is found elsewhere (such as in the blood stream,
possibly as a result of tooth extraction), it may cause
diseases such as septicemia and endocarditis.
The four growth requirements for bacteria are
TEMPERATURE REQUIREMENTS .
Temperature requirements are divided into the
following three categories.
Psychrophilicbacteria that reproduce best at
15EC to 20EC
Mesophilicbacteria that reproduce best at
20EC to 45EC
Thermophilicbacteria that reproduce best at
50EC to 55EC
OXYGEN REQUIREMENTS.The amount of
oxygen needed for an organism to grow or reproduce
varies with the type of organism.
organisms that reproduce in the presence of oxygen.
Obligate aerobes are organisms that grow only in the