Transcript Detection, Prophylaxis and Treatment of Bacterial Infection

Detection, Prophylaxis
and Treatment of
Bacterial Infection
Diagnosis of Bacterial
Infection
Step 1.
• Samples of body fluids (e.g. blood, urine, cerebrospinal
fluid) are streaked on culture plates and isolated colonies of
bacteria (which are visible to the naked eye) appear after
incubation for one - several days .
• Each colony consists of millions of bacterial cells.
Observation of these colonies for size, texture, color, and (if
grown on blood agar) hemolysis reactions, is highly
important as a first step in bacterial identification.
• Whether the organism requires oxygen for growth is
another important differentiating characteristic.
Step 2.
• Colonies are Gram stained and individual bacterial
cells observed under the microscope.
Step 3
• The bacteria are speciated using these isolated
colonies. This often requires an additional 24 hr of
growth.
• Identification: biochemical reactions; immunological
method (using known antisera); drug sensitivity test;
etc.
Approaches to rapid diagnosis
without prior culture
• Certain human pathogens (including the causative
agents of tuberculosis, Lyme disease and syphilis)
either cannot be isolated in the laboratory or grow
extremely poorly. Successful isolation can be slow
and in some instances impossible. Direct detection
of bacteria without culture is possible in some cases.
A simple approach to rapid diagnosis-1
• antigen detection is used in many doctor's offices
for the group A streptococcus. The patient's
throat is swabbed and streptococcal antigen
extracted directly from the swab (without prior
bacteriological culture). The bacterial antigen is
detected by aggregation (agglutination) of
antibody coated latex beads.
Simple approach to rapid diagnosis-2
• Bacterial DNA sequences can be amplified directly
from human body fluids (the polymerase chain
reaction, PCR). In this fashion large amounts of
specific genes or portions of genes can be
generated and readily detected. For example, great
success has been achieved in rapid diagnosis of
tuberculosis.
Simple approach to rapid diagnosis-3
• Direct microscopic observation of certain clinical
samples for the presence of bacteria can be helpful
(e.g. detection of M. tuberculosis in sputum).
Simple approach to rapid diagnosis-4
• Serologic identification of an antibody response (in
patient's serum) to the infecting agent can only be
successful several weeks after an infection has
occurred.
• include agglutination,precipitation, complement
fixation test,neutralization, etc.
Artificial active immunization
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Inactivated vaccine
Attenuated Vaccine
Toxoid
Autovaccine
Polysaccharide vaccine
Artificial active immunization
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Chemical vaccine
Synthetic Vaccine
Gene-defective vaccine
DNA recombinant vaccine
Idiotype vaccine
Artificial passive immunization
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Antitoxin
Antibacterial antibody
Placental globulin
Gamma globulin
TF
IFN
IL-2
Treatment