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 Inactivated vaccine Attenuated Vaccine Toxoid Autovaccine Polysaccharide vaccine

Artificial active immunization Chemical vaccine Synthetic Vaccine Gene-defective vaccine DNA recombinant vaccine Idiotype vaccine

Artificial passive immunization Antitoxin Antibacterial antibody Placental globulin Gamma globulin TF IFN IL-2

Treatment