Methods used for identification of microbes

METHODS USED FOR IDENTIFICATION OF MICROBES

Microbes are considered as unseen enemies of man. They can be seen only under microscope. To identify the specific microbes, the following methods are done.

SMEAR, 

FIXING, 

HANGING DROP PREPARATION,

STAINING, 

CULTURE, 

ANIMAL INOCULATION,

SEROLOGICAL TESTS.

MICROSCOPE:

Microscope is the instrument, which is used to magnify objects, and structure, which are too small to see by the naked eye. Since the science of microbiology is concerned with the microorganisms, we can appreciate that microscope is the most essential piece of equipment in the laboratory to identify bacteria. There are varieties of microscopes of which three are most important.

The compound optical microscope, which is used for routine bacteriological examinations.

The dark field microscope, which is used to identify spirochaetes, e.g. trepenoma pallidum

The electron microscope is the most powerful microscope used to maginify the object by 100,000 times. This is used in the identification of viruses.

Smear:  Place  a  drop  of  specimen,  which  is  to  be examined,  on  the  middle  of  a  slide.   Place  a  drop  of distilled water (Water is needed only for solid specimen, e.g. motion) with a sterile loop, and spread the specimen uniformly on the slide.  This kind of examination is known       as direct microscopic examination.

Fixing: Fix the smear by flaming the slide.         Flaming is done  by passing  the  slide  on  a flame  for  three  or  four        times.  Fixing can also be done by using chemicals such as formalin, methyl alcohol, mercuric chloride.

Hanging Drop Preparation: It is often used to determine whether the bacteria are motile or non-motile.

Hanging drop preparation aids in studying the organisms in living state.

Human Immuno Deficiency Virus: It is identified by ELISA and Westernblot tests.

TYPES OF SPECIMEN COLLECTED:

1.              Swabs: It is usually collected in a sterile test tube. Care should be taken so as to prevent contaminations of specimen.

2.              Throat swab for cultures: These should be taken only with a view of the throat, in a good light and using a tongue depressor. Materials should be taken only from the infected area.

3.              Sputum: It should be collected in a sterile container having wide mouth. Sputum should be collected directly after a cough and sent immediately to the laboratory.

4.              Urine: Urine  specimen  for  chemical  and  microscopic

5.              examinations can be collected in a clean container or test tube, but for culture it should be collected in a sterile test tube.

6.              Faeces: Fresh stools should be collected for bacteriological examination.

7.              Blood: It should be collected in a sterile container. The nurse should assist while collecting other specimens like cerebro spinal fluid. Etc. When assisting the physician, she should adopt aseptic precautions so as to avoid contamination of specimen.