Infection control - Classification of Micro Organisms

1Knowledge of microbiology is an essential component in nursing for practicing disinfections and sterilization to eliminate pathogenic microbes causing infectious disease.

Microbiology is a study of life process of the smallest living organisms (microbes). Microbes are so small that they can be seen only with the aid of a microscope.

CLASSIFICATION OF MICRO ORGANISMS.

Microorganisms are classified as follows:

Virus.

Bacteria

Protozoa (Parasites)

Fungi

Rickettsiae.

Virus: Viruses are very minute living organisms, which

can pass through bacterial filters and can be seen only under electron microscope.

Bacteria: Bacteria are heterogenous and belong to both animal and plant kingdom.

Streptococci: They are round shaped organisms arranged in chain. They are gram positive, non-motile, highly pathogenic and do not grow in ordinary media. They grow in blood and serum media.

Staphylococci: Staphylococci are arranged in clusters like grapes. They are gram positive and violet in colour when stained. They are non-motile and non-spore forming organisms. There are two types of pathogenic staphylococci

Staphylococcus  albus and

Staphyloccus aureus.

Diplococci: Diplococci are arranged in pairs and they are gram-negative organisms. Examples of diplococci are Neisseria gonococci and Neisseria meningococci. They grow in special culture media of heated blood.

Pneumococci: Pneumococci are also arranged in pairs. They are gram-positive and found in nasopharynx.

Bacillus: Bacilli are rod shaped organisms. These are gram positive and gram-negative organisms. Gram-positive bacilli are Corynebacterium diptheriae, clostridium tetani and bacillus anthracis and mycobacterium tuberculosis.

Clostridium Tetani: Clostridium tetani or bacillus tetani

are rod shaped spore forming organisms.  Mostly they are found in the intestinal tract of man and animals. They are also present in soil.

Bacillus anthracis: Bacilli anthracis are large rods with spores. They are found in animal hairs, wool, soil, water and dust.

Escherichia coli: These are small rod shaped organisms,

sometimes motile and sometimes encapsulated. They are found in the intestinal tracts of man and animals and they are non-pathogenic.

Salmonella: Like E.coli, Salmonella also are small, motile and rod shaped bacilli.

Vibrio: Vibrio are cama shaped, motile, gram negative

and non-spore forming organisms

Rickettsiae: Rickettsiae are larger than virus and smaller than bacteria in size. They are variously shaped like minute rods or spheres.