Classification of Microorganisms

Learning Objective: Examine how microorganisms are identified.
Although the medical assistant is not responsible for identifying microorganisms, a working knowledge of the terminology used in the naming of microorganisms is essential.

Microorganisms
Learning Objective: List the types of microorganisms.
Microorganisms are too small to be seen without magnification. Bacteria, fungi, and protozoa are all microorganisms that can be seen with a microscope. Parasitic worm infections are also identified in the microbiology laboratory because their eggs are visible under the microscope. Viruses are the smallest microbe and are visible only with a highly magnified electron microscope.

Naming Microorganisms
Learning Objective: Describe the naming of microorganisms.
Scientists use the binomial system of nomenclature developed by Swedish botanist Carl Linnaeus to name all living organisms: animals, plants, fungi, protozoa, and bacteria. This binomial system assigns two names, which are both either italicized or underlined when written:
            • Genus: First name; begins with a capital letter. After the organism’s full genus and species names are given once in a report, subsequent references can just use a single letter to represent the genus. For example, Escherichia coli is commonly referred to as E. coli.
            • Species: Second name; begins with a lowercase letter.
            • When microbiology laboratory results are reported, it is essential that both the genus and species names are recorded. Different species may cause different symptoms or require different antibiotic treatments. For example, Streptococcus pyogenes causes strep throat, whereas Streptococcus viridans is normal flora in the throat.