Staphylococcus aureus
Lauren Dubbert

Staphylococcus aureus is a facultative anaerobe, Gram-positive, nonmotile, non-spore-forming coccus. When looking at this organism under a microscope it appears to be in clusters that look like grapes.  The round colonies appear to be golden in color hence the origin of the name aureus in Latin means “golden.”

Golden clusters of Staphylococcus aureus

There are simple tests that can be performed to distinguish Staphylococcus aureus from streptococci and even from other types of staphylococci.  S. aureus produces and enzyme known as catalase, which is used to do a catalase test to differentiate staphylococci and streptococci. This can be done by the conversion of hydrogen peroxide into oxygen and water by adding 3% hydrogen peroxide to a colony on an agar plate.  If the colony is catalase-positive the oxygen will be produced and bubbles will form. Avoid doing this test on a blood agar plate because catalase is present in blood and will produce inaccurate results. Another test, known as the coagulase test, is done to tell apart S.aureus from other types of staphylococci.  This test is valuable because of the production of coagulase, a clot forming enzyme, in S. aureus that is not produced in most other Staphylococcus organisms.

Gram-stain of S. aureus

Since staphylococci are facultative anaerobes so they can either grow by aerobic respiration or by fermentation yielding primarily lactic acid.  Growth of S. aureus can occur at temperatures varying from 15 to 45 degrees centigrade and at NaCl concentrations no higher than 15 percent.

Staphylococcus aureus is a human pathogenic organism that plays a role in causing health problems and producing virulent factors leading to disease.   There are over 30 different types of staphylococci and among these S. aureus is the most common infection causing organism in humans.  Staphylococci can be found on 20-30% of healthy people, most commonly in their nose or on their skin.  In most of these cases the bacteria do not cause disease. On the other hand, if the skin gets damaged in some way or some other injury happens, it allows the protective mechanisms of the body to be overcome by the bacteria and soon thereafter cause infection.  Infection can be spread in a variety of ways including coming in contact with pus from an infected wound, and coming in contact with towels, sheets, clothing or even athletic equipment used by an infected person.  This is why most workout facilities, including ours, have disinfectant sprays to use before and after use of the equipment preventing the spread of infection.

Although it is rare that staph infections progress to cause disease, it is possible.  Diseases such as impetigo, cellullitis, scalded skin syndrome and mastitis can develop.  More severe infections may occur as well.  If the bacterium gets into the blood flow and spread throughout the body’s organs, infections such as pneumonia, endocarditis, osteomyelitis, and sepsis are likely to arise.  Toxins can also be produced and secreted, depending on the strain of S. aureus, many of which are associated with specific diseases.

Osteomyelitis: a more severe infection caused by S. aureus getting into the bone by way of the bloodstream.

“Microbial Life” Textbook

*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.


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