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What is Staphylococcus Aureus? - Definition & Characteristics

Instructor: Thomas Higginbotham

Tom has taught math / science at secondary & post-secondary, and a K-12 school administrator. He has a B.S. in Biology and a PhD in Curriculum & Instruction.

Zits and lesions and rashes, oh my! Oh, and MRSA for good measure. In this lesson learn about one of the most common, mildly annoying, and occasionally lethal bacteria in the natural world, ''Staphylococcus aureus.''

S. aureus, S. aureus Everywhere!

If you took a look at the surface of your skin under a microscope, you would find a veritable world-class zoo of microorganisms there, from dust mites to fungi to bacteria of any shape and size. One of the bacteria you might notice is Staphylococcus aureus. 'Wait,' you might think. 'Isn't that the one that causes Staph infections?!? I have to shower to scrub them off!' Don't worry about that. First, you'd never get rid of them all. Second, they only cause problems in certain situations.

What Is Staphylococcus aureus

Staphylococcus aureus (S. aureus) is a gram-positive bacterium that is found on the skin and in the nasal passages of about a quarter of humans. It is a facultative anaerobe, meaning it can produce energy (and thus survive) either in the presence or absence of oxygen. It is also the causative agent for many skin illnesses and other illnesses that will be discussed later. Infections caused by S. aureus are often referred to colloquially as Staph infections. Despite its capacity to produce some toe-curlingly disgusting skin conditions, it is actually a fascinating, adaptive little bug, that does not often cause fatal infections.

How Does S. aureus Cause Illness?

In most cases, having S. aureus present does not harm, and is occasionally even thought to be helpful to a host. However, if a host is immunocompromised (e.g., old, ill, very young, or recovering from a surgery) or if there is a large point of potential entry (i.e., a wound), the quantity of S. aureus individuals overwhelms the host's capacity to effectively coexist with the bacterium, and an illness can result. The exact mechanism of infection depends on location, but results from toxins or enzymes produced by the bacterium that can damage skin or other tissue. In the most severe cases, S. aureus infecting the bloodstream can release massive amounts of superantigens that can cause the often-fatal toxic shock syndrome.

S. aureus Skin Illnesses

S. aureus is an extremely common cause of skin infections, especially in health care facilities. It is also very often the cause for skin infections at communally-encountered areas, such as artificial turf and wrestling mats. Its prevalence in these areas comes from its ability to survive outside a host on a surface (such as turf), and from its ability to spread from contact (e.g., it can be spread through the close contact between two wrestlers. Open S. aureus infections (e.g., pustules or lesions) have the capacity to leave high concentrations of the bacterium on whatever surface the infection touches. Some of the more common illnesses or conditions caused by S. aureus include impetigo, pimples, abscesses, and folliculitis. One of the best ways to prevent S. aureus infections is through basic hygiene such as handwashing and using ethanol to clean communal surfaces.

S. aureus Internal Illnesses

One of the more common internal illnesses caused by S. aureus is pneumonia (an inflammation of lung tissue), which often occurs after a bout with influenza or other respiratory illness. S. aureus is able to take advantage of weakened lung tissue to invade and infect. Other less common illnesses caused by S. aureus include urinary tract infections, meningitis, and food poisoning.

S. aureus Fatal Illnesses

As mentioned earlier, if S. aureus infects the bloodstream (sepsis), acceleration of severe and toxic symptoms can occur rapidly. If left untreated, death can quickly result, as the body's attempt to fight off the invading S. aureus results in a cascade of effects, including inflammation of tissues and organ failure.

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