Colonizing bacteria
Staphylococcus aureus is a spherical, Gram-positive bacteria that grows in clusters resembling bunches of grapes. Staphylococcus aureus is part of the normal flora of the human body. It inhabits the body without causing harm most of the time. Staphylococcus aureus is a facultative anaerobe; it can perform both anaerobic and aerobic respiration. Staphylococcus aureus can be pathogenic--causing disease. MRSA (or methicillin-resistant Staphylococcus aureus) is a pathogenic strain that is most commonly picked up in hospitals.
Identification
Bacteria are often subjected to a classification test called a Gram stain. The Gram stain classifies bacteria based on the structure of their cell walls. The Gram stain test is a series of steps that add different dyes to the bacterial cell. Gram-positive bacteria, like Staphylococcus aureus, have a very thick cell wall. The thick wall keeps the stain inside the cell and causes the cell to appear purple under a microscope. The Gram stain doesn't determine the pathogenicity, or ability to cause disease. Both Gram-positive and Gram-negative bacteria can cause disease.
Effects
Staphylococcus aureus is a natural resident of the human body. It can be found on the skin and in mucous membranes like the nose. Staphylococcus aureus can cause disease or infection if normal conditions change--for example, if the immune system is already suppressed due to a cold or other minor infection. Staphylococcus aureus can cause boils, food poisoning, toxic shock syndrome and pneumonia.
Considerations
Staphylococcus aureus is also responsible for nosocomial infections, or infections picked up in the hospital. These infections are often severe because they are antibiotic resistant. MRSA and VISA/VRSA (or vancomysin intermediate/resistant Staphylococcus aureus) are both strains that have developed immunity to the effects of antibiotics. This characteristic makes these Staphylococcus aureus strains difficult to treat and they can be potentially fatal.
Biochemical Characteristics
Staphylococcus aureus converts high energy molecules like glucose--a six-carbon sugar--into energy through a process called cellular respiration. Cellular respiration is a series of metabolic processes that creates energy in the form of ATP. ATP is an efficient form of stored energy that can be readily used by cells. There are two types of cellular respiration: aerobic and anaerobic. Aerobic respiration can only take place in the presence of oxygen. Anaerobic respiration, also called fermentation, can take place without oxygen. Staphylococcus aureus is a facultative anaerobe. This means it will normally perform aerobic cellular respiration, but if oxygen is unavailable it can perform anaerobic respiration for energy production. Staphylococcus aureus produces an enzyme called catalase. Catalase helps Staphylococcus aureus break down hydrogen peroxide in oxygen a water. Hydrogen peroxide can be a toxin for some organisms.
Prevention
According to the Centers for Disease Control, the number of MRSA infections has been steadily increasing. Skin infections account for the majority, while invasive infections account for less. However, invasive--or serious infections--cause about 19,000 deaths per year. The best way to combat these infections is through preventative efforts like thorough hand washing between patient contact.
Tags: Staphylococcus aureus, Gram stain, cause disease, cellular respiration, aureus cause, aureus facultative, aureus facultative anaerobe
