s. epidermidis

Helpful Bacteria: Staphylococcus Aureus and Staphylococcus Epidermidis

Bacteria, Viruses and Health

Kristin Lake

Kingdom: Bacteria

Phylum: Firmicutes

Class: Bacilli

Order: Bacillales

Family: Staphylococcaceae

Genus: Staphylococcus

Species: Aureus and Epidermidis

Staphylococcus is a Gram-positive bacteria that has over 40 known species.  It is part of the normal human flora and is found on the skin, ocular conjunctiva, mucous membranes of the upper respiratory tract, the lower gastrointestinal tract and the urogenital tract in the anterior urethra and vagina.  S. aureus and S. epidermidis flourishes on the uppermost layers of the epidermis and the associated hair follicles as well as the nasal membranes.  S. aureus and S. epidermidis pose as potential pathogens and can cause overwhelming infection in many systems of the body but they are also mutually beneficial to humans.  The oral cavity contains many microbial entities and S. aureus and S. epidermidis are part of the normal flora. This normal flora provides many benefits to its human host by inhibiting and killing non-indigenous species of microbes, colonizing throughout to prevent the establishment of non-indigenous species of microbes which may be pathogenic in nature, synthesizing and excreting vitamins and nutrient byproducts, and stimulating antibody production as well as tissue development.  There is little contrast between the benefits of S. aureus and S. epidermidis, however most strains of S. epidermidis usually are not harmful to the host or pathogenic in nature unless a strain with inherent or acquired resistance is present.

S. epidermidis and S. aureus have the potential to be the culprit of nosocomial infections (hospital-borne illnesses) in patients post-surgically at wound sites.  Purulent discharge and necrosis of tissues can occur in susceptible individuals with openings on the skin to allow S. epidermidis and S. aureus an entry to deeper layers of the tissue.  Despite their pathogenic qualities, S. aureus helps to prevent pseudomembranous colitis which is another common nosocomial infection caused by the bacteria Clostridium difficile or more commonly known in the medical field as “C. diff.”  Prolonged antibiotic usage in ill patients can cause an imbalance in the gut flora which allows C. difficile to flourish.  S. aureus is found in the lower gastrointestinal tract in much smaller numbers than other enteric microbes, but remains a part of the normal flora which is responsible for keeping the numbers of C. difficile bacteria under control by acting as a microbial antagonist.


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