Our first line of defense and the largest organ of the body is the skin. The surface of the skin is never sterile, even when it is clean. That means that human skin is populated with a mixture of microorganisms usually called normal skin flora (1) which creates a active barrier that protects from harmful pathogens at bay.
Certain percentage of the general population will be carriers of a pathogen that displaces some of their normal flora (also colonizes locations on our body) at any time.
Generally, normal skin flora and colonizing microorganisms do not cause infections and also do not the stimulate immune system of your organism. In case of a break in the skin or if the immune system becomes compromised, any pathogen can cause cellulitis infection or other types of skin infection.
Cellulitis generally may be caused by normal skin flora or by exogenous bacteria, in most cases found at the area where skin was previously broken (cuts, blisters, burns, cracks in the skin, surgical wounds , sites of intravenous catheter insertion etc).
Group A Streptococus bacteria is the most frequent cause of cellulitis in people with no previous history in this condition. This bacteria is commonly found on the skin and in the throat. Injuries on the skin or problems with the lymphatic system may make you susceptible to developing any form of cellulitis. Having in mind that the bacteria which causes cellulitis is present on your skin, you see how easy it is for this disease to be developed.
Although doctors are aware of the causes, they can not explain why one person is more susceptible to developing one form of cellulitis, and the other will stay immune to every one.
The Usual Causes
The most widespread cause of cellulitis in adults is group A streptococcus. This bacteria is common on the skin and in the throat of every person and the biggest causer of this infection.
The second biggest is Staphylococcus aureus (S. aureus). This bacteria is commonly found on a person’s skin and near the lining of the mouth and nose (medically mucosa).
There are special cases, when cellulitis is not caused by any of the above mentioned bacteria. If cellulitis develops, it is usually a result of medical conditions like HIV,diabetes or AIDS, or if the infection of a specific body area populated by other bacteria.
Other types of bacteria may be the cause of this common skin medical condition too. Children till the age of six get cellulitis by Hemophilus influenza e (H. flu) bacteria, which usually manifests itself on the arms, face and the upper body.
If you get bitten by a dog or a cat, than it is possible that the bacteria pasteurella multocida, which has a very short incubation period (4-24 hours only ) and is found in their saliva, get in the contact with your tissue and cause cellulitis. If this happens make sure you clean your wound thoroughly and with antibacterial cleanser as soon as possible.
Bacterias Aeronomas hydrohilia and Vibrio vulnificus which can be found in seawater or tap water, may also be your cause.
Bacteria pseudomonas aeruginosa , P. aeruginosa, Vibrio vulnificus, Methicillin-resistant S. aureus (MRSA), Clostridium septicum, Group B streptococcus , E. coli, Erysipelothrix are all possible causes of this desease.
You do not have to know exactly what type of bacteria caused your inflammation, because symptoms and the treatment is the same for that type of cellulitis
(1) Microorganisms that live harmlessly on or in the body and do not cause disease unless the normal protective barriers (skin, mucosa) are compromised.
©2001 – 2010 by American Association for Clinical Chemistry