Most cellulitis infections are caused by either strep (Streptococcus) or staph (Staphylococcus) bacteria.1 Streptococcus pyogenes leads to about 75 percent of cellulitis cases today, while Staphylococcus makes up almost 25 percent.2
Beta-hemolytic streptococci (including groups A, B, C, G and F) are the most common types of strep bacteria that cause cellulitis. Another form of strep bacteria-caused cellulitis (which is actually rather superficial in nature) is called erysipelas.This condition is characterized by a bright red circumscribed area on the skin with a sharp, raised border and is warm to the touch. Erysipelas is more common in young children.3
Staphylococcus aureus bacteria are commonly found on the skin and noses of healthy people,4 so how do you get cellulitis from this type of strain? The problem arises when the bacteria enter your skin through open cracks or tears. But aside from causing cellulitis, there's more alarming danger that Staph bacteria pose, particularly the Methicillin-resistant Staphylococcus aureus (MRSA) strain.
The Dangers of the MRSA Bacteria Strain Go Beyond Cellulitis
More and more MRSA-related community-acquired infections are being reported today. MRSA infection, which is more common in health care settings such as hospitals and clinics, is highly alarming, as this serious illness can affect your entire body.
Aside from causing a skin infection like cellulitis, MRSA can cause severe damage to your joints, bones, lungs, heart valves and bloodstream, and may even lead to severe pain or death. What's more, MRSA is continuously adapting. Not only is it resistant to conventional broad-spectrum antibiotics like methicillin, penicillin, amoxicillin and amoxicillin, but even newly produced antibiotics are now also being thwarted by MRSA.
Other Rare Causes of Cellulitis
In some cases, fungi may be to blame for cellulitis. However, this is rare, as most fungal cellulitis cases are usually seen only in people with a severely weakened immune system (immunocompromised). These include people in the final stages of an HIV infection who are no longer responding to treatment.5 There are other bacteria strains that can lead to rare cases of cellulitis. These include:6
- Haemophilus influenzae — causes facial cellulitis in children under 6 years of age
- Pasteurella multocida — obtained from cat or dog bites (this has a very short incubation period of only four to 24 hours)
- Vibrio vulnificus — picked up from salt water exposure (such as following coral injury)
- Aeromonas hydrophila — acquired from fresh or salt water exposure (such as through leech bites)
- Pseudomonas aeruginosa — may be caused by a puncture wound on the hand or foot
- Erysipelothrix (erysipeloid) — transmitted in contaminated animal meat, such as pigs (butchers are one group that may be at risk)
- Anaerobes, Eikenella and Streptococcus viridans — may be passed on through human bites
If any of these harmful microorganisms infiltrate your dermis through open cracks or tears, then you become at high risk of contracting cellulitis. Remember, though, that while some of these bacteria may not be avoidable, there are others that you can actively stay away from. For example, MRSA proliferates in healthcare settings, so making a conscious effort to stay healthy so you can avoid going to hospitals and emergency rooms can reduce your risk of being infected.