MRSA and “Usual” Staph Aureus Pictures
It is impossible to say from staph skin infection pictures, if the cause of infection is MRSA (Methicilin Resistant Staphylococcus Aureus) or an “usual” staph - MSSA (Methicillin Sensitive Staphylococcus Aureus). Even a staph carrier without any symptoms can have MRSA. Folliculitis, which is usually a mild infection, may also be caused by MRSA or MSSA (folliculitis pictures).
Picture 1. A boil below the knee, caused by MRSA
(source: phil.cdc.gov)
Pictures obtained by a light or electron microscope cannot help in distinguishing between MRSA and usual staph.
Picture 2.Staph aureus under the light microscope, magnified about 100x
(source phil.cdc.gov)
Picture 3. Cluster of MRSA bacteria as seen under the electron microscope
(source phil.cdc.gov )
MRSA can be distinguished from MSSA by:
1. Antibiotic susceptibility test: an inhibitory zone (no bacteria growth) is seen around the methicillin (today oxacillin is used) disc put onto a staph colony, if a strain of staphylococci bacteria is methicillin sensitive. If bacteria are methicillin resistant, no inhibitory zone around the disc is seen.
2. PCR (Polymerase Chain Reaction) (see lab tests for staph)
Picture of MRSA after PCR and chromatography
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Article reviewed by Dr. Greg. Last updated on April 23, 2011
