Scanning electron micrograph (SEM) of Staphylococcus aureus. Numerous clumps of methicillin-resistant Staphylococcus aureus bacteria, commonly referred to by the acronym, MRSA; Magnified 4780×.
Text&Photo CDC, Public Health Image Library (PHIL)
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Methicillin-resistant Staphylococcus aureus infections, e.g., bloodstream, pneumonia, bone infections, occur most frequently among persons in hospitals and healthcare facilities, including nursing homes, and dialysis centers.
Those who acquire a MRSA infection usually have a weakened immune system, however, the manifestation of MRSA infections that are acquired by otherwise healthy individuals, who have not been recently hospitalized, or had a medical procedure
such as dialysis, or surgery, first began to emerged in the mid- to late-1990's.
Methicillin-resistant Staphylococcus aureus on sheep blood agar. Only weak beta-hemolysis. This strain produces only narrow zones of hemolysis that do not extend much beyond the edge of the colonies. Cultivation 24 hours, aerobic atmosphere, 37°C.
B
MRSA on oxacillin resistance screening agar. Medium contains 5.5% of NaCl (salt inhibits most bacteria other than staphylococci) and oxacillin at 2 mg/litre (inhibits methicillin sensitive Staphylococcus aureus). Typical colonies of
methicillin-resistant Staphylococcus aureus(MRSA) are intense blue (mannitol fermentation in presence of aniline blue as a pH indicator). Cultivation 24 hours in an aerobic atmosphere, 37°C.
C
Disk diffusion susceptibility test on methicillin-resistant Staphylococcus aureus grown on Mueller-Hinton agar with co-trimoxazole (susceptible), erythromycin (resistant), clindamycin (resistant), gentamicin (susceptible), cefoxitin (resistant), and tetracycline (susceptible).
