MRSA refers to methicillin-resistant Staphylococcus aureus (Staph aureus) resulting in infections that can be challenging to treat. Staph aureus is a G+, coagulase +, non-correlating cocci and is normally found on the skin, nares, nasopharynx and perineum of both animals and humans. However, it is also an opportunistic pathogen given the right conditions. Staph aureus was first discovered in the 1800's and pre-World War II the mortality rate due to Staph aureus infections was 80%. The first penicillin resistant strain of Staph aureus was identified in 1942, first in hospitals and then in the community. By 1960, 80% of Staph aureus was penicillin-resistant and by 1961 the first methicillin-resistant Staph aureus was identified just 2 years after theintroduction of this semi-synthetic penicillin developed to combat penicillin-resistant Staph aureus. Over the next few decades several hospital-associated MRSAs (HA-MRSA) disseminated worldwide and in the 1990's community-associated MRSA (CA-MRSA) was identified. Now although both CA-MRSA and HA-MRSA infections exist, the distinctions appear to be blurring.
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