Community MRSA is re-emergence of 1950's
pandemic
April 3, 2005, News-Medical.Net
This "re-equipping and re-emergence" of a clone that caused a pandemic
40-50 years ago could mean that community acquired MRSA will spread
faster and be more widespread than previously expected, warns an
international team of researchers who have been studying the bacteria
First isolated in Australia and Canada in 1953, type 80/81
penicillin-resistant Staphylococcus aureus bacteria caused skin
lesions, sepsis and pneumonia in children and young adults around the
world. This pandemic of both hospital and community acquired
infections waned throughout the 1960s as the antibiotic methicillin
was used to treat these infections. Now researchers have shown that
one of the key clones of community acquired MRSA (CA-MRSA) -
infections picked up in public places which are resistant to treatment
by powerful methicillin antibiotics - may have evolved from this
earlier pandemic-causing strain. The researchers have sequenced key
genes from 80/81 samples isolated between 1955 and 1969 in Australia,
England and the USA, and compared them with the same regions in genes
from a clone of one of the most common CA MRSAs which has been found
in England and Scotland. They found that these key regions in nearly
all of the 80/81 isolates were identical to the CA-MRSA clone, and
also that they share the same highly-virulent toxin, called Panton-Valentine
leucocidin. They believe that their findings suggest that this
particular CA MRSA clone has evolved from the earlier 80/81 type,
developing resistance to methicillin antibiotics over the last 30-40
years, possibly through several intermediate steps. "At the time of
the 1950s pandemic, many doctors thought that these isolates were
unusually transmissible and virulent," said Dr Mark Enright from
Department of Biology and Biochemistry the University of Bath (UK) who
is leading the research. "We have shown that 80/81 and its souped-up
community acquired MRSA descendent share many of the same features,
which explains why 1950s pandemic was so successful, but also shows
why community acquired MRSA could pose such a serious public health
challenge in coming years." The community acquired MRSA clone has a
toxin and other traits with a proven track record for causing serious
diseases in healthier and younger age groups than those currently
regarded as at risk. The increased resistance to antibiotics of the
community acquired MRSA clone over its 80/81 ancestor mean that there
could also be other factors which complicate the treatment of the
disease it causes."
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