Research: Fifties superbug returns2 April 2005 A 1950s penicillin-resistant strain of Staphylococcus aureus is re-emerging in the community, now resistant to methicillin. |
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Infections with methicillin-resistant S. aureus (MRSA) occur most often in hospitals, but some, with increasing frequency, are found in public places. These community-acquired MRSA strains differ from hospital strains, Dr Mark Enright (University of Bath and now Imperial College London) and colleagues have found, and some are descended from a penicillin-resistant strain that appeared in the 1950s and was supposedly vanquished by methicillin in the 1960s.
Rather than affecting elderly hospitalised patients, community-acquired MRSA seems to cause disease in children and young adults. The strains involved are resistant to fewer antibiotics than hospital MRSA, but produce a dangerous toxin that can cause large boils, septic shock or, in rare cases, a devastating pneumonia that kills more than 40 per cent of those affected.
By comparing the 'DNA fingerprints' of various MRSA strains (using a technique called multilocus sequence typing, or MLST), Dr Enright found that community-acquired strains are not 'feral' hospital strains, and have a different evolutionary history. Some of the community strains are descended from the 'type 80/81' strain, notable for being unusually transmissible and virulent, and probably the most frequent cause of severe staphylococcal disease in the mid-to-late 1950s. At the time, the strain was sensitive to methicillin, and so was suppressed when this antibiotic was deployed in the 1960s. Now, however, the strain is reemerging in the community, having gained resistance to methicillin.
Although only about 100 cases of community-acquired MRSA infection have been identified in the UK in the last three years, such cases are more common in the USA, mainland Europe and Australia, and the researchers point out that these strains could pose a serious public health challenge in coming years.
See also
External links
- Robinson DA et al. Re-emergence of early pandemic Staphylococcus aureus as a community-acquired methicillin-resistant clone. Lancet 2005;365:1256–8.
- The Pathogen Sequencing Unit (Wellcome Trust Sanger Institute)