DOCTORS are warning that a bacterial strain that caused widespread infections among healthy young people in the 1950s has acquired resistance to most modern antibiotics, and poses a serious threat once again.
鈥淚 have no doubt that this is going to cause serious public health problems in the UK and elsewhere in coming years,鈥� says Mark Enright of the University of Bath, UK, a member of an international team that has studied the bacterium. 鈥淭his is a very aggressive pathogen and it鈥檚 spreading rapidly.鈥�
In 1953, a virulent strain of the Staphylococcus aureus bacterium called 80/81 was identified in babies in Australia. It went on to cause serious outbreaks of skin infections, sepsis and pneumonia worldwide, often in healthy young people and children, both in hospitals and in the community. The 80/81 strain was resistant to penicillin, but with the introduction of antibiotics such as methicillin it was largely eliminated in the 1960s.
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In recent years methicillin-resistant forms of S. aureus, better known as MRSA superbugs, have become a huge problem in hospitals. Genetically distinct strains, called community-acquired MRSAs, have also begun spreading in otherwise healthy people outside hospitals (New 杏吧原创, 8 March 2003, p 4). While most of these bacteria still succumb to a few antibiotics, treatment can be complicated.
To find out how these modern strains relate to 80/81, the researchers sequenced parts of several genes in old samples of 80/81 and compared them with 1000 modern strains. They found that 80/81 is closely related to MRSA16, one of the superbugs causing problems in hospitals. What鈥檚 more, a community-acquired strain known as ST30-MRSA-IV, or the south-west Pacific clone because it was first found in this region, is almost identical to 80/81 (The Lancet, vol 365, p 1256).
The team suggests that both these MRSA strains are descendants of 80/81 that have somehow acquired resistance to methicillin. The ST30 strain remains rare, but it has caused fatal cases of pneumonia in France, Sweden and Latvia. The team predicts that it will become a much greater threat in future.
Their work also confirms that one of the reasons 80/81 was so dangerous was that it produced a toxin called PVL, which destroys immune cells. Many other strains of community-acquired MRSA also produce this toxin.
Other experts agree that ST30 could be a problem, but point out that while cases of community-acquired MRSA are growing rapidly, most are caused by other strains. 鈥淎mong hundreds of CA-MRSA strains now typed in Chicago, none is ST30,鈥� says Robert Daum at the University of Chicago. 鈥淏ut their finding does provide documentation that at least a few of the isolates fuelling the epidemic may be the old 80/81. It clearly did not disappear completely.鈥�
