Pandemic bug returns as community MRSA strain

时间:2019-03-02 09:05:00166网络整理admin

By Clara Penn A virulent type of community-acquired MRSA “superbug” that attacks healthy, young people has been found to be the descendent of a penicillin-resistant strain that caused serious infections worldwide 50 years ago. Scientists fear that this offspring superbug strain – which causes serious boils and abscesses and can lead to a severe pneumonia – could pose a major public health threat in the future. Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) is genetically distinct from the strains prevalent in hospitals, and can cause infections in young people with no connection to healthcare environments. Sickness ranges from relatively minor skin and soft tissue infections to a necrotizing pneumonia which destroys the lungs so rapidly that it can kill just 24 hours after infection. This is because most CA-MRSA strains carry a particularly vicious cytotoxin called Panton-Valentine leukocidin (PVL) toxin which destroys leukocytes. Cases are still relatively rare but have been reported throughout the world, though this form of MRSA is a particular problem in the United States, where in some areas it accounts for 70% of all reported MRSA infections. While these bacteria are not multi-drug resistant – and can still succumb to the antibiotic vancomycin – treatment can be complicated. An international team of scientists has found that a strain of CA-MRSA known as the southwest Pacific clone is closely related to an older form of Staphylococcus aureus that caused a pandemic in the 1950s. This older strain, known as phage type 80/81, was first discovered in neonatal infections in Australia in 1953 and went on to cause serious outbreaks of skin lesions, sepsis and pneumonia worldwide, often in young people and children. It was eliminated through the introduction of synthetic penicillins, such as methicillin, in the 1960s. The team sequenced key genes from preserved specimens of 80/81, and compared these to genes from more than 1000 samples of Staphylococcus aureus. The older strain was almost identical to the southwest Pacific clone, and also closely related to another strain called the MRSA16 clone – commonly found in UK hospitals. Notably, the older strain also carried the genes for the PVL toxin. The southwest Pacific clone has spread into Europe, where it has caused fatal pneumonia in France, Sweden and Latvia. Only two specimens have so far been found in the UK. Mark Enright at the University of Bath, who led the study, says the results are alarming. “I have no doubt that this is going to cause serious public health problems in the UK and elsewhere in coming years. This is a very aggressive pathogen and it’s spreading rapidly.” Journal reference: The Lancet (vol 365,