New tests ordered on lethal bacterium

PUBLIC health experts investigating an outbreak of a rare infection in Gloucestershire yesterday ordered new tests on samples taken from the five victims. They are trying to find out what has turned a normally harmless microbe into one that can kill within hours.

Scientists are alarmed by the virulence of the bacterium, haemolytic streptococcus Group A. They believe some strains have started producing lethal toxins that attack different body organs simultaneously and overpower the immune system.

A spokeswoman for the Central Public Health Laboratory Service, London, which is co-ordinating the investigations, said scientists at the laboratory had started detailed molecular tests.

Two people died in February and three others are recovering after surgery and skin grafts for disfiguring wounds in what is believed to be the first outbreak of infection with haemolytic streptococcus Group A. Dr Cliodna McNulty, a consultant microbiologist with Gloucestershire Health Authority, said yesterday that it was possible for the cases to have arisen by chance but 'it is amazingly rare'. A change in the bacterium's genetic material may have caused it to produce more damaging toxins.

The bacterium is carried by 10 per cent of the population in the throat and nasal passages and is normally harmless. However, it can cause life-threatening infections if it reaches tissues beneath the skin, liquefying fat cells and causing gangrene. A cluster of cases is unprecedented.

Microbiologists are speculating that some strains of the bacterium have become infected with a virus, known as a bacteriophage, which has 'switched on' dormant genes which make it more virulent.