Two patients have died in Scotland's largest outbreaks of a rare and highly-virulent strain of hospital superbug.

Two patients have died in Scotland's largest outbreaks of a rare and highly-virulent strain of hospital superbug.

Nine people were taken ill in two separate clusters, one in Glasgow and one in Aberdeen, of a form of Clostridium difficile.

It was confirmed yesterday that the patients at Aberdeen Royal Infirmary and Glasgow's Stobhill Hospital were infected by the highly-toxic 027 strain, which has until now rarely been seen in Scotland. It was the 027 strain which was implicated in the deaths of 65 patients at Stoke Mandeville Hospital in Aylesbury, Buckinghamshire, between 2003 and 2005.

Last night, Health Protection Scotland (HPS) confirmed that four patients at Aberdeen Royal Infirmary were hit by the bug and one later died, though health officials said the bug was "a contributory factor" but not the main cause of death.

In a separate outbreak, five patients at Glasgow's Stobhill Hospital fell victim to the bug, one of whom later died. Again, C. diff was said to be a contributory factor, though not the main cause of death.

One of the Glasgow patients is now said to be fully recovered.

HPS said laboratory tests had confirmed both "clusters" involved the virulent 027 strain of the bug but were unrelated to each other. Strict infection control procedures are being maintained at both hospitals to control the number of cases.

Health chiefs have written to all health boards reinforcing advice on how to control the bug.

Anne Eastaway, consultant microbiologist at HPS, said: "These two clusters are unrelated and we are in regular contact with the infection control teams at both NHS Grampian and NHS Greater Glasgow and Clyde. We have previously seen a small number of isolated cases of this strain in Scotland."

C.diff is a potentially fatal bug which mainly affects the elderly, and usually grows in the large intestine.

Spores can survive for a long time in the environment, with areas around hospital beds and toilet areas common.

Health officials have been concerned that the "hyper-virulent" 027 strain could become more common in Scotland as it spreads from England and a C.diff "reference laboratory" has been established in Scotland, to help identify more virulent strains including 027, which might not be picked up otherwise, and help understand the bug's characteristics.

The 027 strain produces more toxins than other types, has caused large outbreaks of severe disease in hospitals in Canada and the US since the beginning of the decade and has now been detected in more than 80 hospitals in England and Wales.

The first Scottish case of 027 was diagnosed in October 2006. Then, in November last year, an unnamed female patient died in the West of Scotland, due to a "combination of factors", after being infected with the 027 strain.

Figures show all strains of C.diff caused 100 deaths in Scotland in 2005 against 57 in 2001. Cases increased by 10% in three months.