A more 'toxic' form of MRSA has claimed the lives of a nurse and patient at a Staffordshire hospital.

The deadly Panton-Valentine Leukocidin (PVL)-producing strain of the superbug was identified at University Hospital of North Staffordshire Trust, in Stoke-on-Trent, during a retrospective analysis of isolate cultures.

The patient died 24 hours after the blood sample was taken and developed a hospital-acquired pneumonia while on the ward. A previously fit nurse died in September after developing blood sepsis, septic shock and pneumonia following surgery.

It is the first time PVL – a particularly virulent form of MRSA which attacks healthy young people – has caused infection and deaths in a UK hospital. Eleven cases have been recorded by the trust in its reports to the Health Protection Agency (HPA).

The trust, which runs the Royal Infirmary and the City General hospitals, named itself following reports that the hospital superbug had claimed two victims in the Midlands.

An investigation at the hospital found six other people had also contracted the same strain but survived, and three more cases have since come to light, including a former patient.

Symptoms include minor skin or soft tissue infections, abcesses which can lead to blood poisoning, septic arthritis and pneumonia.

An HPA spokesman said: "Eight cases of PVL-positive community-associated MRSA have been identified among individuals in a hospital and their close household contacts in the Midlands.

"Four of these individuals developed an infection, two of whom subsequently died.

"This outbreak is the first time transmission and deaths due to this strain are known to have occurred in a healthcare setting in England and Wales."

An article in the current edition of the Communicable Diseases Review highlighted the cases at University Hospital of North Staffordshire.

Nearly 200 people, including 130 staff, have been tested for PVL since the cases came to light. Last year University Hospital of North Staffordshire reported 119 cases of MRSA, but so far in 2006/07 only 55 have been recorded.

Dr Angela Kearns, an MRSA expert with the HPA, said: "When people contract PVL-producing strains of MRSA, they usually experience a skin infection such as a boil or abscess.

"Most infections can be treated successfully with everyday antibiotics but occasionally a more severe infection may occur." Last month the trust confirmed a strain of MRSA not previously seen at the hospital had been identified in two former patients; all staff who treated them were screened for the superbug.

A trust spokesman said: "No current patients have been identified as affected. All those affected have been informed and there is no need for any other patient to be concerned.

"With the exception of one infection it is not clear at this stage whether transmission has occurred within the hospital or, as is more common, in the community.

"The hospital is continuing to take advice from the Health Protection Agency on management of the outbreak."

He added that some patients, such as those having invasive surgery, are routinely screened for superbugs like MRSA.

"PVL can be very nasty, as can MRSA, but this is not something that's rampant or slaughtering people left, right and centre.

"Patients should not be concerned as they are at no more risk of picking up this superbug here than at any other hospital." Last night the Department of Health urged medics to be "extra vigilant".

A spokesman said: "Infections caused by the staphylococcus aureus bacteria which produce PVL are extremely rare in the UK but PVL-producing strains of staphylococcus aureus are treatable with several antibiotics. Clinicians have been asked to be extra vigilant and report cases direct to the HPA which is seeking additional expert advice."