The report highlighted new infection-control measures on wards

The Communicable Disease Surveillance Centre (CDSC) said this was the first notable annual downturn in its four years of monitoring the superbug.

Between April 2004 and March 2005, 242 cases were recorded: this was 65 cases (21%) fewer than the previous year.

CDSC director Dr Brian Smyth said it was encouraging, but stressed there was no room for complacency.

"It is very welcome to see a reduction in the overall number of cases and to witness this in hospitals throughout Northern Ireland," he said.

"However, it remains a challenging task to sustain this trend over future years, and this must now form the focus of ongoing work."

The reduction was down to the introduction of new and substantive infection-control measures within all hospitals, according to the report's coordinator, consultant microbiologist Dr Tim Wyatt.

'Downward trend'

"The next objectives are to try and maintain this downward trend and to further develop the surveillance programme that we have put in place," he added.

Ten of the 12 hospital trusts recorded a decrease in the rate of MRSA isolation, the report said.

Dr Wyatt said the MRSA increase in two trusts was not a major cause for concern and did not mask the overall improving trend.

"Because hospitals are treating patients with different and often complex illnesses, the proportion of people at higher risk from MRSA will always vary," he said.

MRSA stands for methicillin-resistant Staphylococcus aureus, but is shorthand for any strain of Staphylococcus bacteria which is resistant to one or more conventional antibiotics.

We have produced a visitors' policy, whereby we are encouraging people who are unwell not to come in to visit their sick relatives Mary McIlroy Mater Hospital

It is more common in hospitals as sick patients are more vulnerable to picking up infections.

Also, conditions on wards, which involve lots of people living in close proximity, examined by doctors and nurses who have just touched other patients, are the perfect environment for the transmission of a variety of infections.

The report said there were 568 patient episodes of Staphylococcus aureus (S. aureus) bacteraemia across all hospitals between April 2004 and March 2005.

This was 109 (16%) fewer than the previous year.

S. aureus is a bacteria commonly carried on the skin and can occasionally lead to blood-stream infections, should it enter the body through skin or wound infections.

Mary McIlroy, the senior infection control nurse at Belfast's Mater Hospital, said staff were working very hard to tackle the problem.

"We have really been concentrating on things like audits and training all of our staff," she said.

"We have also been trying to introduce measures for the public, so that any visitors coming in are encouraged to wash their hands and also to take measures.