Raymond Yung Wai-hung, head of the centre's infection control branch, said yesterday that the infection of community-acquired MRSA had remained stable at about 14 cases a month this year.

But it would be a long-term battle against the infection because the growth of bacteria was fast and it was difficult to monitor the use of antibiotics in the community.

Several major public hospitals had run a pilot study to check on the use of antibiotics in the past two years. Also, all hospitals had stepped up infectious disease control measures after the Sars outbreak in 2003, he said.

'It is difficult to conduct a city-wide MRSA screening to see how many people may carry the superbug.

'But we may conduct a pilot screening project in some correctional institutions because some overseas studies have shown that correctional facilities are one of the high-risk places of community-acquired MRSA outbreaks,' Dr Yung said.

Other high-risk settings included newborn nurseries, military services and gay sex among men.

Dr Yung said the centre had run tests on the families of people infected with community-acquired MRSA, but, so far, no clustering cases had been identified.

'We are monitoring the infection of MRSA very closely because we are worried that the community-acquired MRSA and the hospital-acquired MRSA may mix and mutate, which could result in new drug resistance,' he said.

The government would increase public education on the proper use of antibiotics, he said.

Seto Wing-hong, the Hospital Authority's chief infection control officer, said MRSA accounted for about 39.6 per cent of the total Staphylococcus aureus cases in public hospitals, which was lower than many other developed countries, such as the United States with 60.2 per cent and Singapore with 60 per cent.

In the latest case of community-acquired MRSA confirmed on Thursday, a 34-year-old Australian living in Sheung Wan developed severe pneumonia and septicaemia. He is in stable condition.