The number of cases of hospital superbug C. difficile rose by 6 percent in the first three months of the year, but the number of MRSA infections fell sharply, the Health Protection Agency said on Thursday.

The HPA said there had been 10,586 cases of Clostridium difficile reported in patients aged 65 and over between January and March, a six percent rise in this age group from the previous quarter.

However, annual figures showed that there had been a nine percent fall in the number of cases in 2007 compared to the previous year.

"Although there has been mandatory reporting of C. difficile since 2004, this past year has seen major changes to improve the reporting system," said Dr Georgia Duckworth, head of the HPA's Healthcare-Associated Infection and Antimicrobial Resistance Department.

"We now have a more robust system that will enable us to measure the levels of this infection better and help trusts manage and monitor the effectiveness of their interventions to improve infection control."

The HPA, established three years ago to integrate the fight against infectious diseases, also said that the number of MRSA reports had dropped by 11 percent in the first three months of 2008.

Annual figures showed there were 4,438 cases of MRSA, or methicillin-resistant Staphylococcus aureus, which is a deadly bloodstream infection resistant to treatment with most available antibiotics, compared to 6,383 in 2006.

That represented a 30 percent decrease.

"The substantial drop we have seen in MRSA bloodstream infections over the past year is impressive and a credit to the hard work of our colleagues in the NHS, strengthening good practice in infection control," Duckworth said.

"If we are to continue this reduction in healthcare associated infections, it is vital that the measures which have won this significant success remain in place and that the public and healthcare workers recognise their importance."

Last month the Healthcare Commission, the government's health watchdog, said a quarter of NHS trusts in England and Wales are at risk of losing their licence to treat patients because of a failure to comply with hygiene regulations.

The commission said 41 hospitals and 62 other NHS organisations had admitted failing to observe one or more core parts of the hygiene code, introduced in 2006 amid concern about the spread of MRSA, C. difficile and other hospital "superbugs".