The number of people catching a killer bug during their stay in Welsh hospitals has dropped by more than a third in a year, a new report has revealed.

According to the latest figures, the total reported cases of Clostridium difficile during 2011-12 was 1,295 - more than 600 fewer than the previous 12 months.

Officials credit a “zero-tolerance approach” for the change, which was the equivalent of 30 lives being saved.

Clostridium difficile is a bacteria usually found in the gut, but antibiotics administered in hospitals can cause it to multiply to high levels and resulting in severe diarrhoea and fever.

The figures came to light in the latest “annual check up” of Wales’ NHS by its chief executive David Sissling.

Opposition parties in the Assembly criticised the report - saying it had taken a “rose tinted” look at the service.

But its author insisted while there were still a number of challenges facing the NHS, “significant improvements” had been made in the past 12 months.

Mr Sissling said: “I am pleased to report a pattern of general improvement which shows the NHS has risen to the challenge set by the minister for health and social services, Lesley Griffiths, to focus on delivery.

“In particular, the improvements in stroke care are considerable, with every health board delivering fast access to thrombolysis - clot-busting drugs which improve survival rates - 24 hours a day, seven days a week.

“The Royal College of Physicians has noted NHS Wales as the fastest improving system in the history of their audit on stroke services in the UK.

“Quality of care is improving, for example with the reductions in cases of C.difficile, where prevalence rates are lower than many European countries.”