ONE in 20 patients admitted to hospitals are picking up infections, some of them life-threatening.
A survey of 50 hospitals in May found 467 of the 9,030 patients caught an infection after admission, the equivalent of 5.2pc.
The most common types were surgical wound infections and pneumonia, also known as a chest infection.
Other bugs were urinary tract infections, which may include infections of the bladder or kidneys, blood-stream infections such as MRSA and gastrointestinal infections, including C difficile and gastroenteritis.
The survey was carried out by the Health Protection Surveillance Centre as part of a wider examination of antibiotic prescribing in the hospitals.
It found that patients who had these infections were more likely to have some of the common "risk factors" such as having had an operation, having a drip or a bladder catheter.
The higher risk also applied to patients in intensive care units, older people or very young patients. People receiving antibiotics also had a greater chance of picking up infection.
The watchdog's microbiologist, Dr Robert Cunney, said: ''As different hospitals may admit different types of patients and have different medical and surgical specialists working within the hospital, it is not possible to directly compare the results between hospitals."
High rates were found in Beaumont Hospital, St Luke's Hospital in Rathgar, Roscommon County Hospital, Tallaght Hospital and St Vincent's.
Dr Cunney pointed out there were three key components to preventing a hospital-acquired infection, including ensuring appropriate antibiotic use, good handwashing practice and proper use of intravenous lines and urinary catheters.
"Not every infection can be prevented but every effort should be taken to prevent it wherever possible," he added.
This survey found that 34pc of the 9,030 patients were prescribed antibiotics.
Dr Cunney said it showed that antibiotic prescribing is very common in Irish hospitals.