A hospital at the centre of a Clostridium difficile outbreak which caused 33 deaths will not face criminal proceedings, safety officials say.
C. difficile causes diarrhoea but can also lead to more serious infections
The Health and Safety Executive ruled there was not enough admissible evidence to prosecute Stoke Mandeville Hospital bosses in Buckinghamshire.
But the HSE said there were areas where the hospital could have done more.
It comes after a watchdog found "serious failings" by management in their handling of the outbreaks.
The Healthcare Commission said the hospital, run by the Buckinghamshire Hospitals NHS Trust, failed to follow advice on stopping the spread of infection.
Two outbreaks took place at the Aylesbury hospital between October 2003 and June 2005, and overall 334 patients were infected.
The bacterium usually cause diarrhoea but can lead to fevers or more serious infections.
An investigation into the handling of C. difficile outbreaks at Maidstone and Tunbridge Wells NHS Trust in which 90 people died is still being carried out by the HSE and Kent Police.
Sandra Caldwell, HSE director of field operations said they launched the investigation into Stoke Mandeville because there was the possibility that serious criminal offences had been committed.
But added: "On the basis of the evidence available, HSE did not find sufficient admissible evidence to be able to bring criminal proceedings against the Trust, alleging a link between management failures and particular deaths."
"However, the investigation did reveal a number of areas where more could have been done by Stoke Mandeville.
"We understand these have already been implemented by the Trust."
The bacteria are naturally present in the intestine but kept under control by other bacteria
Antibiotics can kill some of these, allowing C. difficile to take hold
Overuse of antibiotics is linked to the infection's rise
C. difficile is not resistant to treatment, but some cases are difficult to treat
The strain seen at Stoke Mandeville hospital is related to one which has emerged in the US and Canada
One particular concern highlighted by the report was that the Trust did not have a contingency plan in place meaning managers were always on the "back foot".
Recent inspections by the Healthcare Commission have revealed that Stoke Mandeville Hospital has made "sufficient progress" in improving standards.
However, more needs to be done on hand washing by doctors and staffing levels on wards.
Ian Biggs, head of the Healthcare Commission in the South West said the hospital was now a "much safer place".
"We have confidence that a large proportion of recommendations we made have been followed through by the Trust."
But he said they had spotted some doctors were not routinely washing their hands between patients.
"The Trust have now launched disciplinary proceedings against doctors who are not compliant."
Anne Eden, chief executive of the Buckinghamshire Hospitals NHS Trust said she would like to express her sincerest sympathies to all those affected by the outbreaks.
She added the Healthcare Commission report reflected the hard work that had taken place throughout the Trust to improve standards.
"But we can never be complacent, and will continue to strive to realise our aim to eliminate avoidable infections in our hospitals."
A spokesperson for the Clostridium Difficile Support Group said hospitals needed to be made accountable.
"If tougher measures were implemented in these hospitals who have failed the public I am sure this would be a lesson to all hospitals around the country who would have to continue to work hard to keep these lethal infections at bay."