Some doctors doing hospital ward rounds fail to wash their hands, says a report on NHS hygiene in Wales.
Health inspectors took pictures in Bronglais Hospital, Aberystwyth
More work is needed to give health staff education and guidance, says the auditor general for Wales.
Patients are also being urged to challenge hospital staff if they are unhappy with cleanliness standards.
As another report said simple measures could cut the risk, ministers promised action against trusts which fail to take steps to cut infections.
Responding to both reports, Health Minister Edwina Hart said: "Patients must have the confidence that when they go into hospital they will receive safe and effective treatment.
"For the vast majority that is the case, but dirty and untidy hospitals can dent confidence."
Last month, the minister ordered spot checks on two NHS hospitals in a crackdown on hygiene.
In the report from Healthcare Inspectorate Wales (HIW), it emerges a further nine investigations have taken place - five at NHS hospitals and four at independent healthcare providers - across Wales.
The inspectorate said it found evidence of good practice in many places, with a "high level of commitment and enthusiasm" from specialist infection control staff.
However, the report also highlighted several areas of concern.
It listed "inadequate domestic cleaning hours" and ward managers having no direct responsibility for cleaning services in Welsh NHS organisations.
The report also called for all staff working in healthcare to be trained on controlling infections.
Watchdog chief executive Peter Higson said: "Some of the improvements that need to be put in place are simple and inexpensive.
"However, by far the biggest challenge is to ensure that all staff, patients and visitors think 'hygiene and cleanliness' while in a hospital."
In his report, Auditor General for Wales Jeremy Colman said: "It is unacceptable to the public that patients should run the risk of acquiring infections as a result of their interaction with the NHS.
"Everyone in the NHS should be taking personal responsibility to minimise infections."
Mr Colman also criticised cleaning regimes and suggested that there were confusion and doubts over responsibilities.
The Welsh NHS Confederation, which represents trusts and health boards, has welcomed the reports.
The confederation said the findings showed that the health service is getting better at tackling infections, with rates now lower than England or Scotland.
"But there is more still to do, and these two reports will help us identify ways of reducing the rates still further," said confederation director Mike Ponton.
"We strongly support the auditor general's view that infection prevention and control is 'everyone's business'. As HIW point out, it is critical that all staff, patients and visitors think 'hygiene and cleanliness' while in a hospital."