A study of Welsh ambulances found many were contaminated with bacteria which could cause serious infections in vulnerable patients.

The authors, from the University of Wales, said there was nothing to suggest ambulances in the rest of the UK were any better.

They said rules for ensuring cleanliness of vehicles were inadequate.

The study was published in the Emergency Medicine Journal on Thursday.

The team of researchers studied ambulances in three Welsh regions during 2000, using swabs to pick up bacterial samples both before and after cleaning.

They found bacteria virtually everywhere - folds in stretcher mattresses, cupboards, inside breathing masks and floor rails.

Three out of five swabs they took from different areas of the vehicle came back positive for some kind of bacterium prior to cleaning - and 35% afterwards.

Even steering wheels were contaminated, leading to fears that paramedics could inadvertantly transfer bugs to seriously-ill patients.

Sometimes the paramedics didn't have time to clean up after a patient had spilled blood and guts on the floor, Dr Yamni Nigam, University of Wales in Swansea

In some parts of the vehicle, things got worse after cleaning - a third of the swabs revealed bacteria before cleaning, and 40% afterwards.

The bacteria found were mostly harmless strains found naturally on the skin, but some from the Staphylococcus and Streptococcus families were found.

These could potentially cause problems to patients with depleted immune systems or with serious wounds, who might not be able to fight off infection.

In addition, coliform bacteria - mostly found in faecal matter - were "abundant".

Staphylococcus aureus was found

The researchers wrote: "Their presence in and on many sites within emergency vehicles is an indicator of high levels of cross-contamination.

"This may introduce further complications in an already traumatised patient."

Questionnaires given to ambulance crews revealed that occasionally, during a busy eight hour shift, there was only one opportunity to clean up the inside of the vehicle, regardless of the nature of the casualties it had carried in the preceding hours.

"It is essential that disinfection of spillages of blood and body fluids should be carried out promptly with a suitable chlorine releasing disinfectant, as viruses such as HIV and hepatitis B have been found to survive in dried blood for weeks or months," the researchers wrote.

UK problem

Lead researcher Dr Yamni Nigam said she undertook the project after paramedics expressed concern that they were being asked to eat their lunches sitting in the ambulance ready to receive calls.

She said cleaning was "clearly inadequate" at that time.

"Sometimes the paramedics didn't have time to clean up after a patient had spilled blood and guts on the floor," she said.

While the study was confined to Welsh ambulances, she said, there was no evidence to suggest that matters were worse in the principality compared with the rest of the UK.

Dr Nigam told BBC News Online it was "very likely" this was a problem shared by more than one ambulance service elsewhere in the UK.

The Welsh Ambulances Services NHS Trust has beefed up its infection control procedures since the research was carried out - a move welcomed by the researchers.