About 220 hospital workers could lose their jobs after hospital service provider Spotless lost its contract at Flinders Medical Centre and Modbury Hospital.
Staff from Spotless were told on Friday that the company's contracts would not be renewed, with competitor ISS Australia taking over the contracts from December.
The union representing the workers — United Voice — said there were approximately 100 Spotless workers employed at Modbury Hospital and 120 at Flinders Medical Centre.
A spokeswoman said it was hoped some staff could find work with the new hospital services provider, with the union pledging to work with both companies during the transition.
"United Voice will be working with both the outgoing and incoming contractors to minimise any adverse affects to workers, and to ensure that all workers' rights and entitlements are respected," she said.
A SA Health spokeswoman said in a statement that all service contracts were subject to a "transparent procurement process".
"Any new contract is generally awarded through an open market process where quality and price are key considerations," she said.
"We are working with both suppliers to develop and implement appropriate transition plans."
ISS already delivers services at the Lyell McEwin Hospital and the Queen Elizabeth Hospital, while Spotless is still contracted to provide services at the Women's and Children's Hospital and the Royal Adelaide Hospital.
Spotless has come under scrutiny since the opening of the new Royal Adelaide Hospital, with complaints about the quality of services provided including food, cleaning and provision of surgical instruments.
Under the $397 million annual contract struck by the former Labor state government, the Royal Adelaide Hospital's private operator Celsus sub-contracts the provision of essential services within the hospital to Spotless.
The government's contract with Celsus includes all catering, hospitality, cleaning, laundry and maintenance services until 2046.
Last month, Health Minister Stephen Wade said the quality of the food that had been delivered over the six months since the hospital was opened did not fulfil the contract with the State Government.
"We'll be looking for abatements on the next payment through SA Health," he said.
"Taxpayers should not have to pay for services that are not delivered."
On November 27 Spotless warned its contract to deliver services at the Royal Adelaide Hospital was losing money, and that it would not contribute to earnings in 2017-18.
