The Victorian Department of Health and Human Services said it had identified a number of cases of the infection linked to lettuce grown and packaged by Victorian company Tripod Farmers.
It is sold at Coles and Woolworths as Coles 4 Leaf Mix, Woolworths salad mix, SupaSalad Supamix and Wash N Toss salad mix.
The affected products have best before dates leading up to and including February 14.
The health department identified the lettuce after recording an unusually high level of salmonella anatum strain infections and traced a number of those back to the products.
"Normally we only see a handful of cases of this strain each year, but so far this year there have been 28 adult cases of salmonella anatum – mostly adults - notified to the department," the department's senior medical advisor Dr Finn Romanes said.
"As a result of following up the food histories of a number of people we have discovered a common source - the Tripod Farmers lettuce.
"Tests of three products from two batches have also tested positive for salmonella anatum bacterium."
Dr Romanes said two of the 28 people affected by the outbreak had been hospitalised, and that the infection could be fatal for people with compromised immune systems, babies and elderly people.
Several varieties of Woolworths salad have been recalled.
Given the prevalence of the products and their distribution through supermarkets, he said the cases known to date were likely to be the "tip of the iceberg".
"We do expect to see more cases," he said.
"We are working with the company to understand what may have occurred... They have instituted a comprehensive clean-up to make sure any risk is minimised."
He said the 28 cases were mostly adults. No pregnant women had been affected so far and no deaths had been linked to the outbreak.
Dr Romanes said the department of health became aware of the link between the outbreak and the bacteria at Tripod Farmers in Bacchus Marsh, in Melbourne's outer-west, on Wednesday. Since then, the department has been working with the company on a recall of affected products.
He said the anatum strain of salmonella was uncommon and could be found in chicken and egg products. He suggested that fertiliser including affected chicken and eggs may have caused the bacteria to spread at the Tripod Farmers market in Bacchus Marsh.
Tripod Farmers is issuing a national recall of the products and anyone who has them at home should either throw them out or return them to the place of purchase.
Dr Romanes said if people were unwell and concerned they should see their doctor and get a simple test for salmonella.