Tests have proved the listeria in Conroy's corned beef was the same strain that contributed to the death of Royal Adelaide Hospital patient Richard Formosa.

Test results proved listeria found on his factory's equipment and corned beef was the same bacteria as that detected in the RAH kitchen and the two RAH patients, including Formosa. Formosa, who contracted listeria while in the RAH being treated for severe diabetes, died on October 31, just days after his 53rd birthday.

A second RAH patient is recovering from listeria poisoning. Australian Head of Communicable Diseases Dr Rod Givney yesterday said it was possible more cases would surface.

Of the 21 cases, 12 were associated with attending or working at a metropolitan child-care centre . Dr Givney would not name the centre. The nine other community cases were predominantly in metropolitan Adelaide.