The national health department has confirmed the listeria bacteria found at the Rainbow Chicken polony factory is not the ST6 strain that caused 91% of cases.

The National Institute for Communicable Diseases completed the whole genome sequencing of the strains taken from the RCL factory in Wolwehoek‚ Free State‚ this week.

"This corroborates the results reported by RCL Foods at a French laboratory‚" read a health ministry statement.

The fact that the Rainbow Chicken RCL factory does not have the strain that caused most of the 183 deaths‚ means that the case against Tiger Brands Enterprise's factory even stronger‚ according to a NICD expert.

The deadly strain ST6 bacteria was found in 26 places in the Tiger Brands Polokwane Enterprise factory and on the outside of two rolls of polony.

Head of the Centre for Enteric Diseases at the National Institute for Communicable Diseases Dr Juno Thomas said: "The fact that we haven’t found the ST6 listeria monocytogenes strain in retail Rainbow polony or in the RCL foods production facility adds further strength to the findings that it is the Enterprise facility that is causing the outbreak."

Rainbow Chicken‚ whose polony was also recalled‚ still had other strains of listeria bacteria in its polony and in its factory‚ which can make people sick and require corrective action and monitoring‚ health spokesman Popo Maja said.

Lawyer Richard Spoor is expected to file class action papers against Tiger Brands within days to sue them on behalf of many families who lost loved ones and survivors who were disabled by the disease. He is finalising the papers.

He told TimesLIVE previously he will argue that the deadly outbreak was from a single source‚ the Tiger Brands Enterprise factory.