So far Austrian and German food safety bodies have traced seven deaths to acid curd cheese produced by Prolactal. AGES, the Austrian food safety agency, found that the victims had bought Prolactal cheese and then found Listeria monocytogenes in samples taken at the company.
Prolactal has since investigated the causes of the contamination and concluded that human error and failure to adhere to the company control system could be to blame.
Dung beetles
The cheese manufacturer first became aware of a listeria problem in autumn last year. Discovery of listeria within a permitted range in samples, led to lab analysis of UV insect traps that found dung beetles on adhesive tape.
As dung beetles live in an environment that contains listeria, Prolactal concluded that the insects could have caused the contamination. It is suspected that they entered the production area through a well lit window that had been kept open for building work, albeit with a fitted mesh fly screen.
Prolactal then cleaned its facilities and switched to protective cultures in its cheese production to eradicate the listeria.
Culture error
A renewed examination of the production process has revealed that an error may have been made at this stage. Prolactal said in a statement: “Today we must assume that owing to an error in November 2009 the protective cultures were exchanged twice and cultures were employed that have now been shown to provide insufficient protection against listeria.”
Prolactal said information should have been shared about the change to a different culture via the internal warning and control system but that this did not happen. Executive management was only informed of the change in January.
In its conclusion, Prolactal said: “Regrettably, it cannot be excluded that in this way, curd cheese lacking an effective Listeria inhibiter entered the retail process, something about which the company only became aware in view of subsequent events.”
The precise sequence of events is now the subject of official investigations. Prolactal said it is continuing to seek full clarification of the matter to establish the extent to which curd cheese produced by the company might be connected to the deaths in Austria and Germany.