An investigation by officials in New Zealand has traced the source of several Listeria infections to a meat supplier.

The Ministry for Primary Industries (MPI)’s New Zealand Food Safety and Nelson Marlborough Public Health Service investigated six listeriosis patients spread over four years.

The incident led to recalls of ham products from a number of South Island supermarkets and three stores in the greater Wellington region in late 2020. Investigations into the source involved follow-up with the suppliers of cooked ready-to-eat meats to the supermarkets.

Contamination originated at Pestell’s Rai Bacon Company Ltd., wher Listeria was found in products and the processing environment. This was confirmed by DNA testing. After the recall in December, Pestell’s stopped producing and selling ready-to-eat (RTE) ham products.

In October, routine testing by supermarket Pak’n Save Blenheim detected Listeria in some packaged meat products and these items were recalled. Analysis identified the Listeria found was the same as that in Pestell’s products.

The Institute of Environmental Science and Research (ESR) did genome sequencing on samples.

Common food source
Melinda Sando, New Zealand Food Safety’s food compliance services national manager, said: “We knew wher the supermarket was getting its stock from. We went to Pestell’s and took samples for testing from their processing environment and their products.

“The sequencing of those isolates showed they were identical, which means they are from a specific source. Nobody wants to put their customers at risk. We worked quickly to minimize the risk to the public and resolve the issues.”

The Nelson Marlborough Public Health Service received four recent reports of listeriosis. One each in December 2019, and August, September and November of 2020. There are also two historic patients from 2016 and 2018.

Dr. Andrew Lindsay, Nelson Marlborough Public Health Service medical officer of health, said the agency would monitor the situation with New Zealand Food Safety to see if other cases emerge.

“To date, no further cases associated with the recalled products have been identified. However, as Listeria can survive freezing, consumers are reminded to check food in their fridges and freezers and if they have any of the recalled product follow the advice from New Zealand Food Safety.”