More than 700 sick and 60 dead in South African Listeria outbreak
Most of the 717 cases are from Gauteng (61%, 436), Western Cape (13%, 92) and KwaZulu-Natal (7%, 50) provinces.
Final outcome data is available for only 19% of cases. They have been diagnosed in public (66%) and private (34%) healthcare sectors.
Where age is known (683 cases) it ranges from birth to 93 years. Females account for 55% (382/692) of cases where gender is identified.
NICD: Outbreak ongoing and source not confirmed
Numbers from the National Institute for Communicable Diseases (NICD) update the 557 cases and 36 deaths given by the National Department of Health in South Africa at the start of December.
The agency said the outbreak is ongoing and the source has not been confirmed.
Listeria from patients, foods and the environment are being tested at the NICD by whole genome sequencing (WGS) to see if strains are related.
Over 85% of the Listeria from patients so far belongs to a single strain (the ST6 strain).
NICD said this supports the hypothesis of a single source of food contamination causing the outbreak, i.e. a single widely consumed product or multiple products made at a single facility.
The incubation period can be as much as 70 days after exposure for listeriosis but symptoms usually appear within two to 30 days.
Thoroughly cooking the product to an internal temperature of 165ºF/74ºC will kill the bacteria.
Traceback investigation
Environmental health from the city of Tshwane investigated a patient hospitalised with listeriosis.
A chicken sample from the fridge at the patient’s home tested positive for L. monocytogenes. This chicken was traced back to the store and then to the abattoir it was sourced from – run by Sovereign Foods.
The environmental health team visited the abattoir and collected food and environmental samples, several of which tested positive for L. monocytogenes. The abattoir was closed pending further investigations.
Isolates are undergoing WGS to see if they are related to the ST6 outbreak strain or not.
Blaine van Rensburg, Sovereign Foods’ group executive for production, said the prohibition notice issued to the Hartbeespoort abattoir by the Tshwane Department of Health was ‘premature and unfounded’ and it has started legal action.
The DoH samples were submitted to the National Health Services Laboratory (NHSL) in Parktown at the Charlotte Maxeke Infection Control Laboratory.
Duplicate samples taken by Sovereign Foods went for independent analysis by Deltamune – a SANAS accredited facility accredited to test for Listeria in food and hygiene samples.
Different results
Deltamune found no traces of Listeria in the Sovereign Foods samples.
The NHLS lab found eight of the 14 samples taken from the abattoir positive for L. monocytogenes.
“While the NHLS lab is a SANAS accredited facility, unlike Deltamune it is not specifically accredited for detection and enumeration of Listeria Monocytogenes on food or hygiene samples and its current set of accreditations (as per their website) are not specifically applicable to food products or Listeria,” said van Rensburg.
“Despite discrepancies in these results, representatives from the Tshwane Department of Health served a prohibition notice…on Sovereign Foods management that insists that the abattoir not operate until they inspected and resampled the environment on 27 December 2017.
“While we recognise the severity of the Listeria outbreak in the country, due to the discrepancy between the NHLS and Deltamune’s independent results, we believe the prohibition notice to be premature and unfounded and have initiated legal proceedings to rectify the matter.”
South Africa has no legislation with regard to microbiological criteria for L. monocytogenes in raw meat products.
Sovereign Foods added it has adopted a standard of 100cfu/g for L. monocytogenes on raw poultry meat in line with international ready-to-eat (RTE) limits.
