Team’s tireless hunt for source

THE head of Enteric Disease at the National Institute for Communicable Diseases, Dr Juno Thomas, who was part of the investigative team that worked tirelessly to track the source of the listeriosis outbreak, is convinced the bacteria has been contained.

After months of intense research, an Enterprise Foods factory in Polokwane was identified as the source. Thomas said listeriosis was not a notifiable medical condition and that at the beginning of the investigation there was no data available on the number of people infected.

“We had to get data from private and public sector laboratories around the country to see how many cases were recorded in a year. “We started asking colleagues working in hospitals to be on the lookout for listeriosis cases. Then we realised there was an increase.

“When there were reports that the bacteria had spread to the Western Cape and Kwazulu-natal we realised there was an outbreak.”

During research that began in 2017, blood samples of people who were infected were subjected to whole genome sequencing. The process is a DNA test that determines the Sequence Type (ST) strain of bacteria the infected person has. Sequence Type (ST) 6 was the common strain found.

The breakthrough in finding the source came when a group of children at a Soweto crêche fell ill and were admitted to hospital and an environmental practitioner was sent to the crêche to collect samples of food.

“Samples taken from the crêche of two polony brands (Rainbow and Enterprise) were sent for analysis. Both brands tested positive for listeriosis. Tests for the type of bacteria were also done through genetic finger testing (DNA) and enterprise polony had shown the ST 6 strain,” she said.

“We went to the Polokwane Enterprise polony plant in February and ran tests. We took samples of everything, from the machinery, the floor, equipment and the products.

“When the results emerged, it showed the polony from the crêche and DNA of the infected people all had shown listeriosis ST 6. I would say their food safety protocols and monitoring programmes were not sufficient,” said Thomas.

The institute was now awaiting results of tests run at Rainbow Chicken to determine the listeriosis bacteria type, she said.