Expert: US case that killed 30 sheds light on rockmelon outbreak

A food science expert says a similar case overseas may provide clues to the cause of a recent deadly outbreak of listeria in Australia, which was linked to contaminated rockmelons grown near Griffith.  

Two people died after consuming rockmelons reportedly grown at a farm in Nericon.  

Dr Conner Thomas, a senior lecturer in molecular and cellular biology at the University of Adelaide, noted a far more deadly outbreak in the United States. 

“In 2011, there was a major outbreak of listeriosis that resulted from contamined rockmelon … in Colorodo”. 

Some 146 people were infected, with a reported 30 consumers dying. 

“As a result of the investigation that followed that, [it was found] the source of the listeria had come primarily from the processing environment”. 

Up to 10 people across Australia have been hit by a bug after eating rockmelon from a NSW grower.

Up to 10 people across Australia have been hit by a bug after eating rockmelon from a NSW grower.

Dr Thomas said the listeria is found widely in soil and water, so the fruit cleaning procedure needs to be rigorous. 

“Fruit is going to have a bit of dirt on it, so to present them properly for sale they need to be washed”. 

“There’s a process that’s followed through where water is used to wash any dirt of the fruit, before it’s sent off”. 

“The problem comes if the water is recirculated, as it often is, so you can get a build up for bacteria and sugars from the fruit itself… and it provides a good environment for bacteria to grow”. 

“That’s just an hypothesis, I don’t think anyone has sat down and worked this out”. 

Dr Vincent Ho, a gastroenterologist from the University of Western Sydney, wrote in The Conversation that fruit can be contaminated by listeria “anywhere along the chain of food production: planting, harvesting, packing, distribution, preparation and serving”.

He noted listeria contamination can also occur, and spread, in restaurants and home kitchens. 

The contaminated melons from NSW were grown near Lake Wyangan, which has high levels of toxic bacteria – blue green algae – in its water

Wetlands expert Geoff Sainty, who has been critical of turbid water being sourced for irrigation, said there’s no evidence lake problems are connected to this incident.  

“No, this has come straight out of left field”.

Dr Thomas said he was not aware of any evidence of a link between blue-green algae and listeria; nor the particulars of the outbreak linked to the NSW farm.