There is a pressing need to have a "zero tolerance" policy with listeria bacteria which has been responsible for recent food poisoning outbreaks that have claimed many lives, an international food safety conference in Cork has been told.
Infection caused by listeria monocytogenes, which resulted in more than 20 deaths in the US and 12 in France in recent outbreaks, strongly indicated it was odd but "very talented micro-organism", said UCC microbiologist Dr Colin Hill.
The fear of such outbreaks, and absence of definitive data on the number of cells needed to cause an infection of the immune system, meant some countries had identified the need to "declare zero tolerance for listeria in certain products", he told food scientists meeting in UCC under an Irish-US initiative.
Listeria outbreaks have been associated with various foods, notably soft cheese, delicatessen products and hot dogs, and can cause spontaneous abortion, meningitis and encephalitis. It was not a "mainline" threat on a par with salmonella, but those with compromised immune systems, particularly older people, were especially vulnerable.
Its symptoms were often mistaken, Dr Hill said. Yet where there was good surveillance massive outbreaks were being detected. Although food industries here had rigorous checks for it, "in Ireland, we are not aware of it, but it must be there," he warned.
His research with UCC scientists has identified how exposure of the bacterium to medium stress - heat or acid, for example - gives it the ability to later withstand harsher conditions. Therefore, it can exploit mild preservation procedures in food processing.
"This ability to sense and react to its environment, we believe, contributes significantly to its survival in foods."
The director of food safety at McDonald's Corporation, Dr Skip Seward, said there was significant challenges for those in the food service sector, especially with "high employee turnover rates".
He outlined how it was possible to "design food safety into food service equipment" - for example, the development of a "self-pasteurising shake and sundae machine which pasteurises the product mix and internal surfaces each night".
While identifying "critical control points" now widely used in food manufacturing was of value, this had to be carefully adapted. They had to be flexible and a routine part of daily operation whether it involved bakeries or vending machines.
Their research, he added, had found internal temperature provided the best indication of whether meat was properly cooked, rather than relying totally on internal colour and not consuming until juices "run clear" - as was frequently the health advice given to consumers.
Scientists in Northern Ireland have found circumstantial evidence that the bacterium implicated as a cause of Crohn's disease forms tiny clumps, which give it the ability to withstand pasteurisation.
Mycobacterium paratuberculosis, the known cause of Crohn's disease in cattle, is attracting intense interest because of its possible link with the chronic inflammatory bowel disease in humans - its incidence is rising but the cause is eluding scientists.
Dr Michael Rowe of Queen's University Belfast said the tendency to clump seemed to be associated with its "heat resistance". When present in high numbers it can survive heat treatment. He outlined how milk pasteurisation strategies could be altered to reduce the risk of its survival.
