Listeria threatens Hispanic-style cheese market in US
Dairy foods are linked to almost one quarter of infections caused by the food-borne pathogen, Listeria monocytogenes, accounting for over $700 million (€623.9m) in annual healthcare costs in the US. Many of these have been traced to Hispanic-style and soft-ripened cheeses.
Researchers propose a foundation for improving food safety to meet public health needs and market demands in a review published in the Journal of Dairy Science. They also report on an effective antimicrobial agent to fight Listeria that may address limitations of current antilisterial processes for fresh cheeses.
Listeria infections can develop into pneumonia, bacteremia and meningitis. It can cause complications in pregnancy and may result in miscarriage or stillbirth. Although rare, its high fatality rate among young, elderly or pregnant individuals has led the US to declare Listeria as one of three zero-tolerance microorganisms in ready-to-eat foods.
Michael J. Miller, associate professor of food microbiology in the Department of Food Science and Human Nutrition at the University of Illinois, says, “Food safety concerns over Listeria stifle wide-spread commercial growth of fresh cheeses and especially the Hispanic-style cheese market.
“The rise of consumption and production of Hispanic-style cheeses is expected to continue in the years to come, which has increased the need for proper awareness of the microbial safety concerns of this group of cheeses.”
Recent studies have suggested that Listeria contamination occurs predominantly through transportation and storage of finished products and food contact surfaces rather than raw or improperly pasteurised milk. Consumer handling and storage are also known to increase the risk.
“It is unclear to what extent different manufacturing steps and variations in the finished product affect listeriosis risk factors, as our knowledge of Listeria monocytogenes in commercial products is largely outdated and limited to queso fresco, especially in the US,” comments Miller.
The research team also assessed the antimicrobial efficacy of a Listeria bacteriophage endolysin that may address limitations of current antilisterial processes for fresh cheeses. In this study, enzyme PlyP100 provides a promising alternative preservation for addressing a notorious food safety issue.
According to Miller, “This study reflects a rapidly growing trend for targeting intractable microbial problems via a biotechnological approach, in this case providing an alternative preservative for addressing a notorious food safety issue.”
The team studied the effects of endolysin PlyP100 and compared its lytic activity in vitro in several different environments and target organisms. They then incorporated it into a fresh cheese model challenged with a cocktail of Listeria monocytogenes. They showed that PlyP100 demonstrates optimal activity under pH and salt concentrations consistent with a low-acid food matrix such as fresh cheese.
