Research round-up: Campylobacter, S. aureus and Listeria control

We start with research from Manchester, Bangor and Liverpool universities finding a trend to serve ‘rare’ chicken livers is potentially exposing the public to Campylobacter food poisoning.

The study investigated cooking times for chicken liver included in popular current recipes. Many recommend serving chicken livers pink and cooking them for times insufficient to kill Campylobacter.

Rare chicken liver​

The research also found between 19% and 52% of 141 chefs from professional kitchens wanted to serve chicken livers so rare they would not reach the 70˚C temperature necessary to kill the pathogen.

Dr Paul Cross, of Bangor University’s School of Environment, Natural Resources and Geography, said they asked the public and chefs about their preferences, and whether they could identify safely cooked meats.

“The public were not able to identify safely cooked chicken livers by sight. Almost a third of the public participants identified livers as ‘safe’ which in fact had predicted Campylobacter survival rates of between 48% and 98%.”​

Professor Dan Rigby of The University of Manchester, one of the lead authors, said: “We found that many chefs were able to identify cooked livers that reached the temperature necessary to kill the pathogens but their preferences for the taste and texture of pink livers may be overriding their knowledge of food safety."​

Swiss estimates of illness​

Gastrointestinal illnesses cost the health care sector up to €45m per year, according to a study by the Swiss Tropical and Public Health Institute​ (Swiss TPH).

In 2012, health care costs were between €29 to €45m. This includes costs for visiting a doctor, hospitalisation, laboratory-based diagnostic tests and medicines.

Infections with Campylobacter generate costs of estimated €8m annually. This is the most commonly reported cause of foodborne disease in Switzerland (up to 8,500 people each year).

“These cost estimates are very conservative. The economic costs, such as absences from work, as well as other indirect costs have not been taken into account yet​,” said Dr Daniel Mäusezahl, epidemiologist at the Swiss TPH.

The authors said that cases of campylobacteriosis could be reduced through hygiene measures by meat producers and consumers. ​

Controlling Listeria​

Riina Tolvanen, a licentiate of veterinary medicine and part of Evira's Section for Hygiene in Processing Establishments Unit, ​looked at controlling Listeria monocytogenes as part of a dissertation​.

The research studied the contamination routes of L. monocytogenes bacteria in a food site and survival of strains in the manufacture of non-perishable sausages.

A comparison was made between isolated strains regarding acidity and resistance to heat, and effectiveness of using ultrasonic cleaning on conveyor belts contaminated by L. monocytogenes bacteria was examined.

L. monocytogenes strains exhibited large variation in acid and heat tolerance.

Ultrasonic cleaning was efficient for all materials, but reduction of L. monocytogenes was significantly greater in stainless steel than in plastic materials.

An increase in temperature improved the effect of ultrasonic treatment, and 10 seconds at 50 °C reduced L. monocytogenes counts by more than 5 log units.

Staphylococcus aureus​ progress​

Next, MRC Centre for Molecular Bacteriology and Infection (CMBI) researchers have discovered​ a novel c-di-AMP binding receptor in Staphylococcus aureus.

Preservation techniques use salt to make foods stay fresh and prevent growth of unwanted bacteria.

However, S. aureus is more resistant to salt than many other organisms, and understanding this mechanism is important to develop ways to battle foodborne S. aureus infections.

The receptor protein is part of a larger transporter responsible for the uptake of small molecules that can act as molecular sponges. Overproducing the essential second messenger c-di-AMP made the cells take up less of these molecular sponges.

Professor Angelika Gründling, the lead author of the study, said: "Although this research is at an early stage, we hope this knowledge will someday help us to prevent foodborne staphylococcal infections, as well as open new possibilities for a type of treatment that may work alongside antibiotics.”​

Finally, a Dundee researcher has designed equipment that applies ultrasound to overcome the limitations of chromatography and mass spectrometry.

Problems include the test substance interacting with the column particles, back pressure affecting column performance and mass spectrometry only works on ionised substances.

Ultrasound agitates liquids and particles in a sample and can be used to improve sensitivity and resolving power of both methodologies.

An ultrasound ‘add-on’ device can be retrofitted to combined chromatography and mass spectrometry systems to provide enhanced performance of the system, producing improved peak shape, reduced non-specific binding and enhanced ionisation efficiency and reproducibility.

• Let us know what research you are doing on food safety and quality control for your chance to be included in our monthly round-up. Send details to wbr.juvgjbegu@jeoz.pbz​