The role of food in human exposure to antimicrobial resistant bacteria

The use of antimicrobial agents[1] in animals, plants and food production contributes to a growing, diverse range of resistant bacteria and of bacteria-borne resistant genes that can be passed on to humans through food, the European Food Safety Authority’s BIOHAZ Panel[2] said in a “self-task”[3] draft opinion today. EFSA asked its BIOHAZ Panel to identify, from a public health perspective, the extent of how food serves as a vehicle for antimicrobial resistance and the BIOHAZ Panel has launched a public consultation on this opinion and a call for additional scientific data both with a deadline of 27 May, 2008.

The draft opinion says that general principles applied to the prevention and control of the transmission of harmful bacteria to humans through food, including the sustained practice of improved hygiene at all stages of the food chain, will contribute to the prevention and control of the transmission of antimicrobial-resistant bacteria by this route.

“Overall, control of all the routes by which antimicrobial resistant bacteria and their related genes can arise in the human patient, of which food is but one such route, requires a response from all stakeholders who acknowledge their responsibilities for preventing both the development and spread of antimicrobial resistance, each in their own area of activity including medicine, veterinary medicine, primary food animal production, food processing and food preparation, as well as in the regulation of food safety,” the Panel recommended in the draft opinion.

Antimicrobial resistance of bacteria is a growing concern as antimicrobials become less effective in fighting human infections. This coincides with a rise in bacterial resistance to antimicrobials in animal populations. Resistant Salmonella and Campylobacter involved in human disease are mostly spread through food. The principal foods carrying such antimicrobial resistant bacteria are poultry meat, eggs, pork or beef. Contamination during preparation, handling and processing of fresh food of plant origin, such as salads, is also of concern.

The Panel identified several instances in which food may become a vehicle for transmitting bacteria with antimicrobial resistance, to humans:

  • transfer of antimicrobial-resistant bacteria directly to humans from contaminated food originating from animals carrying resistant bacteria, which can colonise or infect a human being after ingestion;
  • ingestion of antimicrobial resistant bacteria on fresh produce from land recently irrigated with water contaminated by farm slurry or municipal sewage containing such bacteria;
  • transfer of antimicrobial resistance to the natural flora of the human gut from resistant bacteria on ingested food of both animal and non-animal origin, contaminated during the handling and preparation process

The Panel recommended that these potential contamination routes and the control measures currently in place be reviewed in light of the most recent scientific data.

The Panel also said that bacteria deliberately introduced into the food and feed chain for manufacturing and preservation processes, such as fermentation cultures, and also probiotics, have on occasion exhibited antimicrobial resistance and should also be considered as a possible route for the transfer of antimicrobial resistance through food.

The Panel considered that animal-derived food products can be a potential route for the human infection Meticillin-resistant Staphylococcus aureus (MRSA)[4] and may be an emerging food-related risk. The Panel said however, that the data currently available pointed to a more immediate occupational risk for pig farmers and abattoir workers, in addition to that posed for hospitalised patients.

The consultation process on the draft opinion will finalize by 27 May.

[1] Antimicrobials are antibacterial, antiviral, antifungal and antiparasitic agents. E.g. antibiotics are antimicrobials used for killing bacteria.
[2] Panel on Biological Hazards.
[3] A “self-task” Opinion or activity is generally an important risk assessment issue which EFSA identifies and undertakes to do as part of its on-going work programme of activities.
[4] Methicillin-resistant Staphylococcus aureus is a bacterium which has evolved an ability to survive treatment with some of the most commonly used antibiotics and is responsible for difficult-to-treat infections in humans.

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