Bacteria most frequently causing food-borne infections, such as Salmonella and Campylobacter, show significant resistance to common antimicrobials, according to a report released this week by EU food safety watchdog EFSA and the European Centre for Disease prevention and Control (ECDC).

The report, which covered growing resistance to drugs in zoonotic bacteria (those that can pass between different species of animal, causing illness), showed that resistance to critically important drugs was low, but that in many cases illness-causing bacteria had become tolerant of commonly used antimicrobials.

The authors said that, although medicines deemed 'critically important' appear to still be effective – suggesting treatment options for serious infections are available in most cases – the fact that antimicrobial resistance is commonly detected remains a "cause for concern."

This is concerning because, if bacteria become clinically resistant to several antimicrobials (called multidrug-resistance), treating the infections they cause becomes extremely difficult or even impossible, if this scale of resistance is allowed to grow it will humans without one of the key developments of our recent history. Resistance in animals can also compromise the effective treatment of human infections, as resistant bacteria and resistance genes may be transferred to humans from animals and food, EFSA said.

As a result, Marta Hugas, Acting Head of EFSA's Risk Assessment and Scientific Assistance Department, warned that use of antibiotics on animals, as well as humans, should be investigated and brought under control.

Key findings

ECDC chief scientist Johan Giesecke added, "In humans, the levels of clinical resistance to antimicrobials showed a great variability across the Member States." He said this was due to different investigative methods used between the 28 member states, but said that standardised monitoring being introduced this year would provide a better picture in future.

'Harmonising' the monitoring of antimicrobial resistance in Salmonella and Campylobacter in humans will begin this year. "Thus," Johan said, "we expect to get more accurate data from countries and as a result better comparability of data."

At the EU level, clinical resistance in humans to commonly used drugs was worryingly high. Almost half of the salmonella isolates in humans tested showed resistance to at least one drug and almost 30 percent were multi-drug resistant (meaning bacteria were resistant to three or more drugs). The authors of the joint report said that resistance to critically important medicines was "low."

Of the farm animals studied, resistance to commonly used drugs was "frequently detected" in broilers, pigs and turkeys. Resistance to critically important drug ciprofloxacin was also high, but resistance to other important antimicrobials was either not detected or reported at very low levels.

For Campylobacter, the results were, if anything, more concerning still. Clinical resistance to common antimicrobials was frequently detected and almost half of campylobacter isolates were resistant to critically important drug ciprofloxacin. EFSA noted that "increasing trends [were] observed in several Member States." Resistance to commonly used drugs was also frequently detected in animals tested.

E.Coli resistant to commonly used drugs was also found at high levels in pigs and broilers.

The two groups said that the joint report would contribute to monitoring work on antibacterial resistance, in line with recommendations made by the EU Commission in 2011. However, although a more unified approach to monitoring on an EU level means a clearer picture of antimicrobial resistance can be developed, opinion on how to curb growing resistance remains split.

Vets clash with Chief Medical Officer

In the UK, the British Veterinary Association clashed with Chief Medical Officer Sally Davies this week, after the CMO reportedly told conference delegates in Cambridge that drastic steps should be taken to reduce the risk of antimicrobial resistance developing in farm animals, and then being passed onto humans.

The BVA said it is seeking "a clarification of remarks" made by Professor Dame Davies, who apparently recommended that very sick animals be slaughtered rather than treated as part of a strategy to reduce antibiotic resistance in humans. Speaking at the Cambridge Science Festival, the chief Medical Officer called for a reduction in the use of antibiotics in farm animals and said that she had urged veterinary surgeons to slaughter badly infected animals rather than treat them.

However, BVA President Robin Hargreaves said the organisation disagrees that there is a need for such extreme action. Hargreaves said, "As veterinary surgeons our first duty is to the animals under our care, and that means providing the most appropriate treatment. Badly infected animals may need to be slaughtered for their own good or for the good of the herd or flock. But those that have a good chance of recovery and the opportunity to be productive should be treated with the appropriate antibiotics used responsibly."

Hargreaves said BVA believe there may be an economic case for treating animals, adding, "To suggest that treatable animals should be slaughtered makes no sense in terms of animal health, public health, or the rural economy," and continued, "It is unclear from the reported comments how such a strategy would be deployed and whether it would be extended to all animals, including pets. We are seeking clarification of the CMO's comments to ensure that the debate is based on facts.

The BVA president offered assurance that the Association is "not complacent about the role of antibiotics… in veterinary medicine and we are one of the leading voices in the campaign for the responsible use of antibiotics in all species."

A spokesperson for the CMO's office at the Department of Health said on Thursday that reports of Professor Dame Davies' comments had "not [been] entirely accurate."

Responding to the BVA President's comments, Professor Dame Davies said, "We have reached a critical point and must act now on a global scale to slow down Antimicrobial Resistance. In Europe, 25,000 people a year already die from infections which are resistant to our drugs of last resort."

"Issues with antimicrobial resistance faced by human medicine are primarily the result of antibiotic use in people, rather than the use of antibiotics in animals. However, animal use is an important factor which contributes to the wider pool of resistance and this may have long term consequences. We need to support responsible antimicrobial use across all sectors to minimise antibiotic use and reduce resistance. The timely and appropriate treatment of probable bacterial infection is essential, for both animals and humans — but the Department of Health works closely with Defra to make sure the right drug, right dose and right duration is used to limit unnecessary antibiotic exposure."

The Department of Health spokesperson added "The Chief Medical Officer has not suggested that animals should be slaughtered rather than treated with antibiotics in order to combat the global threat of antimicrobial resistance. However, she does recognise that one of the key differences between human and animal use of antibiotics is that in animals, there may be some circumstances in which veterinarians or farmers make the decision to slaughter an infected animal to prevent onwards transmission, rather than treat a flock or herd with antibiotics."

**Update 27/03/14 12:15. Response from CMO Sally Davies Added**