LINKING HUMANS AND ANIMALS
The transfer of disease between humans and another species is known as zoonosis. Two leading resistant zoonotic pathogens are Campylobacter and Salmonella.
There is disagreement over how much contamination arises in humans from bacteria from livestock environments. However, the consensus is that there is potential for cross over.
Samples from humans in 2010 showed Salmonella resistance to ampicillin, tetracyclines and sulphonamides was high.
The impact of this is not as great as resistance to cefotaxime (a third-generation cephalosporin) and ciprofloxacin (a flouraquinalone), both classed as critically important, which were reported as having ‘relatively low’ resistance.
The findings appeared in a European Food Safety Authority (EFSA) journal article in 2010 which summarised resistance of indicator bacteria from humans, animals and food. This meant a focus around E.Coli, Salmonella and Campylobacter bacteria.
The report provided figures to show how poultry production was the main source of resistant bacteria.
Over a quarter (28 per cent) of Salmonella isolates in Turkeys and 24 per cent in broiler chickens were found to be resistant to ciprofloxacin. Resistance of E.coli isolates was reported as 29 per cent in broilers and 2 per cent in pigs.
Widespread campylobacter resistance was observed for ciprofloxacin, ranging from 37 per cent to 85 per cent in cattle, pigs and chickens.
Campylobacter jejuni bacteria pose a threat on raw chicken leading to gastrointestinal problems in humans
Campylobacter resistance is especially linked to flouroquinolones and macrolides.
One way resistant pathogens reach humans is through the food chain. This is typically through raw meats and untreated milk. One such example is Campylobacter jejuni on poultry meat which, if not cooked sufficiently, can be fatal, killing 100 people in the US each year.
Likewise, Salmonella strains pose a foodborne threat to human health, now causing tens of millions of infections every year after resistant strains were first reported in the early 1990’s.
Food safety precautions, such as pasteurising milk and ensuring thorough cooking of raw chicken are recommended as basic measures against bacteria on food.
The EFSA report stated: "Resistance to antimicrobials was commonly found in isolates of Salmonella,Campylobacter and indicator E. coli and enterococci from animals and food in the EU."
Resistance to ampicillin, sulfonamides and tetracyclines was reported as being as high as 75 per cent for Salmonella. For Campylobacter, resistance to ciproflaxacin, nalidixic acid and tetracylines ranged from 21 to 84 per cent.
But, the dangers extend beyond food. There is also occupational risk, which may be greater where there are links to high antimicrobial usage, such as intensive husbandry systems. This poses a threat to farm workers and the people with whom they regularly come into contact.
The OIE recognises that antimicrobial resistance is a concern to human and animal health and has followed the WHO in an effort to ensure veterinarians and producers use antimicrobials responsibly to preserve their therapeutic effect.
To this end, the OIE has drawn up a list of critically important antibiotics to protect animal health and established monitoring standards to quantify drug usage and resistance levels because, although the overall impact of agriculture on antimicrobial resistance is debatable, the ability to control infections in food production is vital.