High antibiotic residues and E. coli superbugs found in milk fed to calves

11 April 2012

New research by Government scientists has found that 21% of waste milk fed to calves on most of Britain’s dairy farms contain residues of the antibiotic cefquinome, and 4% of samples are contaminated by the extremely antibiotic-resistant extended-spectrum beta-lactamase (ESBL) E. coli. [1][2]

Cefquinome is a modern cephalosporin and the second most widely used antibiotic for treating mastitis infections in milking cows in the UK. [3] Modern cephalosporins are classified by the World Health Organization as ‘critically important antibiotics in human medicine’, and are important treatments for complicated urinary-tract infections, blood-poisoning and meningitis.

Defra scientists found that some waste milk samples contained residues of cefquinome at up to 235 times the maximum residue level permitted in milk for human consumption. Residues of older cephalosporin antibiotics were also found.

ESBL E. coli have developed resistance to all modern cephalosporins, so the use of these antibiotics can promote the spread of the superbug. Defra scientists found that 6% of waste milk samples contained ESBL bacteria, two thirds of which were E. coli. All samples with ESBL bacteria also had cefquinome residues.

Earlier Defra research found that waste milk is fed to calves on 81% of British dairy farms. [3] In combination with the latest research, this appears to explain the extremely rapid spread of ESBL E. coli on British cattle farms. Despite only first being identified on a dairy farm in Wales in 2004, in 2010 a Defra study found that 37% of cattle farms had ESBL E. coli. Calves are much more likely to carry ESBL E. coli than older animals. [4] The Defra scientists concluded that: ‘feeding untreated waste milk to calves can lead to exposure to antibiotic resistant bacteria’.

A recent Soil Association report estimated that 60,000 human ESBL E. coli infections occur each year in the UK, and showed that there is now overwhelming scientific evidence that antibiotic use on farms contributes significantly to the spread of resistant E. coli in humans. [5]

Soil Association-certified organic farmers are not allowed to feed waste milk containing antibiotic residues to calves and can only use modern cephalosporins if they get an exemption in situations when alternative antibiotics are likely to be ineffective.

The Soil Association is campaigning with its partners in the Alliance to Save Our Antibiotics, Sustain and Compassion in World Farming, for specific controls on the farm use of ‘critically important’ medical antibiotics. [8]

Richard Young, Soil Association policy advisor, said:
“This research vindicates the Soil Association’s precautionary approach regarding waste milk and modern cephalosporins. We are now calling for a ban on feeding calves waste milk from cows which have recently received antibiotics, unless it can be shown that the milk can be treated so that antibiotic residues are destroyed and resistant bacteria killed, and that the resulting milk still remains sufficiently wholesome to be fed to calves. Veterinary datasheets for modern cephalosporins need to be amended so that that these antibiotics are only prescribed when other antibiotics are likely to be ineffective. If these restrictions don’t greatly reduce their farm use, then regulators should implement a complete ban.” [6][7]

Ends

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Notes to editor:

[1] The research findings were presented on Monday 2 April at the 22nd European Congress of Clinical Microbiology and Infectious Diseases being held in London. The abstracts showing the findings can be viewed here:
http://registration.akm.ch/einsicht.php?XNABSTRACT_ID=142425&XNSPRACHE_ID=2&XNKONGRESS_ID=161&XNMASKEN_ID=900
http://registration.akm.ch/einsicht.php?XNABSTRACT_ID=140902&XNSPRACHE_ID=2&XNKONGRESS_ID=161&XNMASKEN_ID=900

[2] Waste milk can be milk from cows with infections such as mastitis, or it can be milk from cows which have recently been treated with medicines, including antibiotics. When a cow is treated with antibiotics, there is usually a withdrawal period, during which the milk cannot be sold for human consumption because of the high levels of residues.

[3] A survey of current farming practices in England and Wales relating to the use of antimicrobials in dairy cattle and feeding of waste milk, 

[4] Coldham N., 2010. Epidemiology of ESBL E. coli on cattle farms, abstract presented at the VLA & GVS/AGV National Conference 2010, Warwick University

[5] E. coli superbugs on farms and food

[6] The Defra scientists showed that incubating milk at 18°C for 72 hours, or at 37°C for 24 hours, can effectively decrease the concentration of cefquinome in spiked unpasteurised milk. However, the effect of this incubation on the resistant E. coli bacteria and on other antibiotic residues found in the milk has not yet been evaluated.

[7] Some Veterinary Medicine Directorate datasheets for newly introduced generic modern cephalosporin veterinary medicines already include the statement that use of the product ‘selects for resistant strains such as bacteria carrying extended spectrum betalactamases (ESBL) and may constitute a risk to human health if these strains disseminate to humans e.g. via food’ and so ‘should be reserved for the treatment of clinical conditions which have responded poorly, or are expected to respond poorly (refers to very acute cases when treatment must be initiated without bacteriological diagnosis) to first line treatment’.

The Soil Association is calling for this statement to be added to all datasheets for modern cephalosporin injectable and intramammary products, and for this policy to be properly implemented.

[8] Read more about the Alliance to Save Our Antibiotics: http://www.soilassociation.org/animalwelfare/antibiotics/alliancetosaveourantibiotics