The antimicrobial storm clouds are appearing to gather yet again. The WHO and FDA have produced their Lists of 'Critical (C), Highly Important (HI) and Important (I)' antimicrobials for use in human medicine and now the OIE is collecting the data together to establish there own Critical List of antimicrobials for animal health/veterinary use.

As this is the year, we have seen the withdrawal of the license for the fluoroquinolone, enrofloxacin, in poultry in the USA and the 31^st of December marks the last day of antimicrobial growth promoter use in the EU, we wonder what future restrictions may be imposed on the animal production industry and veterinarians, who try to maintain the health of the industry.

The criteria used for 'Critical' classification by the WHO and the FDA are different, the former uses a combination of 'sole therapy or one of few alternatives to treat serious human disease' and 'antibacterial used to treat diseases caused by organisms that may be transmitted via non-human sources or diseases caused by organisms that may acquire resistance genes from non-human sources'. The FDA used 'antimicrobial drugs used to treat enteric pathogens that cause food-borne disease' as their number one criterion and similarly to WHO 'sole therapy or one of few alternatives to treat serious human disease or drug is essential component among many antimicrobials in treatment of human disease'.

On this basis, the WHO selected 16 classes of critical antimicrobial and the FDA only four (see Table 1). Where both agree (C/C rating) and they are also used in animal health, the figure falls to three and presumably the future battle ground will be primarily but not necessarily only here and these are the fluoroquinolones (not surprisingly), macrolides and the third generation cephalosporins. Other classes where they are identified as 'critical, highly important (C/HI rating) and used in animal health' include the aminoglycosides, 4th generation cephalosporins, penicillins (natural and synthetic), streptogramins (virginiamycin is still used as a growth promoter outside the EU) and the trimethoprim/sulphas (FDA critical list).

Interestingly, the growth promoters that have been banned in the EU, tylosin (macrolide) has a 'C/C' rating, avoparcin and virginiamycin have a 'C/HI' one and bacitracin an 'I/-' rating only. The ones that are going next year avilamycin, flavophospholipol, monensin and salinomycin are not rated as their classes are not used in human medicine. Monensin and salinomycin (ionophores) will remain as important anticoccidials in the poultry industry. The pleuromutilins are the only other major class of antimicrobial not currently used in human medicine.

Where the future negotiations take us next year is unsure territory, both technically and politically. It must be hoped though that in their deliberations they do not forget that animals, which provide food for the world, need antimicrobial therapy also for their health and welfare.

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WHO & FDA Lists: Antimicrobials for human use: Excel Spreadsheet
 
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