1 University of London, London, UK; 2 Cox Associates, Denver, CO; 3 Kansas State University, Manhattan, KS, and Livestock Information Services, Callaway, NE; 5 JMI Laboratories, North Liberty, IA; 6 Hartford Hospital, University of Connecticut, 80 Seymour St., Hartford, CT 06102-5037; 7 Texas Tech University, Lubbock, TX; 8 Sutton Veterinary Clinic, Sutton, NE, USA; 4 Royal Veterinary and Agricultural University, Copenhagen, Denmark
Keywords: antibiotics, animal husbandry, resistance
Sir,
We would like to reply to some of the points made by John Turnidge1 in response to our recent paper on the potential risks to human health arising from the use of antibiotics in food animals,2 and another on the consequences of the ban of growth-promoting antibiotics in Europe.3
Firstly, he characterized our position as being that no action is required. This is incorrect. Our belief is that to achieve better human health, risk managers must base their actions on a full and fair consideration of all relevant scientific evidence, including evidence of both benefit and risk. We also believe that risk managers need to know when there is scientific consensus and when this is lackingsomething that has not always been made clear. Furthermore, we believe that evidence has sometimes been used selectively to support a particular viewpoint, and we therefore drew attention to scientific findings that we believed had not been adequately taken into account, particularly those that suggested that the use of antibiotics in animals might not pose a risk to human health, and that the abandonment of the use of growth-promoting antibiotics might have adverse as well as advantageous effects. We also drew attention to the need for more and better scientific informationto the same extent as those who described the application of the Precautionary Principle as requiring that additional information necessary for a more objective assessment of risk will be sought4 agreeing with John Turnidge. We had little to say on the process of risk management, believing this to be the concern of risk managers, although we might agree that actions taken that are uninformed by full consideration of the relevant scientific information might lead to undesirable human health consequences.
Secondly, we agree that resistance is likely to be selected whatever the context of use, but do not presume that an antibiotic used in both animals and humans will be more likely to select for resistance as a consequence of animal rather than human usage. After all, the use of antibiotics in humans, acting both as selector and amplifier, is believed to be the major driver of resistance for most human pathogens. The use of virginiamycin in animals over decades did not appear to result in resistance in relevant human pathogens,5,6 but when quinupristindalfopristin was introduced, streptogramin-resistant Enterococcus faecium were immediately observed, but with a resistance mechanism unlike that hitherto reported in animals.2,6
Thirdly, we urge that debate should continue, and should indeed be broadened, but not in an adversarial manner. It is simply not good enough for us as scientists to say that it is likely that [resistant commensal] species are... important reservoirs of resistance genes that can be transmitted to the human gut flora. Surely it is not beyond our competence to make appropriate epidemiological, microbiological and clinical observations and devise relevant experiments to provide unequivocal quantitative answers!
Our aimabout which John Turnidge expressed confusionhas been to try to ensure that the scientific debate should be even-handed, making it clear to risk-analysts and managers where there is agreement, where there is disagreement, and where there is a lack of adequate information, in the science on which they base their actions. We remain disinterested in relation to scientific findings. We are neither trying to reverse bans nor to define prudent antibiotic use, merely trying to ensure that scientific data and process are used even-handedly by those who are involved in these activities.
Footnotes
* Corresponding author. Tel: +1- 860-545-2865; E-mail: cnighti{at}harthosp.org
References
1
.
Turnidge, J. (2004). Antibiotic use in animalsprejudices, perceptions and realities. Journal of Antimicrobial Chemotherapy 53, 267.
2
.
Phillips, I., Casewell, M., Cox, T. et al. (2004). Does the use of antibiotics in food animals pose a risk to human health? A critical review of published data. Journal of Antimicrobial Chemotherapy 53, 2852.
3
.
Casewell, M., Friis, C., Marco, E. et al. (2003). The European ban on growth-promoting antibiotics and emerging consequences for human and animal health. Journal of Antimicrobial Chemotherapy 52, 15961.
4 . Commission of the European Communities. (2000). Communication from the Commission on the Precautionary Principle. Com(2000) 1, Brussels, 02022000.
5 . Low, D. E., Keller, N., Barth, A. et al. (2001). Clinical prevalence, antimicrobial susceptibility, and geographic resistance patterns of enterococci: results from the SENTRY Antimicrobial Surveillance Program, 19971999. Clinical Infectious Diseases 32, S13345.[CrossRef][ISI][Medline]
6
.
Bell, J. M., Turnidge, J. D., Ballow, C. H. et al. (2003) Multicentre evaluation of the in vitro activity of linezolid in the Western Pacific. Journal of Antimicrobial Chemotherapy 51, 33945.
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