Centers for Disease Control and Prevention, Atlanta, GA, USA
Keywords: antimicrobial resistance , food animals
Sir,
Several studies conducted by the Centers for Disease Control and Prevention (CDC) were cited in the recent article in JAC by Phillips et al.1 Unfortunately, Phillips et al.1 have incorrectly linked these studies to statements that do not summarize the conclusions of the authors. Among several examples, we would like to describe three incorrect summaries.
Phillips et al.1 cite a CDC article in the New England Journal of Medicine on the emergence of multidrug-resistant Salmonella to support the statement: the resistance prevalence varies from time to time and place to place with no obvious relationship to current antibiotic usage patterns in humans or animals.1 To the contrary, the article by Glynn et al.,2 which concerns Salmonella serotype Typhimurium DT104 R-type ACSSuT, states the proportion of isolates with five-drug pattern of resistance has increased from less than 1 percent in 197980 to 34 percent in 1996, and therefore describes increasing, not variable, prevalence. The article also states, the emergence of antimicrobial-drug resistance in Salmonella isolates is associated with the therapeutic use and non-therapeutic use of antimicrobial agents in food animals. Prudent use of antimicrobial agents in farm animals and more effective disease prevention on farms is necessary to reduce the dissemination of five-drug-resistant Typhimurium DT104 and to slow the evolution of resistance to additional agents in this and other strains of Salmonella.2 This statement was made based on the direct relationship between use of antimicrobial agents in food animals and the emergence of antimicrobial-resistant Salmonella, which results in increased transmission of these resistant pathogens to humans and increased likelihood of compromising treatment options. This relationship and its consequences are supported by numerous lines of evidence.3
In citing CDC authored articles in the Journal of Infectious Diseases and Review of Infectious Diseases, Phillips et al.1 write: it might be thought that antibiotic-resistant salmonellae would have a devastating clinical effect, but this is rarely the case in developed countries. However, neither of these articles support this statement. In the first article, Lee et al.4 reported that patients with antimicrobial-resistant Salmonella infections were more likely to be hospitalized than those with susceptible infections, concluding that these data show that treatment of Salmonella infections may be complicated by growing resistance to clinically important antimicrobial agents and by increasing frequencies of extraintestinal complications. In the second article, Holmberg et al.5 evaluated investigations of Salmonella outbreaks and found that the data show higher rates of hospitalization and mortality associated with drug resistant than with drug-susceptible strains. Although Phillips et al.1 do not define devastating, we assume they would agree that excess hospitalization and mortality would merit such characterization and, rare or not, would not be a consequence that should be dismissed.
Phillips et al.1 cite a CDC abstract from the 2000 International Conference on Emerging Infectious Diseases to support the statement: Marano et al.6 reported a 4 day decrease in the duration of diarrhoea (from 12 to 8 days) for patients infected with fluoroquinolone-resistant strains treated with ciprofloxacin (but paradoxically no decrease for susceptible strains6 days for both treated and untreated patients). This statement does not represent conclusions from the study. In fact, Marano et al.6 reported that patients with ciprofloxacin-resistant Campylobacter infections had a longer duration of diarrhoea than those with susceptible infections and that the longer duration occurred both among patients who took ciprofloxacin and those who did not.
There are many opportunities to reduce the overuse and misuse of antimicrobial agents in food animals. Reductions in overuse and misuse now and in the future would benefit human health by slowing the emergence and spread of resistant food-borne infections.
Footnotes
* Corresponding author. Email: tnc3{at}cdc.gov
References
1 . Phillips, I., Casewell, M., Cox, T. et al. (2003). 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.[CrossRef][ISI][Medline]
2
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Glynn, M. K., Boop, C., Dewitt, W. et al. (1998). Emergence of multidrug-resistant Salmonella enterica serotype Typhimurium DT104 infections in the United States. New England Journal of Medicine 338, 13338.
3 . Angulo, F. J., Johnson, K., Tauxe, R. et al. (2000). Origins and consequences of antimicrobial-resistant nontyphoidal Salmonella: implications for the use of fluoroquinolones in food animals. Microbial Drug Resistance 6, 7783.[ISI][Medline]
4 . Lee, L. A., Puhr, N. D., Maloney, E. K. et al. (1994). Increase in antimicrobial-resistant Salmonella infections in the United States, 19891990. Journal of Infectious Diseases 170, 12834.[ISI][Medline]
5 . Holmberg, S. D., Solomon, S. L. & Blake, P. A. (1987). Health and economic impacts of antimicrobial resistance. Review of Infectious Diseases 9, 106578.[ISI][Medline]
6 . Marano, N., Vugia, D., Fiorentino, T. et al. (2000). Fluoroquinolone-resistant Campylobacter causes longer duration of diarrhea than fluoroquinolone-susceptible Campylobacter strains in FoodNet sites. Second International Conference on Emerging Infectious Diseases, Atlanta, GA, USA, 2000.
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