Comment on: Does the use of antibiotics in food animals pose a risk to human health? A critical review of published data

Beth E. Karp1,* and Jørgen Engberg2

1 Center for Veterinary Medicine, Food and Drug Administration, 7519 Standish Place, Rockville, MD 20855, USA; 2Statens Serum Institut, Artillerivej 5, DK-2300 Copenhagen S, Denmark

Keywords: antimicrobial resistance , food animals

Sir,

In a recently published article, Phillips et al.1 claim that they ‘attempt to draw out facts among much misinformation’. In actuality, their article is fraught with inaccurate and misleading citations and other errors. Moreover, their ‘review’ article is far from an unbiased scientific review of the literature, as the authors appear to report only those studies and findings which they interpret as being supportive of their opinions. Due to word and reference limitations, our comments address only a portion of the authors' discussion of Campylobacter.

In their efforts to persuade readers that chicken is not a risk factor for human Campylobacter infection (despite the multitude of evidence demonstrating that it is), Phillips et al.1 state ‘Once venue is taken into account, chicken is no longer a risk factor (Tables 2 and 3)’. Phillips et al.1 incorrectly cite an article by Engberg et al.2 for this statement. In fact, Engberg et al.2 state, ‘Campylobacteriosis is primarily a zoonosis. Evidence to indicate that fresh raw meat, especially poultry, is a major source of infection is ample...’. Phillips et al.1 also incorrectly state that Table 2, which lists odds ratios for ‘protective factors’, is based on Neimann3 and Engberg et al.2 The Engberg et al.2 article neither refers to protective factors nor presents odds ratios, but it does state, ‘Fluoroquinolone resistance in Campylobacter from food animals is now recognized as an emerging public health problem’. Furthermore, Tables 2 and 3 incorrectly state in their titles that the data they provide are for Campylobacter jejuni, when in fact, the references and studies upon which the tables are based are not limited to C. jejuni.

With regard to the human health consequences of resistance in Campylobacter, Phillips et al.1 misrepresent one study and omit the findings of three pertinent ones. Phillips et al.1 state ‘Marano et al. 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 strains—6 days for both treated and untreated patients)’. Marano et al.4 actually 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. Furthermore, Phillips et al.1 fail to mention that two other studies known to them (references 158 and 165 of their paper) found that quinolone resistance in Campylobacter was associated with a longer duration of illness. Smith et al.5 found that among patients treated with a fluoroquinolone after the collection of a stool specimen, the median duration of diarrhoea was 3 days longer for patients with quinolone-resistant C. jejuni infections than for patients with quinolone-susceptible infections (P=0.03). (It should be noted that the Smith et al.5 paper can actually be found on pages 1525–1532 of the cited volume, not pages 1581–1582, as referenced by Phillips et al.1) Similarly, Neimann3 reported that among Campylobacter cases treated with fluoroquinolones (or other antibiotics of unknown kind), the median duration of illness was 14 days for cases with resistant isolates, but only 9 days in those with susceptible isolates. Another study, which is not referenced by Phillips et al.,1 found that patients with quinolone-resistant Campylobacter infections were hospitalized more frequently than those with quinolone-susceptible infections (P<0.05).6

Other adverse human health consequences associated with antimicrobial resistance in Campylobacter are coming to light. A recently completed study in Denmark found that persons with fluoroquinolone-resistant or erythromycin-resistant Campylobacter infections were more likely to have bloodstream infections or die in the 90 days following specimen collection than those with susceptible infections.7

A truly objective scientific review of the literature reveals that there is accumulating evidence that antimicrobial resistance originating from the use of antimicrobials in food animals adversely affects human health.

Footnotes

* Corresponding author. Tel: +1-301-827-3336; Email: bkarp{at}cvm.fda.gov

References

1 . 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, 28–52.[Abstract/Free Full Text]

2 . Engberg, J., Aarestrup, F. M., Taylor, D. E. et al. (2001). Quinolone and macrolide resistance in Campylobacter jejuni and C. coli: resistance mechanisms and trends in human isolates. Emerging Infectious Diseases 7, 24–34.[ISI][Medline]

3 . Neimann,J. (2001). The epidemiology of sporadic campylobacteriosis in Denmark investigated by a case-control study and strain characterization of patient isolates. PhD thesis, 2001. The Royal Veterinary and Agricultural University, Denmark

4 . 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, 2000. [Online]. http://www.cdc.gov/narms/pub/presentations/2000/marano_n_3.htm (13 February 2004, date last accessed).

5 . Smith, K. E., Besser, J. M., Hedberg, C. W. et al. (1999). Quinolone-resistant Campylobacter jejuni infections in Minnesota, 1992–1998. New England Journal of Medicine 340, 1525–32.[Abstract/Free Full Text]

6 . Friedman, C. R., Yang, S., Rocourt, J. et al. (1998). Fluoroquinolone-resistant Campylobacter infections in the United States: a pilot case-control study in FoodNet sites. Thirty-sixth Annual Meeting of the Infectious Diseases Society of America, Denver, CO, 1998. [Online.] http://www.cdc.gov/foodnet/pub/idsa/1998/friedman_c.htm (13 February 2004, date last accessed).

7 . FAO, OIE, WHO (2003). Joint First FAO/OIE/WHO Expert Workshop on Non-Human Antimicrobial Usage and Antimicrobial Resistance: Scientific Assessment, Geneva, 1–5 December, 2003. [Online.] http://www.who.int/foodsafety/micro/meetings/nov2003/en/ (13 February 2004, date last accessed).





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