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Letter
Antimicrobial Resistance in
Campylobacter
To the Editor: Iovine and Blaser (1) write,
"This therapeutic use [of enrofloxacin] was withdrawn (2)
but is now under appeal" and "Despite the restrictions on enrofloxacin
use, emergence of fluoroquinolone-resistant Campylobacter species,
with poultry as an important source, has been documented in the United
States… Therefore, our conclusion remains: use of enrofloxacin in poultry
materially contributed to increase in human infection by fluoroquinolone-resistant
Campylobacter species."
These claims propagate the following important errors. First, the therapeutic
use of enrofloxacin was not withdrawn. Judge Davidson's order to withdraw
the approval was an initial decision, to which exceptions were filed in
2004. A final decision rests with the US Food and Drug Administration
Commissioner.
Second, poultry has not been identified as an important source of fluoroquinolone
resistance in human Campylobacter isolates. The raw data of the
cited Smith et al. article (3) indicate a nonsignificant
negative association between chicken consumption and fluoroquinolone resistance
in human isolates. Substantial resistance levels in Northern Hemisphere
countries with and without enrofloxacin use, which occurred well before
fluoroquinolones were ever used in animals (3–5), also
suggest that attribution of such resistance to enrofloxacin is simplistic.
Finally, rational decision-making is based on probable future consequences
of a decision, not past history or causes of the current situation. Iovine
and Blaser's claim, "Thus the decision to withdraw therapeutic use
of enrofloxacin (3) was warranted," is not implied, even if enrofloxacin
use caused the emergence of fluoroquinolone resistance. If withdrawing
enrofloxacin increases campylobacteriosis from airsacculitis-positive
chickens, withdrawal may greatly harm human health. A rational withdrawal
decision cannot be justified. In summary, Iovine and Blaser's view that
enrofloxacin should be banned is not supported by the data that they have
cited or by principles of sound risk management and decision-making.
Louis Anthony Cox, Jr.,*
Dennis Copeland,† and Michael Vaughn†
*Cox Associates, Denver, Colorado, USA; and †Bayer HealthCare, Shawnee,
Kansas, USA
Suggested citation
for this article:
Cox LA Jr, Copeland
D, Vaughn M. Antimicrobial resistance in Campylobacter [letter].
Emerg Infect Dis [serial on the Internet]. 2005 Jun [date cited].
Available from http://www.cdc.gov/ncidod/EID/vol11no06/04-0689_05-0266.htm
References
- Iovine NM, Blaser MJ. Antimicrobial
resistance in Campylobacter. Emerg Infect Dis. 2004;10:1346.
- Vanhoof R, Vanderlinden MP, Dierickx R, Lauwers S, Yourassowsky E,
Butzler JP. Susceptibility
of Campylobacter fetus subsp. jejuni to twenty-nine antimicrobial
agents. Antimicrob Agents Chemother. 1978;14:553–6.
- Smith KE, Besser JM, Hedberg CW, Leano FT, Bender JB, Wicklund JH,
et al. Quinolone-resistant
Campylobacter jejuni infections in Minnesota, 1992–1998.
Investigation Team. N Engl J Med. 1999;340:1525–32.
- Svedhem A, Kaijser B, Sjogren E. Antimicrobial
susceptibility of Campylobacter jejuni isolated from humans with
diarrhea and from healthy chickens. J Antimicrob Chemother. 1981;7:301–5.
- Hollander R. [In
vitro activity of 23 chemotherapeutic agents against Campylobacter
jejuni/coli strains isolated from feces]. Zentralbl Bakteriol
Mikrobiol Hyg [A]. 1983;256:196–201.
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To the Editor: Cox and colleagues raised
3 major points. For the first point, we stated (1) "This
therapeutic use was withdrawn but is now under appeal." The actual
language of US Federal Drug Administration Judge Davidson's ruling is
"Enrofloxacin found not shown to be safe under the conditions of
use upon the basis of which the application was approved as required under
§ 512(e)(1)(B) of the Federal Food, Drug, and Cosmetic Act (the Act) [21
U.S.C. § 360 b(e)(1)(B)]. Approval of NADA1
for enrofloxacin ordered withdrawn" (1). The drug
manufacturer now is appealing the ruling.
For the second point, the authors state that poultry has not been identified
as an important source of fluoroquinolone resistance in human Campylobacter
isolates. In both Denmark and Spain, introduction of fluoroquinolones
into poultry led to a rapid rise in resistance to Campylobacter
in both poultry and human isolates (2–5), and banning
their use in Denmark led to a rapid fall in resistance (6).
Cox and colleagues may maintain that there is no "proof of a causal
relationship," but the relationship is sufficiently strong, temporally
restricted, biologically plausible, and coherent to convince disinterested
observers, including Judge Davidson and ourselves, otherwise.
For the third point, that decisions must consider probable consequences,
we agree. However, Cox et al. appear to use "possible" as their
standard. In fact, nearly everything is possible, including the reasoning
that they offer. However, in our opinion, based on experience as scientists
and microbiologists, we deem the possible consequences described by Cox
et al. as insubstantial compared to the clear and present danger to human
health of continuing fluoroquinolone use in poultry. Obfuscation and delay
have been effective tactics used to maintain profitability even when the
facts indicate a different course of action. We hope that the FDA Commissioner
will carefully weigh the actual evidence of the risk to human health imposed
by the use of fluoroquinolones in poultry.
Nicole M. Iovine* and Martin J. Blaser*†
*New York University School of Medicine, New York, NY, USA; and †New York
Harbor Department of Veterans Affairs Medical Center, New York, NY, USA
Suggested citation
for this article:
Iovine NM, Blaser MJ.
Antimicrobial resistance in Campylobacter [response to letter].
Emerg Infect Dis [serial on the Internet]. 2005 Jun [date cited].
Available from http://www.cdc.gov/ncidod/EID/vol11no06/04-0689_05-0266.htm
References
- Daniel J. Davidson FALJ. In: The matter of enrofloxacin
for poultry: withdrawal of approval of Bayer Corporation's new animal
drug application 1 (NADA) 140-828 (Baytril). In: FDA Docket No 00N-1571;
2004.
- Endtz HP, Ruijs GJ, van Klingeren B, Jansen WH, van der Reyden T,
Mouton RP. Quinolone
resistance in Campylobacter isolated from man and poultry following
the introduction of fluoroquinolones in veterinary medicine. J Antimicrob
Chemother. 1991;27:199–208.
- Reina J, Borrell N, Serra A. Emergence
of resistance to erythromycin and fluoroquinolones in thermotolerant
Campylobacter strains isolated from feces 1987–1991. Eur
J Clin Microbiol Infect Dis. 1992;11:1163–6.
- Sanchez R, Fernandez-Baca V, Diaz MD, Munoz P, Rodriguez-Creixems
M, Bouza E. Evolution
of susceptibilities of Campylobacter spp. to quinolones and macrolides.
Antimicrob Agents Chemother. 1994;38:1879–82.
- Velazquez JB, Jimenez A, Chomon B, Villa TG. Incidence
and transmission of antibiotic resistance in Campylobacter jejuni
and Campylobacter coli. J Antimicrob Chemother. 1995;35:173–8.
- Use of antimicrobial agents and occurrence of antimicrobial resistance
in bacteria from food animals, foods and humans in Denmark. Copenhagen:
Danish Zoonosis Center, Danish Veterinary Institute; 2003.
1New Animal Drug Application
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