Ciprofloxacin Resistance in Campylobacter jejuni Evolves Rapidly
in Chickens Treated with Fluoroquinolones
Patrick F. McDermott, Sonya M. Bodeis,
Linda L. English, David G. White, Robert D. Walker,
Shaohua Zhao, Shabbir Simjee, and David D. Wagner
Division of Animal and Food Microbiology, Center for Veterinary
Medicine, US Food and Drug Administration, Laurel, Maryland
Fluoroquinolones are commonly used to treat gastroenteritis caused by Campylobacter species.
Domestically acquired fluoroquinolone-resistant Campylobacter infection has been documented
recently in the United States. It has been proposed that the increase in resistance is due, in part,
to the use of fluoroquinolones in poultry. In separate experiments, the effects of sarafloxacin
and enrofloxacin treatment of Campylobacter jejuni–infected chickens on the development of
ciprofloxacin resistance were measured. Fecal samples were collected before and after treatment
and were cultured for C. jejuni. When enrofloxacin or sarafloxacin was used at US Food and Drug
Administration–approved doses in broiler chickens, resistance developed rapidly and persisted
in C. jejuni. MICs of ciprofloxacin increased from a base of 0.25 mg/mL to 32 mg/mL within the
5-day treatment time frame. These results show that the use of these drugs in chickens rapidly se-
lects for resistant Campylobacter organisms and may result in less effective fluoroquinolone
therapy for cases of human campylobacteriosis acquired from exposure to contaminated chicken.
Campylobacter jejuni is recognized as the leading cause of
bacterial gastroenteritis in the United States, accounting for
sporadic cases have indicated that chicken is the most common
source of human infection [2, 3]. In addition, survey data show
Campylobacter infection causes acute inflammatory enteritis
that may be indistinguishable from that caused by Salmonella
infection. Although Campylobacter enteritis is usually a self-
limiting diarrheal disease, infrequent cases of serious invasive
may require antibiotic therapy. When antimicrobials are used to
treat adults with enteritis, they are most effective in limiting the
duration of illness when given early in the course of infection,
before the etiologic agent is confirmed by culture . Because
pylobacter infections, the emergence of resistant strains will
limit the therapeutic usefulness of these drugs.
The fluoroquinolones sarafloxacin and enrofloxacin were li-
censed in 1995 and 1996, respectively, for controlling mortality
associated with Escherichia coli infections in chickens. Both
antimicrobials are administered to the entire chicken house ad
libitum in water for up to 5 days for sarafloxacin and for 5–7
days for enrofloxacin. Surveillance data suggest a temporal as-
sociation between the approval of these drugs in poultry and
tions [6, 3]. To measure the impact of fluoroquinolone use in
C. jejuni isolates were collected over time, and fluoroquinolone
MICs were measured.
Materials and Methods
Newly hatched broiler chicks from a commercial source were
allocated randomly to 2 groups of 50 (sarafloxacin treated) or 25
(enrofloxacin treated) birds each. The chickens were reared under
conventional conditions on pine-shave bedding with continuous
lighting. Animals were fed a standard antibiotic-free broiler starter/
grower diet, which was prepared on site, and were given access to
feed and water ad libitum. To help insure that exogenous Campylo-
bacter species were not introduced via the feed, 20 feed samples
were collected at approximately equal intervals from the mixer
exit streamimmediately after preparation offeed andwerecultured
using standard methods .
sity of Maryland was screened for fluoroquinolone susceptibil-
ity. Five fluoroquinolone-susceptible isolates were identified, each
with the following MICs: ciprofloxacin, 0.25 mg/mL; sarafloxacin,
0.125 mg/mL; and enrofloxacin, 0.06 mg/mL. A mixture containing
The Journal of Infectious Diseases
This article is in the public domain, and no copyright is claimed.
Presented in part: 101st annual meeting of the American Society for
Microbiology, Orlando, FL, May 2001 (poster Z-20).
Financial support: US Food and Drug Administration Center for Veteri-
Reprints or correspondence: Dr. Patrick F. McDermott, Office of Research,
Center for Veterinary Medicine, US Food and Drug Administration, 8401
Muirkirk Rd., Laurel, MD 20708 (email@example.com).
Received 29 August 2001; revised 19 October 2001; electronically published
8 February 2002.
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