Antimicrobial-resistant Campylobacter Table 1. Antimicrobial resistance among Campylobacter isolates by species, National Antimicrobial Resistance Monitoring System 1997–2001 % resistant C. jejuni C. coli C. upsaliensis C. lari C. fetus Undetermineda Total Antimicrobial agent (n = 1,471) (n = 63) (n = 7) (n = 2) (n = 5) (n = 5 ) (n = 1,553) Azithromycinb 2 9 0 0 0 0 2 Chloramphenicol 0.3 5 0 0 0 40 0.6 Ciprofloxacin 16 30c 14 0 0 0 16 Clindamycin 1 9 0 0 0 20 2 Erythromycin 2 8 0 0 0 20 2 Gentamicinb 0 2 0 0 0 0 0.1 Nalidixic acid 17 36c 14 100 80 20 18 Tetracycline 43 43 0 0 20 0 43 aUndetermined isolates were hippurate-negative Campylobacter that could not be further speciated with available polymerase chain reaction primers. bFor azithromycin and gentamicin, only 1,336 isolates were tested. cComparison of proportion of resistant C. coli to resistant C. jejuni was statistically significant for ciprofloxacin and nalidixic acid but not tetracycline (p < 0.01) 1997 Retrospective Case-Comparison Study Sixteen (57%) of 28 ciprofloxacin-resistant Campylo- bacter (CipR) case-patients and 31 ciprofloxacin-sensitive (CipS) case-patients were interviewed. The median age was 46 years (range 9–76 years) for CipR patients and 24 years (range 1–87 years) for CipS patients (Wilcoxon rank-sum, p = 0.08). CipR patients did not differ signifi- cantly from CipS patients in terms of sex (40% vs. 42% female, p = 0.1), race (87% vs. 77% white, p = 0.08), and place of residence (87% vs. 61% urban/suburban areas, p = 0.06). Five (31%) CipR patients were hospitalized for gastroenteritis compared with 1 (3%) CipS patient (matched odds ratio [mOR] = 13.6, 95% confidence inter- val [CI] 1.4 to 130.1). Eight (57%) CipR case-patients reported having bloody diarrhea compared with eight (30%) CipS patients (mOR = 3.2, 95% CI 0.8 to 12.1). Seven (44%) of 16 CipR patients compared with 1 (3%) of 31 CipS patients traveled to a foreign country in the 7 days before illness onset (mOR = 23.3, 95% CI 2.5 to 215.6); 5 (71%) of 7 CipR patients traveled to Europe while 1 CipS patient traveled to the Caribbean. Among all case-patients, 35 of 47 reported treatment with an antimicrobial agent for their illness. Of those who recalled the name of the antimi- crobial drug, 75% reported taking a fluoroquinolone, 16% reported taking a macrolide, and 8% took trimethoprim- sulfamethoxazole (TMP/SMX). One CipR patient and one CipS patient took fluoroquinolones between onset of ill- ness and collection of stool specimens. Among the eight CipR patients who did not travel and did not take fluoro- quinolones between illness onset and stool specimen col- lection, seven (87%) consumed poultry in the 7 days before infection; this finding was not statistically different from that in CipS patients. No other exposures were signif- icantly associated with ciprofloxacin-resistant infection, including having pets, drinking raw milk, or being exposed to a farm (data not shown). 1999 Retail Survey Among the 180 retail chicken products purchased, rep- resenting 18 domestic brand names from 22 grocery stores, Campylobacter was isolated from 80 (44%) samples. Sixty-two (77%) were C. jejuni, 16 (20%) were C. coli, and 2 (2%) were undetermined (i.e., determination by 16S study did not identify a species). The prevalence of Campylobacter isolated was 33% (20 of 60) in Georgia, 37% (22 of 60) in Maryland, and 63% (38 of 60) in Minnesota. This difference among sites was in part due to the difference in isolation rates of C. coli; 14 (87%) of the Table 2. Antimicrobial resistance among human Campylobacter jejuni strains, 1990–2001 % resistant 1989-1990 1997 1998 1999 2000 2001 Total Antimicrobial agent (n = 286)a,b (n = 209) (n = 297) (n = 294) (n = 306) (n = 365) (n = 1,757) Azithromycinc 1 – 1 3 2 2 1 Chloramphenicol 0 1 1 0.3 0 0 0.3 Ciprofloxacin 0 12 14 18 14 18 13 Clindamycin 1 1 1 1 1 2 1 Erythromycin 1 1 2 2 1 2 2 Gentamicinc 0 – 0 0 0 0 0 Nalidixic acid 1 13 16 20 16 19 14 Tetracycline 42 47 46 46 39 40 43 a1989–1990 U.S. sentinel county study used different sampling and laboratory methods (microbroth dilution testing) than NARMS (Etest). However, studies have concluded that broth microdilution and Etest give equivalent results for ciprofloxacin susceptibility testing of Campylobacter (44). bIn 1989–1990 U.S. county study, only 285 isolates were tested for azithromycin and nalidixic acid susceptibility. cFor azithromycin and gentamicin, only isolates received between 1998 and 2001 were tested (N = 1,262). Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 10, No. 6, June 2004 1105