| Summary: | Antibiotic resistance is a major challenge worldwide and increased resistance to quinolones in <i>Campylobacter</i> is being reported. Analysis of antibiotic resistance was performed on 157 <i>Campylobacter</i> strains (123 <i>C. jejuni</i> and 34 <i>C. coli</i>) from conventional and organic chickens produced in Sweden. Susceptibility for tetracycline, ciprofloxacin, erythromycin, nalidixic acid, streptomycin, and gentamycin was determined by microdilution. All 77 isolates from organic chickens were sensitive to all antibiotics, except two <i>C. jejuni</i> that were resistant to tetracycline. Of the 80 isolates from conventional chickens, 22.5% of <i>C. jejuni</i> and 11.1% of <i>C. coli</i> were resistant to quinolones and 5.6% of <i>C. jejuni</i> were resistant to tetracycline. Whole-genome sequencing resulted in 50 different sequence types of <i>C. jejuni</i> and six of <i>C. coli.</i> Nine sequence types were found in both organic and conventional chickens. Two of these (ST-19 and ST-257) included isolates from conventional broilers with different resistance phenotypes to the remaining isolates from conventional and organic broilers. There are management differences between the production systems, such as feed, breed, use of coccidiostats, and access to outdoor area. It is unlikely that quinolone resistance has arisen due to use of antimicrobials, since fluoroquinolones are not permitted in Swedish broiler production.
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