Ciprofloxacin resistance in Campylobacter jejuni: Case-case analysis as a tool for elucidating risks at home and abroad

Objective: To determine factors independently associated with the acquisition of a ciprofloxacin-resistant Campylobacter jejuni infection. Methods: Self-completion questionnaires were used to collect clinical, demographic and exposure data from cases of campylobacter infection reported to a sentinel surveillance scheme in England and Wales. Isolates from those cases were referred to the Public Health Laboratory Service Campylobacter Reference Unit for speciation, subtyping and antimicrobial resistance testing. Cases infected with a ciprofloxacin-resistant C. jejuni were compared with cases infected with a sensitive strain using case-case analysis. Single risk variable analysis and logistic regression analysis were employed. The analysis was restricted by travel status to control for the confounding effect of foreign travel. Results and conclusion: Over half (55%) of the campylobacter infections acquired abroad were resistant to ciprofloxacin, compared with 10% of UK-acquired strains [relative risk 5.23; 95% confidence interval (CI) 4.58-5.96]. For travel-associated cases, ciprofloxacin-resistant infections were independently associated with travel to Spain [odds ratio (OR) 6.87; 95% CI 3.52-13.38], Portugal (OR 22.40; 95% CI 4.36-114.99) or Cyprus (OR 11.74; 95% CI 1.28-108.02), and the consumption of chicken (OR 4.95; 95% CI 2.12-11.56) or bottled water (OR 3.70; 95% CI 1.69-8.10). Indigenous cases infected with a ciprofloxacin-resistant strain were more likely to report the consumption of pre-cooked cold meats (OR 2.13; 95% CI 1.44-3.13). The risk of acquiring a ciprofloxacin-resistant campylobacter infection was strongly associated with foreign travel. Restricting the analyses by travel status revealed different sets of risk exposures for acquiring a resistant C. jejuni strain, suggesting that different intervention strategies will be required.