Lack of correlation between the 257C-to-T mutation in the gyrA gene and clinical severity of Campylobacter jejuni infection in a region of high incidence of ciprofloxacin resistance

Background: Fluoroquinolone resistance is increasingly detected in Campylobacter jejuni worldwide. Despite the fact that a point mutation in the gyrA gene has been linked with increased fitness in animals, the association of resistant organisms with more severe infections in man remains controversial. Methods: Erythromycin and quinolone susceptibility of 147 C. jejuni strains isolated from individual patients with diarrhoea in southwest Hungary were investigated and the molecular background of fluoroquinolone resistance was determined. Hospitalization and the presence of macroscopic blood in the stool were correlated with the presence of 257C-to-T mutation of the gyrA gene causing resistance to fluoroquinolones. Results: Isolates showed an extensive genetic heterogeneity by macrorestriction analysis of the chromosome. While all strains retained susceptibility to erythromycin, 68% were non-susceptible to ciprofloxacin. The mutation causing a Thr-86-to-Ile replacement in the gyrA gene was present in 98% of non-susceptible isolates. Infection caused by isolates containing this mutation did not show any significant association with either hospitalization or with the development of bloody diarrhoea. Conclusions: Our findings indicate that in a region with high-level ciprofloxacin resistance in C. jejuni, non-susceptibility to this antibiotic did not correlate with the severity of infection.