Molecular epidemiology of nalidixic acid-resistant campylobacter isolates from humans and poultry by pulsed-field gel electrophoresis and flagellin gene analysis

To investigate the potential of poultry products as the source of human infections associated with quinolone-resistant campylobacters, 140 human and 75 poultry isolates of nalidixic acid-resistant campylobacters were collected between 1996 and 1998, and analysed by two molecular typing methods. By the analysis of restriction fragment length polymorphism of the flagellin gene, 33 distinct patterns were obtained, with 18 of which shared by both human (89%) and poultry (93%) isolates. By the pulsed-field gel electrophoresis of SmaI-restricted macrofragments, 105 different profiles were obtained, and 11 were found in both human (40%) and poultry (23%) isolates. When the two typing methods were combined, 112 unique genotypes were obtained, 11 of which were shared by both populations, including 53 (38%) human isolates and 14 (19%) poultry isolates. Although domestic poultry products are still important sources of the quinolone-resistant campylobacter infections in humans, there are other factors that might contribute to these increasing infections simultaneously. A more stringent policy in the use of antimicrobial agents in food animals can no longer be ignored.