Reduction in fluoroquinolone susceptibility among non-typhoidal strains of Salmonella enterica isolated from Finnish patients

Objectives: The proportion of Salmonella isolates with reduced susceptibility to fluoroquinolones has increased during recent years in many countries, especially in South-east Asia. The present study was performed to evaluate the incidence of and changes in quinolone resistance in Salmonella isolates of either foreign or domestic origin in Finland. Methods: A total of 1004 Salmonella isolates collected from Finnish patients between 2000 and 2004 were analysed for ciprofloxacin susceptibility. Of these isolates, 504 were of domestic origin and 500 were of foreign origin, collected from travellers to 43 different countries. The Salmonella collection consisted of 89 different serotypes. All isolates belonged to non-typhoidal Salmonella enterica. Results: Of all isolates, 3 (0.3%) were ciprofloxacin-resistant (MIC >= 4 mg/L) and 214 (21.3%) exhibited reduced susceptibility to ciprofloxacin (MIC >= 0.125-2 mg/L). The annual proportion of reduced susceptibility varied between 3 and 15% among the domestic Salmonella isolates (P = 0.123). Between 2000 and 2004, the annual proportion of reduced susceptibility increased significantly (from 23 to 39%; P = 0.001) among all foreign isolates as well as among those from Spain alone (from 4 to 73%; P < 0.001). Among the isolates from Thailand, reduced ciprofloxacin susceptibility remained at a constantly high level (52-66%) throughout the study. Conclusions: Our results show that reduced fluoroquinolone susceptibility in S. enterica is not restricted to South-east Asia alone but continues to grow rapidly in many parts of the world including countries of the European Union.