Epidemiology and Infection

Emerging antibiotic resistance in Salmonella Typhimurium in Norway

T. M. LEEGAARD a1c1, D. A. CAUGANT a1, L. O. FRØHOLM a1, E. A. HØIBY a1 and J. LASSEN a1
a1 Department of Bacteriology, National Institute of Public Health, Oslo, Norway


The antimicrobial resistance of 809 Salmonella Typhimurium isolates collected from humans in Norway between 1975 and 1998 was studied. The material was subdivided into domestic and foreign isolates according to whether the patient had recently travelled abroad or not. In imported isolates the largest increase in resistance was in 1996 when 35% of the isolates were multi-resistant. The first multi-resistant isolate acquired in Norway appeared in 1994, but already in 1998 23% of the isolates domestically acquired were multi-resistant, and a majority were S. Typhimurium DT104. We found no ciprofloxacin resistance in domestically acquired isolates. Amplified fragment length polymorphism analysis was performed on selected multi-resistant isolates. The method discriminated well between different multi-resistant isolates, but not between DT104 isolates. Resistant and multi-resistant S. Typhimurium were until 1998 essentially recovered from patients who had travelled abroad, but multi-resistant isolates, mainly DT104, are now also being transmitted within the country.

(Accepted July 26 2000)

c1 Author for correspondence: Department of Bacteriology, National Institute of Public Health, P.O. Box 4404 Torshov, N-0403 Oslo, Norway.