Characterization of Salmonella enterica serovar Typhimurium DT104 isolated from Denmark and comparison with isolates from Europe and the United States

• Published in: Journal of clinical microbiology 2000-04, Vol.38 (4), p.1581-1586
• Main Authors: Baggesen, D.L, Sandvang, D, Aarestrup, F.M
• Format: Article
• Language: English
• Subjects: Animals; Anti-Bacterial Agents - pharmacology; Bacterial Typing Techniques; Bacteriology; Biological and medical sciences; British Isles; cattle; Denmark; Denmark - epidemiology; drug resistance; Drug Resistance, Microbial; Drug Resistance, Multiple; Electrophoresis, Gel, Pulsed-Field; Epidemiology; Europe - epidemiology; Fundamental and applied biological sciences. Psychology; Germany; Humans; Italy; Microbial Sensitivity Tests; Microbiology; plasmids; Plasmids - genetics; restriction mapping; Salmonella enterica typhimurium; Salmonella Infections - epidemiology; Salmonella Infections - microbiology; Salmonella Infections, Animal - epidemiology; Salmonella Infections, Animal - microbiology; Salmonella typhimurium - classification; Salmonella typhimurium - drug effects; Salmonella typhimurium - isolation & purification; Spain; Swine; Swine Diseases - microbiology; United States - epidemiology; USA
• ISSN: 0095-1137; 1098-660X
• DOI: 10.1128/JCM.38.4.1581-1586.2000

A total of 136 isolates of Salmonella enterica serovar Typhimurium DT104 from Denmark (n = 93), Germany (n = 10), Italy (n = 4), Spain (n = 5), and the United Kingdom (n = 9) were characterized by antimicrobial resistance analysis, plasmid profiling, pulsed-field gel electrophoresis (PFGE) with the restriction enzymes XbaI and BlnI, and analysis for the presence of integrons and antibiotic resistance genes. The isolates from Denmark were from nine pig herds, while the isolates from other countries were both of animal and of human origin. All but 10 isolates were resistant to ampicillin, chloramphenicol, spectinomycin, streptomycin, sulfonamides, and tetracycline. Five isolates from the United Kingdom and Spain were sensitive to all antibiotics examined, whereas four isolates from the United Kingdom and the United States were also resistant to one or more of the antibiotics, namely, gentamicin, neomycin, and trimethoprim. All but two strains had the same PFGE profiles when the XbaI restriction enzyme was used, while seven different profiles were observed when the BlnI restriction enzyme was used. Different dominating BlnI types were observed among European isolates compared with the types observed among those from the United States. All the isolates harbored common 95-kb plasmids either alone or in combination with smaller plasmids, and a total of 11 different plasmid profiles were observed. Furthermore, all but one of the multidrug-resistant isolates contained two integrons, ant (3")-Ia and pse-1. Sensitive isolates contained no integrons, and isolates that were resistant to spectinomycin, streptomycin, and sulfonamides had only one integron containing ant (3")-Ia. When restriction enzyme BlnI was used, the 14 isolates from one of the nine herds in Denmark showed unique profiles, whereas isolates from the remaining herds were homogeneous. Among isolates from seven of nine herds, the same plasmid profile (95 kb) was observed, but isolates from two herds had different profiles. Thus, either PFGE (with BlnI) or plasmid profiling could distinguish isolates from three of nine pig herds in Denmark. The epidemiological markers (antimicrobial susceptibility testing, plasmid profiling, and PFGE) applied demonstrated high in vivo stability in the Danish herds. This may indicate that some different strains of multidrug-resistant S. enterica serovar Typhimurium DT104 have been introduced into Danish food animal herds. The presence of isolates from six different countr