title: Further characterization of porcine Brachyspira hyodysenteriae isolates with decreased susceptibility to tiamulin.
abstract: Brachyspira hyodysenteriae is the causative agent of swine dysentery, a severe diarrhoeal disease in pigs. Few drugs are available to treat the disease, owing to both antimicrobial resistance and withdrawal of drugs authorized for use in pigs. Tiamulin is the drug of choice in many countries, but isolates with decreased susceptibility have recently been reported. The mechanism of tiamulin resistance in B. hyodysenteriae is not known and this facet is essential to understand the dissemination of the trait. To study the resistance epidemiology of B. hyodysenteriae, further characterization of a set of isolates from Germany (n = 16) and the UK (n = 6) with decreased susceptibility to tiamulin was performed. The relatedness between the isolates was studied by comparing PFGE patterns, and the in vitro susceptibility to five other antimicrobials (aivlosin, doxycycline, salinomycin, chloramphenicol and avilamycin) was also determined. For comparison of the antimicrobial-susceptibility pattern, Swedish (n = 20) and British (n = 4) tiamulin-susceptible isolates were tested. The German isolates represented several different PFGE patterns, indicating that tiamulin usage has been sufficient to select clones with decreased tiamulin susceptibility at different farms in Germany. The PFGE pattern for the six British isolates with decreased tiamulin susceptibility was identical to that of the German isolates, and they had a similar antimicrobial-susceptibility pattern, except for resistance to aivlosin, which was only found in a few German isolates. No other co-resistance with tiamulin was found.
authors.affiliation: Department of Antibiotics1 and Department of Bacteriology2, National Veterinary Institute, SE-751 89 Uppsala, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Karlsson
authors.affiliation: Department of Antibiotics1 and Department of Bacteriology2, National Veterinary Institute, SE-751 89 Uppsala, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Aspán
authors.affiliation: Department of Antibiotics1 and Department of Bacteriology2, National Veterinary Institute, SE-751 89 Uppsala, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Landén
authors.affiliation: Department of Antibiotics1 and Department of Bacteriology2, National Veterinary Institute, SE-751 89 Uppsala, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Franklin
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D017401:Brachyspira hyodysenteriae / Q000145:classification / Q000187:drug effects* / Q000235:genetics; D004224:Diterpenes / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D004403:Dysentery / Q000382:microbiology / Q000662:veterinary; D016521:Electrophoresis, Gel, Pulsed-Field / Q000662:veterinary; D004739:England; D005858:Germany; D008826:Microbial Sensitivity Tests / Q000662:veterinary; D013145:Spirochaetales Infections / Q000382:microbiology / Q000662:veterinary; D013548:Sweden; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology; D015645:Tylosin / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D004224:Diterpenes; C509469:aivlosin; C014224:tiamulin; D015645:Tylosin