title: Antimicrobial susceptibility and occurrence of resistance genes among Salmonella enterica serovar Weltevreden from different countries.
abstract: OBJECTIVE
  This study was conducted to investigate the occurrence of antimicrobial resistance among Salmonella Weltevreden isolates from different sources in South-East Asia (Indonesia, Laos, Malaysia, Taiwan, Thailand, Vietnam), Australia, Denmark, New Zealand and the USA.
  
  
  METHODS
  A total of 503 isolates were examined for susceptibility to antimicrobial agents, and resistant isolates were examined for the presence of selected resistance genes by PCR.
  
  
  RESULTS
  Only 48 (9.5%) of the isolates were resistant to one or more of the antimicrobial agents tested. A low frequency of resistance was found towards ampicillin (1.8%), chloramphenicol (1.6%), florphenicol (0.4%), nalidixic acid (1.6%), neomycin (0.6%), streptomycin (4.4%), sulfamethoxazole (4.2%), tetracycline (4.0%) and trimethoprim (1.4%), whereas all isolates were susceptible to co-amoxiclav, ceftiofur, ciprofloxacin, colistin and gentamicin. All nine ampicillin-resistant isolates contained a sequence similar to the blaTEM-1b gene, one of the eight chloramphenicol-resistant isolates a sequence similar to the catA1 gene, all three neomycin-resistant isolates a sequence similar to the aphA-2 gene, 16 (73%) of the 22 streptomycin-resistant isolates a sequence similar to the aadA gene, the remaining six (27%) a sequence similar to the strA gene, and all 21 sulfamethoxazole-resistant isolates a sequence similar to the sul2 gene. Thirteen (65%) of the 20 tetracycline-resistant isolates contained the tet(A) gene, four (20%) the tet(B) gene, and one (5%) the tet(C) gene.
  
  
  CONCLUSIONS
  This study showed a low frequency of resistance among Salmonella Weltevreden isolated from humans and other reservoirs in South-East Asia and elsewhere. There was no major difference in the occurrence of resistance between source or geographical origin.
authors.affiliation: WHO Collaborating Centre for Antimicrobial Resistance in Bacteria from Food animals and Food of Animal Origin, Danish Veterinary Institute, Bülowsvej 27, DK-1790 Copenhagen V, Denmark. faa@vetinst.dk
authors.forename: Frank M
authors.initials: FM
authors.lastname: Aarestrup
authors.forename: Monton
authors.initials: M
authors.lastname: Lertworapreecha
authors.forename: Mary C
authors.initials: MC
authors.lastname: Evans
authors.forename: Aroon
authors.initials: A
authors.lastname: Bangtrakulnonth
authors.forename: Thongchai
authors.initials: T
authors.lastname: Chalermchaikit
authors.forename: Rene Sjøgren
authors.initials: RS
authors.lastname: Hendriksen
authors.forename: Henrik Caspar
authors.initials: HC
authors.lastname: Wegener
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology*; D001210:Asia, Southeastern; D004352:Drug Resistance, Microbial / Q000235:genetics*; D006801:Humans; D008826:Microbial Sensitivity Tests; D019779:Salmonella enterica / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification
chemical_list: D000890:Anti-Infective Agents