Antimicrobial susceptibility and occurrence of resistance genes among Salmonella enterica serovar Weltevreden from different countries.
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.
Aarestrup
Frank M
FM
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
Lertworapreecha
Monton
M
Evans
Mary C
MC
Bangtrakulnonth
Aroon
A
Chalermchaikit
Thongchai
T
Hendriksen
Rene Sjøgren
RS
Wegener
Henrik Caspar
HC
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
D000890:Anti-Infective Agents