CHARACTERIZATION OF RECENTLY EMERGED MULTIPLE ANTIBIOTIC-RESISTANT SALMONELLA-ENTERICA SEROVAR TYPHIMURIUM DT104 AND OTHER MULTIRESISTANT PHAGE TYPES FROM DANISH PIG HERDS

A total of 670 isolates of Salmonella enterica were isolated from Dani sh pig herds, phage typed and tested for susceptibility to amoxycillin + clavulanate, ampicillin, colistin, enrofloxacin, gentamicin, neomyc in, spectinomycin, streptomycin, tetracyclines, and trimethoprim + sul phadiazine. S enterica serovar typhimurium (S typhimurium) isolates re sistant to ampicillin, streptomycin and tetracycline and three isolate s of S typhimurium DT104, two from 1994 and one from 1995, were furthe r tested for resistance against chloramphenicol and sulphonamide and a nalysed by pulsed-field gel electrophoresis (PFGE) using the restricti on enzyme Xba I, Overall, 66 per cent of the 670 isolates were sensiti ve to all the antimicrobial agents tested. Eleven isolates of S typhim urium were resistant to ampicillin, streptomycin and tetracycline and also resistant to other antibiotics in different resistance patterns. Seven different multiresistant clones were identified, The most common clones were four isolates of DT104 and three isolates of DT193, TWO O f the three S typhimurium DT104 from 1994 and 1995 were sensitive to a ll the antimicrobials tested whereas the remaining isolate from 1994 w as resistant to spectinomycin, streptomycin and sulphonamides. All thr ee isolates showed PFGE profiles identical to the four multiresistant DT104 isolates. Compared with most other countries antimicrobial resis tance among S enterica isolated from Danish pig herds is uncommon, How ever, several different multiresistant clones were found.