Epidemiology and characterization of animal Salmonella enterica subspeciesEnterica serotype typhimurium DT104 in Hungary

Reports on the internationally emerging significance of multiresistant zoon otic Salmonella in animals and man prompted studies to estimate the signifi cance of multiresistant Salmonella enterica subspecies enterica serotype Ty phimurium (S. Typhimurium) phage type DT104 of animal origin in Hungary. A collection of 231 strains (primarily of goose, turkey, poultry and porcine origin from the years 1997-1998) was tested for resistance against 7 select ed antibiotics (ampicillin, chloramphenicol, enrofloxacin, nalidixic acid, streptomycin, tetracycline and sulphamethoxazole). Strains with resistance against 3 or more were defined as multiresistant. All strains were phage ty ped using Felix-Callow's S. Typhimurium phage typing system, and 91 of them (suspect DT104) were also typed according to Anderson's definitive typing (DT) system. In this study, 14% of animal strains from 1997-1998 was classi fied as DT104, for which turkey, pig and duck seemed to be the main carrier s, and the multiresistant non-DT104 strains represented a further 6% of thi s collection. The prevalence of DT104 was highest among strains of turkey o rigin (50%), followed by strains of pig (29%), chicken (25%), duck (19%), a nd goose (3%) origin. The other DT104 related phage types (DT12 and U302) w ere only detected in the case of 4 strains (2 of porcine, and one each of t urkey and of goose origin). The DT104 corresponded to the Felix-Callow type s 2/3 or 2c/3 in each case, except in the case of 3 turkey strains where th ey corresponded to type 35/3. Nalidixic acid resistance was detected in all multiresistant turkey strains and in some of other animal origin but none of these strains were resistant to enrofloxacin. A retrospective analysis ( based on the above relationship) indicated that S. Typhimurium strains corr esponding to DT104 could be present and increase in the Hungarian farm anim al population from about 2% to 20% between 1985 and 1990, in a manner simil ar to the emergence of human DT104, as reported elsewhere (Paszti et al., 2 000). The 91 suspect DT104 strains were also tested for plasmid profile and for spvC gene indicating the presence of the large serotype specific plasm id (Ssp). No characteristic plasmid profile could be attributed to S. Typhi murium DT104. The serovar-specific large plasmid was detected by PCR for sp vC in 100% of DT104 strains and in 77% of the non-DT104 strains. The virule nce of two DT104 strains was tested in orally infected day-old chicks and c ompared with virulence of 4 non-DT104 strains. Higher colonizing virulence of DT104 strains could be established as compared to the other strains.