APH 1998, 56, 39-52:

Plasmid typing and antibiotic susceptibility of Salmonella Enteritidis isolates.

M. Yde

Keywords: antibiotic resistance, plasmids, Salmonella Enteritidis, transconjugation

Isolates of Salmonelia Enteritidis of various origin (human stools, poultty and poultry products, other animals, meat, beach and surface water) were subjected to plasmid typing and antimicrobial susceptibility tests. A large majority of the strains (80% of human, 71 % of non-human origin) harboured one single plasmid (56 kb). The remaining group presented a great variety of plasmid profiles that were infrequently encountered. Most of these proffies included also the 56 kb plasmid. Plasmid-free strains were found in 8.6% of the human and 13.4% of the non-human isolates; beach and surface water isolates were relatively more often plasmid-free. 92% of the human and non-human strains proved to
be antibiotic sensitive. An increasing number of nalidixic acid monoresistant strains was noted among human and non-human isolates.  Gentamicin resistance was acquired by two strains on a total of 339 investigated, all strains displayed susceptibility to norfloxacin.  Transconjugation experiments highlighted the role of R+ plasmids in the acquisition of antibiotic resistance. The virulence plasmid (56 kb) could be co-transconjugated with a cryptic 83 kb plasmid. Plasmid typing and antibiotic sensitivity testing do not contribute to a further differentiation of the majority of
S. Enteritidis isolates.