Genetic properties of R plasmids in Shigella isolates of swine origin in Korea

돈(豚)에서 분리(分離)한 Shigella균유래(菌由來) R plasmid의 유전적(遺傳的) 특성(特性)에 관한 연구(硏究)

This paper dealt with the distribution of Shigella spp. on 5 piggeries in Taegu and Kyungpook during the period from August to October 1987. Isolated Shigella were examined for serogrouping, antimicrobial drug resistance and detection of R plasmid. Genetic properties of R plasmid in Shigella have examined to fertility inhibition (Fi) and gel electrophoresis was performed for the isolation of plasmid DNA. The results obtained were summarised as followings; 1. Of total 2,978 samples from 5 piggeries, 82 strains (2.8%) of Shigella spp. were isolated from 82 samples. The isolated strains were identified as S dysenteriae (60 strains), S flexneri (20 strains) and S sonnei (2 strains). 2. Of the 82 strains examined 67 (95.1%) were resistant to one or more antibiotics, such as ampicillin (Am), chloramphenicol (Cm), kanamycin (Km), nalidixic acid (Na), rifampicin (Rf), streptomycin (Sm), sulfademethoxine (Su), and tetracycline (Tc) and higher resistant to Su (90.2%), Sm (63.4%) and Tc (63.4%). 3. Of the 78 resistant Shigella strains 26 (33.3%) harbored conjugative R plasmids and the transfer frequency of Sm (50.0%), Cm(33.3%) resistance was much higher than that of the other drug resistance. 4. The most common resistant patterns were SmSuTc, Su and AmSmSuTc. 5. Out of the 26 Shigella R plasm ids examined for Fi, 14(53.8%) were $Fi^+$ and the remainder were $Fi^-$. 6. The plasmid DNA profiles in Shigella spp. (9 strains) isolated from pigs were confirmed as being 2 to 9 fragments by the gel electrophoresis. Their molecular size ranged 2.17 to 87.62 kilobase (Kb). All strains of Shigella spp. consisted in 15.4 Kb plasmids.