대장균의 chloramphenicol 내성 R-plasmid의 염기서열분석

Necleotide sequencing of R-plasmid against chloramphenicol in escherichia coli

The multiple antibiotic resistances in 143 strains of chloramphenicol resistant E. coli isolated from pigs were determined, and molecular cloning and nucleotide sequencing of R-plasmid DNA encoding resistance to chloramphenicol were done as follows. MICs of chloramphenicol were evaluated highly as＞200㎍/ml and ≥50㎍/ml for 5.6% and 83.3% of 143 strains, respectively. All strains of chloramphenicol resistant E. coli were sensitive to amikacin, cefazolin, cephalexin, colistin, moxalatam, nalidaixic acid and rifampicin. On the other hand, 23.8% to 81.8% of the strains were resistant to ampicillin, cephalothin, clindamycin, erythromycin, gentamicin, kanamycin, neomycin, penicillin, spectinomycin, streptomycin, tetracycline and tobramycin. Moreover, all E. coli strains were multiply resistant against three to twelve antibiotics including chloramphenicol. To ampicillin, chloramphenicol, clindamycin, erythromycin, penicillin and tetracycline, E. coli strains harboured resistances which supposed to be mediated by R-plasmids. The properties of R-plasmids, however, were recognized as unrelated to the multiplicity and differences of antibiotics to which the host bacteria exhibited resistances, and chloramphenicol resistance was observed in both R-plasmid and chromosome of the host bacteria. Plasmid DNA of 1438 nucleotides encoding chloramphenicol resistance was cloned and sequenced as 391 adenines, 349 cytosines, 320 guanines and 378 thymines in which 4 open reading frames were found. The plasmid DNA coincidentally harboured resistance to tetracycline.