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. 1999 Mar;43(3):693-6.
doi: 10.1128/AAC.43.3.693.

Antibiotic resistance conferred by a conjugative plasmid and a class I integron in Vibrio cholerae O1 El Tor strains isolated in Albania and Italy

V Falbo  1 , A Carattoli, F Tosini, C Pezzella, A M Dionisi, I Luzzi
Affiliations

Antibiotic resistance conferred by a conjugative plasmid and a class I integron in Vibrio cholerae O1 El Tor strains isolated in Albania and Italy

V Falbo et al. Antimicrob Agents Chemother. 1999 Mar.

Abstract

Multidrug-resistant Vibrio cholerae O1 El Tor strains isolated during the 1994 outbreak of cholera in Albania and Italy were characterized for the molecular basis of antibiotic resistance. All strains were found to be resistant to tetracycline, streptomycin, spectinomycin, trimethoprim, sulfathiazole, and the vibriostatic compound O/129 (2,4-diamino-6,7-diisopropylteridine). Resistance genes were self-transferable by a conjugative plasmid of about 60 MDa, with the exception of spectinomycin resistance, which was conferred by the aadA1 gene cassette located in the bacterial chromosome within a class 1 integron. The resistance to trimethoprim and O/129 was conferred by the dfrA1 gene, which was present on the plasmid. Although the dfrA1 gene is known to be borne on an integron cassette, class 1, 2, or 3 intI genes were not detected as part of the plasmid DNA from the strains studied.

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Figures

FIG. 1
FIG. 1
16 S and 23 S BglI ribotypes of representative V. cholerae O1 isolates from the 1994 outbreak in Albania (AL 885-94) and Italy (BA 03-94) are compared with a V. cholerae O1 strain isolated from an imported case in Italy from the same year (El S -94).
FIG. 2
FIG. 2
Localization of the dfrA1 gene within the V. cholerae R plasmid. Plasmid DNA was extracted from AL885 (pISS AL 885A) and BA03 (pISS BA 03A) V. cholerae isolates and hybridized with the DH1-DH2 PCR product as a specific probe for the dfrA1 gene. E. coli containing the R483 plasmid that includes Tn7 harboring the dfrA1 gene cassette and genomic DNA from E. coli HB101 were used as positive and negative controls, respectively. Chromosomal DNA lit up because of a weak trapping of the plasmid. Plasmid molecular weight was estimated by comparing the plasmid’s mobility during agarose gel electrophoresis with those of R40a, R483, RP4, RSa, and S6K plasmids (22).
FIG. 3
FIG. 3
Southern blot analysis of V. cholerae class 1 integron. Genomic DNA was extracted from a V. cholerae BA03 isolate, an E. coli strain harboring the pACYC184::Tn21 plasmid, and a V. cholerae NA2 strain; digested with BamHI-PvuII (B-P), BamHI-HindIII (B-H), and BamHI (B); and hybridized with the intI1 probe specific for the class 1 integrase gene. Molecular size standards (in base pairs) are indicated to the left of the DNA ladder (lane M).
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