The Complete Nucleotide Sequence of pZM3, a 1970 FIA:FIB:FII Plasmid Carrying Antibiotic Resistance and Virulence Determinants.

The multiresistance plasmid, pZM3, from a 1970 serovar Wien isolate from Algeria represents the multiresistance FI-type plasmids conferring resistance to ampicillin, chloramphenicol, kanamycin, neomycin, sulfonamides, streptomycin, spectinomycin, tetracycline, and mercuric ions circulating in the Middle East in the 1970s. pZM3 was sequenced to determine the relationship between IS, the IS-like insertion sequence it carries, and IS. IS is identical to IS. pZM3 is a 166.8-kb plasmid with three replicons typed as FIA-1, FIB-1, and FII-1, consistent with other FI plasmids. However, Tn, containing the ampicillin resistance gene, disrupts the FII gene. pZM3 also contains an IS-flanked virulence region, including the and aerobactin operons, shared with many other FIB-1 virulence plasmids. The remaining resistance genes are located in a 44.7-kb complex resistance island that includes the Tn-like transposon, Tn, identified previously. Relative to Tn, Tn includes an additional gene cassette, , and Tn in . Tn is in the same Tn context as Tn in NR1, and identity to NR1 extends beyond the IS flanking the gene. On the other side, IS-mediated events have brought in a Tn remnant and inverted part of it, highlighting the role of IS in resistance region evolution. The backbone of pZM3 was found to be almost identical to that of pRSB225, recovered in Germany in 2013, and their resistance islands are in the same position. The pRSB225 resistance island has evolved from the pZM3 configuration through an insertion, a replacement, and an inversion.