Complete Nucleotide Sequence of the Conjugative Tetracycline Resistance Plasmid pFBAOT6, a Member of a Group of IncU Plasmids with Global Ubiquity

Abstract

This study presents the first complete sequence of an IncU plasmid, pFBAOT6. This plasmid was originally isolated from a strain of Aeromonas caviae from hospital effluent (Westmorland General Hospital, Kendal, United Kingdom) in September 1997 (G. Rhodes, G. Huys, J. Swings, P. McGann, M. Hiney, P. Smith, and R. W. Pickup, Appl. Environ. Microbiol. 66:3883-3890, 2000) and belongs to a group of related plasmids with global ubiquity. pFBAOT6 is 84,748 bp long and has 94 predicted coding sequences, only 12 of which do not have a possible function that has been attributed. Putative replication, maintenance, and transfer functions have been identified and are located in a region in the first 31 kb of the plasmid. The replication region is poorly understood but exhibits some identity at the protein level with replication proteins from the gram-positive bacteria Bacillus and Clostridium. The mating pair formation system is a virB homologue, type IV secretory pathway that is similar in its structural organization to the mating pair formation systems of the related broad-host-range (BHR) environmental plasmids pIPO2, pXF51, and pSB102 from plant-associated bacteria. Partitioning and maintenance genes are homologues of genes in IncP plasmids. The DNA transfer genes and the putative oriT site also exhibit high levels of similarity with those of plasmids pIPO2, pXF51, and pSB102. The genetic load region encompasses 54 kb, comprises the resistance genes, and includes a class I integron, an IS630 relative, and other transposable elements in a 43-kb region that may be a novel Tn1721-flanked composite transposon. This region also contains 24 genes that exhibit the highest levels of identity to chromosomal genes of several plant-associated bacteria. The features of the backbone of pFBAOT6 that are shared with this newly defined group of environmental BHR plasmids suggest that pFBAOT6 may be a relative of this group, but a relative that was isolated from a clinical bacterial environment rather than a plant-associated bacterial environment.

Unexpected Occurrence of Plasmid-Mediated Quinolone Resistance Determinants in EnvironmentalAeromonasspp.

“…In addition, our study demonstrated that this IncU-type plasmid-mediated qnrS2 gene was expressed and able to confer reduced susceptibility to quinolones, at least in E. coli. Aeromonas species and IncU plasmids, which are ubiquitous in a wide range of environments, might therefore act as important vectors for transfer of plasmid-mediated quinolone resistance determinants (23). As opposed to most qnrA and qnrB genes, qnrS genes have never been reported to be associated with sul1-type class 1 integrons (6,8).…”

“…In addition, cloning of EcoRI-restricted DNA from whole-cell DNA of A. media 42 showed that the qnrS2 gene was inserted into the mpR gene in plasmid p42. No tetA gene encoding resistance to tetracycline was detected by PCR in plasmids p37 and p42, whereas it was identifi ed in plasmid pFBAOT6 (23).…”

“…Cloning of EcoRI-restricted DNA from whole-cell DNA of A. punctata 37 produced a recombinant plasmid, pAS37, containing a 19,050-bp insert that contained the qnrS2 gene. Sequencing showed that the qnrS2 gene was located in a plasmid-encoded genetic structure previously identifi ed in an IncU-related plasmid, pFBAOT6 (84,748 bp), isolated from an A. punctata strain recovered from hospital sewage in Kendal (United Kingdom) in 1997 (23). This region consisted of 15 open reading frames ( Figure 2).…”

Similarity in the Structure of <i>tetD</i>-Carrying Mobile Genetic Elements in Bacterial Strains of Different Genera Isolated from Cultured Yellowtail

“…The flanking region by IS26-Left and -Right was identical to the structure found in Photobacterium damselae Kim et al, 2008;Kim and Aoki, 1994 except for the ISRSB101. The inserted ISRSB101 was 100% identical to that of plasmid pFBOAT6 of Aeromonas punctata Rhodes et al, 2004 , and was bordered by direct repeats of 9 nucleotide 5 -TGTTGCAAA-3 originating from IS26-Inner. By nucleotide sequencing of PCR-amplified products, we confirmed the presence of the same structures in Citrobacter sp.…”

“…TA3 pTCKM3 . Solid bars indicate the regions which exhibit homology to the reported sequences; pP99-018 from Photobacterium damselae Kim et al, 2008;Kim and Aoki, 1994 , Salmonella serovar Ordnez Allard et al, 1993 , and pFBAOT6 from Aeromonas punctata Rhodes et al, 2004 . B The structure found in Salmonella sp.…”