CHARACTERIZATION OF AN INTEGRATIVE AND CONJUGATIVE ELEMENT IN A CLINICAL ISOLATE OF Shewanella spp.

GISELA PARMECIANO DI NOTO; DANIELA CENTRÓN; CECILIA QUIROGA

Cordoba

Congreso; XI Congreso Argentino de Microbiología General; 2015

SAMIGE

Shewanella is a gamma-proteobacteria composed by more than 50 species. It has the ability to reduce heavy metals and toxic compounds and is able to proliferate under aerobic and anaerobic conditions. Shewanella is an environmental bacterium, however it can cause clinical infections. Therefore it is considered an emerging opportunistic pathogen. Pathogenicity and multirresistance in bacteria are inherently related with the acquisition of mobile genetic elements by lateral transfer. The aim of our study was to find and characterize mobile genetic elements encoded in the genome of clinical isolates of Shewanella spp.. We searched for mobile elements in the fully sequenced genome of a strain from our collection, Shewanella sp. Sh95, and found an integrative and conjugative element (ICE), named ICESh95. ICEs are mobile elements widely distributed among bacteria responsible for the lateral transfer of virulence determinants, antibiotic resistance genes and other bacterial traits. ICESh95 belongs to the SXT/R391 family of ICE, which was first described in Vibrio cholerae. To date, there is only one homolog of this element in a marine isolate of Shewanella spp. (ICESpuPO1). ICESh95 has all the necessary genes for its mobilization and transfer (int, setD, setC and tra) as well as the origin of transfer, oriT. Comparative sequence analysis between ICESh95 and ICESpuPO1 showed two different regions. While function of genes from the first variable region was unclear, the second region contained an SXT integron with an intI9 integrase gene interrupted by an IS4 insertion sequence. This integron had two gene cassettes, qacH and drfA15. The dfrA15 gene cassette was found interrupted by a class C-attC group II intron highly identical to the C-attC intron of reference, S.ma.I2. Additionally, we tested for the presence of members of the SXT/R391 ICE family in 10 clinical isolates of Shewanella spp. by PCR using specific primers. As a result we observed that three of them also contained an SXT/R391 ICE. Insertion of SXT/R391 ICE always occurs at the prfC gene located in the chromosome. We analyzed the genetic surroundings of ICESh95 and we found that it is upstream of the pabA gene, instead of prfC, evidencing that this ICE invaded a novel site. Moreover, we conducted a conjugation assay that allowed us to prove that ICESh95 is capable of transferring into Escherichia coli HB101. ICE elements are multi-talented entities that can be involved in the dissemination of virulence and resistance genes. Taken together our results show the role of this element in the exchange of DNA between clinical and environmental niches thus participating in bacterial adaptation and evolution. ICESh95 not only acquired an SXT integron harboring antimicrobial resistance genes, it also adapted to invade a novel insertion site and proved its ability to use its own machinery for conjugation and transfer.