Brovedan, M. | bioRxiv Science

bioRxiv2020

Pseudomonas putida group species serve as reservoirs of conjugative plasmids disseminating Tn402-like class 1 integrons carrying blaVIM-2 metallo-β-lactamase genes

The Pseudomonas putida group (P. putida G) is composed of at least 21 species associated to a wide range of environments, including the clinical setting. Here, we characterized 13 carbapenem-resistant P. putida G clinical isolates carrying blaVIM-2 from different hospitals of Argentina. Multilocus sequencing (MLSA) and phylogenetic analyses based on the 16S rDNA, gyrB and rpoD sequences comparison allowed us to assign them to 7 well-differentiated species. Sequencing analysis revealed that blaVIM-2 genes were carried in these isolates by three different class 1 integrons (In41, In899 and In528) embedded into Tn402-like transposons. Those harboring In41 and In899 were designated Tn6335 and Tn6336, respectively, with the former found among 10 isolates. Both encompassed complete transposition modules and inverted repeats boundaries characteristic of the Tn5053/Tn402 family, whereas the third, bearing In528, exhibited a defective tni module. Tn6335 and Tn6336 were located in conjugative pLD209-type plasmids in P. asiatica, P. juntendi, P. putida G/II, and P. putida G/V isolates, and could be mobilized to Escherichia coli and P. aeruginosa indicating a relevant mechanism of blaVIM-2 dissemination. In other P. asiatica and P. putida G/II isolates, Tn6335 was found inserted into the Tn21 subgroup transposons-res region, indicating capability for intragenomic mobilization and further dissemination associated to Tn3 family transposons. The Tn402-like defective element was also found inserted into the res region of another Tn3 family transposon in a P. monteilii isolate, but in an atypical orientation. Overall findings shed light on the mechanisms by which resistance genes move through environmental and opportunist Pseudomonas species.

microbiology↗

bioRxiv2019

The plasmid diversity of Acinetobacter bereziniae HPC229 provides clues on the ability of the species to thrive on both clinical and environmental habitats

Acinetobacter bereziniae is an environmental microorganism with increasing clinical incidence, and may thus provide a model for a bacterial species bridging the gap between the environment and the clinical setting. A. bereziniae plasmids have been poorly studied, and their characterization could offer clues on the causes underlying the leap between these two radically different habitats. Here we characterized the whole plasmid content of A. bereziniae HPC229, a clinical strain previously reported to harbor a 44-kbp plasmid, pNDM229, conferring carbapenem and aminoglycoside resistance. We identified five extra plasmids in HPC229 ranging from 114 to 1.3 kbp, including pAbe229-114 (114 kbp) encoding a MOBP111 relaxase and carrying heavy metal resistance, a bacteriophage defense BREX system and four different toxin-antitoxin (TA) systems. Two other replicons, pAbe229-15 (15.4 kbp) and pAbe229-9 (9.1 kbp), both encoding MOBQ1 relaxases and also carrying TA systems, were found. The three latter plasmids contained Acinetobacter Rep_3 superfamily replication initiator protein genes. HPC229 also harbors two smaller plasmids, pAbe229-4 (4.4 kbp) and pAbe229-1 (1.3 kbp), the former bearing a ColE1-type replicon and a TA system, and the latter lacking known replication functions. Comparative sequence analyses against deposited Acinetobacter genomes indicated that the above five HPC229 plasmids were unique, although some regions were also present in other of these genomes. The transfer, replication, and adaptive modules in pAbe229-15, and the stability module in pAbe229-9, were bordered by sites potentially recognized by XerC/XerD site-specific tyrosine recombinases, thus suggesting a potential mechanism for their acquisition. The presence of Rep_3 and ColE1-based replication modules, different mob genes, distinct adaptive functions including resistance to heavy metal and other environmental stressors, as well as antimicrobial resistance genes, and a high content of XerC/XerD sites among HPC229 plasmids provide evidence of substantial links with bacterial species derived from both environmental and clinical habitats.

microbiology↗