Biology subjects

Viale, A. M.

Publications and source records attributed to Viale, A. M..

3 recordsLinked to original sources

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↗

bioRxiv2020

Acinetobacter baumannii NCIMB8209: A rare environmental strain displaying extensive insertion sequence-mediated genome remodeling resulting in the loss of exposed cell structures and defensive mechanisms

Acinetobacter baumannii represents nowadays an important nosocomial pathogen of poorly defined reservoirs outside the clinical setting. Here we conducted whole-genome sequencing analysis of the Acinetobacter sp. NCIMB8209 collection strain, isolated in 1943 from the aerobic degradation (retting) of desert guayule shrubs. NCIMB8209 contained a 3.75 Mb chromosome and a plasmid of 134 kb. Phylogenetic analysis based on core genes indicated NCIMB8209 affiliation to A. baumannii, a result supported by the identification of a chromosomal blaOXA-51-like gene. Seven genomic islands lacking antimicrobial resistance determinants, 5 regions encompassing phage-related genes and, notably, 93 insertion sequences (IS) were found in this genome. NCIMB8209 harbors most genes linked to persistence and virulence described in contemporary A. baumannii clinical strains, but many of them encoding components of surface structures are interrupted by IS. Moreover, defense genetic islands against biological aggressors such as type 6 secretion systems or crispr/cas are absent from this genome. These findings correlate with a low capacity of NCIMB8209 to form biofilm and pellicle, low motility on semisolid medium, and low virulence towards Galleria mellonella and Caenorhabitis elegans. Searching for catabolic genes and concomitant metabolic assays revealed the ability of NCIMB8209 to grow on a wide range of substances produced by plants including aromatic acids and defense compounds against external aggressors. All the above features strongly suggest that NCIMB8209 has evolved specific adaptive features to a particular environmental niche. Moreover, they also revealed that the remarkable genetic plasticity identified in contemporary A. baumannii clinical strains represents an intrinsic characteristic of the species. IMPORTANCEAcinetobacter baumannii (Ab) is an ESKAPE opportunistic pathogen, with poorly defined natural habitats/reservoirs outside the clinical setting. Ab arose from the Acb complex as the result of a population bottleneck, followed by a recent population expansion from a few clinically-relevant clones endowed with an arsenal of resistance and virulence genes. Still, the identification of virulence traits and the evolutionary paths leading to a pathogenic lifestyle has remained elusive, and thus the study of non-clinical ("environmental") Ab isolates is necessary. We conducted here comparative genomic and virulence studies on Ab NCMBI8209 isolated in 1943 from the microbiota responsible of the decomposition of guayule, and therefore well differentiated both temporally and epidemiologically from the nowadays predominant multidrug-resistant strains. Our work provides insights on the adaptive strategies used by Ab to escape from host defenses, and may help the adoption of measures aimed to limit its further dissemination.

microbiology↗

bioRxiv2019

Microevolution in the major outer membrane protein OmpA of Acinetobacter baumannii

Acinetobacter baumannii is nowadays a relevant nosocomial pathogen characterized by multidrug resistance (MDR) and concomitant difficulties to treat infections. OmpA is the most abundant A. baumannii outer membrane (OM) protein, and is involved in virulence, host cell recognition, biofilm formation, regulation of OM stability, permeability, and antibiotic resistance. OmpA members are two-domain proteins with an N-terminal eight-stranded {beta}-barrel domain with four external loops (ELs) interacting with the environment, and a C-terminal periplasmic domain binding non-covalently to the peptidoglycan. Here, we combined data from genome sequencing, phylogenetic, and multilocus sequence analyses from 242 strains of the Acinetobacter calcoaceticus/Acinetobacter baumannii complex (ACB), 222 from A. baumannii, to explore ompA microevolutionary divergence. Five major ompA variant groups were identified (V1 to V5) comprising 50 different alleles coding for 29 different proteins. Polymorphisms were concentrated in 5 regions corresponding to the four ELs and the C-terminal end, and provided evidence for different intra-genic recombination events. ompA variants were not randomly distributed across the A. baumannii phylogeny, with the most frequent V1a1 allele almost exclusive to clonal complex 1 (CC1) strains and the second most frequent V2a1 allele found in the majority of CC2 strains. Evidence was found for assortative exchanges of ompA alleles not only between different A. baumannii clonal lineages, but also different ACB species. Within A. baumannii ompA non-synonymous substitutions were concentrated in the ELs regions, but were more abundant in the transmembrane regions between different Acinetobacter species. The overall results have implications for A. baumannii evolution, epidemiology, virulence, and vaccine design.\n\nImportanceAcinetobacter baumannii is an increasing MDR threat in nosocomial settings associated with prolonged hospitalization and concomitantly increased healthcare costs. The main A. baumannii OM protein, OmpA, is a multifaceted two-domain protein implicated in host cell recognition and adhesion, cytotoxicity, biofilm formation, and as a slow porin for antibiotics and small hydrophilic nutrients. A. baumannii OmpA has been proposed as a potential target for anti-virulence drugs and as a vaccine candidate. Given the many interactions of this protein with environmental factors including host defenses, it is certainly subjected to many selective pressures. Here, we analyzed the microevolution of this OM protein in the A. baumannii population to obtain clues on the extent to which selection in the clinical setting has shaped this protein. The results provide relevant information on the main causes driving evolution of this protein, with potential implications in A. baumannii epidemiology, virulence, and vaccine design.

microbiology↗