Achromobacter aestuarii sp. nov., Isolated from an Estuary

Detection and analysis of an Achromobacter xylosoxidans outbreak in a urodynamics unit

INTRODUCTION

Achromobacter xylosoxidans is a gramnegative bacillus resistant to multiple antibiotics, present both in the environment and in hospitals. This study describes an outbreak of colonizations and infections by A. xylosoxidans in the urodynamics unit of the Puigvert Foundation.

METHODS

On November 11, 2022, a patient developed a fever, and A. xylosoxidans was detected in their urine and blood. The case was linked to a recent urodynamic study. As a result, all A. xylosoxidans cases since 2018 were reviewed, and inspections were conducted in the unit, along with the collection of 24 environmental samples.

RESULTS

The review identified 21 patients with A. xylosoxidans infections after urodynamic procedures since April 2022. Environmental microbiological controls revealed that pressure transducers were the likely source of infection. Corrective measures included the temporary closure of the unit, thorough cleaning with hypochlorite, use of single-use urinary catheters, daily replacement of equipment lines and pressure transducers, as well as other improvements in disinfection, handling, and workflows. A multidisciplinary team was formed to implement and supervise these actions.

CONCLUSIONS

The measures resulted in the elimination of the outbreak and the safe resumption of activities in the unit. This incident highlights the importance of continuous surveillance and rapid response in clinical settings to prevent infections and improve patient safety.

Genomic characterization of Achromobacter genogroup 20 and identification of a potential species-specific marker

OBJECTIVE

To describe the genome of Achromobacter genogroup 20 and explore the presence of resistance determinants.

METHODS

Isolate 413638 was identified through nrdA and MLST analysis. Antimicrobial susceptibility testing was performed according CLSI 2024. NGS was conducted using Illumina MiSeq, on the NextSeq500 platform with 150 bp paired-end reads, and de novo assembly was assessed using Unicycler (Galaxy). Coding sequences were predicted and confirmed with RAST and BLAST, and resistance determinants were evaluated using Resfinder and manual curation. All Achromobacter spp. genomes were obtained from NCBI, and the presence of blaOXA was investigated. Average nucleotide identity (ANI) and tetranucleotide analysis (TETRA) were calculated. Phylogenetic analysis of the new OXA variant was conducted against other species-specific markers in Achromobacter.

RESULTS

Isolate 413638 was identified as Achromobacter genogroup 20 ST365, showing resistance to third- and fourth-generation cephalosporins, aminoglycosides, and fluoroquinolones. The genome included coding sequences for three putative β-lactamases (one new OXA type-class D β -lactamase and two new class C), 32 efflux pump proteins, two aminoglycoside-modifying enzymes and a dihydropteroate synthase; also, substitutions in parC and parE were detected. The OXA enzyme, designated OXA-1238 (PP446293), differs from OXA-114a by 85 amino acids, with 69% identity. In silico analysis found OXA-1238 variants in three additional Achromobacter spp. genomes, with 97% identity. Based on ANI and tetra analysis, the three genomes corresponded to Achromobacter genogroup 20.

CONCLUSION

Several resistance markers were found, probably contributing to the resistance profile observed in Achromobacter genogroup 20 ST365. The new OXA variant identified, OXA-1238, could constitute a useful molecular marker for species identification.

Schauerella fraxinea gen. nov., sp. nov., a bacterial species that colonises ash trees tolerant to dieback caused by Hymenoscyphus fraxineus

The tolerance of ash trees against the pathogen Hymenoscyphus fraxineus seems to be associated with the occurrence of specific microbial taxa on leaves. A group of bacterial isolates, primarily identified on tolerant trees, was investigated with regard to their taxonomic classification and their potential to suppress the ash dieback pathogen. Examination of OGRI values revealed a separate species position. A phylogenomic analysis, based on orthologous and marker genes, indicated a separate genus position along with the species Achromobacter aestuarii. Furthermore, analysis of the ratio of average nucleotide identities and genome alignment fractions demonstrated genomic dissimilarities typically observed for inter-genera comparisons within this family. As a result of these investigations, the strains are considered to represent a separate species within a new genus, for which the name Schauerella fraxinea gen. nov., sp. nov. is proposed, with the type strain B3P038T (=LMG 33092 T = DSM 115926 T). Additionally, a reclassification of the species Achromobacter aestuarii as Schauerella aestuarii comb. nov. is proposed. In a co-cultivation assay, the strains were able to inhibit the growth of a H. fraxineus strain. Accordingly, a functional analysis of the genome of S. fraxinea B3P038T revealed genes mediating the production of antifungal substances. This potential, combined with the prevalent presence in the phyllosphere of tolerant ash trees, makes this group interesting for an inoculation experiment with the aim of controlling the pathogen in an integrative approach. For future field trials, a strain-specific qPCR system was developed to establish an efficient method for monitoring the inoculation success.

Slc11 Synapomorphy: A Conserved 3D Framework Articulating Carrier Conformation Switch

Transmembrane carriers of the Slc11 family catalyze proton (H+)-dependent uptake of divalent metal ions (Me2+) such as manganese and iron-vital elements coveted during infection. The Slc11 mechanism of high-affinity Me2+ cell import is selective and conserved between prokaryotic (MntH) and eukaryotic (Nramp) homologs, though processes coupling the use of the proton motive force to Me2+ uptake evolved repeatedly. Adding bacterial piracy of Nramp genes spread in distinct environmental niches suggests selective gain of function that may benefit opportunistic pathogens. To better understand Slc11 evolution, Alphafold (AF2)/Colabfold (CF) 3D predictions for bacterial sequences from sister clades of eukaryotic descent (MCb and MCg) were compared using both native and mutant templates. AF2/CF model an array of native MCb intermediates spanning the transition from outwardly open (OO) to inwardly open (IO) carriers. In silico mutagenesis targeting (i) a set of (evolutionarily coupled) sites that may define Slc11 function (putative synapomorphy) and (ii) residues from networked communities evolving during MCb transition indicates that Slc11 synapomorphy primarily instructs a Me2+-selective conformation switch which unlocks carrier inner gate and contributes to Me2+ binding site occlusion and outer gate locking. Inner gate opening apparently proceeds from interaction between transmembrane helix (h) h5, h8 and h1a. MCg1 xenologs revealed marked differences in carrier shape and plasticity, owing partly to an altered intramolecular H+ network. Yet, targeting Slc11 synapomorphy also converted MCg1 IO models to an OO state, apparently mobilizing the same residues to control gates. But MCg1 response to mutagenesis differed, with extensive divergence within this clade correlating with MCb-like modeling properties. Notably, MCg1 divergent epistasis marks the emergence of the genus Bordetella-Achromobacter. Slc11 synapomorphy localizes to the 3D areas that deviate least among MCb and MCg1 models (either IO or OO) implying that it constitutes a 3D network of residues articulating a Me2+-selective carrier conformation switch which is maintained in fast-evolving clades at the cost of divergent epistatic interactions impacting carrier shape and dynamics.

Tributyltin degrading microbial enzymes: A promising remediation approach

Brazil is one of the countries most impacted along the entire coastline by the presence of tributyltin (TBT), a biocide used in antifouling paints. Despite being banned since 2008, its use is still registered in the country, and it is possible to find recent inputs of this substance in places under the influence of shipyards, marinas, and fishing ports. In this study, a bacterium isolated from TBT-contaminated sediment from Santos and São Vicente Estuarine System (SESS) in Brazil, identified as Achromobacter sp., proved to be resistant to this compound. Furthermore, its crude enzymatic extract presented the ability to reduce up to 25 % of the initial TBT concentration in the liquid phase in 1 h, demonstrating to be a simple, fast, effective procedure and a potential tool for the environmental attenuation of TBT.

Report of two events of nosocomial outbreak and pseudo-outbreak due to contamination with Achromobacter spp

Achromobacter spp. are increasingly recognized as emerging pathogens in immunocompromised patients or suffering cystic fibrosis, but unusual in immunocompetent hosts or individuals that underwent surgery. In this study we describe two simultaneous events attributable to two different Achromobacter spp. contaminated sources. One event was related to an episode of pseudo-bacteremia due to sodium citrate blood collection tubes contaminated with Achromobacter insuavis and the other to Achromobacter genogroup 20 infection and colonization caused by an intrinsically contaminated chlorhexidine soap solution. Both threatened the appropriate use of antimicrobials. Molecular approaches were critical to achieving the accurate species identification and to assess the clonal relationship, strengthening the need for dedicated, multidisciplinary and collaborative work of microbiologists, specialists in infectious diseases, epidemiologists and nurses in the control of infections to clarify these epidemiological situations.