Biology subjects

Scortti, M.

Publications and source records attributed to Scortti, M..

5 recordsLinked to original sources

bioRxiv2025

Multidrug-resistant Rhodococcus equi (MDR-RE): detection in East Asia confirms global spread

Macrolide (multidrug)-resistant Rhodococcus equi (MDR-RE) emerged in the early 2000s and has since been disseminating across equine farms in the United States. In 2016, it was found in Ireland, presumably introduced through horse imports. Here, we report its identification in Japan, together with evidence of its presence in China. A recent isolate from Ireland suggests ongoing importation events. These findings highlight the continued international spread of MDR-RE and its potential to become globally established. Currently circulating among horses, MDR-RE is likely to arise in humans over time. Active surveillance is essential to monitor and control this emerging zoonotic antimicrobial resistance threat worldwide.

microbiology↗

bioRxiv2025

Leveraging the subgenus category to address genus over-splitting exemplified with Prescottella and other recently proposed Mycobacteriales genera.

Three related circumstances are compromising the stability of prokaryotic taxonomy and nomenclature, with a significant impact in the field of pathogenic microorganisms: (i) the growing trend of subdividing existing genera by arbitrary phylogenomics-based demarcations, creating an increasing number of new genera; (ii) the priority of databases towards the last validly published names; and (iii) the irreversibility of new names in databases even if changes in taxonomic opinion support reverting to previous classifications. Given the understandable end-user reluctance to name changes affecting well-known pathogens, parallel nomenclatures coexist, creating confusion. Here, we address this problem by exploiting the subgenus category to form new combinations that can be adopted by databases as per their latest validly published name priority policy. The proposed approach consists in lowering to subgenus rank the new genera arising from genus splits considered to be unwarranted. According to the Prokaryotic Code, the species in question would be designated with their previous generic synonym and, in parentheses, the subgenus name (which would correspond to the latest synonym used by the databases). Being the subgenus an optional taxonomic category, it can be omitted, but its use may facilitate the mapping of the synonyms in databases and the literature. For illustration, we apply the strategy to recent genus splits in the Mycobacteriales, specifically the new nested genus Prescottella within the rhodococcal radiation and the several new genera into which Mycobacterium was subdivided.

microbiology↗

bioRxiv2024

Rhodococcus parequi sp. nov., a new species isolated from equine farm soil closely related to the pathogen Rhodococcus equi.

We present the description of the new species, Rhodococcus (Prescottella) parequi, found during phylogenomic investigations of a global collection of strains identified as Rhodococcus (Prescottella) equi. Strain PAM 2766 was isolated from horse-breeding farm soil in Normandy, France, and was indistinguishable from R. equi based on the usual identification tests. Whole-genome phylogenetic analyses located PAM 2766 in the same Rhodococcus sublineage as R. equi, together with Rhodococcus agglutinans, Rhodococcus defluvii, Rhodococcus soli, Rhodococcus subtropicus, Rhodococcus spongiicola and Rhodococcus xishaensis. PAM 2766 is most closely related to, but sufficiently distinct from R. equi DSM 20307T to be considered as a separate species. Average Nucleotide Identity (ANI) and Average Amino Acid Identity (AAI) values are 88.60% and 92.35, respectively, well below the species cutoff. The PAM 2766 draft genome is [~]5.3 Mb in size with 68.98% G+C mol content. PAM 2766T is aerobic, non-motile, and produces smooth creamy to buff-coloured colonies very similar to those of R. equi. It phenotypically differs from the latter by the ability to grow at 5{degrees}C, a strongly positive urease test at 24 h, and specificities in the carbon and nitrogen source utilization profile as determined by phenotype microarray screens. Our data indicate that PAM 2766 belongs to a novel species, for which the name Rhodococcus parequi sp. nov. is proposed. R. parequi was avirulent in macrophage infection assays and is assumed to be non-pathogenic. The type strain is PAM 2766T (=CETC 30995T = NCTC 14987T).

microbiology↗

bioRxiv2024

Structural basis of promiscuous inhibition of Listeria virulence activator PrfA by oligopeptides

The facultative pathogen Listeria monocytogenes uses a master regulator, PrfA, to tightly control the fitness-costly expression of its virulence factors. We found that PrfA activity is repressed via competitive occupancy of the binding site for the PrfA-activating cofactor glutathione by exogenous nutritional oligopeptides. The inhibitory peptides show different sequence and physicochemical properties, but how such wide variety of oligopeptides can bind PrfA was unclear. Using crystal structure analysis of PrfA complexed with inhibitory tri- and tetrapeptides, we show here that the binding promiscuity is due to the ability of PrfA {beta}5 in the glutathione-binding tunnel to establish parallel or antiparallel {beta}-sheet-like interactions with the peptide backbone. Spacious tunnel pockets provide additional flexibility for unspecific peptide accommodation while providing selectivity for hydrophobic residues. Hydrophobic contributions from two adjacent peptide residues appears to be critical for PrfA inhibitory binding. In contrast to glutathione, peptide binding prevents the conformational change required for PrfA activation and formation of the DNA-binding helix-turn-helix motifs, effectively inhibiting virulence expression.

biochemistry↗

bioRxiv2022

International spread of emerging multidrug-resistant Rhodococcus equi

The recently characterized multidrug-resistant clone of the animal and human zoonotic pathogen Rhodococcus equi, MDR-RE 2287, has been circulating among horse farms in the United States (US) since the early 2000s. Here, we report the first documented detection of the MDR-RE 2287 clone outside the US. The finding highlights the risk of MDR-RE spreading internationally with the movement of horses.

microbiology↗