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PubMed2025

Novel, rapid, and reliable typing of vancomycin-resistant Enterococcus faecium CC17/ST80 strains using MALDI-TOF MS.

Vancomycin-resistant Enterococcus faecium (VREfm) is an important nosocomial pathogen. The recent emergence of the highly virulent clonal complex 17 (CC17) is posing a challenge for both therapeutic interventions and hospital infection control measures. Hence, prompt discrimination of CC17 VREfm from unrelated and less-virulent VREfm strains is essential for preventing its spread in hospitals and beyond. Between January 2022 and November 2024, 340 VREfm primary isolates have been identified in our lab and underwent genotyping by pulsed-field gel electrophoresis (PFGE) to survey a potential outbreak in the Tyrol region. In addition, whole-genome sequencing (WGS) was performed on a selected subset (n = 40). To curtail the lengthy time-to-result (TTR) of these methods, a novel typing protocol using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was established, validated, and optimized for rapid sample processing. PFGE and WGS showed that 61.2% of isolates (n = 208) belonged to a specific VREfm cluster identified as CC17 sequence type (ST) 80 vanA VREfm. A comprehensive MALDI-TOF MS analysis identified a distinct peak pattern specific to this lineage. This phenotypic characterization was used as a novel typing method with excellent performance (sensitivity: 1.00 [0.98-1.00], specificity: 0.89 [0.70-0.97]) and demonstrated a short TTR of 1 day after the cultural growth of VREfm. A rapid and novel MALDI-TOF MS-based typing approach for a specific CC17/ST80 vanA VREfm cluster was developed and enabled real-life application in routine diagnostics to assure accurate infection prevention and control measures. Future outbreak investigations may benefit from adopting this cost- and labor-efficient approach.IMPORTANCEThis study addresses the urgent need for faster ways to detect problematic hospital bacteria. A highly transmissible strain of Enterococcus faecium (CC17) has been spreading in healthcare settings, making infections harder to treat and control. Traditional methods to identify and track outbreaks are accurate but slow and resource-intensive, delaying critical infection control actions. By developing and validating a new method using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, the researchers demonstrated that this strain can be identified quickly, reliably, and at lower cost. Importantly, the new approach delivers results within a day, compared to the lengthy turnaround times of existing methods. This rapid detection tool provides hospitals with a practical solution to respond to outbreaks more effectively, prevent further spread, and protect vulnerable patients. The findings highlight a valuable step forward in strengthening hospital infection control and improving patient safety.

Enterococcus faecium↗

PubMed2026

Genomic characterisation of ST233 Pseudomonas aeruginosa co-producing KPC-2 and VIM-2 in Northeastern Brazil during the COVID-19 pandemic: Evidence of independent horizontal acquisition events.

BACKGROUND: Dual-carbapenemase-producing Pseudomonas aeruginosa poses a major therapeutic and epidemiological challenge worldwide, yet systematic data on KPC and VIM co-production in Brazil remain limited. The COVID-19 pandemic intensified antimicrobial use, a period temporally associated with increased carbapenemase detection globally. OBJECTIVES: To characterise the molecular epidemiology and resistance profiles of KPC and VIM co-producing P. aeruginosa isolates from Brazil (2019-2023). METHODS: Between 2019 and 2023, 1489 multidrug-resistant P. aeruginosa isolates were screened by multiplex PCR for carbapenemase-encoding genes. Co-producing isolates underwent pulsed-field gel electrophoresis (PFGE) for clonal profiling, followed by whole-genome sequencing (WGS) for high-resolution phylogenomic analysis. Antimicrobial susceptibility testing and plasmid characterisation using next-generation sequencing platforms were also performed. RESULTS: Forty-two isolates (2.8%) harboured both blaKPC-2 and blaVIM-2, with detection occurring exclusively between 2020 and 2023, temporally coinciding with the COVID-19 pandemic. PFGE identified eight distinct clonal groups, providing evidence for independent horizontal gene transfer (HGT) events, whilst WGS confirmed all isolates as the high-risk ST233 lineage. Chromosomally integrated blaVIM-2 within class 1 integrons predominated; 2 isolates carried dual chromosomal copies. Plasmid-borne blaKPC-2 was identified across heterogeneous replicons (43.3-430.1 kb), suggesting multiple independent acquisition events. All co-producing isolates displayed extensive drug resistance, retaining in vitro susceptibility only to cefiderocol and colistin. CONCLUSIONS: ST233 co-producing KPC and VIM, represents a high-risk resistance phenotype of epidemiological significance. Divergent genomic architectures suggest active horizontal dissemination across diverse genetic backgrounds rather than clonal expansion, highlighting the need for enhanced surveillance and infection control strategies.

Bacterial genomic characterisation↗

PubMed2025

Understanding recurrence in Mycobacterium avium complex pulmonary disease: genotypic strategies to support clinical decision-making.

Pulmonary disease caused by Mycobacterium avium complex (MAC-PD) is a chronic, recurrent disease, and its high recurrence rate after treatment makes clinical management difficult. Distinguishing whether recurrence is due to persistence of existing strains or reinfection with new strains is essential for establishing treatment strategies, preventing overuse of antimicrobials, and establishing infection control measures. According to reports, 54%-74% of MAC-PD recurrence is due to reinfection, which may be mainly related to environmental reservoirs such as household water supply. In this review, we present various clinical scenarios in which MAC-PD recurrence may occur and examine genotyping techniques as a strategy to distinguish and respond to them. From traditional methods such as IS1245-based restriction fragment length polymorphism, pulsed-field gel electrophoresis, and hsp65 and rpoB gene sequencing to high-resolution analysis techniques such as multilocus sequence testing and whole-genome sequencing, the latest molecular typing methods are comprehensively summarized. Integrating these genotype data into clinical settings, standardizing single-nucleotide polymorphism-based interpretation thresholds, and promoting the establishment of a global MAC strain database will make a substantial contribution to more accurately distinguishing the recurrence mechanisms of MAC-PD and establishing personalized treatment strategies.IMPORTANCEThe global burden of nontuberculous mycobacterial pulmonary disease (PD) is increasing, with Mycobacterium avium (MAC)-PD being the most prevalent and clinically challenging form. Its low treatment success rates, high frequency of recurrence, and persistent environmental exposure complicate both diagnosis and management. A critical clinical issue is determining whether recurrence represents true relapse, due to persistence of the original strain, or reinfection with a new strain, as this guides treatment and prevents overtreatment. Genotypic strategies capable of resolving strain-level differences can improve diagnostic accuracy, prevent misclassification, and ultimately support more informed treatment decisions. Therefore, integrating genotyping data into clinical workflows, standardizing single-nucleotide polymorphism thresholds, and establishing a global MAC strain database will not only support personalized treatment but also enhance the broader public health response to this disease.

Humans↗

PubMed2005

Characterization of the genetic lineages responsible for pneumococcal invasive disease in Portugal.

The availability of a conjugate vaccine has the potential to reduce the disease burden of pneumococci and to alter the serotype frequency in the disease-causing population through immunoselection. These changes will probably be reflected in the distributions of individual genetic lineages within the population. We present a characterization of a collection of recent (1999 to 2002) invasive isolates from Portugal (n = 465) by macrorestriction profiling with pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing. During this time, serotypes 14, 1, 3, 4, 8, 9V, 23F, 7F, 19A, and 12B were the 10 most prevalent overall by decreasing rank order. By combining the PFGE data with the sequence types (STs) of 104 isolates, we were able to identify the genetic lineages of the majority of the isolates. We found 66 STs, including 20 novel STs, corresponding to 47 different lineages by e-BURST analysis. We found in our collection a number of previously identified internationally disseminated lineages, especially among macrolide-resistant and penicillin-resistant isolates, and these accounted for most of the isolates. Most of the major lineages (17 of 25) were identified in all years of the study, suggesting that the pneumococcal population associated with invasive disease was stable. This study provides a characterization of the pneumococcal population associated with invasive disease that will be useful for detecting potential selective effects of the novel conjugate vaccine.

Alleles↗

PubMed2026

Phenotypic and phylogenomic characterization of Lactococcus garvieae isolates from rainbow trout (Oncorhynchus mykiss) in Türkiye.

Lactococcosis is an important bacterial disease of farmed fish and causes substantial economic losses in rainbow trout (Oncorhynchus mykiss) aquaculture. In this study, Lactococcus garvieae isolates recovered from rainbow trout farms in Türkiye were characterized using phenotypic, molecular, and phylogenomic methods. Among 32 presumptive Lactococcus isolates recovered from 127 dead rainbow trout, four were confirmed as L. garvieae and exhibited identical biochemical characteristics, Pulsed Field Gel Electrophoresis (PFGE) profiles, and broad growth tolerance across different pH, salinity, and temperature conditions. All isolates were presumptively classified as resistant to ciprofloxacin and florfenicol, while remaining susceptible to tetracycline and penicillin. Based on the AMR profiles, strain LG2, which exhibited the most susceptible antimicrobial profile among the isolates, was selected for whole-genome sequencing (WGS). WGS of the representative isolate LG2 generated a single 2,214,687-bp chromosomal contig with 38.5% GC content and 99.0% BUSCO completeness. In silico PCR assigned LG2 to serotype I, and the genome contained an intact capsule-associated cps/kps locus. The chromosomal lsa(D) determinant and an mdt(A)-like efflux-associated gene were detected, whereas no plasmid replicons or acquired quinolone or florfenicol resistance genes were identified, indicating discordance between the phenotypic and genomic AMR results. Taxonomic verification of 236 publicly available Lactococcus assemblies yielded 41 verified public L. garvieae genomes, which, together with LG2, formed a 42-genome within-species dataset. LG2 was most closely related to the Turkish isolate OS-37, sharing 99.96% ANI and differing by three core SNPs; both belonged to ST109, whereas the other Turkish isolates belonged to ST139. cgMLST identified a conserved genomic backbone, while pan-genome analysis identified 5,655 gene clusters and an open pan-genome characterized by a large cloud-gene fraction. These findings demonstrate the importance of species verification in Lactococcus population genomics and reveal substantial accessory-genome diversity within L. garvieae. The genomic features of LG2 provide a basis for future pathogenicity and immunogenicity studies, although experimental validation is required. Overall, these findings highlight the importance of local genomic surveillance for understanding L. garvieae population structure and provide a genomic framework for future region-specific vaccine research.

Animals↗

PubMed2003

First report of capsule replacement among electrophoretic type 37 Neisseria meningitidis strains in Italy.

This report describes the C-to-B capsular switching in four Neisseria meningitidis strains belonging to the electrophoretic type 37 (ET-37) complex. In particular, one strain belonged to the new sequence type 1860, which was first detected in the year 2000 in Italy and is now frequently isolated. The presence of switched serogroup B strains deserves special attention if they prove as able to spread as their serogroup C progenitors belonging to the hypervirulent ET-37 complex.

DNA Transposable Elements↗