Biology subjects

McGeer, A.

Publications and source records attributed to McGeer, A..

5 recordsLinked to original sources

bioRxiv2025

Neighbour Typing Using Long Read Sequencing Provides Rapid Prediction of Sequence Type and Antimicrobial Susceptibility of Klebsiella pneumoniae

The rapid genome-based diagnostic approach of long read sequencing coupled with neighbor typing offers the potential to improve empiric treatment of infection. However, this approach is still in development, and clinical validation is needed to support its use. In this study, we present an assessment of a neighbour typing method (RASE - resistance associated sequence elements) to predict lineage or sequence type (ST) and antimicrobial susceptibility in real time for Klebsiella pneumoniae sensu lato. We analysed the initial reads generated during the early phase of long read sequencing from pure culture (n=99), mock communities (n=20) and metagenomic samples (n=20). RASE accurately identified 69.7% and 70% of STs in pure culture and metagenomes, respectively, and identified the STs of the isolates representing the highest proportion in mock communities. Regarding antimicrobial susceptibility prediction, the probability of susceptibility increased to 72% (95% CI 63%-80%) across all tested antibiotics, when RASE predicted susceptibility, and decreased probability of susceptibility to 8.9% (95% CI 6.4%-9.6%) when was indicative of a resistant phenotype. Our study confirmed that genomic neighbor typing in K. pneumoniae sensu lato is capable of providing informative predictions of ST and antibiotic susceptibility in less than ten minutes (after the start of sequencing) with 200-500 reads. IMPORTANCEThe growing burden of antimicrobial resistance is leading to high rates of mortality and morbidity worldwide. This situation has made the selection of empirical antibiotic therapy challenging, due to the risk of treatment failure and the overuse of last-resort antibiotics. The development of new sequencing technologies is helping to reduce the waiting time for a microbiological diagnosis, providing information in the early phase of bacterial infections, which could help improve clinical outcomes in a time of rising antimicrobial resistance. In this context, we assessed the performance of RASE (resistance associated sequence elements) in Klebsiella pneumoniae, an opportunistic pathogen frequently associated with nosocomial infections, which can rapidly acquire antibiotic resistance genes. Thus, in our study we provide insights that may aid in the validation of RASE for clinical use.

genomics↗

bioRxiv2025

Identification of plasmid-mediated tigecycline resistance tet(x4) and New Delhi Metallo-β-lactamase (NDM) in an Escherichia coli isolate from Canada

SynopsisRapid spread of carbapenemase producing Enterobacterales is a global health threat for which Tigecycline is one of the few remaining therapeutic options. Resistance by tet(x4) is particularly worrisome given its presence on mobile genetic elements. Here we report on a tigecycline-resistant E.coli strain isolated from a patient returning from Pakistan. A tet(x4) gene was found on an IncFII plasmid isolated from an ST410 E.coli co-harbouring NDM-5. The combination of carbapenemase and tet(x4) is concerning.

microbiology↗

bioRxiv2024

mRNA Vaccine-Induced SARS-CoV-2 Spike-Specific IFN-γ and IL-2 T-cell Responses are Predictive of Serological Neutralization and are Transiently Enhanced by Pre-Existing Cross-Reactive Immunity

The contributions of SARS-CoV-2-specific T-cells to vaccine efficacy and durability are unclear. We investigated the relationships between mRNA vaccine-induced spike-specific IFN-{gamma} and IL-2 T-cell responses, anti-spike/RBD IgG/IgA antibodies, and live virus neutralizing capacity in long-term-care-home staff doubly vaccinated with BNT162b2 or mRNA-1273. The impacts of pre-existing cross-reactive T-cell immunity to SARS-CoV-2 on cellular and humoral responses to vaccination were additionally assessed. Mathematical modelling of the kinetics of spike-specific IFN-{gamma} and IL-2 T-cell responses over 6-months post-second dose was bifurcated into recipients who exhibited gradual increases (54% and 42%, respectively) with doubling times of 173 days, or decreases (46% and 58%, respectively) with half-lives of 115 days. Differences in kinetics did not correlate with any clinical phenotypes, although increases were proposed to be due to subclinical viral exposures. Serological anti-spike/RBD IgG/IgA antibody levels had otherwise decayed in all participants with half-lives of 55, 53, 76, and 59 days, respectively. Spike-specific T-cell responses induced at 2-6 weeks correlated with live viral neutralization at 6-months post-second dose, especially in hybrid immune individuals. Participants with pre-existing cross-reactive T-cell immunity to SARS-CoV-2 exhibited greater spike-specific T-cell responses, reduced anti-RBD IgA antibody levels, and a trending increase in neutralization at 2-6 weeks post-second dose. Non-spike-specific T-cells predominantly targeted SARS-CoV-2 non-structural protein at 6-months post-second dose in cross-reactive participants. mRNA vaccination was lastly shown to induce off-target T-cell responses against unrelated antigens. In summary, vaccine-induced spike-specific T-cell immunity appeared to influence serological neutralizing capacity, with only a modest effect induced by pre-existing cross-reactivity. IMPORTANCEOur findings provide important insights on the potential contributions of mRNA vaccine-induced spike-specific T-cell responses to the durability of neutralizing antibody levels in both uninfected and hybrid immune recipients. Our study additionally sheds light on the precise impacts of pre-existing cross-reactive T-cell immunity to SARS-CoV-2 on the magnitude and kinetics of cellular and humoral responses to vaccination. This study should ultimately inform the development of novel pan-coronavirus vaccines and vaccine regimens that can maximize the durability and breadth of protection against both current and future human coronaviruses of concern.

immunology↗

bioRxiv2022

Highly divergent white-tailed deer SARS-CoV-2 with potential deer-to-human transmission

Wildlife reservoirs of SARS-CoV-2 may enable viral adaptation and spillback from animals to humans. In North America, there is evidence of unsustained spillover of SARS-CoV-2 from humans to white-tailed deer (Odocoileus virginianus), but no evidence of transmission from deer to humans. Through a biosurveillance program in Ontario, Canada we identified a new and highly divergent lineage of SARS-CoV-2 in white-tailed deer. This lineage is the most divergent SARS-CoV-2 lineage identified to date, with 76 consensus mutations (including 37 previously associated with non-human animal hosts) and signatures of considerable evolution and transmission within wildlife. Phylogenetic analysis also revealed an epidemiologically linked human case. Together, our findings represent the first clear evidence of sustained evolution of SARS-CoV-2 in white-tailed deer and of deer-to-human transmission.

microbiology↗

bioRxiv2022

Longitudinal Assessment of SARS-CoV-2 Specific T Cell Cytokine-Producing Responses for 1 Year Reveals Persistence of Multi-Cytokine Proliferative Responses, with Greater Immunity Associated with Disease Severity

Cellular-mediated immunity is critical for long-term protection against most viral infections, including coronaviruses. We studied 23 SARS-CoV-2-infected survivors over a one year post symptom onset (PSO) interval by ex vivo cytokine ELISpot assay. All subjects demonstrated SARS-CoV-2-specific IFN-{gamma}, IL-2, and Granzyme B (GzmB) T cell responses at presentation, with greater frequencies in severe disease. Cytokines, mainly produced by CD4+ T cells, targeted all structural proteins (Nucleocapsid, Membrane, Spike) except Envelope, with GzmB > IL-2 > IFN-{gamma}. Mathematical modeling predicted that: 1) cytokine responses peaked at 6 days for IFN-{gamma}, 36 days for IL-2, and 7 days for GzmB, 2) severe illness was associated with reduced IFN-{gamma} and GzmB, but increased IL-2 production rates, 3) males displayed greater production of IFN-{gamma}, whereas females produced more GzmB. Ex vivo responses declined over time with persistence of IL-2 in 86% and of IFN-{gamma} and GzmB in 70% of subjects at a median of 336 days PSO. The average half-life of SARS-CoV-2-specific cytokine-producing cells was modelled to be 139 days ([~]4.6 months). Potent T cell proliferative responses persisted throughout observation, were CD4 dominant, and were capable of producing all 3 cytokines. Several immunodominant CD4 and CD8 epitopes identified in this study were shared by seasonal coronaviruses or SARS-CoV-1 in the Nucleocapsid and Membrane regions. Both SARS-CoV-2-specific CD4+ and CD8+ T cell clones were able to kill target cells, though CD8 tended to be more potent. ImportanceOur findings highlight the relative importance of SARS-CoV-2-specific GzmB-producing T cell responses in SARS-CoV-2 control, shared CD4 and CD8 immunodominant epitopes in seasonal coronaviruses or SARS-CoV-1, and indicate robust persistence of T cell memory at least one year after infection. Our findings should inform future strategies to induce T cell vaccines against SARS-CoV-2 and other coronaviruses.

immunology↗