Biology subjects

Merhi, G.

Publications and source records attributed to Merhi, G..

3 recordsLinked to original sources

bioRxiv2025

Telomere-to-telomere assembly detects genomic diversity in Canadian strains of Borrelia burgdorferi

Borrelia burgdorferi, the bacteria causing Lyme disease, has a complex genome comprising a linear chromosome and a combination of linear and circular plasmids. The atypical hairpin structure at the telomere of linear replicons and the highly paralogous plasmids make the genome assembly challenging. We developed a genome assembly pipeline using Oxford Nanopore Technologies (ONT) long read and Illumina short read to overcome these challenges. Using ONT reads enabled us to completely assemble the hairpin telomeres of the linear replicons along with a novel lp28 subtype plasmid and the complete circular plasmids of nine B. burgdorferi strains from five geographical regions in Canada. Although these strains are highly similar across the conserved genomic regions, variability was observed predominantly at the right telomeric ends. Comparative analyses revealed that all nine strains carry a [~]2-10 kb right telomeric end identical to the linear plasmid lp28-1, which leads to variability in the telomere length and the gene content. Additionally, we observed diversity at the hairpin telomeric sequences of the linear chromosomes. Further analysis showed that the nine strains belong to seven ospC types and have diverse plasmid profile, highlighting the genomic diversity among the strains from the same geographical locations. Overall, these findings suggest that even the B. burgdorferi strains from close geographical locations can carry substantial genomic variation, especially at the telomeres and with respect to their plasmid content, emphasizing it to be a possible mechanism of rapid evolution within these Canadian strains.

genomics↗

bioRxiv2022

Whole genome-based characterization of multi-drug resistant Enterobacter and Klebsiella aerogenes isolates from Lebanon

BackgroundEnterobacter spp. are rod-shaped Gram-negative opportunistic pathogens belonging to Enterobacterales. This study aimed at the molecular and genomic characterization of multi-drug resistant Enterobacter spp. isolates recovered from hospitalized patients in a tertiary care hospital in Lebanon. MaterialsA total of 59 Enterobacter spp. clinical isolates consisting of 41 carbapenem-resistant and 18 susceptible by E-test were included in this study. Genotypic identification through whole-genome sequencing was performed and confirmed in silico. Resistance and plasmid profiles were studied using ResFinder4.0 and Plasmid-Finder2.1. Multi-locus sequence typing (MLST) was used to determine the isolates clonality. ResultsANI identified and confirmed that 47 (80%) isolates were E. hormaechei, 11 (18%) were Klebsiella aerogenes and 1 (2%) was an E. cloacae. Carbapenem-resistance was detected among 41 isolates all showing an MIC90 of [≥] 32 {micro}g/ml for ertapenem, imipenem, and meropenem. blaNDM-1 (58.5%), blaACT-16 (54%), and blaOXA-1 (54%) were the most common detected {beta}-lactamases, while blaCTX-M-15 gene (68%) was the main detected extended-spectrum {beta}-lactamase (ESBL) encoding gene. Chromosomal ampC gene, carbapenemase encoding genes, and porin modifications were among the detected carbapenem resistance determinants. The carbapenemase encoding genes were linked to three well-defined plasmid Inc groups, IncFII/IncFIB, IncX3, and IncL. MLST typing revealed the diversity within the studied isolates, with ST114 being the most common amongst the studied E. hormaechei. ConclusionThe spread of carbapenem-resistant isolates in clinical settings in Lebanon is a serious challenge. Screening and continuous monitoring through WGS analysis could effectively limit the dissemination of drug-resistant isolates in hospitalized patients. ImportanceDrug resistance is an increasing global public health threat that involves most disease-causing organisms and antimicrobial drugs. Drug-resistant organisms spread in healthcare settings, and resistance to multiple drugs is common. Our study demonstrated the mechanisms leading to resistance against the last resort antimicrobial agents among members of the Enterobacteriaceae family. The spread of carbapenem-resistant bacteria in clinical settings is a serious challenge. Screening and continuous monitoring could effectively limit the dissemination of drug-resistant isolates in hospitalized patients.

genomics↗

bioRxiv2020

SARS-CoV-2 and ORF3a: Non-Synonymous Mutations and Polyproline Regions

The effect of the rapid accumulation of non-synonymous mutations on the pathogenesis of SARS-CoV-2 is not yet known. To predict the impact of non-synonymous mutations and polyproline regions identified in ORF3a on the formation of B-cell epitopes and their role in evading the immune response, nucleotide and protein sequences of 537 available SARS-CoV-2 genomes were analyzed for the presence of non-synonymous mutations and polyproline regions. Mutations were correlated with changes in epitope formation. A total of 19 different non-synonymous amino acids substitutions were detected in ORF3a among 537 SARS-CoV-2 strains. G251V was the most common and identified in 9.9% (n=53) of the strains and was predicted to lead to the loss of a B-cell like epitope in ORF3a. Polyproline regions were detected in two strains (EPI_ISL_410486, France and EPI_ISL_407079, Finland) and affected epitopes formation. The accumulation of non-synonymous mutations and detected polyproline regions in ORF3a of SARS-CoV-2 could be driving the evasion of the host immune response thus favoring viral spread. Rapid mutations accumulating in ORF3a should be closely monitored throughout the COVID-19 pandemic. ImportanceAt the surge of the COVID-19 pandemic and after three months of the identification of SARS-CoV-2 as the disease-causing pathogen, nucleic acid changes due to host-pathogen interactions are insightful into the evolution of this virus. In this paper, we have identified a set of non-synonymous mutations in ORF3a and predicted their impact on B-cell like epitope formation. The accumulation of non-synonymous mutations in ORF3a could be driving protein changes that mediate immune evasion and favoring viral spread.

genomics↗