Biology subjects

Dhariwal, A.

Publications and source records attributed to Dhariwal, A..

8 recordsLinked to original sources

bioRxiv2025

Impact of the RaS-RiPP tryglysin and culturing conditions on ex-vivo oral microbiomes.

Natural products are ubiquitously produced by many species that we encounter during our daily lives. One genus, Streptococcus, can produce a wide array of quorum sensing linked natural products known as RaS-RiPPs (ribosomally synthesized and post-translationally modified peptides). Their production is triggered by the induction of an Rgg-SHP quorum sensing system, which senses the presence of SHPs (short hydrophobic peptides) and induces the gene expression of these operons. Previous work has found that streptococcal RaS-RiPPs modulate the growth of different streptococci and might play a role in antibiotic tolerance. This is of particular importance to the oral microbiome, where streptococci are a predominant genus. This study examines the impact of the RaS-RiPP Tryglysin A on ex-vivo oral systems and provides the groundwork for determining how producer Streptococci might impact the composition and function of oral microbiome communities. We additionally explore important factors to consider when culturing ex-vivo oral systems.

microbiology↗

bioRxiv2025

Large-scale global molecular epidemiology of antibiotic resistance determinants in Streptococcus pneumoniae

BackgroundStreptococcus pneumoniae is a leading pathogen in terms of deaths attributable to or associated with antimicrobial resistance globally. Thus, monitoring antibiotic resistance determinants constitutes a key aspect of surveillance efforts. AimLeveraging on publicly available whole-genome sequencing data, we aimed to investigate the presence and distribution patterns of antibiotic resistance in S. pneumoniae with a focus on multi-drug resistance and serotype distribution. MethodsMetadata and genomes were obtained from the National Center for Biotechnology Information Pathogen Detection database. Curation and harmonization were performed in R and SPSS. Data on resistance patterns was defined according to AMRFinderPlus and a combination of prediction tools were employed for in silico serotyping. ResultsAnalyses involved 75,161 genomes totaling 122,673 gene/allele counts from 14 antibiotic classes. Multi-drug resistance was observed in 16.7% of isolates with the highest increasing rates in Asia and South America. Within antibiotic classes, increase in macrolide resistance genes was highlighted, particularly in the proportion of genomes presenting mefA/msrD. Over a third of isolates with serotypes 19F, 23F, 15A, 6B, and 19A showed multi-drug resistance. We further observed the highest significant increases in the presence of resistance in 33F, 22F, 10A, and 23A. Serotype 13, not included in any vaccine formulation, presented high multi-drug resistance rates with a strong increasing trend. ConclusionsThe findings of this study highlight variations in resistance determinants globally and across serotypes over time. Collectively these data underscore the added value of utilizing public whole-genome sequencing data to investigate the effectiveness and repercussions of treatment and vaccination strategies on managing antibiotic resistance.

microbiology↗

bioRxiv2023

HAMLET, a human milk protein-lipid complex, modulates amoxicillin-induced changes in an ex vivo biofilm model of the oral microbiome

Challenges from infections caused by biofilms and antimicrobial resistance highlight the need for novel antimicrobials that work synergistically with antibiotics and minimize resistance risk. In this study we investigated the potential synergistic effect of HAMLET (human alpha-lactalbumin made lethal to tumor cells), a human milk protein-lipid complex and amoxicillin on microbial ecology using an ex-vivo oral biofilm model. HAMLET was chosen due to its multi-targeted antimicrobial mechanism, together with its synergistic effect with antibiotics on single species pathogens, and low risk of resistance development. The combination of HAMLET and amoxicillin significantly reduced biofilm viability, while each of them alone had little or no impact. Using a whole metagenomics approach, we found that the combination group promoted a most remarkable shift in overall microbial composition compared to the untreated samples. Up to 90% of the bacterial species in the combined treatment were Lactobacillus crispatus, a species with probiotic effects, whereas it was detected in minor fraction in untreated samples. Resistome analysis indicated no major shifts on alpha-diversity, while beta-diversity revealed distinct clustering patterns for each treatment group, signifying that each treatment group harbors a unique resistome. TEM beta-lactamase genes were detected in low proportions in all treated samples but absent in untreated samples. Our study highlights the potential of HAMLET to synergize with amoxicillin in an ex-vivo model of the oral microbiome and modulate the proportion of probiotic bacteria. The findings extend the knowledge on the synergistic effects of HAMLET and antibiotics from single-species studies to polymicrobial biofilms of human origin. ImportancePolymicrobial infections are challenging to treat and prevent, requiring the use of antibiotics that exhibit reduced efficacy due to biofilm formation. HAMLET has recently emerged as an antimicrobial agent that can synergize with antibiotics while limiting microbial resistance. We investigated the effects of HAMLET, alone and combined with low concentrations of amoxicillin, on ex vivo oral biofilms to simulate complex microbial interactions observed in the oral cavity. The combination of HAMLET and amoxicillin effectively targeted polymicrobial biofilms and led to an increase in Lactobacillus crispatus. The potency of this combination appears to be due to the synergistic effect of HAMLET and amoxicillin. These findings underscore the potential of combining antimicrobials with different modes of action for the development of more effective strategies for preventing and treating polymicrobial infections.

immunology↗

bioRxiv2023

Unravelling the landscape of antibiotic resistance determinants in the nasopharynx and the impact of antibiotics: a longitudinal study of preterm infants

Respiratory pathogens, commonly colonizing nasopharynx, are among the leading causes of death due to antimicrobial resistance. Yet, antibiotic resistance determinants within nasopharyngeal microbial communities remain poorly understood. Utilizing shotgun metagenomics, we investigated the nasopharynx resistome development in preterm infants, assessed early antibiotic impact on its trajectory, and explored its association with clinical covariates. Our findings revealed widespread nasopharyngeal carriage of antibiotic resistance genes (ARGs) with resistomes undergoing transient changes, including increased ARG diversity, abundance, and composition alterations due to early antibiotic exposure. ARGs associated with the critical nosocomial pathogen Serratia marcescens persisted up to 8-10 months of age, representing a long-lasting hospitalization signature. The nasopharyngeal resistome strongly correlated with microbiome composition, with inter-individual differences and postnatal age explaining most of the variation. Our report on the collateral effects of antibiotics and prolonged hospitalization underscores the urgency of further studies focused on this relatively unexplored reservoir of pathogens and ARGs.

microbiology↗

bioRxiv2020

Overexpression of human alpha-synuclein leads to dysregulated microbiome and metabolites with ageing in a rat model of Parkinson disease

Since Braaks hypothesis stating that sporadic Parkinsons disease follows a specific progression of the pathology from the peripheral to the central nervous system and can be monitored by detecting accumulation of the alpha-Synuclein protein. There is growing interest in understanding how the gut (commensal) microbiome can regulate alpha-Synuclein accumulation which can lead to PD. We studied a transgenic rat model overexpressing the human alpha-Synuclein and found that the protein overexpression resulted in gut alpha-Synuclein expression and aggregation in the gut neurons with advancing age. A progressive gut microbial composition alteration characterized by the reduction of Firmicutes to Bacteroidetes ratio could be detected in the young transgenic rat model and interestingly this ratio was then increased with aging. This observation was accompanied in older animals by intestinal inflammation, increase gut permeability and a robust alteration in metabolites production characterized by the increase of succinate level in the feces and serum. Manipulation of the gut bacteria by short-term antibiotics treatment revealed a complete loss of short-chain fatty acids (SCFAs) and reduction in succinate levels. Although antibiotics treatment did not change alpha-synuclein expression in the enteric nervous system of the colon, it can reduce alpha-synuclein expression in the olfactory bulb of the transgenic rats. In summary, synchronous with ageing, our data emphasize that the gut microbiome dysbiosis leads to a specific alteration of gut metabolites which are reflected in the serum and can be modulated by the environment.

neuroscience↗

bioRxiv2020

ResistoXplorer: a web-based tool for visual, statistical and exploratory data analysis of resistome data

The study of resistomes using whole metagenomic sequencing enables high throughput identification of resistance genes in complex microbial communities, such as the human microbiome. Over recent years, sophisticated and diverse pipelines have been established to facilitate raw data processing and annotation. Despite the progress, there are no easy-to-use tools for comprehensive visual, statistical, and functional analysis of resistome data. Thus, exploration of the resulting large complex datasets remains a key bottleneck requiring robust computational resources and technical expertise, which creates a significant hurdle for advancements in the field. Here, we introduce ResistoXplorer, a user-friendly tool that integrates recent advancements in statistics and visualization, coupled with extensive functional annotations and phenotype collection, to enable high-throughput analysis of common outputs generated from metagenomic resistome studies. ResistoXplorer contains three modules- the Antimicrobial Resistance Gene Table module offers various options for composition profiling, functional profiling and comparative analysis of resistome data; the Integration module supports integrative exploratory analysis of resistome and microbiome abundance profiles derived from metagenomic samples; finally, the Antimicrobial Resistance Gene List module enables users to intuitively explore the associations between antimicrobial resistance genes and the microbial hosts using network visual analytics to gain biological insights. ResistoXplorer is publicly available at http://www.resistoxplorer.no.

microbiology↗

bioRxiv2019

DJ-1 (Park7) affects the gut microbiome, metabolites, and development of Innate Lymphoid Cells (ILCs)

The proper communication between gut and brain is pivotal for maintenance of health and dysregulation of the gut-brain axis can lead to several clinical disorders. Also, in Parkinsons disease (PD) 85% of all patients experienced constipation long before showing any signs of motor phenotypes. For differential diagnosis and when it comes to preventive treatment there is an urgent need for the identification of biomarkers indicating early disease stages long before the disease phenotype manifests. DJ-1 is a chaperon protein involved in the protection against PD and genetic mutations in this protein have been shown to cause familial PD. However, how the deficiency of DJ-1 modifies the PD risk remains incompletely understood. In the present study we provide evidence that DJ-1 is implicated in shaping the gut microbiome including their metabolite production or innate immune cells (ILCs) development. We revealed that in 4 months old mice genetic deficiency of DJ-1 leads to significantly decrease in several bacterial genera and significantly increase in two specific genera, namely Alistipes and Rikenella. DJ-1 deficient mice have a higher production of calprotectin/MCP-1 inflammatory protein - a known protein involved in colonic inflammation - and significantly higher expression of glial fibrillary acidic protein (GFAP) than control littermates. Expression of a-Synuclein, a key protein in Lewy bodies, in the colon was not significantly different between genotypes. Metabolic profiles of feces extracts analysed by H1-NMR spectroscopy showed increased short chain fatty acids (SCFAs) and decreased amino acid levels, suggesting a general switch from protein towards fibre degrading strains in DJ-1 deficient mice. We observed that Malonate - which is known to influence the immune system - has significantly higher concentrations in DJ-1 deficient mice. Moreover, DJ-1 deficient mice have high levels of the phenol derivate 3-(3-Hydroxyphenyl) propanoic acid (3-HPPA) which is a breakdown product of aromatic substrates like tyrosine, phenylalanine and polyphenols. DJ-1 deficient mice also showed significantly reduced percentage of ILCs. Thus, our data suggests that absence of DJ-1 leads to increase in gut inflammatory bacteria composition, deregulated metabolites and dysregulated innate immunity which could be a key factor in the initiation of PD disease in the gut, and potentially also in brain during disease progression.

immunology↗

bioRxiv2019

Impact of narrow spectrum Penicillin V on the oral and fecal resistome in a young child treated for otitis media

BackgroundAntibiotic overuse has led to a global emergence of resistant bacteria, and children are among the frequent users. Most studies with broad-spectrum antibiotics show severe impact on the resistome development of patients. Although narrow-spectrum antibiotics are believed to have less side-effects, their impact on the microbiome and resistome is mostly unknown. The aim of this study was to investigate the impact of the narrow-spectrum antibiotic phenoxymethylpenicillin (Penicillin V) on the microbiome and resistome of a child treated for acute otitis media (OM).\n\nMethodsOral and fecal samples were collected from a one-year child before (day 0) and after (day 5 and 30) receiving Penicillin V against OM. Metagenomic sequencing data was analysed to determine taxonomic profiling, using Kraken and Bracken software, and resistance profiling, using KMA in combination with the ResFinder database.\n\nResultsIn the oral samples, 11 antimicrobial resistance genes (ARGs), belonging to four classes, were identified at baseline. At day 5, the abundance of some ARGs was increased, some remained unchanged, while others disappeared. At day 30, most ARGs had returned to baseline levels, or lower. In the fecal samples we observed seven ARGs at baseline and five at day 5, with only one gene observed at day 5 being present at baseline. At day 30 the number of ARGs increased to 21 ARGs from 7 different classes.\n\nConclusionsPenicillin V had a remarkable impact on the fecal resistome indicating that even narrow-pectrum antibiotics may have important consequences in selecting for a more resistant microbiome.

microbiology↗