Biology subjects

Snitkin, E. S.

Publications and source records attributed to Snitkin, E. S..

17 recordsLinked to original sources

bioRxiv2026

Defining the Candidozyma auris pan-genome and essentiality

Candidozyma auris is a multi-drug resistant fungal pathogen that causes hospital outbreaks, but genetic variation and gene function in this organism remain undercharacterized. Here, we performed pangenome analysis on 695 genetically representative isolates of C. auris and found that only 2.6% of gene families varied in their presence, mainly consisting of gene loss events or clade-specific genes, highlighting the clonal nature of these strains. Using microbial genome-wide association, we identified two loci associated with altered keratinocyte adherence, including genes with unknown function. To look broadly at gene function, we developed a genome-scale insertional mutagenesis approach and identified 614 high-confidence essential genes. Nearly one-third of these genes exhibited divergent essentiality compared to the model yeasts Candida albicans and Saccharomyces cerevisiae. Together, this study highlights organism-specific biology and provides a comprehensive resource for identifying species-specific determinants of virulence and targets for antifungal drug development.

microbiology↗

bioRxiv2025

A Novel Technique to Characterize Klebsiella pneumoniae Populations Indicates that Mono-Colonization is Associated with Risk of Infection

Klebsiella pneumoniae and related species are a common cause of healthcare-associated infections. The gut is a major Klebsiella reservoir and gut colonization is a risk factor for developing an extraintestinal Klebsiella infection. Patients can be colonized by multiple Klebsiella strains or even species in the gut simultaneously, and there is high concordance between the gut colonizing- and infection causing-strains. The detection and characterization of colonizing strains is critical for a better understanding of the progression to infection and for developing interventions for colonized patients. However, the association between mixed or mono-colonization and subsequent infection is unknown. In this study, we developed an amplicon-based sequencing method called wzi-Seq that enables the detection and quantification of Klebsiella strains from complex samples and mixtures using the conserved capsule gene wzi as a molecular barcode. This method is highly accurate and precise with a sensitivity of 93% and specificity of 99.8% in mixtures containing as many as 58 unique wzi types. The assay was validated analytically and applied to an established case and control cohort. We determined that 63.2% (108/171) patients were mono-colonized with a single Klebsiella strain while 36.8% (63/171) had mixed colonization with multiple Klebsiella strains. Controlling for patient variables in multivariate analysis, we determined that mono-colonization was significantly (p = 0.034) associated with infection. Characterization of Klebsiella colonizing populations could improve the accuracy of assessing infection risk and enable targeted interventions to prevent these healthcare-associated infections. ImportanceKlebsiella gut colonization is a major risk factor the development of extraintestinal Klebsiella infections in hospitalized settings. However, it is unknown if patients are colonized by one or multiple strains of Klebsiella and how the population structure of Klebsiella in the gut impacts infection risk. Here we describe the development of a novel technique, wzi-Seq, to detect and quantify multiple Klebsiella strains from complex samples using standard techniques and rapid DNA sequencing. We applied wzi-Seq to rectal swabs from a well-characterized patient cohort and found that Klebsiella colonization with a single strain was more prevalent than colonization with multiple strains. Furthermore, mono-colonized patients had a significantly higher risk of developing a Klebsiella infection than mixed colonized patients. This work validates a new tool to study Klebsiella populations and reveals that population structure in the gut influences the risk of healthcare associated infections.

microbiology↗

bioRxiv2025

Uncertainty in joint Ancestral State Reconstruction: Improving accuracy and biological interpretability of ancestral state prediction

Ancestral state reconstruction (ASR) is a foundational tool in comparative biology, offering insights into the evolutionary history of lineages. With each new evolutionary model, our ability to estimate ancestral states has improved alongside the increased biological realism of these models. However, the field has primarily relied on reconstructions that focus on individual nodes, known as marginal reconstructions. This framework is analytically tractable but may not accurately represent what biologists want in inference, as evolution is dependent, and phenotypic transitions deeper in time can lead to consistent changes later. We argue that evolutionary history is better represented by joint reconstructions, which estimate the full sequence of states across nodes. Traditionally, joint reconstruction algorithms only estimated the single most likely sequence, but here we develop novel algorithms to estimate all relevant ancestral histories efficiently and provide tools to quantify the uncertainty of joint ASR. Furthermore, through simulations and an empirical case study, we demonstrate that joint reconstructions have higher accuracy than their marginal counterparts, and that the uncertainty surrounding the best joint reconstruction can be biologically meaningful and summarized using novel clustering algorithms. We apply our methods to epidemic multidrug-resistant Klebsiella pneumoniae and find that the evolution of antibiotic resistance is not a single narrative but a series of competing histories. Each of these histories exhibits distinct phenotype-genotype transitions that traditional approaches would struggle to identify, yet have critical implications for predicting resistance evolution.

evolutionary biology↗

bioRxiv2025

Tracking blaKPC Plasmid Dissemination within and between Enterobacterales across Michigan Over a Decade

AbstractblaKPC is endemic among Enterobacterales in the USA. While present on diverse plasmids, blaKPC burden is often associated with the clonal spread of multi-drug resistant (MDR) epidemic lineages. In this study we sought to determine the relative contributions of clonal spread and plasmid transfer to blaKPC burden across Michigan healthcare facilities over a decade. To this end we performed whole-genome sequencing of 1,058 KPC-producing isolates collected from 47 Michigan healthcare facilities between 2013 and 2022, including long-read sequencing for 527 isolates to enable precise plasmid tracking. Analysis with MOB-suite identified 64 distinct KPC plasmid types ("secondary clusters"), with the AK975 broad-host range plasmid being the most prevalent, found in 27% of isolates, spanning 20 species and 92 sequence types. Among genomes with AK975, 30% were from epidemic and 70% non-epidemic lineages, highlighting its broad role in regional blaKPC spread. Epidemic lineages of various species constituted 46% of the study population. Epidemic lineages differed in their primary plasmids, and even within epidemic lineages there were clonal expansions with distinct blaKPC plasmids, including in some cases AK975. These findings highlight two patterns of KPC spread: transmission of epidemic lineages harboring broad-range and lineage-specific KPC plasmids; and broader spread of AK975 among diverse species. Traditional surveillance studies often focus on common MDR lineages, potentially overlooking rare species and lineages that mediate the spread of plasmid-borne antimicrobial resistance (AMR) genes. Here we show how longitudinal studies tracking plasmids across species are essential to understand the pathways leading to AMR infections in hospitals. ImportanceThis decade-long longitudinal study highlights the persistence and spread of key KPC- carrying plasmid across multiple bacterial species in the region, including some uncommon ones. It also emphasizes the differences in KPC plasmids across lineages within the same species. While some lineages acquire multiple plasmids with resistance, they are unable to successfully maintain the plasmids. In contrast, clonal sub-populations of KPC-producing bacteria disseminate selected plasmids, establishing a stable host-plasmid combination. Comprehensive genomic surveillance that includes all pathogenic species and plasmids is crucial to understanding the regional transmission dynamics of plasmid-borne antimicrobial resistance (AMR). While outbreak studies define the blowup of a successful lineage and associated plasmids, longitudinal studies identify the reservoir-species and circulating plasmids in the context of plasmid- borne AMR.

genomics↗

bioRxiv2024

Multiplexed PCR to measure in situ growth rates of uropathogenic E. coli during experimental urinary tract infection.

Measuring bacterial growth rates in vitro is routine, however, determining growth rates during infection within a host has been more challenging. Peak-to-trough ratio (PTR) is a technique for studying microbial growth dynamics, calculated using the ratio of replication origin (ori) copies to those of the terminus (ter), as originally defined by whole genome sequencing (WGS). WGS presents significant challenges in terms of expense and data analysis complexity due to the presence of host DNA in the samples. Here, we used multiplexed PCR with fluorescent probes to estimate bacterial growth rates based on the abundance of ori- and ter-adjacent loci, without the need for WGS. We establish the utility of this approach by comparing growth rates of the uropathogenic Escherichia coli (UPEC) strain HM86 by WGS (PTR) and qPCR to measure the equivalent ori:ter (O:TPCR). We found that PTR and O:TPCR were highly correlated and that O:TPCR reliably predicted growth rates calculated by conventional methods. O:TPCR was then used to calculate the in situ E. coli growth rates in urine, bladder, and kidneys collected over the course of a week from a murine model of urinary tract infection (UTI). These analyses revealed that growth rate of UPEC strains gradually increased during the early stages of infection (0-6h), followed by a slow decrease in growth rates during later time points (1-7 days). This rapid and convenient method provides valuable insights into bacterial growth dynamics during infection and can be applied to other bacterial species in both animal models and clinical infections. ImportanceAccurately measuring bacterial growth rates in the host, which plays a crucial role in determining the success of pathogens in establishing infections, poses significant challenges. To address this, bacterial replication rate has been measured as a proxy for growth rate estimation. While whole genome sequencing (WGS) has been used for this purpose, it comes with drawbacks such as high costs and difficulties in analyzing bacterial sequences due to the overwhelming presence of host DNA. In this study, we validate a more accessible PCR-based approach compared to the established WGS method and confirmed the reliability of our PCR-based technique. We then applied it to measure the growth rate of Escherichia coli during experimental urinary tract infection in a mouse model. This study provides a cost-effective and efficient alternative to WGS for studying bacterial replication dynamics during infection, potentially offering new insights into pathogen behavior and host-microbe interactions.

microbiology↗

bioRxiv2023

Flagellar switch inverted repeat sequence variation impacts Clostridioides difficile RT027/MLST1 virulence.

Clostridioides difficile RT027 strains cause infections that vary in severity from asymptomatic to lethal, but the molecular basis for this variability is poorly understood. Through comparative analyses of RT027 clinical isolates, we determined that isolates that exhibit greater variability in their flagellar gene expression exhibit greater virulence in vivo. C. difficile flagellar genes are phase-variably expressed due to the site-specific inversion of the flgB 5UTR region, which reversibly generates ON vs. OFF orientations for the flagellar switch. We found that longer inverted repeat (IR) sequences in this switch region correlate with greater disease severity, with RT027 strains carrying 6A/6T IR sequences exhibiting greater phenotypic heterogeneity in flagellar gene expression (60%-75% ON) and causing more severe disease than those with shorter IRs (> 99% ON or OFF). Taken together, our results reveal that phenotypic heterogeneity in flagellar gene expression may contribute to the variable disease severity observed in C. difficile patients.

microbiology↗

bioRxiv2023

Virulence and genomic diversity among clinical isolates of ST1 (BI/NAP1/027) Clostridioides difficile

Clostridioides difficile (C. difficile), a leading cause of nosocomial infection, produces toxins that damage the colonic epithelium and results in colitis that varies from mild to fulminant. Variation in disease severity is poorly understood and has been attributed to host factors (age, immune competence and intestinal microbiome composition) and/or virulence differences between C. difficile strains, with some, such as the epidemic BI/NAP1/027 (MLST1) strain, being associated with greater virulence. We tested 23 MLST1(ST1) C. difficile clinical isolates for virulence in antibiotic-treated C57BL/6 mice. All isolates encoded a complete Tcd pathogenicity locus and achieved similar colonization densities in mice. Disease severity varied, however, with 5 isolates causing lethal infections, 16 isolates causing a range of moderate infections and 2 isolates resulting in no detectable disease. The avirulent ST1 isolates did not cause disease in highly susceptible Myd88-/- or germ-free mice. Genomic analysis of the avirulent isolates revealed a 69 base-pair deletion in the N-terminus of the cdtR gene, which encodes a response regulator for binary toxin (CDT) expression. Genetic deletion of the 69 base-pair cdtR sequence in the highly virulent ST1 R20291 C. difficile strain rendered it avirulent and reduced toxin gene transcription in cecal contents. Our study demonstrates that a natural deletion within cdtR attenuates virulence in the epidemic ST1 C. difficile strain without reducing colonization and persistence in the gut. Distinguishing strains on the basis of cdtR may enhance the specificity of diagnostic tests for C. difficile colitis.

microbiology↗

bioRxiv2021

Strain variation in Clostridioides difficile toxin activity associated with genomic variation at both PaLoc and non-PaLoc loci

Clinical disease from Clostridioides difficile infection can be mediated by two toxins and their neighboring regulatory genes encoded within the five-gene pathogenicity locus (PaLoc). We provide several lines of evidence that the toxin activity of C. difficile may be modulated by genomic variants outside of the PaLoc. We used a phylogenetic tree-based approach to demonstrate discordance between toxin activity and PaLoc evolutionary history, an elastic net method to show the insufficiency of PaLoc variants alone to model toxin activity, and a convergence-based bacterial genome-wide association study (GWAS) to identify correlations between non-PaLoc loci with changes in toxin activity. Combined, these data support a model of C. difficile disease wherein toxin activity may be strongly affected by many non-PaLoc loci. Additionally, we characterize multiple other in vitro phenotypes relevant to human infections including germination and sporulation. These phenotypes vary greatly in their clonality, variability, convergence, and concordance with genomic variation. Lastly, we highlight the intersection of loci identified by GWAS for different phenotypes and clinical severity. This strategy to identify the overlapping loci can facilitate the identification of genetic variation linking phenotypic variation to clinical outcomes. IMPORTANCEClostridioides difficile has two major disease mediating toxins, A and B, encoded within the pathogenicity locus (PaLoc). In this study we demonstrate via multiple approaches that genomic variants outside of the PaLoc are associated with changes in toxin activity. These genomic variants may provide new avenues of exploration in the hunt for novel disease modifying interventions. Additionally, we provide insight into the evolution of several additional phenotypes also critical to clinical infection such as sporulation, germination, and growth rate. These in vitro phenotypes display a range of responses to evolutionary pressures and as such vary in their appropriateness for certain bacterial genome wide association study approaches. We used a convergence-based association method to identify the genomic variants most correlated with both changes in these phenotypes and disease severity. These overlapping loci may be important to both bacterial function and human clinical disease.

microbiology↗

bioRxiv2021

Ferric Citrate Uptake is a Virulence Factor in Uropathogenic Escherichia coli

More than half of women will experience a urinary tract infection (UTI) with uropathogenic Escherichia coli (UPEC) causing [~]80% of uncomplicated cases. Iron acquisition systems are essential for uropathogenesis, and UPEC encode functionally redundant iron acquisition systems, underlining their importance. However, a recent UPEC clinical isolate, HM7 lacks this functional redundancy and instead encodes a sole siderophore, enterobactin. To determine if E. coli HM7 possesses unidentified iron acquisition systems, we performed RNA-sequencing under iron-limiting conditions and demonstrated that the ferric citrate uptake system (fecABCDE and fecIR) was highly upregulated. Importantly, there are high levels of citrate within urine, some of which is bound to iron, and the fec system is highly enriched in UPEC isolates compared to environmental or fecal strains. Therefore, we hypothesized that HM7 and other similar strains use the fec system to acquire iron in the host. Deletion of both enterobactin biosynthesis and ferric citrate uptake ({Delta}entB/{Delta}fecA) abrogates use of ferric citrate as an iron source and fecA provides an advantage in human urine in absence of enterobactin. However, in a UTI mouse model, fecA is a fitness factor independent of enterobactin production, likely due to the action of host Lipocalin-2 chelating ferrienterobactin. These findings indicate that ferric citrate uptake is used as an iron source when siderophore efficacy is limited, such as in the host during UTI. Defining these novel compensatory mechanisms and understanding the nutritional hierarchy of preferred iron sources within the urinary tract are important in the search for new approaches to combat UTI. ImportanceUPEC, the primary causative agent of uncomplicated UTI is responsible for five billion dollars in healthcare costs in the US each year. Rates of antibiotic resistance are on the rise therefore it is vital to understand the mechanisms of UPEC pathogenesis to uncover potential targets for novel therapeutics. Iron acquisition systems used to obtain iron from sequestered host sources are essential for UPEC survival during UTI and have been used as vaccine targets to prevent infection. This study reveals the ferric citrate uptake system is another important iron acquisition system that is highly enriched in UPEC strains. Ferric citrate uptake has not previously been associated with these pathogenic isolates, underlining the importance of the continued study of these strains to fully understand their mechanisms of pathogenesis.

microbiology↗

bioRxiv2021

Phenotypic and genomic diversification in complex carbohydrate degrading human gut bacteria

Symbiotic bacteria are responsible for the majority of complex carbohydrate digestion in the human colon. Since the identities and amounts of dietary polysaccharides directly impact the gut microbiota, determining which microorganisms consume specific nutrients is central to defining the relationship between diet and gut microbial ecology. Using a custom phenotyping array, we determined carbohydrate utilization profiles for 354 members of the Bacteroidetes, a dominant saccharolytic phylum. There was wide variation in the numbers and types of substrates degraded by individual bacteria, but phenotype-based clustering grouped members of the same species indicating that each species performs characteristic roles. The ability to utilize dietary polysaccharides and endogenous mucin glycans was negatively correlated, suggesting exclusion between these niches. By analyzing related Bacteroides ovatus/xylanisolvens strains that vary in their ability to utilize mucin glycans, we addressed whether gene clusters that confer this complex, multi-locus trait are being gained or lost in individual strains. Pangenome reconstruction of these strains revealed a remarkably mosaic architecture in which genes involved in polysaccharide metabolism are highly variable and bioinformatics data provide evidence of interspecies gene transfer that might explain this genomic heterogeneity. Global transcriptomic analyses suggest that the ability to utilize mucin has been lost in some lineages of B. ovatus and B. xylanisolvens, which still harbor residual gene clusters that are involved in mucin utilization by strains that still actively express this phenotype. Our data provide insight into the breadth and complexity of carbohydrate metabolism in the microbiome and the underlying genomic events that shape these behaviors.

microbiology↗

bioRxiv2020

Strain population structure varies widely across bacterial species and predicts strain colonization in unrelated individuals

The population structure of strains within a bacterial species is poorly defined, despite the functional importance of strain variation in the human gut microbiota on health. Here we analyzed >1000 sequenced bacterial strains from the fecal microbiota of 47 individuals from two countries and combined them with >150,000 bacterial genomes from NCBI to quantify the strain population size of different bacterial species, as well as the frequency of finding the same strain colonized in unrelated individuals who had no opportunities for direct microbial strain transmission. Strain population sizes ranged from tens to over one-hundred thousand per species. Prevalent strains in common gut microbiota species with small population sizes were the most likely to be harbored in two or more unrelated individuals. The finite strain population size of certain species creates the opportunity to comprehensively sequence the entirety of these species prevalent strains and associate their presence in different individuals with health outcomes.

microbiology↗

bioRxiv2020

cognac: rapid generation of concatenated gene alignments for phylogenetic inferencefrom large whole genome sequencing datasets

The quantity of genomic data is expanding at an increasing rate. Tools for phylogenetic analysis which scale to the quantity of available data are required. We present cognac, a user-friendly software package to rapidly generate concatenated gene alignments for phylogenetic analysis. We applied this tool to generate core gene alignments for very large genomic datasets, including a dataset of over 11,000 genomes from the genus Escherichia containing 1,353 genes, which was constructed in less than 17 hours. We have released cognac as an R package (https://github.com/rdcrawford/cognac) with customizable parameters for adaptation to diverse applications.

genomics↗

bioRxiv2020

hogwash: Three Methods for Genome-Wide Association Studies in Bacteria

Bacterial genome-wide association studies (bGWAS) capture associations between genomic variation and phenotypic variation. Convergence based bGWAS methods identify genomic mutations that occur independently multiple times on the phylogenetic tree in the presence of phenotypic variation more often than is expected by chance. This work introduces hogwash, an open source R package that implements three algorithms for convergence based bGWAS. Hogwash additionally contains two burden testing approaches to perform gene- or pathway-analysis to improve power and increase convergence detection for related but weakly penetrant genotypes. To identify optimal use cases, we applied hogwash to data simulated with a variety of phylogenetic signals and convergence distributions. These simulated data are publicly available and contain the relevant metadata regarding convergence and phylogenetic signal for each phenotype and genotype. Hogwash is available for download from GitHub. DATA SUMMARYO_LIhogwash is available from GitHub under the MIT license (https://github.com/katiesaund/hogwash) and can be installed using the R commands install.packages("devtools") devtools::install_github("katiesaund/hogwash") C_LIO_LIThe simulated data used in this manuscript and the code to generate it are available from GitHub (https://github.com/katiesaund/simulate_data_for_convergence_based_bGWAS) C_LI IMPACT STATEMENTWe introduce hogwash, an R package with three methods for bacterial genome-wide association studies. There are two methods for handling binary phenotypes, including an implementation of PhyC(1), as well as one method for handling continuous phenotypes. We formulate novel indices quantifying the relationship between phenotype convergence and genotype convergence on a phylogenetic tree. These indices shape an intuitive understanding for the ability of hogwash to detect significant intersections of phenotype convergence and genotype convergence and how to interpret hogwash outputs.

microbiology↗

bioRxiv2019

prewas: Data pre-processing for more informative bacterial GWAS

While variant identification pipelines are becoming increasingly standardized, less attention has been paid to the pre-processing of variants prior to their use in bacterial genome-wide association studies (bGWAS). Three nuances of variant pre-processing that impact downstream identification of genetic associations include the separation of variants at multiallelic sites, separation of variants in overlapping genes, and referencing of variants relative to ancestral alleles. Here we demonstrate the importance of these variant pre-processing steps on diverse bacterial genomic datasets and present prewas, an R package, that standardizes the pre-processing of multiallelic sites, overlapping genes, and reference alleles before bGWAS. This package facilitates improved reproducibility and interpretability of bGWAS results. Prewas enables users to extract maximal information from bGWAS by implementing multi-line representation for multiallelic sites and variants in overlapping genes. Prewas outputs a binary SNP matrix that can be used for SNP-based bGWAS and will prevent the masking of minor alleles during bGWAS analysis. The optional binary gene matrix output can be used for gene-based bGWAS which will enable users to maximize the power and evolutionary interpretability of their bGWAS studies. Prewas is available for download from GitHub. DATA SUMMARYO_LIprewas is available from GitHub under the MIT License (URL: https://github.com/Snitkin-Lab-Umich/prewas) and can be installed using the command devtools::install_github("Snitkin-Lab-Umich/prewas") C_LIO_LICode to perform analyses is available from GitHub under the MIT License (URL: https://github.com/Snitkin-Lab-Umich/prewas_manuscript_analysis) C_LIO_LIAll genomes are publicly available on NCBI (see Table S1 for more details) C_LI O_TBL View this table: org.highwire.dtl.DTLVardef@137f5b6org.highwire.dtl.DTLVardef@e4a12dorg.highwire.dtl.DTLVardef@11b2a3org.highwire.dtl.DTLVardef@1e71da1org.highwire.dtl.DTLVardef@4a7286_HPS_FORMAT_FIGEXP M_TBL O_FLOATNOTable S1:C_FLOATNO O_TABLECAPTIONSources for bacterial datasets C_TABLECAPTION C_TBL IMPACT STATEMENTIn between variant calling and performing bacterial genome-wide association studies (bGWAS) there are many decisions regarding processing of variants that have the potential to impact bGWAS results. We discuss the benefits and drawbacks of various variant pre-processing decisions and present the R package prewas to standardize single nucleotide polymorphism (SNP) pre-processing, specifically to incorporate multiallelic sites and prepare the data for gene-based analyses. We demonstrate the importance of these considerations by highlighting the prevalence of multiallelic sites and SNPs in overlapping genes within diverse bacterial genomes and the impact of reference allele choice on gene-based analyses.

bioinformatics↗

bioRxiv2019

Evidence that vertical transmission of the vaginal microbiota can persist into adolescence

BackgroundFactors that influence vaginal microbiota composition, including its source, are not well understood. To determine if vaginal microbiota transmission from mother to daughter at birth influences the human vaginal microbiota composition in adolescence, we investigated the relationship between the vaginal microbiota of 13 mother/daughter pairs and the daughters birth mode. ResultsBased on analysis of bacterial 16S rRNA gene sequences, the vaginal microbiotas of mother/daughter pairs were more similar to each other if the daughter was born by vaginal delivery rather than by C-section. Additionally, genome sequences from an important member of the vaginal microbiota, Lactobacillus crispatus, isolated from one mother/daughter pair in which the daughter was born by vaginal delivery, were highly similar. ConclusionsBoth community-level analysis and isolate genome sequence analysis are consistent with birth-mode dependent transmission and persistence of at least some members of the vaginal microbiota. ImportanceThe composition of the human vaginal microbiota is related to many aspects of health from infection susceptibility to preterm birth. Our study provides evidence that transmission of vaginal bacteria from mother to daughter at birth may be an important factor influencing vaginal microbiota composition into adolescence.

microbiology↗

bioRxiv2019

Genetically diverse uropathogenic Escherichia coli adopt a common transcriptional program in patients with urinary tract infections

Uropathogenic Escherichia coli (UPEC) is the major causative agent of uncomplicated urinary tract infections (UTIs). A common virulence genotype of UPEC strains responsible for UTIs is yet to be defined, due to the large variation of virulence factors observed in UPEC strains. We hypothesized that studying UPEC functional responses in patients might reveal universal UPEC features that enable pathogenesis. Here we identify a transcriptional program shared by genetically diverse UPEC strains isolated from 14 patients during uncomplicated UTIs. Strikingly, this in vivo gene expression program is marked by upregulation of translational machinery, providing a mechanism for the rapid growth within the host. Our analysis indicates that switching to a more specialized catabolism and scavenging lifestyle in the host allows for the increased translational output. Our study identifies a common transcriptional program underlying UTIs and illuminates the molecular underpinnings that likely facilitate the fast growth rate of UPEC in infected patients.

microbiology↗

bioRxiv2019

Outbreak of murine infection with Clostridium difficile associated with the administration of a pre- and peri-natal methyl-donor diet

Between October 2016 and June 2017, a C57BL/6J mouse colony that was undergoing a pre- and peri-natal methyl-donor supplementation diet intervention to study the impact of parental nutrition on offspring susceptibility to disease was found to suffer from an epizootic of unexpected deaths. Necropsy revealed the presence of severe colitis, and further investigation linked these outbreak deaths to a Clostridium difficile strain of ribotype 027 we term 16N203. C. difficile infection (CDI) is associated with antibiotic use in humans. Current murine models of CDI rely on antibiotic pretreatment to establish clinical phenotypes. In this report, the C. difficile outbreak occurs in F1 mice linked to alterations in the parental diet. The diagnosis of CDI in the affected mice was confirmed by cecal/colonic histopathology, presence of C. difficile bacteria in fecal/colonic culture, and detection of C. difficile toxins. F1 mice from parents fed the methyl-supplementation diet also had significantly reduced survival (p<0.0001) than F1 mice from parents fed the control diet. When we tested the 16N203 outbreak strain in an established mouse model of antibiotic-induced CDI, we confirmed that this strain is pathogenic. Our serendipitous observations from this spontaneous outbreak of C. difficile in association with a pre- and perinatal methyl-donor diet suggest the important role diet may play in host defense and CDI risk factors.\n\nImportanceClostridium difficile infection (CDI) has become the leading cause of infectious diarrhea in hospitals worldwide, owing its preeminence to the emergence of hyperendemic strains, such as ribotype 027 (RT027). A major CDI risk factor is antibiotic exposure which alters gut microbiota, resulting in the loss of colonization resistance. Current murine models of CDI also depend on pretreatment of antibiotics of animals to establish disease. The outbreak we report here is unique in that the CDI occurred in mice with no antibiotic exposure and is associated to a pre- and peri-natal methyl-supplementation donor diet intervention study. Our investigation subsequently reveals that the outbreak strain we term 16N203 is an RT027 strain, and this isolated strain is also pathogenic in an established murine model of CDI (with antibiotics). Our report of this spontaneous outbreak offers additional insight into the importance of environmental factors, such as diet, and CDI susceptibility.

epidemiology↗