Mycobacterium tuberculosis DosR regulon gene Rv2004c contributes to streptomycin resistance and intracellular survival.

Tuberculosis (TB) is the deadly infectious disease challenging the public health globally and its impact is further aggravated by co-infection with HIV and the emergence of drug resistant strains of Mycobacterium tuberculosis. In this study, we attempted to characterise the Rv2004c encoded protein, a member of DosR regulon, for its role in drug resistance. In silico docking analysis revealed that Rv2004c binds with streptomycin (SM). Phosphotransferase assay demonstrated that Rv2004c possibly mediates SM resistance through the aminoglycoside phosphotransferase activity. Further, E. coli expressing Rv2004c conferred resistance to 100µM of SM in liquid broth cultures indicating a mild aminoglycoside phosphotransferase activity of Rv2004c. Moreover, we investigated the role of MSMEG_3942 (an orthologous gene of Rv2004c) encoded protein in intracellular survival, its effect on in-vitro growth and its expression in different stress conditions by over expressing it in Mycobacterium smegmatis (M. smegmatis). MSMEG_3942 overexpressing recombinant M. smegmatis strains grew faster in acidic medium and also showed higher bacillary counts in infected macrophages when compared to M. smegmatis transformed with vector alone. Our results are likely to contribute to the better understanding of the involvement of Rv2004c in partial drug resistance, intracellular survival and adaptation of bacilli to stress conditions.

Genome Dynamics and Molecular Infection Epidemiology of Multidrug-Resistant Helicobacter pullorum Isolates Obtained from Broiler and Free-Range Chickens in India.

Some life-threatening, foodborne, and zoonotic infections are transmitted through poultry birds. Inappropriate and indiscriminate use of antimicrobials in the livestock industry has led to an increased prevalence of multidrug-resistant bacteria with epidemic potential. Here, we present a functional molecular epidemiological analysis entailing the phenotypic and whole-genome sequence-based characterization of 11 H. pullorum isolates from broiler and free-range chickens sampled from retail wet markets in Hyderabad City, India. Antimicrobial susceptibility tests revealed all of the isolates to be resistant to multiple antibiotic classes such as fluoroquinolones, cephalosporins, sulfonamides, and macrolides. The isolates were also found to be extended-spectrum ß-lactamase producers and were even resistant to clavulanic acid. Whole-genome sequencing and comparative genomic analysis of these isolates revealed the presence of five or six well-characterized antimicrobial resistance genes, including those encoding a resistance-nodulation-division efflux pump(s). Phylogenetic analysis combined with pan-genome analysis revealed a remarkable degree of genetic diversity among the isolates from free-range chickens; in contrast, a high degree of genetic similarity was observed among broiler chicken isolates. Comparative genomic analysis of all publicly available H. pullorum genomes, including our isolates (n = 16), together with the genomes of 17 other Helicobacter species, revealed a high number (8,560) of H. pullorum-specific protein-encoding genes, with an average of 535 such genes per isolate. In silico virulence screening identified 182 important virulence genes and also revealed high strain-specific gene content in isolates from free-range chickens (average, 34) compared to broiler chicken isolates. A significant prevalence of prophages (ranging from 1 to 9) and a significant presence of genomic islands (0 to 4) were observed in free-range and broiler chicken isolates. Taken together, these observations provide significant baseline data for functional molecular infection epidemiology of nonpyloric Helicobacter species such as H. pullorum by unraveling their evolution in chickens and their possible zoonotic transmission to humans. IMPORTANCE: Globally, the poultry industry is expanding with an ever-growing consumer base for chicken meat. Given this, food-associated transmission of multidrug-resistant bacteria represents an important health care issue. Our study involves a critical baseline approach directed at genome sequence-based epidemiology and transmission dynamics of H. pullorum, a poultry pathogen having established zoonotic potential. We believe our studies would facilitate the development of surveillance systems that ensure the safety of food for humans and guide public health policies related to the use of antibiotics in animal feed in countries such as India. We sequenced 11 new genomes of H. pullorum as a part of this study. These genomes would provide much value in addition to the ongoing comparative genomic studies of helicobacters.

Comparative genomic analysis of Helicobacter pylori from Malaysia identifies three distinct lineages suggestive of differential evolution.

The discordant prevalence of Helicobacter pylori and its related diseases, for a long time, fostered certain enigmatic situations observed in the countries of the southern world. Variation in H. pylori infection rates and disease outcomes among different populations in multi-ethnic Malaysia provides a unique opportunity to understand dynamics of host-pathogen interaction and genome evolution. In this study, we extensively analyzed and compared genomes of 27 Malaysian H. pylori isolates and identified three major phylogeographic lineages: hspEastAsia, hpEurope and hpSouthIndia. The analysis of the virulence genes within the core genome, however, revealed a comparable pathogenic potential of the strains. In addition, we identified four genes limited to strains of East-Asian lineage. Our analyses identified a few strain-specific genes encoding restriction modification systems and outlined 311 core genes possibly under differential evolutionary constraints, among the strains representing different ethnic groups. The cagA and vacA genes also showed variations in accordance with the host genetic background of the strains. Moreover, restriction modification genes were found to be significantly enriched in East-Asian strains. An understanding of these variations in the genome content would provide significant insights into various adaptive and host modulation strategies harnessed by H. pylori to effectively persist in a host-specific manner.

Next-generation sequencing and de novo assembly, genome organization, and comparative genomic analyses of the genomes of two Helicobacter pylori isolates from duodenal ulcer patients in India.

The prevalence of different H. pylori genotypes in various geographical regions indicates region-specific adaptations during the course of evolution. Complete genomes of H. pylori from countries with high infection burdens, such as India, have not yet been described. Herein we present genome sequences of two H. pylori strains, NAB47 and NAD1, from India. In this report, we briefly mention the sequencing and finishing approaches, genome assembly with downstream statistics, and important features of the two draft genomes, including their phylogenetic status. We believe that these genome sequences and the comparative genomics emanating thereupon will help us to clearly understand the ancestry and biology of the Indian H. pylori genotypes, and this will be helpful in solving the so-called Indian enigma, by which high infection rates do not corroborate the minuscule number of serious outcomes observed, including gastric cancer.

Insights from the genome sequence of a Salmonella enterica serovar Typhi strain associated with a sporadic case of typhoid fever in Malaysia.

Salmonella enterica serovar Typhi is the causative agent of typhoid fever, which causes nearly 21.7 million illnesses and 217,000 deaths globally. Herein, we describe the whole-genome sequence of the Salmonella Typhi strain ST0208, isolated from a sporadic case of typhoid fever in Kuala Lumpur, Malaysia. The whole-genome sequence and comparative genomics allow an in-depth understanding of the genetic diversity, and its link to pathogenicity and evolutionary dynamics, of this highly clonal pathogen that is endemic to Malaysia.

Genetic fine structure of a Salmonella enterica serovar Typhi strain associated with the 2005 outbreak of typhoid fever in Kelantan, Malaysia.

Among enteric pathogens, Salmonella enterica serovar Typhi is responsible for the largest number of food-borne outbreaks and fatalities. The ability of the pathogen to cause systemic infection for extended durations leads to a high cost of disease control. Chronic carriers play important roles in the evolution of Salmonella Typhi; therefore, identification and in-depth characterization of isolates from clinical cases and carriers, especially those from zones of endemicity where the pathogen has not been extensively studied, are necessary. Here, we describe the genome sequence of the highly virulent Salmonella Typhi strain BL196/05 isolated during the outbreak of typhoid in Kelantan, Malaysia, in 2005. The whole-genome sequence and comparative genomics of this strain should enable us to understand the virulence mechanisms and evolutionary dynamics of this pathogen in Malaysia and elsewhere.

Genome sequence and comparative pathogenomics analysis of a Salmonella enterica Serovar Typhi strain associated with a typhoid carrier in Malaysia.

Salmonella enterica serovar Typhi is a human pathogen that causes typhoid fever predominantly in developing countries. In this article, we describe the whole genome sequence of the S. Typhi strain CR0044 isolated from a typhoid fever carrier in Kelantan, Malaysia. These data will further enhance the understanding of its host persistence and adaptive mechanism.

Whole-genome sequences and comparative genomics of Salmonella enterica serovar Typhi isolates from patients with fatal and nonfatal typhoid fever in Papua New Guinea.

Many of the developing countries of the Southeast Asian region are significantly affected by endemic typhoid fever, possibly as a result of marginal living standards. It is an important public health problem in countries such as Papua New Guinea, which is geographically close to some of the foci of endemicity in Asia. The severity of the disease varies in different regions, and this may be attributable to genetic diversity among the native strains. Genome sequence data on strains from different countries are needed to clearly understand their genetic makeup and virulence potential. We describe the genomes of two Salmonella Typhi isolates from patients with fatal and nonfatal cases of typhoid fever in Papua New Guinea. We discuss in brief the underlying sequencing methodology, assembly, genome statistics, and important features of the two draft genomes, which form an essential step in our functional molecular infection epidemiology program centering on typhoid fever. The comparative genomics of these and other isolates would enable us to identify genetic rearrangements and mechanisms responsible for endemicity and the differential severity of pathogenic salmonellae in Papua New Guinea and elsewhere.

Genome of multidrug-resistant uropathogenic Escherichia coli strain NA114 from India.

Uropathogenic Escherichia coli (UPEC) causes serious infections in people at risk and has a significant environmental prevalence due to contamination by human and animal excreta. In developing countries, UPEC assumes importance in certain dwellings because of poor community/personal hygiene and exposure to contaminated water or soil. We report the complete genome sequence of E. coli strain NA114 from India, a UPEC strain with a multidrug resistance phenotype and the capacity to produce extended-spectrum beta-lactamase. The genome sequence and comparative genomics emanating from it will be significant in under-standing the genetic makeup of diverse UPEC strains and in boosting the development of new diagnostics/vaccines.

Genomes of two chronological isolates (Helicobacter pylori 2017 and 2018) of the West African Helicobacter pylori strain 908 obtained from a single patient.

The diverse clinical outcomes of colonization by Helicobacter pylori reflect the need to understand the genomic rearrangements enabling the bacterium to adapt to host niches and exhibit varied colonization/virulence potential. We describe the genome sequences of the two serial isolates, H. pylori 2017 and 2018 (the chronological subclones of H. pylori 908), cultured in 2003 from the antrum and corpus, respectively, of an African patient who suffered from recrudescent duodenal ulcer disease. When compared with the genome of the parent strain, 908 (isolated from the antrum of the same patient in 1994), the genome sequences revealed genomic alterations relevant to virulence optimization or host-specific adaptation.

Genome of a novel isolate of Paracoccus denitrificans capable of degrading N,N-dimethylformamide.

The bacterial genus Paracoccus is comprised of metabolically versatile organisms having diverse degradative capabilities and potential industrial and environmental applications for bioremediation in particular. We report a de novo-assembled sequence and annotation of the genome of a novel isolate of Paracoccus denitrificans originally sourced from coal mine tailings in India. The isolate was capable of utilizing N,N-dimethylformamide (DMF) as a source of carbon and nitrogen and therefore holds potential for bioremediation and mineralization of industrial pollutants. The genome sequence and biological circuitry revealed thereupon will be invaluable in understanding the metabolic capabilities, functioning, and evolution of this important bacterial organism.

Evolutionary Dynamics Based on Comparative Genomics of Pathogenic Escherichia coli Lineages Harboring Polyketide Synthase (pks) Island.

The genotoxin colibactin is a secondary metabolite produced by the polyketide synthase (pks) island harbored by extraintestinal pathogenic E. coli (ExPEC) and other members of the Enterobacteriaceae that has been increasingly reported to have critical implications in human health. The present study entails a high-throughput whole-genome comparison and phylogenetic analysis of such pathogenic E. coli isolates to gain insights into the patterns of distribution, horizontal transmission, and evolution of the island. For the current study, 23 pks-positive ExPEC genomes were newly sequenced, and their virulome and resistome profiles indicated a preponderance of virulence encoding genes and a reduced number of genes for antimicrobial resistance. In addition, 4,090 E. coli genomes from the public domain were also analyzed for large-scale screening for pks-positive genomes, out of which a total of 530 pks-positive genomes were studied to understand the subtype-based distribution pattern(s). The pks island showed a significant association with the B2 phylogroup (82.2%) and a high prevalence in sequence type 73 (ST73; n = 179) and ST95 (n = 110) and the O6:H1 (n = 110) serotype. Maximum-likelihood (ML) phylogeny of the core genome and intergenic regions (IGRs) of the ST95 model data set, which was selected because it had both pks-positive and pks-negative genomes, displayed clustering in relation to their carriage of the pks island. Prevalence patterns of genes encoding RM systems in the pks-positive and pks-negative genomes were also analyzed to determine their potential role in pks island acquisition and the maintenance capability of the genomes. Further, the maximum-likelihood phylogeny based on the core genome and pks island sequences from 247 genomes with an intact pks island demonstrated horizontal gene transfer of the island across sequence types and serotypes, with few exceptions. This study vitally contributes to understanding of the lineages and subtypes that have a higher propensity to harbor the pks island-encoded genotoxin with possible clinical implications.IMPORTANCE Extraintestinal pathologies caused by highly virulent strains of E. coli amount to clinical implications with high morbidity and mortality rates. Pathogenic E. coli strains are evolving with the horizontal acquisition of mobile genetic elements, including pathogenicity islands such as the pks island, which produces the genotoxin colibactin, resulting in severe clinical outcomes, including colorectal cancer progression. The current study encompasses high-throughput comparative genomics and phylogenetic analyses to address the questions pertaining to the acquisition and evolution pattern of the genomic island in different E. coli subtypes. It is crucial to gain insights into the distribution, transfer, and maintenance of pathogenic islands, as they harbor multiple virulence genes involved in pathogenesis and clinical implications of the infection.

Genome Dynamics of Vibrio cholerae Isolates Linked to Seasonal Outbreaks of Cholera in Dhaka, Bangladesh.

The temporal switching of serotypes from serotype Ogawa to Inaba and back to Ogawa was identified in Vibrio cholerae O1, which was responsible for seasonal outbreaks of cholera in Dhaka during the period 2015 to 2018. In order to delineate the factors responsible for this serotype transition, we performed whole-genome sequencing (WGS) of V. cholerae O1 multidrug-resistant strains belonging to both the serotypes that were isolated during this interval where the emergence and subsequent reduction of the Inaba serotype occurred. The whole-genome-based phylogenetic analysis revealed clonal expansion of the Inaba isolates mainly responsible for the peaks of infection during 2016 to 2017 and that they might have evolved from the prevailing Ogawa strains in 2015 which coclustered with them. Furthermore, the wbeT gene in these Inaba serotype isolates was inactivated due to insertion of a transposable element at the same position signifying the clonal expansion. Also, V. cholerae isolates in the Inaba serotype dominant clade mainly contained classical ctxB allele and revealed differences in the genetic composition of Vibrioseventh pandemic island II (VSP-II) and the SXT integrative and conjugative element (SXT-ICE) compared to those of Ogawa serotype strains which remerged in 2018. The variable presence of phage-inducible chromosomal island-like element 1 (PLE1) was also noted in the isolates of the Inaba serotype dominant clade. The detailed genomic characterization of the sequenced isolates has shed light on the forces which could be responsible for the periodic changes in serotypes of V. cholerae and has also highlighted the need to analyze the mobilome in greater detail to obtain insights into the mechanisms behind serotype switching.IMPORTANCE The switching of serotype from Ogawa to Inaba and back to Ogawa has been observed temporally in Vibrio cholerae O1, which is responsible for endemic cholera in Bangladesh. The serospecificity is key for effective intervention and for preventing cholera, a deadly disease that continues to cause significant morbidity and mortality worldwide. In the present study, WGS of V. cholerae allowed us to better understand the factors associated with the serotype switching events observed during 2015 to 2018. Genomic data analysis of strains isolated during this interval highlighted variations in the genes ctxB, tcpA, and rtxA and also identified significant differences in the genetic content of the mobilome, which included key elements such as SXT ICE, VSP-II, and PLE. Our results indicate that selective forces such as antibiotic resistance and phage resistance might contribute to the clonal expansion and predominance of a particular V. cholerae serotype responsible for an outbreak.

Prevalence of Shigella boydii in Bangladesh: Isolation and Characterization of a Rare Phage MK-13 That Can Robustly Identify Shigellosis Caused by Shigella boydii Type 1.

Shigellosis, caused by Shigella boydii type 1, is understudied and underreported. For 3 years, GEMS study identified 5.4% of all Shigella as S. boydii. We showed the prevalent serotypes of S. boydii in Bangladesh and phage-based diagnosis of S. boydii type 1, a rapid and low-cost approach. Previously typed 793 clinical S. boydii strains were used for serotype distribution. Twenty-eight environmental water samples were collected for isolation of Shigella phages. Forty-eight serotypes of Shigella and other enteric bacteria were used for testing the susceptibility to phage MK-13. Electron microscopy, restriction enzyme analysis, whole genome sequencing (WGS), and annotation were performed for extensive characterization. S. boydii type 1 is the second most prevalent serotype among 20 serotypes of S. boydii in Bangladesh. We isolated a novel phage, MK-13, which specifically lyses S. boydii type 1, but doesn't lyse other 47 serotypes of Shigella or other enteric bacteria tested. The phage belongs to the Myoviridae family and distinct from other phages indicated by electron microscopy and restriction enzyme analysis, respectively. MK-13 genome consists of 158 kbp of circularly permuted double-stranded DNA with G + C content of 49.45%, and encodes 211 open reading frames including four tRNA-coding regions. The genome has 98% identity with previously reported phage, ΦSboM-AG3, reported to have a broader host range infecting most of the S. boydii and other species of Shigella tested. To our knowledge, MK-13 is the first phage reported to be used as a diagnostic marker to detect S. boydii type 1, especially in remote settings with limited laboratory infrastructure.

Molecular Genetic and Functional Analysis of pks-Harboring, Extra-Intestinal Pathogenic Escherichia coli From India.

Colibactin, a genotoxin, encoded by the pks pathogenicity island of Escherichia coli belonging to the B2 phylogroup has been reported as a determinant of bacterial pathogenicity. The present study was carried out to detect the pks pathogenicity island in extraintestinal pathogenic E. coli (ExPEC) isolated from a tertiary hospital in Pune, India. Of 462 isolates analyzed, the pks genomic island was detected in 35 (7.6%) isolates, which predominantly belonged to pathogenic phylogroup B2 (97%), and harbored virulence genes such as fimH, sfaD/E, and usp. Biofilm formation assay revealed 21 of the 35 pks-carrying isolates to be strong (SBF > 1.0), 10 isolates to be moderate (SBF = 0.5-1.0), and 4 as weak (SBF < 0.5) biofilm formers. All of the pks-carrying isolates proved resistant against bactericidal activity of human serum. Assays carried out to detect antimicrobial susceptibility revealed 11% of these isolates to be multidrug resistant, 37% producing ESBL and 25% were positive for bla CTX-M-15. The observed prevalence of multidrug resistance and colibactin producing characteristics among pathogenic E. coli belonging to phylogenetic group B2 advocate urgent need for broader surveillance in order to understand and prevent transmission of these ExPEC in community and hospital settings.

Author Correction: Analysis of mutations in pncA reveals non-overlapping patterns among various lineages of Mycobacterium tuberculosis.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

Analysis of mutations in pncA reveals non-overlapping patterns among various lineages of Mycobacterium tuberculosis.

Pyrazinamide (PZA) is an important first-line anti-tuberculosis drug, resistance to which occurs primarily due to mutations in pncA (Rv2043c) that encodes the pyrazinamidase enzyme responsible for conversion of pro-drug PZA into its active form. Previous studies have reported numerous resistance-conferring mutations distributed across the entire length of pncA without any hotspot regions. As different lineages of Mycobacterium tuberculosis display a strong geographic association, we sought to understand whether the genetic background influenced the distribution of mutations in pncA. We analyzed the whole genome sequence data of 1,480 clinical isolates representing four major M. tuberculosis lineages to identify the distribution of mutations in the complete operon (Rv2044c-pncA-Rv2042c) and its upstream promoter region. We observed a non-overlapping pattern of mutations among various lineages and identified a lineage 3-specific frame-shift deletion in gene Rv2044c upstream of pncA that disrupted the stop codon and led to its fusion with pncA. This resulted in the addition of a novel domain of unknown function (DUF2784) to the pyrazinamidase enzyme. The variant molecule was computationally modelled and physico-chemical parameters determined to ascertain stability. Although the functional impact of this mutation remains unknown, its lineage specific nature highlights the importance of genetic background and warrants further study.

Risk of Transmission of Antimicrobial Resistant Escherichia coli from Commercial Broiler and Free-Range Retail Chicken in India.

Multidrug-resistant Escherichia coli infections are a growing public health concern. This study analyzed the possibility of contamination of commercial poultry meat (broiler and free-range) with pathogenic and or multi-resistant E. coli in retail chain poultry meat markets in India. We analyzed 168 E. coli isolates from broiler and free-range retail poultry (meat/ceca) sampled over a wide geographical area, for their antimicrobial sensitivity, phylogenetic groupings, virulence determinants, extended-spectrum-ß-lactamase (ESBL) genotypes, fingerprinting by Enterobacterial Repetitive Intergenic Consensus (ERIC) PCR and genetic relatedness to human pathogenic E. coli using whole genome sequencing (WGS). The prevalence rates of ESBL producing E. coli among broiler chicken were: meat 46%; ceca 40%. Whereas, those for free range chicken were: meat 15%; ceca 30%. E. coli from broiler and free-range chicken exhibited varied prevalence rates for multi-drug resistance (meat 68%; ceca 64% and meat 8%; ceca 26%, respectively) and extraintestinal pathogenic E. coli (ExPEC) contamination (5 and 0%, respectively). WGS analysis confirmed two globally emergent human pathogenic lineages of E. coli, namely the ST131 (H30-Rx subclone) and ST117 among our poultry E. coli isolates. These results suggest that commercial poultry meat is not only an indirect public health risk by being a possible carrier of non-pathogenic multi-drug resistant (MDR)-E. coli, but could as well be the carrier of human E. coli pathotypes. Further, the free-range chicken appears to carry low risk of contamination with antimicrobial resistant and extraintestinal pathogenic E. coli (ExPEC). Overall, these observations reinforce the understanding that poultry meat in the retail chain could possibly be contaminated by MDR and/or pathogenic E. coli.

Comparative Genomic Analysis of Globally Dominant ST131 Clone with Other Epidemiologically Successful Extraintestinal Pathogenic Escherichia coli (ExPEC) Lineages.

Escherichia coli sequence type 131 (ST131), a pandemic clone responsible for the high incidence of extraintestinal pathogenic E. coli (ExPEC) infections, has been known widely for its contribution to the worldwide dissemination of multidrug resistance. Although other ExPEC-associated and extended-spectrum-ß-lactamase (ESBL)-producing E. coli clones, such as ST38, ST405, and ST648 have been studied widely, no comparative genomic data with respect to other genotypes exist for ST131. In this study, comparative genomic analysis was performed for 99 ST131 E. coli strains with 40 genomes from three other STs, including ST38 (n = 12), ST405 (n = 10), and ST648 (n = 18), and functional studies were performed on five in-house strains corresponding to the four STs. Phylogenomic analysis results from this study corroborated with the sequence type-specific clonality. Results from the genome-wide resistance profiling confirmed that all strains were inherently multidrug resistant. ST131 genomes showed unique virulence profiles, and analysis of mobile genetic elements and their associated methyltransferases (MTases) has revealed that several of them were missing from the majority of the non-ST131 strains. Despite the fact that non-ST131 strains lacked few essential genes belonging to the serum resistome, the in-house strains representing all four STs demonstrated similar resistance levels to serum antibactericidal activity. Core genome analysis data revealed that non-ST131 strains usually lacked several ST131-defined genomic coordinates, and a significant number of genes were missing from the core of the ST131 genomes. Data from this study reinforce adaptive diversification of E. coli strains belonging to the ST131 lineage and provide new insights into the molecular mechanisms underlying clonal diversification of the ST131 lineage.IMPORTANCEE. coli, particularly the ST131 extraintestinal pathogenic E. coli (ExPEC) lineage, is an important cause of community- and hospital-acquired infections, such as urinary tract infections, surgical site infections, bloodstream infections, and sepsis. The treatment of infections caused by ExPEC has become very challenging due to the emergence of resistance to the first-line as well as the last-resort antibiotics. This study analyzes E. coli ST131 against three other important and globally distributed ExPEC lineages (ST38, ST405, and ST648) that also produced extended-spectrum ß-lactamase (ESBL). This is perhaps the first study that employs the high-throughput whole-genome sequence-based approach to compare and study the genomic features of these four ExPEC lineages in relation to their functional properties. Findings from this study highlight the differences in the genomic coordinates of ST131 with respect to the other STs considered here. Results from this comparative genomics study can help in advancing the understanding of ST131 evolution and also offer a framework towards future developments in pathogen identification and targeted therapeutics to prevent diseases caused by this pandemic E. coli ST131 clone.

Contig-Layout-Authenticator (CLA): A Combinatorial Approach to Ordering and Scaffolding of Bacterial Contigs for Comparative Genomics and Molecular Epidemiology.

A wide variety of genome sequencing platforms have emerged in the recent past. High-throughput platforms like Illumina and 454 are essentially adaptations of the shotgun approach generating millions of fragmented single or paired sequencing reads. To reconstruct whole genomes, the reads have to be assembled into contigs, which often require further downstream processing. The contigs can be directly ordered according to a reference, scaffolded based on paired read information, or assembled using a combination of the two approaches. While the reference-based approach appears to mask strain-specific information, scaffolding based on paired-end information suffers when repetitive elements longer than the size of the sequencing reads are present in the genome. Sequencing technologies that produce long reads can solve the problems associated with repetitive elements but are not necessarily easily available to researchers. The most common high-throughput technology currently used is the Illumina short read platform. To improve upon the shortcomings associated with the construction of draft genomes with Illumina paired-end sequencing, we developed Contig-Layout-Authenticator (CLA). The CLA pipeline can scaffold reference-sorted contigs based on paired reads, resulting in better assembled genomes. Moreover, CLA also hints at probable misassemblies and contaminations, for the users to cross-check before constructing the consensus draft. The CLA pipeline was designed and trained extensively on various bacterial genome datasets for the ordering and scaffolding of large repetitive contigs. The tool has been validated and compared favorably with other widely-used scaffolding and ordering tools using both simulated and real sequence datasets. CLA is a user friendly tool that requires a single command line input to generate ordered scaffolds.