The Nature of Immune Responses to Influenza Vaccination in High-Risk Populations.

The current pandemic has brought a renewed appreciation for the critical importance of vaccines for the promotion of both individual and public health. Influenza vaccines have been our primary tool for infection control to prevent seasonal epidemics and pandemics such as the 2009 H1N1 influenza A virus pandemic. Certain high-risk populations, including the elderly, people with obesity, and individuals with comorbidities such as type 2 diabetes mellitus, are more susceptible to increased disease severity and decreased vaccine efficacy. High-risk populations have unique microenvironments and immune responses that contribute to increased vulnerability for influenza infections. This review focuses on these differences as we investigate the variations in immune responses to influenza vaccination. In order to develop better influenza vaccines, it is critical to understand how to improve responses in our ever-growing high-risk populations.

Selective whole genome amplification and sequencing of Coxiella burnetii directly from environmental samples.

Whole genome sequencing (WGS) is a widely available, inexpensive means of providing a wealth of information about an organism's diversity and evolution. However, WGS for many pathogenic bacteria remain limited because they are difficult, slow and/or dangerous to culture. To avoid culturing, metagenomic sequencing can be performed directly on samples, but the sequencing effort required to characterize low frequency organisms can be expensive. Recently developed methods for selective whole genome amplification (SWGA) can enrich target DNA to provide efficient sequencing. We amplified Coxiella burnetii (a bacterial select agent and human/livestock pathogen) from 3 three environmental samples that were overwhelmed with host DNA. The 68- to 147-fold enrichment of the bacterial sequences provided enough genome coverage for SNP analyses and phylogenetic placement. SWGA is a valuable tool for the study of difficult-to-culture organisms and has the potential to facilitate high-throughput population characterizations as well as targeted epidemiological or forensic investigations.

Comparative pan-genomic analyses of Orientia tsutsugamushi reveal an exceptional model of bacterial evolution driving genomic diversity.

Orientia tsutsugamushi, formerly Rickettsia tsutsugamushi, is an obligate intracellular pathogen that causes scrub typhus, an underdiagnosed acute febrile disease with high morbidity. Scrub typhus is transmitted by the larval stage (chigger) of Leptotrombidium mites and is irregularly distributed across endemic regions of Asia, Australia and islands of the western Pacific Ocean. Previous work to understand population genetics in O. tsutsugamushi has been based on sub-genomic sampling methods and whole-genome characterization of two genomes. In this study, we compared 40 genomes from geographically dispersed areas and confirmed patterns of extensive homologous recombination likely driven by transposons, conjugative elements and repetitive sequences. High rates of lateral gene transfer (LGT) among O. tsutsugamushi genomes appear to have effectively eliminated a detectable clonal frame, but not our ability to infer evolutionary relationships and phylogeographical clustering. Pan-genomic comparisons using 31 082 high-quality bacterial genomes from 253 species suggests that genomic duplication in O. tsutsugamushi is almost unparalleled. Unlike other highly recombinant species where the uptake of exogenous DNA largely drives genomic diversity, the pan-genome of O. tsutsugamushi is driven by duplication and divergence. Extensive gene innovation by duplication is most commonly attributed to plants and animals and, in contrast with LGT, is thought to be only a minor evolutionary mechanism for bacteria. The near unprecedented evolutionary characteristics of O. tsutsugamushi, coupled with extensive intra-specific LGT, expand our present understanding of rapid bacterial evolutionary adaptive mechanisms.

More than 50% of Clostridium difficile Isolates from Pet Dogs in Flagstaff, USA, Carry Toxigenic Genotypes.

Nosocomial acquisition of Clostridium difficile is well documented, yet recent studies have highlighted the importance of community acquired infections and identified community associated reservoirs for this pathogen. Multiple studies have implicated companion pets and farm animals as possible sources of community acquired C. difficile infections in humans. To explore the potential role of pet dogs in human C. difficile infections we systematically collected canine fecal samples (n = 197) in Flagstaff, AZ. Additionally, nineteen fecal samples were collected at a local veterinary clinic from diarrheic dogs. We used these combined samples to investigate important questions regarding C. difficile colonization in pet canines: 1) What is the prevalence and diversity of C. difficile in this companion pet population, and 2) Do C. difficile isolates collected from canines genetically overlap with isolates that cause disease in humans? We used a two-step sequence typing approach, including multilocus sequence typing to determine the overall genetic diversity of C. difficile present in Flagstaff canines, and whole-genome sequencing to assess the fine-scale diversity patterns within identical multilocus sequence types from isolates obtained within and among multiple canine hosts. We detected C. difficile in 17% of the canine fecal samples with 10% containing toxigenic strains that are known to cause human disease. Sequencing analyses revealed similar genotypes in dogs and humans. These findings suggest that companion pets are a potential source of community acquired C. difficile infections in humans.

Draft Genome Sequence of the First Pathogenic Leptospira Isolates from Ecuador.

Pathogenic Leptospira spp. cause leptospirosis upon contact with mucosa through wounds or ingestion, leading to headaches, fever, jaundice, kidney or liver failure, or death in about 1.3 million people each year. Here, we present the draft genomes of one L. santarosai isolate and two L. interrogans isolates from Ecuador.

Rapid Drug Susceptibility Testing of Drug-Resistant Mycobacterium tuberculosis Isolates Directly from Clinical Samples by Use of Amplicon Sequencing: a Proof-of-Concept Study.

Increasingly complex drug-resistant tuberculosis (DR-TB) is a major global health concern and one of the primary reasons why TB is now the leading infectious cause of death worldwide. Rapid characterization of a DR-TB patient's complete drug resistance profile would facilitate individualized treatment in place of empirical treatment, improve treatment outcomes, prevent amplification of resistance, and reduce the transmission of DR-TB. The use of targeted next-generation sequencing (NGS) to obtain drug resistance profiles directly from patient sputum samples has the potential to enable comprehensive evidence-based treatment plans to be implemented quickly, rather than in weeks to months, which is currently needed for phenotypic drug susceptibility testing (DST) results. In this pilot study, we evaluated the performance of amplicon sequencing of Mycobacterium tuberculosis DNA from patient sputum samples using a tabletop NGS technology and automated data analysis to provide a rapid DST solution (the Next Gen-RDST assay). One hundred sixty-six out of 176 (94.3%) sputum samples from the Republic of Moldova yielded complete Next Gen-RDST assay profiles for 7 drugs of interest. We found a high level of concordance of our Next Gen-RDST assay results with phenotypic DST (97.0%) and pyrosequencing (97.8%) results from the same clinical samples. Our Next Gen-RDST assay was also able to estimate the proportion of resistant-to-wild-type alleles down to mixtures of ≤1%, which demonstrates the ability to detect very low levels of resistant variants not detected by pyrosequencing and possibly below the threshold for phenotypic growth methods. The assay as described here could be used as a clinical or surveillance tool.

Whole Genome Analysis of Injectional Anthrax Identifies Two Disease Clusters Spanning More Than 13 Years.

BACKGROUND: Anthrax is a rare disease in humans but elicits great public fear because of its past use as an agent of bioterrorism. Injectional anthrax has been occurring sporadically for more than ten years in heroin consumers across multiple European countries and this outbreak has been difficult to trace back to a source. METHODS: We took a molecular epidemiological approach in understanding this disease outbreak, including whole genome sequencing of Bacillus anthracis isolates from the anthrax victims. We also screened two large strain repositories for closely related strains to provide context to the outbreak. FINDINGS: Analyzing 60 Bacillus anthracis isolates associated with injectional anthrax cases and closely related reference strains, we identified 1071 Single Nucleotide Polymorphisms (SNPs). The synapomorphic SNPs (350) were used to reconstruct phylogenetic relationships, infer likely epidemiological sources and explore the dynamics of evolving pathogen populations. Injectional anthrax genomes separated into two tight clusters: one group was exclusively associated with the 2009-10 outbreak and located primarily in Scotland, whereas the second comprised more recent (2012-13) cases but also a single Norwegian case from 2000. INTERPRETATION: Genome-based differentiation of injectional anthrax isolates argues for at least two separate disease events spanning > 12 years. The genomic similarity of the two clusters makes it likely that they are caused by separate contamination events originating from the same geographic region and perhaps the same site of drug manufacturing or processing. Pathogen diversity within single patients challenges assumptions concerning population dynamics of infecting B. anthracis and host defensive barriers for injectional anthrax. FUNDING: This work was supported by the United States Department of Homeland Security grant no. HSHQDC-10-C-00,139 and via a binational cooperative agreement between the United States Government and the Government of Germany. This work was supported by funds from the German Ministry of Defense (Sonderforschungsprojekt 25Z1-S-431,214). Support for sequencing was also obtained from Illumina, Inc. These sources had no role in the data generation or interpretation, and had not role in the manuscript preparation. PANEL 1 RESEARCH IN CONTEXT SYSTEMATIC REVIEW: We searched PubMed for any article published before Jun. 17, 2015, with the terms "Bacillus anthracis" and "heroin", or "injectional anthrax". Other than our previously published work (Price et al., 2012), we found no other relevant studies on elucidating the global phylogenetic relationships of B. anthracis strains associated with injectional anthrax caused by recreational heroin consumption of spore-contaminated drug. There were, however, publically available genome sequences of two strains involved (Price et al., 2012, Grunow et al., 2013) and the draft genome sequence of Bacillus anthracis UR-1, isolated from a German heroin user (Ruckert et al., 2012) with only limited information on the genotyping of closely related strains (Price et al., 2012, Grunow et al., 2013). LAY PERSON INTERPRETATION: Injectional anthrax has been plaguing heroin drug users across Europe for more than 10 years. In order to better understand this outbreak, we assessed genomic relationships of all available injectional anthrax strains from four countries spanning a > 12 year period. Very few differences were identified using genome-based analysis, but these differentiated the isolates into two distinct clusters. This strongly supports a hypothesis of at least two separate anthrax spore contamination events perhaps during the drug production processes. Identification of two events would not have been possible from standard epidemiological analysis. These comprehensive data will be invaluable for classifying future injectional anthrax isolates and for future geographic attribution.