RESUMEN
BACKGROUND: Underlying coinfections may complicate infectious disease states but commonly go unnoticed because an a priori clinical suspicion is usually required so they can be detected via targeted diagnostic tools. Shotgun metagenomics is a broad diagnostic tool that can be useful for identifying multiple microbes simultaneously especially if coupled with lymph node aspirates, a clinical matrix known to house disparate pathogens. The objective of this study was to analyze the utility of this unconventional diagnostic approach (shotgun metagenomics) using clinical samples from human tularemia cases as a test model. Tularemia, caused by the bacterium Francisella tularensis, is an emerging infectious disease in Turkey. This disease commonly manifests as swelling of the lymph nodes nearest to the entry of infection. Because swollen cervical nodes are observed from many different types of human infections we used these clinical sample types to analyze the utility of shotgun metagenomics. METHODS: We conducted an unbiased molecular survey using shotgun metagenomics sequencing of DNA extracts from fine-needle aspirates of neck lymph nodes from eight tularemia patients who displayed protracted symptoms. The resulting metagenomics data were searched for microbial sequences (bacterial and viral). RESULTS: F. tularensis sequences were detected in all samples. In addition, we detected DNA of other known pathogens in three patients. Both Hepatitis B virus (HBV) and Human Parvovirus B-19 were detected in one individual and Human Parvovirus B-19 alone was detected in two other individuals. Subsequent PCR coupled with Sanger sequencing verified the metagenomics results. The HBV status was independently confirmed via serological diagnostics, despite evading notice during the initial assessment. CONCLUSION: Our data highlight that shotgun metagenomics of fine-needle lymph node aspirates is a promising clinical diagnostic strategy to identify coinfections. Given the feasibility of the diagnostic approach demonstrated here, further steps to promote integration of this type of diagnostic capability into mainstream clinical practice are warranted.
Asunto(s)
Coinfección/diagnóstico , Francisella tularensis/genética , Ganglios Linfáticos/microbiología , Metagenómica , Tularemia/diagnóstico , ADN Bacteriano/genética , ADN Bacteriano/metabolismo , Femenino , Francisella tularensis/aislamiento & purificación , Humanos , Ganglios Linfáticos/patología , Masculino , Persona de Mediana Edad , Cuello , Reacción en Cadena de la Polimerasa , Análisis de Secuencia de ADNRESUMEN
A PCR assay was developed to genotypically characterize Francisella tularensis and F. novicida. An integrated and partially redundant set of markers was selected to provide positive identification of these species, identify subspecies of F. tularensis and genotype 14 variable number tandem repeat (VNTR) markers. Assay performance was evaluated with 117 Francisella samples. Sample DNA was amplified, and the masses of the PCR products were determined with electrospray ionization/time of flight mass spectrometry (ESI-MS). The base compositions of the PCR amplicons were derived from these high-accuracy mass measurements and contrasted with databased information associated with each of the 25 assay markers. Species and subspecies determinations for all samples were fully concordant with results from established typing methods, and VNTR markers provided additional discrimination among samples. Sequence variants were observed with a number of assay markers, but these did not interfere with sample characterization, and served to increase the genetic diversity detected by the assay.
Asunto(s)
Técnicas de Tipificación Bacteriana/métodos , Francisella tularensis/clasificación , Francisella tularensis/aislamiento & purificación , Reacción en Cadena de la Polimerasa/métodos , Animales , Composición de Base , ADN Bacteriano/genética , Francisella tularensis/genética , Marcadores Genéticos , Genotipo , Repeticiones de Minisatélite , Polimorfismo de Nucleótido Simple , Especificidad de la Especie , Espectrometría de Masa por Ionización de Electrospray , Garrapatas/microbiología , Tularemia/genéticaRESUMEN
AIM: To investigate the phylogeography of French Francisella tularensis ssp. holarctica isolates. METHODS AND RESULTS: Canonical SNPs and MLVA were used to genotype 103 French F. tularensis ssp. holarctica isolates. We confirmed the presence of one subclade, the central and western European group (B.Br.FTNF002-00), and identified four major MLVA genotypes with no obvious geographical differentiation. CONCLUSIONS: The lack of geographical resolution among MLVA genotypes suggests rapid dispersal, convergent evolution or a combination of the two. SIGNIFICANCE AND IMPACT OF THE STUDY: This study expands knowledge of the phylogeography of one of the two dominant European F. tularensis ssp. holarctica subclades and illustrates the need for additional SNP discovery within this subclade.