Metagenomics for the microbiological diagnosis of hospital-acquired pneumonia and ventilator-associated pneumonia (HAP/VAP) in intensive care unit (ICU): a proof-of-concept study.

BACKGROUND: Hospital-acquired and ventilator-associated-pneumonia (HAP/VAP) are one of the most prevalent health-care associated infections in the intensive care unit (ICU). Culture-independent methods were therefore developed to provide faster route to diagnosis and treatment. Among these, metagenomic next-generation sequencing (mNGS) has shown considerable promise. METHODS: This proof-of-concept study describes the technical feasibility and evaluates the clinical validity of the mNGS for the detection and characterization of the etiologic agents causing hospital-acquired and ventilator-associated pneumonia. We performed a prospective study of all patients with HAP/VAP hospitalized in our intensive care unit for whom a bronchoalveolar lavage (BAL) was performed between July 2017 and November 2018. We compared BAL fluid culture and mNGS results of these patients. RESULTS: A total of 32 BAL fluids were fully analyzed. Of these, 22 (69%) were positive by culture and all pathogens identified were also reported by mNGS. Among the culture-positive BAL samples, additional bacterial species were revealed by mNGS for 12 patients, raising the issue of their pathogenic role (colonization versus coinfection). Among BALF with culture-negative test, 5 were positive in mNGS test. CONCLUSIONS: This study revealed concordant results for pneumonia panel pathogens between mNGS and culture-positive tests and identified additional pathogens potentially implicated in pneumonia without etiologic diagnosis by culture. mNGS has emerged as a promising methodology for infectious disease diagnoses to support conventional methods. Prospective studies with real-time mNGS are warranted to examine the impact on antimicrobial decision-making and clinical outcome.

Biological and Molecular Characterization of an American Sugar Beet-Infecting Beet western yellows virus Isolate.

Three aphid-transmitted viruses belonging to the Polerovirus genus, Beet mild yellowing virus (BMYV), Beet chlorosis virus (BChV), and Beet western yellows virus (BWYV), have been described as pathogens of sugar beet. We present the complete biological, serological, and molecular characterization of an American isolate of Beet western yellows virus (BWYV-USA), collected from yellow beet leaves. The biological data suggested that BWYV-USA displayed a host range similar to that of BMYV, but distinct from those of BChV and the lettuce and rape isolates of Turnip yellows virus. The complete genomic RNA sequence of BWYV-USA showed a genetic organization and expression typical of other Polerovirus members. Comparisons of deduced amino acid sequences showed that P0 and the putative replicase complex (P1-P2) of BWYV-USA are more closely related to Cucurbit aphid-borne yellows virus (CABYV) than to BMYV, whereas alignments of P3, P4, and P5 showed the highest homology with BMYV. Intraspecific and interspecific phylogenetic analyses have suggested that the BWYV-USA genome may be the result of recombination events between a CABYV-like ancestor contributing open reading frame (ORF) 0, ORF 1, and ORF 2, and a beet Polerovirus progenitor providing the 3' ORFs, with a similar mechanism of speciation occurring for BMYV in Europe. Results demonstrate that BWYV-USA is a distinct species in the Polerovirus genus, clarifying the nomenclature of this important group of viruses.