Routine Metagenomics Service for ICU Patients with Respiratory Infection

Rationale: Respiratory metagenomics (RMg) needs evaluation in a pilot service setting to determine utility and inform implementation into routine clinical practice. Objectives: Feasibility, performance, and clinical impacts on antimicrobial prescribing and infection control were recorded during a pilot RMg service. Methods: RMg was performed on 128 samples from 87 patients with suspected lower respiratory tract infection (LRTI) on two general and one specialist respiratory ICUs at Guy's and St Thomas' NHS Foundation Trust, London. Measurements and Main Results: During the first 15 weeks, RMg provided same-day results for 110 samples (86%), with a median turnaround time of 6.7 hours (interquartile range = 6.1-7.5 h). RMg was 93% sensitive and 81% specific for clinically relevant pathogens compared with routine testing. Forty-eight percent of RMg results informed antimicrobial prescribing changes (22% escalation; 26% deescalation) with escalation based on speciation in 20 out of 24 cases and detection of acquired-resistance genes in 4 out of 24 cases. Fastidious or unexpected organisms were reported in 21 samples, including anaerobes (n = 12), Mycobacterium tuberculosis, Tropheryma whipplei, cytomegalovirus, and Legionella pneumophila ST1326, which was subsequently isolated from the bedside water outlet. Application to consecutive severe community-acquired LRTI cases identified Staphylococcus aureus (two with SCCmec and three with luk F/S virulence determinants), Streptococcus pyogenes (emm1-M1uk clone), S. dysgalactiae subspecies equisimilis (STG62647A), and Aspergillus fumigatus with multiple treatments and public health impacts. Conclusions: This pilot study illustrates the potential of RMg testing to provide benefits for antimicrobial treatment, infection control, and public health when provided in a real-world critical care setting. Multicenter studies are now required to inform future translation into routine service.

Feasibility and clinical utility of local rapid Nanopore influenza A virus whole genome sequencing for integrated outbreak management, genotypic resistance detection and timely surveillance

Rapid respiratory viral whole genome sequencing (WGS) in a clinical setting can inform real-time outbreak and patient treatment decisions, but the feasibility and clinical utility of influenza A virus (IAV) WGS using Nanopore technology has not been demonstrated. A 24 h turnaround Nanopore IAV WGS protocol was performed on 128 reverse transcriptase PCR IAV-positive nasopharyngeal samples taken over seven weeks of the 2022-2023 winter influenza season, including 25 from patients with nosocomial IAV infections and 102 from patients attending the Emergency Department. WGS results were reviewed collectively alongside clinical details for interpretation and reported to clinical teams. All eight segments of the IAV genome were recovered for 97/128 samples (75.8 %) and the haemagglutinin gene for 117/128 samples (91.4 %). Infection prevention and control identified nosocomial IAV infections in 19 patients across five wards. IAV WGS revealed two separate clusters on one ward and excluded transmission across different wards with contemporaneous outbreaks. IAV WGS also identified neuraminidase inhibitor resistance in a persistently infected patient and excluded avian influenza in a sample taken from an immunosuppressed patient with a history of travel to Singapore which had failed PCR subtyping. Accurate IAV genomes can be generated in 24 h using a Nanopore protocol accessible to any laboratory with SARS-CoV-2 Nanopore sequencing capacity. In addition to replicating reference laboratory surveillance results, IAV WGS can identify antiviral resistance and exclude avian influenza. IAV WGS also informs management of nosocomial outbreaks, though molecular and clinical epidemiology were concordant in this study, limiting the impact on decision-making.

The ongoing Streptococcus pyogenes (Group A Streptococcus) outbreak in London, United Kingdom, in December 2022: a molecular epidemiology study

OBJECTIVES

Epidemiological and whole-genome sequencing analysis of an ongoing outbreak of Streptococcus pyogenes (Group A Streptococcus) in London (United Kingdom).

METHODS

Prospective identification of Group A Streptococcus cases from a diagnostic laboratory serving central and south London between 27 November and 10 December 2022. Case notes were reviewed and isolates were retrieved. Case numbers were compared with the previous 5 years. Whole-genome sequencing was performed with long-read, nanopore technology for emm typing and identification of superantigen genes. Associations of pathogen-related factors with an invasive disease were assessed by single-variable and multi-variable logistic regression.

RESULTS

Case numbers began increasing in October 2022 from a baseline of 2.0 cases per day, and in December 2022, the average daily case numbers reached 10.8 cases per day, four-fold the number usually seen in winter. A total of 113 cases were identified during the prospective study period. Three quarters (86/113, 76%) were paediatric cases, including 2 deaths. Of 113 cases, 11 (10%) were invasive. In total, 56 isolates were successfully sequenced, including 10 of 11 (91%) invasive isolates. The emm12 (33/56, 59%) and emm1 (9/56, 16%) types were predominant, with 7 of 9 (78%) emm1 isolates being from the M1uk clone. The majority of invasive isolates had superantigen genes spea (7/10, 70%) and spej (8/10, 80%), whereas, in non-invasive isolates, these superantigen genes were found less frequently (spea: 5/46, 11% and spej: 7/46, 15%). By multivariable analysis of pathogen-related factors, spea (OR 8.9, CI 1.4-57, p 0.020) and spej (OR 12, CI 1.8-78, p 0.011) were associated with invasive disease.

CONCLUSIONS

emm12 and emm1 types predominate in the ongoing outbreak, which mainly affects children. In this outbreak, the spea and spej superantigen genes are associated with the severity of presentation.

A framework for real-time monitoring, analysis and adaptive sampling of viral amplicon nanopore sequencing

The ongoing SARS-CoV-2 pandemic demonstrates the utility of real-time sequence analysis in monitoring and surveillance of pathogens. However, cost-effective sequencing requires that samples be PCR amplified and multiplexed via barcoding onto a single flow cell, resulting in challenges with maximising and balancing coverage for each sample. To address this, we developed a real-time analysis pipeline to maximise flow cell performance and optimise sequencing time and costs for any amplicon based sequencing. We extended our nanopore analysis platform MinoTour to incorporate ARTIC network bioinformatics analysis pipelines. MinoTour predicts which samples will reach sufficient coverage for downstream analysis and runs the ARTIC networks Medaka pipeline once sufficient coverage has been reached. We show that stopping a viral sequencing run earlier, at the point that sufficient data has become available, has no negative effect on subsequent down-stream analysis. A separate tool, SwordFish, is used to automate adaptive sampling on Nanopore sequencers during the sequencing run. This enables normalisation of coverage both within (amplicons) and between samples (barcodes) on barcoded sequencing runs. We show that this process enriches under-represented samples and amplicons in a library as well as reducing the time taken to obtain complete genomes without affecting the consensus sequence.

Real-Time Whole Genome Sequencing to Guide Patient-Tailored Therapy of Severe Acute Respiratory Syndrome Coronavirus 2 Infection

The management of coronavirus disease 2019 has become more complex due to the expansion of available therapies. The presence of severe acute respiratory syndrome coronavirus 2 variants and mutations further complicates treatment due to their differing susceptibilities to therapies. Here we outline the use of real-time whole genome sequencing to detect persistent infection, evaluate for mutations confering resistance to treatments, and guide treatment decisions.

Analysis of pir gene expression across the Plasmodium life cycle

Background

Plasmodium interspersed repeat (pir) is the largest multigene family in the genomes of most Plasmodium species. A variety of functions for the PIR proteins which they encode have been proposed, including antigenic variation, immune evasion, sequestration and rosetting. However, direct evidence for these is lacking. The repetitive nature of the family has made it difficult to determine function experimentally. However, there has been some success in using gene expression studies to suggest roles for some members in virulence and chronic infection.

Methods

Here pir gene expression was examined across the life cycle of Plasmodium berghei using publicly available RNAseq data-sets, and at high resolution in the intraerythrocytic development cycle using new data from Plasmodium chabaudi.

Results

Expression of pir genes is greatest in stages of the parasite which invade and reside in red blood cells. The marked exception is that liver merozoites and male gametocytes produce a very large number of pir gene transcripts, notably compared to female gametocytes, which produce relatively few. Within the asexual blood stages different subfamilies peak at different times, suggesting further functional distinctions. Representing a subfamily of its own, the highly conserved ancestral pir gene warrants further investigation due to its potential tractability for functional investigation. It is highly transcribed in multiple life cycle stages and across most studied Plasmodium species and thus is likely to play an important role in parasite biology.

Conclusions

The identification of distinct expression patterns for different pir genes and subfamilies is likely to provide a basis for the design of future experiments to uncover their function.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-021-03979-6.

Evaluating the potential for respiratory metagenomics to improve treatment of secondary infection and detection of nosocomial transmission on expanded COVID-19 intensive care units

BACKGROUND

Clinical metagenomics (CMg) has the potential to be translated from a research tool into routine service to improve antimicrobial treatment and infection control decisions. The SARS-CoV-2 pandemic provides added impetus to realise these benefits, given the increased risk of secondary infection and nosocomial transmission of multi-drug-resistant (MDR) pathogens linked with the expansion of critical care capacity.

METHODS

CMg using nanopore sequencing was evaluated in a proof-of-concept study on 43 respiratory samples from 34 intubated patients across seven intensive care units (ICUs) over a 9-week period during the first COVID-19 pandemic wave.

RESULTS

An 8-h CMg workflow was 92% sensitive (95% CI, 75-99%) and 82% specific (95% CI, 57-96%) for bacterial identification based on culture-positive and culture-negative samples, respectively. CMg sequencing reported the presence or absence of β-lactam-resistant genes carried by Enterobacterales that would modify the initial guideline-recommended antibiotics in every case. CMg was also 100% concordant with quantitative PCR for detecting Aspergillus fumigatus from 4 positive and 39 negative samples. Molecular typing using 24-h sequencing data identified an MDR-K. pneumoniae ST307 outbreak involving 4 patients and an MDR-C. striatum outbreak involving 14 patients across three ICUs.

CONCLUSION

CMg testing provides accurate pathogen detection and antibiotic resistance prediction in a same-day laboratory workflow, with assembled genomes available the next day for genomic surveillance. The provision of this technology in a service setting could fundamentally change the multi-disciplinary team approach to managing ICU infections. The potential to improve the initial targeted treatment and rapidly detect unsuspected outbreaks of MDR-pathogens justifies further expedited clinical assessment of CMg.

Tissue macrophages and interferon-gamma signalling control blood-stage Plasmodium chabaudi infections derived from mosquito-transmitted parasites

Natural infection with Plasmodium parasites, the causative agents of malaria, occurs via mosquito vectors. However, most of our knowledge of the immune response to the blood stages of Plasmodium is from infections initiated by injection of serially blood-passaged infected red blood cells, resulting in an incomplete life cycle in the mammalian host. Vector transmission of the rodent malaria parasite, Plasmodium chabaudi chabaudi AS has been shown to give rise to a more attenuated blood-stage infection in C57Bl/6J mice, when compared to infections initiated with serially blood-passaged P. chabaudi-infected red blood cells. In mouse models, the host immune response induced by parasites derived from natural mosquito transmission is likely to more closely resemble the immune responses to Plasmodium infections in humans. It is therefore important to determine how the host response differs between the two types of infections.

As the spleen is considered to be a major contributor to the protective host response to P. chabaudi, we carried out a comparative transcriptomic analysis of the splenic response to recently mosquito-transmitted and serially blood-passaged parasites in C57Bl/6J mice. The attenuated infection arising from recently mosquito-transmitted parasites is characterised by an earlier and stronger myeloid- and IFNγ-related response. Analyses of spleen lysates from the two infections similarly showed stronger or earlier inflammatory cytokine and chemokine production in the recently mosquito-transmitted blood-stage infections. Furthermore, tissue macrophages, including red pulp macrophages, and IFNγ-signalling in myeloid cells, are required for the early control of P. chabaudi recently mosquito-transmitted parasites, thus contributing to the attenuation of mosquito-transmitted infections.

The molecules responsible for this early activation response to recently-transmitted blood-stage parasites in mice would be important to identify, as they may help to elucidate the nature of the initial interactions between blood-stage parasites and the host immune system in naturally transmitted malaria.

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Attenuation of recently transmitted malaria happens at blood stage of infection.

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Stronger or earlier inflammatory cytokine and chemokine production.

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Tissue macrophages, including red pulp macrophages, contribute to attenuation.

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IFNγ-signalling in myeloid cells is required for early control of P. chabaudi AS.

The landscape of somatic mutation in normal colorectal epithelial cells

The colorectal adenoma-carcinoma sequence has provided a paradigmatic framework for understanding the successive somatic genetic changes and consequent clonal expansions that lead to cancer1. However, our understanding of the earliest phases of colorectal neoplastic changes-which may occur in morphologically normal tissue-is comparatively limited, as for most cancer types. Here we use whole-genome sequencing to analyse hundreds of normal crypts from 42 individuals. Signatures of multiple mutational processes were revealed; some of these were ubiquitous and continuous, whereas others were only found in some individuals, in some crypts or during certain periods of life. Probable driver mutations were present in around 1% of normal colorectal crypts in middle-aged individuals, indicating that adenomas and carcinomas are rare outcomes of a pervasive process of neoplastic change across morphologically normal colorectal epithelium. Colorectal cancers exhibit substantially increased mutational burdens relative to normal cells. Sequencing normal colorectal cells provides quantitative insights into the genomic and clonal evolution of cancer.

Somatic mutations reveal asymmetric cellular dynamics in the early human embryo

Somatic cells acquire mutations throughout the course of an individual's life. Mutations occurring early in embryogenesis are often present in a substantial proportion of, but not all, cells in postnatal humans and thus have particular characteristics and effects. Depending on their location in the genome and the proportion of cells they are present in, these mosaic mutations can cause a wide range of genetic disease syndromes and predispose carriers to cancer. They have a high chance of being transmitted to offspring as de novo germline mutations and, in principle, can provide insights into early human embryonic cell lineages and their contributions to adult tissues. Although it is known that gross chromosomal abnormalities are remarkably common in early human embryos, our understanding of early embryonic somatic mutations is very limited. Here we use whole-genome sequences of normal blood from 241 adults to identify 163 early embryonic mutations. We estimate that approximately three base substitution mutations occur per cell per cell-doubling event in early human embryogenesis and these are mainly attributable to two known mutational signatures. We used the mutations to reconstruct developmental lineages of adult cells and demonstrate that the two daughter cells of many early embryonic cell-doubling events contribute asymmetrically to adult blood at an approximately 2:1 ratio. This study therefore provides insights into the mutation rates, mutational processes and developmental outcomes of cell dynamics that operate during early human embryogenesis.

[Status of radiologic pelvimetry]

The diagnostic value of radiological pelvimetry is subject to controversial interpretation. This examination is being conducted at the Department of Gynaecology in Aarau (Frauenklinik Aarau) mainly in pregnant women in pelvic presentation or during the puerperium after Caesarean section. Based on 164 radiological pelvimetric measurements in breech presentation and 112 X-ray films after Caesarean section an attempt was made to assess the prospective value of this examination. Abnormal shapes of the pelvis and narrow pelvic dimensions were found about equally often. Analysis of the indications of the section yielded both in breech presentation and in the entire group of the patients examined post partum an almost equally high percentage of about 20% of indications for a disproportionate head-pelvis relationship. Radiologically, considerably narrowed pelvic dimensions were seen in 10% of the examined women. The most frequent finding was a funnel-shaped pelvis, whereas an assimilation pelvis was never seen. Every pathologically narrowed funnel-shaped pelvis and generally narrow pelvis was detected also by digital palpation. All cases of conjugata vera masses below 10 cm concerned generally narrow cases of pelvic dimensions and were thus detectable by digital palpation. We recommended to abstain from routine performance of radiometric pelvimetry. Lateral pelvic X-ray can be an additional help in difficulties in pregnant women with regard to determining the mode of birth in breech presentation and after Caesarean section in case there is an urgent suspicion of malproportionate head-pelvis ratios.