Association of sputum microbiota profiles with severity of community-acquired pneumonia in children

Signatures of lower respiratory tract microbiome in children with severe community-acquired pneumonia using shotgun metagenomic sequencing

BACKGROUND

Severe community-acquired pneumonia was associated with high morbidity and mortality in children. However, species-level microbiome of lower airway was sparse, and we used shotgun metagenomic next-generation sequencing to explore microbial signatures.

METHODS

We conducted a prospective cohort study to recruit children under 18 who required admission to an intensive care unit for community-acquired pneumonia between December 2019 and February 2022. Lower respiratory specimens were collected on admission for shotgun metagenomic sequencing. The children were divided into two groups. Critical cases were patients with respiratory failure requiring endotracheal ventilator support, and severe cases did not require intubation. Signatures of lower respiratory tract microbiome were compared between groups using an exact k-mer matching metagenomic analysis pipeline (Kraken 2) and a metagenome-assembled genomes pipeline (MetaWRAP).

RESULTS

Totally 66 children were enrolled, and 27 children were critical cases, and the rest were severe cases. There were significant differences in microbial community structure between different severity groups, and microbial abundance was negatively correlated with disease severity. The results showed that Haemophilus influenzae was more prominent in children who were critical, accompanied with increased expression of intracellular transport, secretion, and vesicle transport genes. Rothia mucilaginosa, Dolosigranulum pigrum, and Prevotella melaninogenica tended to be present in less severe community-acquired pneumonia group.

CONCLUSION

This study demonstrated that significantly different microbial community was associated with severity of community-acquired pneumonia requiring intensive care admission. Species-level shotgun metagenomic sequencing facilitates the exploration of potentially pathogenic or protective microbes and shed the light of probiotic development in lower respiratory tract.

Narrative review of application of metagenomic approaches to study the link between oropharyngeal microbiome and infectious diseases

Context

Viral and bacterial infections are major causes of morbidity and mortality worldwide. The oropharyngeal microbiome could play an important role in preventing invasion of viral and bacterial pathogens by modulating its content and the host's innate immune response. Next Generation Sequencing (NGS) technologies now enable in-depth study of the genomes of microbial communities. The objective of this review is to highlight how metagenomics has contributed to establish links between changes in the oropharyngeal microbiome and emergence of bacterial and viral diseases.

Method

Two search engines, PubMed and Google scholar were used with filters to focus searches on peer-reviewed original articles published between January 2010 and September 2022. Different keywords were used and only articles with metagenomic approaches were included.

Results

This review shows that there were few articles studying the link between oropharyngeal microbiome and infectious diseases. Studies on viruses using metagenomic techniques have been growing exponentially in recent years due to the Covid-19 pandemic. This review shows that most studies still focus on the basic identification of microorganisms in different disease states and multiple microorganisms (Alloprevotella, Prevotella, Bacteroides, Haemophilus, Streptococcus, Klebsiella sp., Acinetobacter sp…), have been associated with development of infections such as childhood wheezing, influenza, Covid-19, pneumonia, meningitis, and tuberculosis.

Conclusion

The oropharyngeal microbiome, despite its importance, remains poorly studied. A limited number of articles were identified but this number has increased exponentially since 2020 due to research conducted on Covid-19. These studies have shown that metagenomic has contributed to the unbiased identification of bacteria that could be used as biomarkers of various diseases and that further research is now needed to capitalize on those findings for human health benefit.

Akkermansia muciniphila in neuropsychiatric disorders: friend or foe?

An accumulating body of evidence suggests that the bacterium Akkermansia muciniphila exhibits positive systemic effects on host health, mainly by improving immunological and metabolic functions, and it is therefore regarded as a promising potential probiotic. Recent clinical and preclinical studies have shown that A. muciniphila plays a vital role in a variety of neuropsychiatric disorders by influencing the host brain through the microbiota-gut-brain axis (MGBA). Numerous studies observed that A. muciniphila and its metabolic substances can effectively improve the symptoms of neuropsychiatric disorders by restoring the gut microbiota, reestablishing the integrity of the gut mucosal barrier, regulating host immunity, and modulating gut and neuroinflammation. However, A. muciniphila was also reported to participate in the development of neuropsychiatric disorders by aggravating inflammation and influencing mucus production. Therefore, the exact mechanism of action of A. muciniphila remains much controversial. This review summarizes the proposed roles and mechanisms of A. muciniphila in various neurological and psychiatric disorders such as depression, anxiety, Parkinson's disease, Alzheimer's disease, multiple sclerosis, strokes, and autism spectrum disorders, and provides insights into the potential therapeutic application of A. muciniphila for the treatment of these conditions.

Methodological comparison of bronchoalveolar lavage fluid-based detection of respiratory pathogens in diagnosis of bacterium/fungus-associated pneumonia in critically ill patients

Background

Bacterium/fungus-associated pneumonia (BAP/FAP) is the prominent cause of high mortality and morbidity with important clinical impacts globally. Effective diagnostic methods and proper specimen types hopefully facilitate early diagnosis of pneumonia and prevent spread of drug-resistant bacteria/fungi among critically ill patients.

Methods

In the present study, 342 bronchoalveolar lavage fluid (BALF) samples were collected from critically ill patients with pulmonary infections between November 2020 and March 2021. The BALF materials were comparatively employed to screen BAP/FAP through microscopy, culture, antigenic marker and PCR-based methods. The limit of detection (LOD) of cultures and PCR for bacteria/fungi was determined by serial dilution assays. Specimen slides were prepared with Gram staining for microscopic examinations. Microbial cultures and identifications underwent routine clinical protocols with the aid of mass spectrometry. (1,3)-β-D-glucan and galactomannan tests with BALF were carried out accordingly. Direct detection of pathogens in BALF was achieved through PCR, followed by sequencing and BLAST in GenBank database for pathogenic identification. The subjects' demographic and clinical characteristics were well evaluated.

Results

BAP/FAP was identified in approximately 47% of the subjects by the BALF-based PCR. The PCR-based diagnostic methods showed improved detection performance for fungi with good LOD, but performed similarly for bacteria, when compared to the cultures. There was poor agreement among traditional microscopy, culture and PCR assays for bacterial detections (kappa value, 0.184 to 0.277). For overall bacterial/fungal detections, the microscopy showed the lowest detecting rate, followed by the cultures, which displayed a slightly higher sensitivity than the microscopy did. The sensitivity of PCR was much higher than that of the other means of interest. However, the traditional cultures rather than antigenic marker-based approaches were moderately consistent with the PCR-based methods in fungal species identification, particularly for Candida and Aspergillus spp. Our findings further revealed that the age, length of hospital stay, invasive procedures and cerebral diseases were likely considered as main risk factors for BAP/FAP.

Conclusion

Screening for BALF in critically ill patients with suspected pneumonia pertaining high risk factors using combined PCR-based molecular detection strategies would hopefully contribute to early diagnosis of BAP/FAP and improved prognosis of the patients.

Realising respiratory microbiomic meta-analyses: time for a standardised framework

In microbiome fields of study, meta-analyses have proven to be a valuable tool for identifying the technical drivers of variation among studies and results of investigations in several diseases, such as those of the gut and sinuses. Meta-analyses also represent a powerful and efficient approach to leverage existing scientific data to both reaffirm existing findings and generate new hypotheses within the field. However, there are currently limited data in other fields, such as the paediatric respiratory tract, where extension of original data becomes even more critical due to samples often being difficult to obtain and process for a range of both technical and ethical reasons. Performing such analyses in an evolving field comes with challenges related to data accessibility and heterogeneity. This is particularly the case in paediatric respiratory microbiomics - a field in which best microbiome-related practices are not yet firmly established, clinical heterogeneity abounds and ethical challenges can complicate sharing of patient data. Having recently conducted a large-scale, individual participant data meta-analysis of the paediatric respiratory microbiota (n = 2624 children from 20 studies), we discuss here some of the unique barriers facing these studies and open and invite a dialogue towards future opportunities. Video Abstract.

Comparative analysis of the lung microbiota in patients with respiratory infections, tuberculosis, and lung cancer: A preliminary study

Recent evidence suggests that lung microbiota can be recognized as one of the ecological determinants of various respiratory diseases. However, alterations in the lung microbiota and associated lung immunity in these respiratory diseases remain unclear. To compare the lung microbiota and lung immune profiles in common respiratory diseases, a total of 78 patients were enrolled in the present study, including 21 patients with primary pulmonary tuberculosis (PTB), eight patients with newly diagnosed lung cancer (LC), and 49 patients with community-acquired pneumonia (CAP). Bronchoalveolar lavage fluid (BALF) was collected for microbiota and cytokine analyses. With MiSeq sequencing system, increased bacterial alpha-diversity and richness were observed in patients with LC than in those with PTB and CAP. Linear discriminant analysis effect size revealed that CAP-associated pulmonary microbiota were significantly different between the PTB and LC groups. More key functionally different genera were found in the PTB and LC groups than in the CAP group. The interaction network revealed stronger positive and negative correlations among these genera in the LC group than in the other two groups. However, increased BALF cytokine profiles were observed in the PTB group than in the other two groups, while BALF cytokines were correlated with key functional bacteria. This comparative study provides evidence for the associations among altered lung microbiota, BALF inflammation, and different respiratory disorders, which provides insight into the possible roles and mechanisms of pulmonary microbiota in the progression of respiratory disorders.

Bacterial Signatures of Paediatric Respiratory Disease: An Individual Participant Data Meta-Analysis

Introduction: The airway microbiota has been linked to specific paediatric respiratory diseases, but studies are often small. It remains unclear whether particular bacteria are associated with a given disease, or if a more general, non-specific microbiota association with disease exists, as suggested for the gut. We investigated overarching patterns of bacterial association with acute and chronic paediatric respiratory disease in an individual participant data (IPD) meta-analysis of 16S rRNA gene sequences from published respiratory microbiota studies. Methods: We obtained raw microbiota data from public repositories or via communication with corresponding authors. Cross-sectional analyses of the paediatric (<18 years) microbiota in acute and chronic respiratory conditions, with >10 case subjects were included. Sequence data were processed using a uniform bioinformatics pipeline, removing a potentially substantial source of variation. Microbiota differences across diagnoses were assessed using alpha- and beta-diversity approaches, machine learning, and biomarker analyses. Results: We ultimately included 20 studies containing individual data from 2624 children. Disease was associated with lower bacterial diversity in nasal and lower airway samples and higher relative abundances of specific nasal taxa including Streptococcus and Haemophilus. Machine learning success in assigning samples to diagnostic groupings varied with anatomical site, with positive predictive value and sensitivity ranging from 43 to 100 and 8 to 99%, respectively. Conclusion: IPD meta-analysis of the respiratory microbiota across multiple diseases allowed identification of a non-specific disease association which cannot be recognised by studying a single disease. Whilst imperfect, machine learning offers promise as a potential additional tool to aid clinical diagnosis.

Exploring the nasopharyngeal microbiota composition in infants with whooping cough: A test-negative case-control study

Purpose

The purpose of this study was to characterize the nasopharyngeal microbiota of infants with possible and confirmed pertussis compared to healthy controls.

Methods

This prospective study included all infants <1 year with microbiologically confirmed diagnosis of pertussis attended at a University Hospital over a 12-month period. For each confirmed case, up to 2 consecutive patients within the same age range and meeting the clinical case definition of pertussis but testing PCR-negative were included as possible cases. A third group of asymptomatic infants (healthy controls) were also included. Nasopharyngeal microbiota was characterized by sequencing the V3-V4 region of the 16S rRNA gene. Common respiratory DNA/RNA viral co-infection was tested by multiplex PCR.

Results

Twelve confirmed cases, 21 possible cases and 9 healthy controls were included. Confirmed whooping cough was primarily driven by detection of Bordetella with no other major changes on nasopharyngeal microbiota. Possible cases had limited abundance or absence of Bordetella and a distinctive microbiota with lower bacterial richness and diversity and higher rates of viral co-infection than both confirmed cases and healthy controls. Bordetella reads determined by 16S rRNA gene sequencing were found in all 12 confirmed cases (100%), 3 out of the 21 possible cases (14.3%) but in any healthy control.

Conclusion

This study supports the usefulness of 16S rRNA gene sequencing for improved sensitivity on pertussis diagnosis compared to real-time PCR and to understand other microbial changes occurring in the nasopharynx in children <1 year old with suspected whooping cough compared to healthy controls.

The association between bacteria colonizing the upper respiratory tract and lower respiratory tract infection in young children: a systematic review and meta-analysis

BACKGROUND

Bacteria colonizing the upper respiratory tract (URT) of young children play a key role in the pathogenesis of lower respiratory tract infection (LRTI).

OBJECTIVES

To systematically review the literature on the association between bacteria colonizing the URT and LRTI among young children.

DATA SOURCES

MEDLINE, Academic Search Premier, Africa-Wide Information and CINAHL, Scopus and Web of Science.

STUDY ELIGIBILITY CRITERIA

Studies published between 1923 and 2020, investigating URT bacteria from LRTI cases and controls.

PARTICIPANTS

Children under 5 years with and without acute LRTI.

METHODS

Three reviewers independently screened titles, abstracts and full texts. Meta-analysis was done using Mantel-Haenszel fixed- or random-effects models.

RESULTS

Most eligible studies (41/50) tested nasopharyngeal specimens when investigating URT bacteria. Most studies were of cross-sectional design (44/50). Twenty-four studies were performed in children in lower- or lower-middle-income countries (LMICs). There was higher prevalence of Haemophilus influenzae (pooled OR 1.60; 95% CI 1.23-2.07) and Klebsiella spp. (pooled OR 2.04; 95% CI 1.17-3.55) from URT specimens of cases versus controls. We observed a positive association between the detection of Streptococcus pneumoniae from URT specimens and LRTI after excluding studies where there was more antibiotic treatment prior to sampling in cases vs. controls (pooled OR 1.41; 95% CI 1.04-1.90). High density colonization with S. pneumoniae (>6.9 log10 copies/mL) was associated with an increased risk for LRTI. The associations between both Streptococcus and Haemophilus URT detection and LRTI were supported, at genus level, by 16S rRNA sequencing. Evidence for the role of Moraxella catarrhalis and Staphylococcus aureus was inconclusive.

CONCLUSIONS

Detection of H. influenzae or Klebsiella spp. in the URT was associated with LRTI, while evidence for association with S. pneumoniae was less conclusive. Longitudinal studies assessing URT microbial communities, together with environmental and host factors are needed to better understand pathogenesis of childhood LRTI.

Clinical factors associated with composition of lung microbiota and important taxa predicting clinical prognosis in patients with severe community-acquired pneumonia

Few studies have described the key features and prognostic roles of lung microbiota in patients with severe community-acquired pneumonia (SCAP). We prospectively enrolled consecutive SCAP patients admitted to ICU. Bronchoscopy was performed at bedside within 48 h of ICU admission, and 16S rRNA gene sequencing was applied to the collected bronchoalveolar lavage fluid. The primary outcome was clinical improvements defined as a decrease of 2 categories and above on a 7-category ordinal scale within 14 days following bronchoscopy. Sixty-seven patients were included. Multivariable permutational multivariate analysis of variance found that positive bacteria lab test results had the strongest independent association with lung microbiota (R² = 0.033; P = 0.018), followed by acute kidney injury (AKI; R² = 0.032; P = 0.011) and plasma MIP-1β level (R² = 0.027; P = 0.044). Random forest identified that the families Prevotellaceae, Moraxellaceae, and Staphylococcaceae were the biomarkers related to the positive bacteria lab test results. Multivariable Cox regression showed that the increase in α-diversity and the abundance of the families Prevotellaceae and Actinomycetaceae were associated with clinical improvements. The positive bacteria lab test results, AKI, and plasma MIP-1β level were associated with patients’ lung microbiota composition on ICU admission. The families Prevotellaceae and Actinomycetaceae on admission predicted clinical improvements.

Biomarkers to distinguish bacterial from viral pediatric clinical pneumonia in a malaria endemic setting

Background

Differential etiologies of pediatric acute febrile respiratory illness pose challenges for all populations globally, but especially in malaria-endemic settings because the pathogens responsible overlap in clinical presentation and frequently occur together. Rapid identification of bacterial pneumonia with high-quality diagnostic tools would enable appropriate, point-of-care antibiotic treatment. Current diagnostics are insufficient, and the discovery and development of new tools is needed. We report a unique biomarker signature identified in blood samples to accomplish this.

Methods

Blood samples from 195 pediatric Mozambican patients with clinical pneumonia were analyzed with an aptamer-based, high-dynamic-range, quantitative assay (~1200 proteins). We identified new biomarkers using a training set of samples from patients with established bacterial, viral, or malarial pneumonia. Proteins with significantly variable abundance across etiologies (false discovery rate <0.01) formed the basis for predictive diagnostic models derived from machine learning techniques (Random Forest, Elastic Net). Validation on a dedicated test set of samples was performed.

Results

Significantly different abundances between bacterial and viral infections (219 proteins) and bacterial infections and mixed (viral and malaria) infections (151 proteins) were found. Predictive models achieved >90% sensitivity and >80% specificity, regardless of number of pathogen classes. Bacterial pneumonia was strongly associated with neutrophil markers—in particular, degranulation including HP, LCN2, LTF, MPO, MMP8, PGLYRP1, RETN, SERPINA1, S100A9, and SLPI.

Conclusions

Blood protein signatures highly associated with neutrophil biology reliably differentiated bacterial pneumonia from other causes. With appropriate technology, these markers could provide the basis for a rapid diagnostic for field-based triage for antibiotic treatment of pediatric pneumonia.

The clinical relevance of the microbiome when managing paediatric infectious diseases-Narrative review

In recent years, the field of infectious diseases has been hit by the overwhelming amount of information generated while the human microbiome is being disentangled. Based on the interaction between the microbiota and the immune system, the implications regarding infectious diseases are probably major and remain a challenge.

AIMS

This review was conceived as a comprehensive tool to provide an overview of the available evidence regarding the influence of the microbiome on infectious diseases in children.

METHODS

We present the main findings aroused from microbiome research in prevention, diagnosis and treatment of infectious disease under a paediatric perspective, to inform clinicians of the potential relevance of microbiome-related knowledge for translation to clinical practice.

RESULTS AND CONCLUSION

The evidence shown in this review highlights the numerous research gaps ahead and supports the need to move forward to integrating the so-called microbiome thinking into our routine clinical practice.

Volatile Organic Compounds, Bacterial Airway Microbiome, Spirometry and Exercise Performance of Patients after Surgical Repair of Congenital Diaphragmatic Hernia

The aim of this study was to analyze the exhaled volatile organic compounds (VOCs) profile, airway microbiome, lung function and exercise performance in congenital diaphragmatic hernia (CDH) patients compared to healthy age and sex-matched controls. A total of nine patients (median age 9 years, range 6-13 years) treated for CDH were included. Exhaled VOCs were measured by GC-MS. Airway microbiome was determined from deep induced sputum by 16S rRNA gene sequencing. Patients underwent conventional spirometry and exhausting bicycle spiroergometry. The exhaled VOC profile showed significantly higher levels of cyclohexane and significantly lower levels of acetone and 2-methylbutane in CDH patients. Microbiome analysis revealed no significant differences for alpha-diversity, beta-diversity and LefSe analysis. CDH patients had significantly lower relative abundances of Pasteurellales and Pasteurellaceae. CDH patients exhibited a significantly reduced Tiffeneau Index. Spiroergometry showed no significant differences. This is the first study to report the VOCs profile and airway microbiome in patients with CDH. Elevations of cyclohexane observed in the CDH group have also been reported in cases of lung cancer and pneumonia. CDH patients had no signs of impaired physical performance capacity, fueling controversial reports in the literature.

Cardiorespiratory performance capacity and airway microbiome in patients following primary repair of esophageal atresia

BACKGROUND

Patients following repair of an esophageal atresia (EA) or tracheoesophageal fistula (TEF) carry an increased risk of long-term cardiopulmonary malaise. The role of the airway microbiome in EA/TEF patients remains unclear.

METHODS

All EA/TEF patients treated between 1980 and 2010 were invited to a prospective clinical examination, spirometry, and spiroergometry. The airway microbiome was determined from deep induced sputum by 16 S rRNA gene sequencing. The results were compared to a healthy age- and sex-matched control group.

RESULTS

Nineteen EA/TEF patients with a mean age of 24.7 ± 7 years and 19 age- and sex-matched controls were included. EA/TEF patients showed a significantly lower muscle mass, lower maximum vital capacity (VC_max), and higher rates of restrictive ventilation disorders. Spiroergometry revealed a significantly lower relative performance capacity and lower peak VO₂ in EA/TEF patients. Alpha- and beta-diversity of the airway microbiome did not differ significantly between the two groups. Linear discriminant effect size analysis revealed significantly enriched species of Prevotella_uncultured, Streptococcus_anginosus, Prevotella_7_Prevotella_enoeca, and Mogibacterium_timidum.

CONCLUSION

EA/TEF patients frequently suffer from restrictive ventilation disorders and impaired cardiopulmonary function associated with minor alterations of the airway microbiome. Long-term examinations of EA/TEF patients seem to be necessary in order to detect impaired cardiopulmonary function.

IMPACT

The key messages of the present study are a significantly decreased VC_max and exercise performance, as well as airway microbiome differences in EA/TEF patients. This study is the first to present parameters of lung function and exercise performance in combination with airway microbiome analysis with a mean follow-up of 24 years in EA/TEF patients. Prospective, long-term studies are needed to unravel possible interactions between alterations of the airway microbiome and impaired pulmonary function in EA/TEF patients.

The Evolving Microbiome from Pregnancy to Early Infancy: A Comprehensive Review

Pregnancy induces a number of immunological, hormonal, and metabolic changes that are necessary for the mother to adapt her body to this new physiological situation. The microbiome of the mother, the placenta and the fetus influence the fetus growth and undoubtedly plays a major role in the adequate development of the newborn infant. Hence, the microbiome modulates the inflammatory mechanisms related to physiological and pathological processes that are involved in the perinatal progress through different mechanisms. The present review summarizes the actual knowledge related to physiological changes in the microbiota occurring in the mother, the fetus, and the child, both during neonatal period and beyond. In addition, we approach some specific pathological situations during the perinatal periods, as well as the influence of the type of delivery and feeding.

Allergic inflammation alters the lung microbiome and hinders synergistic co-infection with H1N1 influenza virus and Streptococcus pneumoniae in C57BL/6 mice

Asthma is a chronic airways condition that can be exacerbated during respiratory infections. Our previous work, together with epidemiologic findings that asthmatics were less likely to suffer from severe influenza during the 2009 pandemic, suggest that additional complications of influenza such as increased susceptibility to bacterial superinfection, may be mitigated in allergic hosts. To test this hypothesis, we developed a murine model of 'triple-disease' in which mice rendered allergic to Aspergillus fumigatus were co-infected with influenza A virus and Streptococcus pneumoniae seven days apart. Significant alterations to known synergistic effects of co-infection were noted in the allergic mice including reduced morbidity and mortality, bacterial burden, maintenance of alveolar macrophages, and reduced lung inflammation and damage. The lung microbiome of allergic mice differed from that of non-allergic mice during co-infection and antibiotic-induced perturbation to the microbiome rendered allergic animals susceptible to severe morbidity. Our data suggest that responses to co-infection in allergic hosts likely depends on the immune and microbiome states and that antibiotics should be used with caution in individuals with underlying chronic lung disease.

An integrated respiratory microbial gene catalogue to better understand the microbial aetiology of Mycoplasma pneumoniae pneumonia

BACKGROUND

The imbalanced respiratory microbiota observed in pneumonia causes high morbidity and mortality in childhood. Respiratory metagenomic analysis demands a comprehensive microbial gene catalogue, which will significantly advance our understanding of host-microorganism interactions.

RESULTS

We collected 334 respiratory microbial samples from 171 healthy children and 76 children with pneumonia. The respiratory microbial gene catalogue we established comprised 2.25 million non-redundant microbial genes, covering 90.52% of prevalent genes. The major oropharyngeal microbial species found in healthy children were Prevotella and Streptococcus. In children with Mycoplasma pneumoniae pneumonia (MPP), oropharyngeal microbial diversity and associated gene numbers decreased compared with those of healthy children. The concurrence network of oropharyngeal microorganisms in patients predominantly featured Staphylococcus spp. and M. pneumoniae. Functional orthologues, which are associated with the metabolism of various lipids, membrane transport, and signal transduction, accumulated in the oropharyngeal microbiome of children with pneumonia. Several antibiotic resistance genes and virulence factor genes were identified in the genomes of M. pneumoniae and 13 other microorganisms reconstructed via metagenomic data. Although the common macrolide/β-lactam resistance genes were not identified in the assembled M. pneumoniae genome, a single-nucleotide polymorphism (A2063G) related to macrolide resistance was identified in a 23S ribosomal RNA gene.

CONCLUSIONS

The results of this study will facilitate exploration of unknown microbial components and host-microorganism interactions in studies of the respiratory microbiome. They will also yield further insights into the microbial aetiology of MPP.

Biomarkers in Pneumonia-Beyond Procalcitonin

Pneumonia is the leading infectious cause of mortality worldwide and one of the most common lower respiratory tract infections that is contributing significantly to the burden of antibiotic consumption. Due to the complexity of its pathophysiology, it is widely accepted that clinical diagnosis and prognosis are inadequate for the accurate assessment of the severity of the disease. The most challenging task for a physician is the risk stratification of patients with community-acquired pneumonia. Herein, early diagnosis is essential in order to reduce hospitalization and mortality. Procalcitonin and C-reactive protein remain the most widely used biomarkers, while interleukin 6 has been of particular interest in the literature. However, none of them appear to be ideal, and the search for novel biomarkers that will most sufficiently predict the severity and treatment response in pneumonia has lately intensified. Although our insight has significantly increased over the last years, a translational approach with the application of genomics, metabolomics, microbiomics, and proteomics is required to better understand the disease. In this review, we discuss this rapidly evolving area and summarize the application of novel biomarkers that appear to be promising for the accurate diagnosis and risk stratification of pneumonia.

Septic patients in the intensive care unit present different nasal microbiotas

AIM

The primary objective of this study was to evaluate correlations among mortality, intensive care unit (ICU) length of stay and airway microbiotas in septic patients.

MATERIALS & METHODS

A deep-sequencing analysis of the 16S rRNA gene V4 region was performed.

RESULTS

The nasal microbiota in septic patients was dominated by three nasal bacterial types (Corynebacterium, Staphylococcus and Acinetobacter). The Acinetobacter type was associated with the lowest diversity and longest length of stay (median: 9 days), and the Corynebacterium type was associated with the shortest length of stay. We found that the Acinetobacter type in the >9-day group was associated with the highest mortality (33%).

CONCLUSION

Septic patients have three nasal microbiota types, and the nasal microbiota is related to the length of stay and mortality.

Lung Microbiota and Pulmonary Inflammatory Cytokines Expression Vary in Children With Tracheomalacia and Adenoviral or Mycoplasma pneumoniae Pneumonia

Community-acquired pneumonia (CAP) is a worldwide infectious disease caused by bacteria, viruses, or a combination of these infectious agents. Mycoplasma pneumoniae is an atypical pneumonia pathogen that causes high morbidity and mortality in children, and adenovirus can lead to severe pneumonia. However, the etiology of different types of pneumonia is still unclear. In this study, we selected a total of 52 inpatients with M. pneumoniae pneumonia (MPP) (n = 21), adenovirus pneumonia (AVP) (n = 16), or tracheomalacia (n = 15) to serve as a disease control. Bronchoalveolar lavage fluid (BALF) samples that had been obtained for clinical use were analyzed. We compared the differences in microbiota and the expression of 10 inflammatory cytokines in samples between MPP, AVP, and tracheomalacia. We found that the bacterial diversity in MPP was lower than that in AVP and tracheomalacia. Mycoplasma, Streptococcus, and Pseudomonas were predominant in samples of MPP, AVP, and tracheomalacia, respectively. The expression levels of IL-6, IL-8, and IL-10 were significantly higher in inpatients with AVP compared to children hospitalized with tracheomalacia or MPP. The lung microbiota in MPP was remarkably correlated with IL-2, IL-4, IL-5, IL-6, TNF-α, and IL-1α expressions, while this was not found in tracheomalacia and AVP. Microbiota analysis identified a high load of multi-drug resistant Acinetobacter baumannii in the lung microbiota of several inpatients, which might be associated with the long hospitalization length and intra-group differences at the individual level. This study will help to understand the microbial etiology of tracheomalacia, AVP, and MPP and to identify effective therapies for these diseases.

Microbiological Diagnosis of Respiratory Illness

A wide variety of microorganisms are potential respiratory pathogens, and the spectrum of known pathogens for each respiratory infection syndrome has not changed markers over recent years. Detection of likely etiologic agents of respiratory infections can help direct management and can also play an important role in disease surveillance. For this purpose, we are still reliant on many traditional diagnostic tools that have been used for decades in order to determine the microbial etiology of respiratory infections. However, these tools have been increasingly supplemented by newer methods, particular molecular diagnostic techniques, which have enabled the more rapid detection of many pathogens that were previously difficult to detect. These advances have particularly lead to improvements in the ability to detect respiratory viruses and also other microorganisms that do not normally colonize the respiratory tract. Recognition of the existence of the lung microbiome has challenged the traditional views of pneumonia pathogenesis and may provide the opportunity for new diagnostic tools that are focused on more than just detection of specific known pathogens. Continued liaison between clinicians and laboratory staff is vital in order to facilitate the most cost-effective use of laboratory diagnostics.

Factors Associated With Pneumonia Severity in Children: A Systematic Review

Community-acquired pneumonia in children is associated with significant morbidity and mortality; however, data are limited in predicting which children will have negative outcomes, including clinical deterioration, severe disease, or development of complications. The Pediatric Infectious Diseases Society/Infectious Diseases Society of America (PIDS/IDSA) pediatric pneumonia guideline includes criteria that were modified from adult criteria and define pneumonia severity to assist with resource allocation and site-of-care decision-making. However, the PIDS/IDSA criteria have not been formally developed or validated in children. Definitions for mild, moderate, and severe pneumonia also vary across the literature, further complicating the development of standardized severity criteria. This systematic review summarizes (1) the current state of the evidence for defining and predicting pneumonia severity in children as well as (2) emerging evidence focused on risk stratification of children with pneumonia.

Distinct Nasopharyngeal and Oropharyngeal Microbiota of Children with Influenza A Virus Compared with Healthy Children

BACKGROUND

Influenza A virus (IAV) has had the highest morbidity globally over the past decade. A growing number of studies indicate that the upper respiratory tract (URT) microbiota plays a key role for respiratory health and that a dysfunctional respiratory microbiota is associated with disease; but the impact of microbiota during influenza is understudied.

METHODS

We recruited 180 children, including 121 IAV patients and 59 age-matched healthy children. Nasopharyngeal (NP) and oropharyngeal (OP) swabs were collected to conduct 16S rDNA sequencing and compare microbiota structures in different individuals.

RESULTS

Both NP and OP microbiota in IAV patients differed from those in healthy individuals. The NP dominated genera in IVA patients, such as Moraxella, Staphylococcus, Corynebacterium, and Dolosigranulum, showed lower abundance than in healthy children. The Streptococcus significantly enriched in patients' NP and Phyllobacterium could be generally detected in patients' NP microbiota. The most abundant genera in OP microbiota showed a decline tendency in patients, including Streptococcus, Neisseria, and Haemophilus. The URT's bacterial concurrence network changed dramatically in patients. NP and OP samples were clustered into subgroups by different dominant genera; and NP and OP microbiota provided the precise indicators to distinguish IAV patients from healthy children.

CONCLUSION

This is the first respiratory microbiome analysis on pediatric IAV infection which reveals distinct NP and OP microbiota in influenza patients. It provides a new insight into IAV research from the microecology aspect and promotes the understanding of IAV pathogenesis.

Microbial Community Dynamics in Mother's Milk and Infant's Mouth and Gut in Moderately Preterm Infants

Mother's own milk represents the optimal source for preterm infant nutrition, as it promotes immune defenses and gastrointestinal function, protects against necrotizing enterocolitis, improves long-term clinical outcome and is hypothesized to drive gut microbiota assembly. Preterm infants at birth usually do not receive their mother's milk directly from the breast, because active suckling and coordination between suckling, swallowing and breathing do not develop until 32-34 weeks gestational age, but actual breastfeeding is usually possible as they grow older. Here, we enrolled moderately preterm infants (gestational age 32-34 weeks) to longitudinally characterize mothers' milk and infants' gut and oral microbiomes, up to more than 200 days after birth, through 16S rRNA sequencing. This peculiar population offers the chance to disentangle the differential contribution of human milk feeding per se vs. actual breastfeeding in the development of infant microbiomes, that have both been acknowledged as crucial contributors to short and long-term infant health status. In this cohort, the milk microbiome composition seemed to change following the infant's latching to the mother's breast, shifting toward a more diverse microbial community dominated by typical oral microbes, i.e., Streptococcus and Rothia. Even if all infants in the present study were fed human milk, features typical of healthy, full term, exclusively breastfed infants, i.e., high percentages of Bifidobacterium and low abundances of Pseudomonas in fecal and oral samples, respectively, were detected in samples taken after actual breastfeeding started. These findings underline the importance of encouraging not only human milk feeding, but also an early start of actual breastfeeding in preterm infants, since the infant's latching to the mother's breast might constitute an independent factor helping the health-promoting assembly of the infant gut microbiome.

The concordance between upper and lower respiratory microbiota in children with Mycoplasma pneumoniae pneumonia

In recent years, the morbidity of Mycoplasma pneumoniae pneumonia (MPP) has dramatically increased in China. An increasing number of studies indicate that an imbalance in the respiratory microbiota is associated with respiratory infection. We selected 28 hospitalized patients infected with M. pneumoniae and 32 healthy children. Nasopharyngeal (NP) and oropharyngeal (OP) swabs were collected from healthy children, whereas NP, OP and bronchoalveolar lavage (BAL) specimens were collected from patients. Microbiota analysis was performed on all microbial samples using 16 S ribosomal RNA (16 S rRNA) sequencing. The NP microbial samples in healthy children were divided into two groups, which were dominated by either Staphylococcus or mixed microbial components. The respiratory microbiota in pneumonia patients harbored a lower microbial diversity compared to healthy children, and both the NP and OP microbiota of patients differed significantly from that of healthy children. Hospitalized MPP children with a higher abundance of Mycoplasma in the BAL fluid (BALF) microbiota tended to suffer longer hospitalization lengths and higher peak fevers and serum C-reactive protein levels. Concordance analysis explained the succession of imbalanced NP microbiota to the OP and lung in diseased children. However, the association of the abundance of Mycoplasma in BALF microbiota with that in NP or OP microbiota varied among individuals, which suggested the sensitivity of BALF in MPP diagnostics, mirroring MPP severity.

Respiratory microbiota and lower respiratory tract disease

INTRODUCTION

The respiratory airways harbor a complex succession of ecological niches with distinct but related bacterial communities. Particular challenges of respiratory microbiome research have led to limited scientific output compared to other human microbiomes. Areas covered: In this review, we summarize the current state of knowledge of the bacterial respiratory microbiome, with a particular focus on associations between the respiratory microbiome and lower respiratory tract conditions. Expert commentary: There is growing evidence that the respiratory microbiome is associated with lower respiratory infectious diseases and related conditions. Most respiratory microbiome reports are metataxonomic cross-sectional or case-control studies with relatively small sample sizes. Large, prospective projects with metatranscriptomics or metabolomics approach are needed to unravel the effect of the respiratory microbiome on health-related conditions. Moreover, standardization in sampling, library preparation, sequencing techniques and data analysis should be encouraged.

Trends in Pediatric Complicated Pneumonia in an Ontario Local Health Integration Network

Following the introduction of 7-valent pneumococcal vaccine (PCV7), while overall rates of invasive pneumococcal disease and pneumococcal pneumonia in children declined, rates of empyema increased. We examined changes in the incidence of hospitalization for pediatric complicated pneumonia (PCOMP) in Eastern Ontario, Canada, particularly since the introduction of the 13-valent vaccine (PCV13). A retrospective chart review was carried out evaluating previously healthy children admitted with PCOMP, which included empyema, parapneumonic effusion, necrotizing pneumonia, and lung abscess between 2002 and 2015. Three-hundred seventy-one children were included. Subjects had a median age of four years, and 188/370 (50.8%) required a chest tube. Admission rates changed markedly during this time period. The number of admissions per year rose most sharply between 2009 and 2012, corresponding to the period following introduction of PCV7 and then the occurrence of pandemic influenza A (H1N1). In children who likely received PCV13, the incidence of PCOMP returned to approximately pre-PCV7 levels. In contrast, rates of PCOMP in older children (who would not have received PCV13) remained elevated during the post-PCV13 time period. While rates of PCOMP, particularly in older children, remain elevated following the introduction of PCV13, this might be expected to resolve with more widespread vaccine coverage with PCV13 and herd immunity.

Severe community-acquired pneumonia: optimal management

PURPOSE OF REVIEW

Community-acquired pneumonia (CAP) is the leading cause of mortality among infectious diseases. Several efforts have been implemented to achieve better outcomes, but an important proportion of patients continue dying. This review focuses on the newest research on prognostic factors and diagnostics, opening new perspectives in the management of CAP.

RECENT FINDINGS

CAP survival improved in recent years despite an increasing incidence of severe presentations. Appropriateness of antimicrobial choice, combination therapy and early administration of antibiotics has proved to be decisive. Novel biomarkers, as monocyte human leukocyte antigen-DR, presepsin and proadrenomedullin, have been explored for the prediction of severe CAP; moreover, the application of new techniques in metabolomics, genomics and microbiomics in the field of infections may contribute to predicting clinical instability and worse outcomes, showing that precise individual phenotypes are key factors for survival. CAP with unidentified organism is still an issue of concern, but new rapid molecular tests improve yield rates, revealing an unexpected high prevalence of viral detection and proving their usefulness also in the recognition of bacterial causes.

SUMMARY

Precision medicine applied to risk stratification and diagnosis, together with rapid microbiologic molecular testing, may contribute to optimizing the management of CAP, with potential additional reduction of mortality rates.

The Alteration of Nasopharyngeal and Oropharyngeal Microbiota in Children with MPP and Non-MPP

Background: In recent years, the morbidity of Mycoplasma pneumoniae pneumonia (MPP) has increased significantly in China. A growing number of studies indicate that imbalanced respiratory microbiota is associated with various respiratory diseases. Methods: We enrolled 119 children, including 60 pneumonia patients and 59 healthy children. Nasopharyngeal (NP) and oropharyngeal (OP) sampling was performed for 16S ribosomal RNA (16S rRNA) gene analysis of all children. Sputum and OP swabs were obtained from patients for pathogen detection. Results: Both the NP and OP microbiota of patients differ significantly from that of healthy children. Diseased children harbor lower microbial diversity and a simpler co-occurrence network in NP and OP. In pneumonia patients, NP and OP microbiota showed greater similarities between each other, suggesting transmission of NP microbiota to the OP. Aside from clinically detected pathogens, NP and OP microbiota analysis has also identified possible pathogens in seven cases with unknown infections. Conclusion: NP and OP microbiota in MPP and non-MPP are definitely similar. Respiratory infection generates imbalanced NP microbiota, which has the potential to transmit to OP. Microbiota analysis also promises to compliment the present means of detecting respiratory pathogens.

The Nasopharyngeal Microbiota of Children With Respiratory Infections in Botswana

BACKGROUND

Nearly half of child pneumonia deaths occur in sub-Saharan Africa. Microbial communities in the nasopharynx are a reservoir for pneumonia pathogens and remain poorly described in African children.

METHODS

Nasopharyngeal swabs were collected from children with pneumonia (N = 204), children with upper respiratory infection symptoms (N = 55) and healthy children (N = 60) in Botswana between April 2012 and April 2014. We sequenced the V3 region of the bacterial 16S ribosomal RNA gene and used partitioning around medoids to cluster samples into microbiota biotypes. We then used multivariable logistic regression to examine whether microbiota biotypes were associated with pneumonia and upper respiratory infection symptoms.

RESULTS

Mean ages of children with pneumonia, children with upper respiratory infection symptoms and healthy children were 8.2, 11.4 and 8.0 months, respectively. Clustering of nasopharyngeal microbiota identified 5 distinct biotypes: Corynebacterium/Dolosigranulum-dominant (23%), Haemophilus-dominant (11%), Moraxella-dominant (24%), Staphylococcus-dominant (13%) and Streptococcus-dominant (28%). The Haemophilus-dominant [odds ratio (OR): 13.55; 95% confidence interval (CI): 2.10-87.26], the Staphylococcus-dominant (OR: 8.27; 95% CI: 2.13-32.14) and the Streptococcus-dominant (OR: 39.97; 95% CI: 6.63-241.00) biotypes were associated with pneumonia. The Moraxella-dominant (OR: 3.71; 95% CI: 1.09-12.64) and Streptococcus-dominant (OR: 12.26; 95% CI: 1.81-83.06) biotypes were associated with upper respiratory infection symptoms. In children with pneumonia, HIV infection was associated with a lower relative abundance of Dolosigranulum (P = 0.03).

CONCLUSIONS

Pneumonia and upper respiratory infection symptoms are associated with distinct nasopharyngeal microbiota biotypes in African children. A lower abundance of the commensal genus Dolosigranulum may contribute to the higher pneumonia risk of HIV-infected children.

Characterization of the nasopharyngeal viral microbiome from children with community-acquired pneumonia but negative for Luminex xTAG respiratory viral panel assay detection

In the present study, 50 nasopharyngeal swabs from children with community‐acquired pneumonia (CAP) but negative for 18 common respiratory viruses, as measured by the Luminex xTAG Respiratory Viral Panel Assay, were subjected to multiplex metagenomic analyses using a next‐generation sequencing platform. Taxonomic analysis showed that all sequence reads could be assigned to a specific species. An average of 95.13% were assigned to the Bacteria kingdom, whereas, only 0.72% were potentially virus derived. This snapshot of the respiratory tract virome revealed most viral reads to be respiratory tract related, classified into four known virus families: Paramyxoviridae, Herpesviridae, Anelloviridae, and Polyomaviridae. Importantly, we detected a novel human parainfluenza virus 3 (HPIV 3) strain with a 32‐bp insertion in the haemagglutinin‐neuraminidase (HN) gene that produced a negative result in the Luminex assay, highlighting the strength of virome metagenomic analysis to identify not only novel viruses but also viruses likely to be missed by ordinary clinical tests. Thus, virome metagenomic analysis could become a viable clinical diagnostic method.