ABSTRACT
Background and objective
Long‐term data on children with PBB has been identified as a research priority. We describe the 5‐year outcomes for children with PBB to ascertain the presence of ...chronic respiratory disease (bronchiectasis, recurrent PBB and asthma) and identify the risk factors for these.
Methods
Prospective cohort study was undertaken at the Queensland Children's Hospital, Brisbane, Australia, of 166 children with PBB and 28 controls (undergoing bronchoscopy for symptoms other than chronic wet cough). Monitoring was by monthly contact via research staff. Clinical review, spirometry and CT chest were performed as clinically indicated.
Results
A total of 194 children were included in the analysis. Median duration of follow‐up was 59 months (IQR: 50–71 months) post‐index PBB episode, 67.5% had ongoing symptoms and 9.6% had bronchiectasis. Significant predictors of bronchiectasis were recurrent PBB in year 1 of follow‐up (ORadj = 9.6, 95% CI: 1.8–50.1) and the presence of Haemophilus influenzae in the BAL (ORadj = 5.1, 95% CI: 1.4–19.1). Clinician‐diagnosed asthma at final follow‐up was present in 27.1% of children with PBB. A significant BDR (FEV1 improvement >12%) was obtained in 63.5% of the children who underwent reversibility testing. Positive allergen‐specific IgE (ORadj = 14.8, 95% CI: 2.2–100.8) at baseline and bronchomalacia (ORadj = 5.9, 95% CI: 1.2–29.7) were significant predictors of asthma diagnosis. Spirometry parameters were in the normal range.
Conclusion
As a significant proportion of children with PBB have ongoing symptoms at 5 years, and outcomes include bronchiectasis and asthma, they should be carefully followed up clinically. Defining biomarkers, endotypes and mechanistic studies elucidating the different outcomes are now required.
In this cohort study of 166 children with PBB, the frequency of wet cough exacerbation decreased with age. At 5‐year follow‐up, a significant proportion had a diagnosis of bronchiectasis, asthma or had persistent wet cough symptoms. Children with PBB require careful follow‐up, appropriate investigation and treatment.
See related Editorial
Background
Obtaining lower airway specimens is important for guiding therapy in chronic lung infection but is difficult in young children unable to expectorate. While culture‐based studies have ...assessed the diagnostic accuracy of nasopharyngeal or oropharyngeal specimens for identifying lower airway infection, none have used both together. We compared respiratory bacterial pathogens cultured from nasopharyngeal and oropharyngeal swabs with bronchoalveolar lavage (BAL) cultures as the “gold standard” to better inform the diagnosis of lower airway infection in children with chronic wet cough.
Methods
Nasopharyngeal and oropharyngeal swabs and BAL fluid specimens were collected concurrently from consecutive children undergoing flexible bronchoscopy for chronic cough and cultured for bacterial pathogens.
Results
In cultures from 309 children (median age, 2.3 years) with chronic endobronchial suppuration, all main pathogens detected (Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis) were more prevalent in nasopharyngeal than oropharyngeal swabs (37%, 34%, and 23% vs 21%, 6.2%, and 3.2%, respectively). Positive and negative predictive values for lower airway infection by any of these three pathogens were 63% (95% confidence interval 95% CI 55, 70) and 85% (95% CI, 78, 91) for nasopharyngeal swabs, 65% (95% CI, 54, 75), and 66% (95% CI, 59, 72) for oropharyngeal swabs, and 61% (95% CI, 54,68), and 88% (95% CI, 81, 93) for both swabs, respectively.
Conclusions
Neither nasopharyngeal nor oropharyngeal swabs, alone or in combination, reliably predicted lower airway infection in children with chronic wet cough. Although upper airway specimens may be useful for bacterial carriage studies and monitoring antimicrobial resistance, their clinical utility in pediatric chronic lung disorders of endobronchial suppuration is limited.
Background
Differentiating lower airway bacterial infection from possible upper airway contamination in children with endobronchial disorders undergoing bronchoalveolar lavage (BAL) is important for ...guiding management. A diagnostic bacterial load threshold based on inflammatory markers has been determined to differentiate infection from upper airway contamination in infants with cystic fibrosis, but not for children with protracted bacterial bronchitis (PBB), chronic suppurative lung disease (CSLD), or bronchiectasis.
Methods
BAL samples from children undergoing bronchoscopy underwent quantitative bacterial culture, cytologic examination, and respiratory virus testing; a subset also had interleukin‐8 examined. Geometric means (GMs) of total cell counts (TCCs) and neutrophil counts were plotted by respiratory pathogen bacterial load. Logistic regression determined associations between age, sex, Indigenous status, antibiotic exposure, virus detection and bacterial load, and elevated TCCs (>400 × 103 cells/mL) and airway neutrophilia (neutrophils >15% BAL leukocytes).
Results
From 2007 to 2016, 655 children with PBB, CSLD, or bronchiectasis were enrolled. In univariate analyses, Indigenous status and bacterial load ≥105 colony‐forming units (CFU)/mL were positively associated with high TCCs. Viruses and bacterial load ≥104 CFU/mL were positively associated with neutrophilia; negative associations were seen for Indigenous status and macrolides. In children who had not received macrolide antibiotics, bacterial load was positively associated in multivariable analyses with high TCCs at ≥104 CFU/mL and with neutrophilia at ≥105 CFU/mL; GMs of TCCs and neutrophil counts were significantly elevated at 104 and 105 CFU/mL compared to negative cultures.
Conclusions
Our findings support a BAL threshold ≥104 CFU/mL to define lower airway infection in children with chronic endobronchial disorders.
Unambiguous identification of nontypeable Haemophilus influenzae (NTHi) is not possible by conventional microbiology. Molecular characterisation of phenotypically defined NTHi isolates suggests that ...up to 40% are Haemophilus haemolyticus (Hh); however, the genetic similarity of NTHi and Hh limits the power of simple molecular techniques such as PCR for species discrimination.
Here we assess the ability of previously published and novel PCR-based assays to identify true NTHi. Sixty phenotypic NTHi isolates, classified by a dual 16S rRNA gene PCR algorithm as NTHi (n = 22), Hh (n = 27) or equivocal (n = 11), were further characterised by sequencing of the 16S rRNA and recA genes then interrogated by PCR-based assays targeting the omp P2, omp P6, lgtC, hpd, 16S rRNA, fucK and iga genes. The sequencing data and PCR results were used to define NTHi for this study. Two hpd real time PCR assays (hpd#1 and hpd#3) and the conventional iga PCR assay were equally efficient at differentiating study-defined NTHi from Hh, each with a receiver operator characteristic curve area of 0.90 0.83; 0.98. The hpd#1 and hpd#3 assays were completely specific against a panel of common respiratory bacteria, unlike the iga PCR, and the hpd#3 assay was able to detect below 10 copies per reaction.
Our data suggest an evolutionary continuum between NTHi and Hh and therefore no single gene target could completely differentiate NTHi from Hh. The hpd#3 real time PCR assay proved to be the superior method for discrimination of NTHi from closely related Haemophilus species with the added potential for quantification of H. influenzae directly from specimens. We suggest the hpd#3 assay would be suitable for routine NTHi surveillance and to assess the impact of antibiotics and vaccines, on H. influenzae carriage rates, carriage density, and disease.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Objectives: To assess vitamin D status in Indigenous mothers and infants in the Northern Territory, and to determine whether cord blood vitamin D levels are correlated with the risk of infant ...hospitalisation for acute lower respiratory infection (ALRI).
Design and participants: Within a nested cohort of 109 Indigenous mother–infant pairs recruited between 2006 and 2011, we used liquid chromatography–mass spectrometry to measure vitamin D (25(OH)D3) levels in maternal blood during pregnancy (n = 33; median gestation, 32 weeks range, 28–36 weeks) and at birth (n = 106; median gestation, 39 weeks range, 34–41 weeks), in cord blood (n = 84; median gestation, 39 weeks range, 36–41 weeks), and in infant blood at age 7 months (n = 37; median age, 7.1 months range, 6.6–8.1 months).
Main outcome measure: ALRI hospitalisations during the first 12 months of infancy, identified using International Classification of Diseases coding (J09–J22, A37–A37.9).
Results: Compared with mean 25(OH)D3 levels in maternal blood during pregnancy (104 nmol/L), mean levels were 23% lower in maternal blood at birth (80 nmol/L) and 48% lower in cord blood samples (54 nmol/L). The mean cord blood 25(OH)D3 concentration in seven infants subsequently hospitalised for an ALRI was 37 nmol/L (95% CI, 25–48 nmol/L), lower than the 56 nmol/L (95% CI, 51–61 nmol/L) in the 77 infants who were not hospitalised with an ALRI (P = 0.025).
Conclusions: Cord blood 25(OH)D3 concentrations were about half those in maternal blood during the third trimester of pregnancy (about 7 weeks earlier). Most cord blood levels (80%) were classified as vitamin D insufficient (< 75 nmol/L) by existing guidelines, and were lower among infants who were subsequently hospitalised with an ALRI.
The rapid expansion of 16S rRNA gene sequencing in challenging clinical contexts has resulted in a growing body of literature of variable quality. To a large extent, this is due to a failure to ...address spurious signal that is characteristic of samples with low levels of bacteria and high levels of non-bacterial DNA. We have developed a workflow based on the paired-end read Illumina MiSeq-based approach, which enables significant improvement in data quality, post-sequencing. We demonstrate the efficacy of this methodology through its application to paediatric upper-respiratory samples from several anatomical sites.
A workflow for processing sequence data was developed based on commonly available tools. Data generated from different sample types showed a marked variation in levels of non-bacterial signal and 'contaminant' bacterial reads. Significant differences in the ability of reference databases to accurately assign identity to operational taxonomic units (OTU) were observed. Three OTU-picking strategies were trialled as follows: de novo, open-reference and closed-reference, with open-reference performing substantially better. Relative abundance of OTUs identified as potential reagent contamination showed a strong inverse correlation with amplicon concentration allowing their objective removal. The removal of the spurious signal showed the greatest improvement in sample types typically containing low levels of bacteria and high levels of human DNA. A substantial impact of pre-filtering data and spurious signal removal was demonstrated by principal coordinate and co-occurrence analysis. For example, analysis of taxon co-occurrence in adenoid swab and middle ear fluid samples indicated that failure to remove the spurious signal resulted in the inclusion of six out of eleven bacterial genera that accounted for 80% of similarity between the sample types.
The application of the presented workflow to a set of challenging clinical samples demonstrates its utility in removing the spurious signal from the dataset, allowing clinical insight to be derived from what would otherwise be highly misleading output. While other approaches could potentially achieve similar improvements, the methodology employed here represents an accessible means to exclude the signal from contamination and other artefacts.
The bacterial factors responsible for the variation in invasive potential between different clones and serotypes of Streptococcus pneumoniae are largely unknown. Therefore, the isolation of rare ...serotype 1 carriage strains in Indigenous Australian communities provided a unique opportunity to compare the genomes of non-invasive and invasive isolates of the same serotype in order to identify such factors. The human virulence status of non-invasive, intermediately virulent and highly virulent serotype 1 isolates was reflected in mice and showed that whilst both human non-invasive and highly virulent isolates were able to colonize the murine nasopharynx equally, only the human highly virulent isolates were able to invade and survive in the murine lungs and blood. Genomic sequencing comparisons between these isolates identified 8 regions >1 kb in size that were specific to only the highly virulent isolates, and included a version of the pneumococcal pathogenicity island 1 variable region (PPI-1v), phage-associated adherence factors, transporters and metabolic enzymes. In particular, a phage-associated endolysin, a putative iron/lead permease and an operon within PPI-1v exhibited niche-specific changes in expression that suggest important roles for these genes in the lungs and blood. Moreover, in vivo competition between pneumococci carrying PPI-1v derivatives representing the two identified versions of the region showed that the version of PPI-1v in the highly virulent isolates was more competitive than the version from the less virulent isolates in the nasopharyngeal tissue, blood and lungs. This study is the first to perform genomic comparisons between serotype 1 isolates with distinct virulence profiles that correlate between mice and humans, and has highlighted the important role that hypervariable genomic loci, such as PPI-1v, play in pneumococcal disease. The findings of this study have important implications for understanding the processes that drive progression from colonization to invasive disease and will help direct the development of novel therapeutic strategies.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Streptococcus pneumoniae (pneumococcus) is the main cause of bacterial pneumonia worldwide and has been studied extensively in this context. However, its role in chronic endobronchial infections and ...accompanying lower airway neutrophilic infiltration has received little attention. Severe and recurrent pneumonia are risk factors for chronic suppurative lung disease (CSLD) and bronchiectasis; the latter causes considerable morbidity and, in some populations, premature death in children and adults. Protracted bacterial bronchitis (PBB) is another chronic endobronchial infection associated with substantial morbidity. In some children, PBB may progress to bronchiectasis. Although nontypeable Haemophilus influenzae is the main pathogen in PBB, CSLD and bronchiectasis, pneumococci are isolated commonly from the lower airways of children with these diagnoses. Here we review what is known currently about pneumococci in PBB, CSLD and bronchiectasis, including the importance of pneumococcal nasopharyngeal colonization and how persistence in the lower airways may contribute to the pathogenesis of these chronic pulmonary disorders. Antibiotic treatments, particularly long‐term azithromycin therapy, are discussed together with antibiotic resistance and the impact of pneumococcal conjugate vaccines. Important areas requiring further investigation are identified, including immune responses associated with pneumococcal lower airway infection, alone and in combination with other respiratory pathogens, and microarray serotyping to improve detection of carriage and infection by multiple serotypes. Genome wide association studies of pneumococci from the upper and lower airways will help identify virulence and resistance determinants, including potential therapeutic targets and vaccine antigens to treat and prevent endobronchial infections. Much work is needed, but the benefits will be substantial.
Effective management of protracted bacterial bronchitis (PBB) is needed to prevent chronic disease (eg, bronchiectasis). Understanding the contributions of ongoing airway infection and inflammation ...is important to achieving optimal PBB treatments. The aim of this study was to compare BAL microbiota, bacterial biomass, and inflammatory markers in children with PBB and age-matched control patients.
BAL was prospectively collected from 28 children with PBB (median age, 1.7 years; range, 0.6-7.4) and 8 control patients (median age, 1.9 years; range, 0.4-4.7). BAL microbiology was determined using culture, 16S ribosomal RNA gene sequencing and bacterial biomass quantification. BAL inflammatory cells, IL-8, and IL-1β were used to assess lower airway inflammation.
Bacterial biomass, neutrophil percentage, IL-8, and IL-1β levels were significantly higher in children with PBB compared with control patients. BAL microbiota in children with PBB was significantly different to that of control patients (permutational multivariate analysis of variance P = .001) and clustered into four distinct profiles that were either dominated by a respiratory pathogen or contained a more diverse microbiota including Prevotella species. Alpha diversity was unrelated to bacterial biomass, culture of recognized respiratory pathogens, or inflammatory markers.
Neutrophilic inflammation in children with PBB was associated with multiple BAL microbiota profiles. Significant associations between inflammatory markers and bacterial biomass, but not alpha diversity, suggest that inflammation in children with PBB is not driven by single pathogenic species. Understanding the role of the entire respiratory microbiota in PBB pathogenesis may be important to determining whether bacteria other than the recognized pathogens contribute to disease recurrence and progression to bronchiectasis.
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