Analysis of Risk Factors of Bronchiolitis Obliterans in Children with Mycoplasma pneumoniae Bronchiolitis.

OBJECTIVE: To investigate the related risk factors for bronchiolitis obliterans (BO) in children with mycoplasma pneumonia (MP) bronchiolitis. METHOD: The clinical data of 227 children with MP bronchiolitis who were admitted to the II Department of Respiratory of Children's Hospital of Hebei Province from January 2018 to June 2020 were retrospectively analyzed. According to the sequelae of BO, they were divided into 32 cases in the BO group and 195 cases in the non-BO group. The univariate analysis was performed on the clinical and laboratory parameters of the two groups, and the multifactor logistic regression was performed further to determine the independent risk factors for the occurrence of BO in MP bronchiolitis, and then, the cut-off value with the maximum diagnostic value of indicators was found through the ROC curve analysis. RESULTS: The results of univariate and multivariate logistic regression analysis showed that the independent risk factors for the occurrence of BO in MP bronchioles were longer duration of moist rales (OR = 1.203, P = 0.003), higher levels of serum lactate dehydrogenase (LDH) (OR = 1.005, P = 0.036), hypoxemia (OR = 7.442, P = 0.035), and pleural effusion (OR = 4.437, P = 0.004). The area under the ROC curve was 78.2%, 72.0%, 68.2%, and 71.0%, respectively (P < 0.001). The cut-off value of duration of moist rales and levels of serum LDH are 7.5 d and 330 U/L, respectively. CONCLUSION: Children with MP bronchiolitis with high serum LDH level (≥330 U/L), combined with hypoxemia, pleural effusion, and lung wet rale duration (≥7.5 d), may be more prone to BO, in which lung wet rale duration prediction value is the largest. Among them, duration of pulmonary moist rales has the highest predictive value.

Lack of association of Aspergillus colonization with the development of bronchiolitis obliterans syndrome in lung transplant recipients: An international cohort study.

BACKGROUND: Bronchiolitis obliterans syndrome (BOS) is a major limitation in the long-term survival of lung transplant recipients (LTRs). However, the risk factors in the development of BOS remain undetermined. We conducted an international cohort study of LTRs to assess whether Aspergillus colonization with large or small conidia is a risk factor for the development of BOS. METHODS: Consecutive LTRs from January 2005 to December 2008 were evaluated. Rates of BOS and associated risk factors were recorded at 4 years. International Society of Heart and Lung Transplantation criteria were used to define fungal and other infections. A Cox proportional-hazards-model was constructed to assess the association between Aspergillus colonization and the development of BOS controlling for confounders. RESULTS: A total of 747 LTRs were included. The cumulative incidence of BOS at 4 years after transplant was 33% (250 of 747). Additionally, 22% of LTRs experienced Aspergillus colonization after transplantation. Aspergillus colonization with either large (hazard ratio [HR] = 0.6, 95% confidence interval [CI] = 0.3-1.2, p = 0.12) or small conidia (HR = 0.9, 95% CI = 0.6-1.4, p = 0.74) was not associated with the development of BOS. Factors associated with increased risk of development of BOS were the male gender (HR = 1.4, 95% CI = 1.1-1.8, p = 0.02) and episodes of acute rejection (1-2 episodes, HR = 1.5, 95% CI = 1.1-2.1, p = 0.014; 3-4 episodes, HR = 1.6, 95% CI = 1.0-2.6, p = 0.036; >4 episodes, HR = 2.2, 95% CI = 1.1-4.3, p = 0.02), whereas tacrolimus use was associated with reduced risk of BOS (HR = 0.6, 95% CI = 0.5-0.9, p = 0.007). CONCLUSIONS: We conclude from this large multicenter cohort of lung transplant patients, that Aspergillus colonization with large or small conidia did not show an association with the development of BOS.

Bronchiolitis obliterans syndrome susceptibility and the pulmonary microbiome.

BACKGROUND: Lung transplantation outcomes remain complicated by bronchiolitis obliterans syndrome (BOS), a major cause of mortality and retransplantation for patients. A variety of factors linking inflammation and BOS have emerged, meriting further exploration of the microbiome as a source of inflammation. In this analysis, we determined features of the pulmonary microbiome associated with BOS susceptibility. METHODS: Bronchoalveolar lavage (BAL) samples were collected from 25 patients during standard of care bronchoscopies before BOS onset. Microbial DNA was isolated from BAL fluid and prepared for metagenomics shotgun sequencing. Patient microbiomes were phenotyped using k-means clustering and compared to determine effects on BOS-free survival. RESULTS: Clustering identified 3 microbiome phenotypes: Actinobacteria dominant (AD), mixed, and Proteobacteria dominant. AD microbiomes, distinguished by enrichment with Gram-positive organisms, conferred reduced odds and risks for patients to develop acute rejection and BOS compared with non-AD microbiomes. These findings were independent of treatment models. Microbiome findings were correlated with BAL cell counts and polymorphonuclear cell percentages. CONCLUSIONS: In some populations, features of the microbiome may be used to assess BOS susceptibility. Namely, a Gram-positive enriched pulmonary microbiome may predict resilience to BOS.

Rehabilitación respiratoria en niños y adolescentes con bronquiolitis obliterante post infecciosa / Pulmonary rehabilitation in children and adolescents with post-infectious bronchiolitis obliterans

Post-infectious bronchiolitis obliterans (PIBO) is a lung disease characterized by chronic airflow limitation associated with small airway fibrosis and obliteration, caused by viral infection in the first years of life. According to the current clinical guidelines in our country, the bases of its treatment involve pharmacological and non-pharmacological strategies. Among non-pharmacological strategies, pulmonary rehabilitation (PR) is the standout, which consists of diagnostic and therapeutic management designed to evaluate and reverse function deterioration, and aimed at improving the quality of life and the prognosis of these patients.The objective of this review is to describe and discuss the components associated with pulmonary rehabilitation of PIBO patients, emphasizing the properties and attributes of the evaluation methods and the main treatment strategies that contribute to improving these patients' functionality

La bronquiolitis obliterante post infecciosa (BOPI) es una enfermedad pulmonar caracterizada por limitación crónica al flujo de aire asociado a fibrosis y obliteración de la vía aérea pequeña, que se produce como consecuencia de un cuadro infeccioso de origen viral durante los primeros años de vida. De acuerdo a la guía clínica vigente en nuestro país, las bases de su tratamiento se sustentan en estrategias farmacológicas y no farmacológicas. Entre las estrategias no farmacológicas destaca la rehabilitación respiratoria (RR), que se estructura a partir de la ejecución de protocolos de intervención con fines diagnósticos y terapéuticos, dirigidos a evaluar y revertir el deterioro funcional, teniendo como propósito central el mejorar la calidad de vida y el pronóstico de estos pacientes. El objetivo de la presente revisión es describir y discutir los componentes asociados a la rehabilitación pulmonar de los pacientes con BOPI, haciendo énfasis en las propiedades y atributos de los métodos de evaluación y en las principales estrategias de tratamiento que contribuyen a mejorar la funcionalidad de estos pacientes

Mycoplasma pneumoniae-Associated Bronchiolitis Obliterans Following Acute Bronchiolitis.

The characteristics of Mycoplasma pneumonia (M. pneumoniae)-associated bronchiolitis obliterans (BO) are not well known. We retrospectively reviewed 17 patients with M. pneumoniae-associated BO. All patients had M. pneumoniae-associated acute bronchiolitis prior to the development of BO. In the acute bronchiolitis stage, all patients had fever and cough; six patients also had wheezing and dyspnoea. BO was diagnosed approximately 1.5-8 months later based on clinical manifestations and chest high-resolution computed tomography (HRCT) findings. All patients presented with wheezing and/or dyspnoea at the time of diagnosis of BO. HRCT findings included mosaic attenuation, pronounced air trapping, central bronchiectasis and emphysema, according to disease severity. Lung function tests revealed mild to severe airway obstruction. Fourteen of 17 patients had a greater than 12% increase in forced expiratory volume in 1 second values after taking salbutamol. All patients had positive allergy test results and family or personal history of atopic disease. Four patients had a history of asthma before M. pneumonia bronchiolitis. Asthma was diagnosed before, at the time of or after the diagnosis of BO in 11 cases. M. pneumoniae-associated BO may therefore develop following M. pneumonia bronchiolitis and overlap with asthma.

Respiratory reactance in children aged three to five years with postinfectious bronchiolitis obliterans is higher than in those with asthma.

AIM: We investigated airway function in preschoolers with postinfectious bronchiolitis obliterans (PIBO) using impulse oscillometry (IOS). METHODS: This study enrolled 182 children aged three to five years: 12 with PIBO, 135 with asthma and 35 nonatopic controls. Respiratory resistance and reactance were assessed using IOS. RESULTS: The percentage predicted (% predicted) of prebronchodilator respiratory resistance at 5 Hz was significantly higher in children with PIBO (177.9 ± 118.4%) than the asthma (126.1 ± 30.5%, p = 0.013) or control (121.1 ± 21.8%, p = 0.014) groups. After bronchodilator use, children with PIBO did not reach the values of Rrs5% predicted in the asthma and control groups. Respiratory reactance (Xrs5% predicted) in children with PIBO (337.1 ± 478.5%) was significantly higher than both asthma (130.0 ± 80.0%, p = 0.004) and control (105.1 ± 30.8%, p < 0.001) groups before bronchodilator use and significantly higher than the two groups after bronchodilator use (p = 0.010 and p = 0.004, respectively). The changes in Rrs5 and Xrs5 were not significantly different between the children with PIBO and asthma. CONCLUSION: Measuring Rrs5 and Xrs5 before and after bronchodilator use may help to discriminate PIBO from asthma in children aged three to five years with chronic or recurrent respiratory symptoms.

Lung transplantation for non-cystic fibrosis bronchiectasis.

BACKGROUND: Lung transplantation (LTx) is a well-established treatment for end-stage pulmonary disease. However, data regarding microbiology and outcome of patients with non-cystic fibrosis bronchiectasis (NCFB) after lung transplantation are limited. METHODS: A retrospective analysis between August 1992 and September 2014 of all patients undergoing lung transplantation at our program of all recipients with a primary diagnosis of bronchiectasis was performed. Microbiology of sputum and bronchoalveolar lavage specimens, lung function and clinical parameters pre- and post-LTx were assessed retrospectively. Overall survival was compared to the total cohort of lung transplant recipients at institution. The survival and development of chronic lung allograft dysfunction (CLAD) was compared in patients with and without chronic Pseudomonas aeruginosa (PSA) infection after LTx. RESULTS: 34 patients were transplanted. Median age at transplantation was 40 (IQR 33-52) years. The most common etiologies of bronchiectasis were idiopathic (41%), chronic obstructive pulmonary disease (COPD) (21%) and post-infectious (15%). The most common organism of pre- and posttransplant chronic airway infection was PSA. One-year Kaplan-Meier survival for patients with bronchiectasis was 85% and 5-year survival was 73% and similar to the entire cohort. All three patients with an associated diagnosis of immunodeficiency died due to infection and sepsis within the first year. Patients with persistent colonization with Pseudomonas aeruginosa after transplantation had worse long-term survival by trend and developed chronic lung allograft dysfunction more frequently. CONCLUSIONS: Overall survival of patients with bronchiectasis after LTx is comparable to other underlying diseases. A reduced survival was observed in patients with the underlying diagnosis of immunodeficiency.

Staphylococcus via an interaction with the ELR+ CXC chemokine ENA-78 is associated with BOS.

Staphylococcus aureus is the most commonly isolated gram-positive bacterium after lung transplantation (LT) and has been associated with poor posttransplant outcomes, but its effect on bronchiolitis obliterans syndrome (BOS) and death in the context of the allograft inflammatory environment has not been studied. A three-state Cox semi-Markovian model was used to determine the influence of allograft S. aureus and the ELR+ CXC chemokines on the survival rates and cause-specific hazards for movement from lung transplant (State 1) to BOS (State 2), from transplant (State 1) to death (State 3), and from BOS (State 2) to death (State 3). Acute rejection, pseudomonas pneumonia, bronchoalveolar lavage fluid (BALF) CXCL5 and its interaction with S. aureus all increased the likelihood of transition from transplant to BOS. Transition to death from transplant was facilitated by pseudomonas infection and single lung transplant. Movement from BOS to death was affected by the interaction between aspergillus, pseudomonas and CXCL5, but not S. aureus. S. aureus isolation had state specific effects after LT and only in concert with elevated BALF CXCL5 concentrations did it augment the risk of BOS. Pseudomonas and elevated BALF concentrations of CXCL5 continued as significant risk factors for BOS and death after BOS in lung transplantation.

Post-infectious bronchiolitis obliterans in children: a review of 42 cases.

BACKGROUND: This study aimed to describe the clinical characteristics, radiological features and outcomes of 42 children with post-infectious bronchiolitis obliterans (PIBO). METHODS: Forty-two children diagnosed with PIBO were prospectively studied at the First Hospital of Jilin University in northern China between January, 2008 and January, 2013. Their clinical characteristics, lung high resolution computed tomography (HRCT) findings and pulmonary function tests were reported. RESULTS: In children with PIBO, adenovirus was the most common etiologic agent (21/42), followed by Mycoplasma pneumoniae (M. pneumoniae). All of the patients presented with repeated wheezing and tachypnea. In addition, 22 patients required intensive management, while six patients required home oxygen therapy. HRCT findings were consistent with the PIBO diagnosis in all of the patients. Pulmonary function testing was useful in evaluating therapeutic responses. Systemic steroids combined with azithromycin were effective for PIBO treatment. CONCLUSIONS: Severe adenovirus bronchiolitis and M. pneumoniae infections have a higher risk of development for PIBO. HRCT and pulmonary function testing are useful in the diagnosis of PIBO. The degree of airway obstruction did not differ significantly between adenovirus and M. pneumoniae. A combination of steroids and azithromycin offers some benefit in treating these patients.

Parametric response mapping as an indicator of bronchiolitis obliterans syndrome after hematopoietic stem cell transplantation.

The management of bronchiolitis obliterans syndrome (BOS) after hematopoietic cell transplantation presents many challenges, both diagnostically and therapeutically. We developed a computed tomography (CT) voxel-wise methodology termed parametric response mapping (PRM) that quantifies normal parenchyma, functional small airway disease (PRM(fSAD)), emphysema, and parenchymal disease as relative lung volumes. We now investigate the use of PRM as an imaging biomarker in the diagnosis of BOS. PRM was applied to CT data from 4 patient cohorts: acute infection (n = 11), BOS at onset (n = 34), BOS plus infection (n = 9), and age-matched, nontransplant control subjects (n = 23). Pulmonary function tests and bronchoalveolar lavage were used for group classification. Mean values for PRM(fSAD) were significantly greater in patients with BOS (38% ± 2%) when compared with those with infection alone (17% ± 4%, P < .0001) and age-matched control subjects (8.4% ± 1%, P < .0001). Patients with BOS had similar PRM(fSAD) profiles, whether a concurrent infection was present or not. An optimal cut-point for PRM(fSAD) of 28% of the total lung volume was identified, with values >28% highly indicative of BOS occurrence. PRM may provide a major advance in our ability to identify the small airway obstruction that characterizes BOS, even in the presence of concurrent infection.

Changes in the lung microbiome following lung transplantation include the emergence of two distinct Pseudomonas species with distinct clinical associations.

BACKGROUND: Multiple independent culture-based studies have identified the presence of Pseudomonas aeruginosa in respiratory samples as a positive risk factor for bronchiolitis obliterans syndrome (BOS). Yet, culture-independent microbiological techniques have identified a negative association between Pseudomonas species and BOS. Our objective was to investigate whether there may be a unifying explanation for these apparently dichotomous results. METHODS: We performed bronchoscopies with bronchoalveolar lavage (BAL) on lung transplant recipients (46 procedures in 33 patients) and 26 non-transplant control subjects. We analyzed bacterial communities in the BAL fluid using qPCR and pyrosequencing of 16S rRNA gene amplicons and compared the culture-independent data with the clinical metadata and culture results from these subjects. FINDINGS: Route of bronchoscopy (via nose or via mouth) was not associated with changes in BAL microbiota (p = 0.90). Among the subjects with positive Pseudomonas bacterial culture, P. aeruginosa was also identified by culture-independent methods. In contrast, a distinct Pseudomonas species, P. fluorescens, was often identified in asymptomatic transplant subjects by pyrosequencing but not detected via standard bacterial culture. The subject populations harboring these two distinct pseudomonads differed significantly with respect to associated symptoms, BAL neutrophilia, bacterial DNA burden and microbial diversity. Despite notable differences in culturability, a global database search of UM Hospital Clinical Microbiology Laboratory records indicated that P. fluorescens is commonly isolated from respiratory specimens. INTERPRETATION: We have reported for the first time that two prominent and distinct Pseudomonas species (P. fluorescens and P. aeruginosa) exist within the post-transplant lung microbiome, each with unique genomic and microbiologic features and widely divergent clinical associations, including presence during acute infection.

Postinfectious bronchiolitis obliterans in children: the South American contribution.

UNLABELLED: Postinfectious bronchiolitis obliterans (PIBO) is an infrequent chronic lung that causes irreversible obstruction and, or, obliteration of the smaller airways. This review particularly focuses on more than 30 studies from South America. CONCLUSION: The initial PIBO event occurs in the early years of life and is strongly associated with adenovirus infection and the need for mechanical ventilator support. Treatment requires a multidisciplinary strategy. Multicentre studies are needed to determine progression, optimal management and long-term follow-up.

The lung microbiome after lung transplantation.

Lung transplantation survival remains significantly impacted by infections and the development of chronic rejection manifesting as bronchiolitis obliterans syndrome (BOS). Traditional microbiologic data has provided insight into the role of infections in BOS. Now, new non-culture-based techniques have been developed to characterize the entire population of microbes resident on the surfaces of the body, also known as the human microbiome. Early studies have identified that lung transplant patients have a different lung microbiome and have demonstrated the important finding that the transplant lung microbiome changes over time. Furthermore, both unique bacterial populations and longitudinal changes in the lung microbiome have now been suggested to play a role in the development of BOS. In the future, this technology will need to be combined with functional assays and assessment of the immune responses in the lung to help further explain the microbiome's role in the failing lung allograft.

Achromobacter xylosoxidans induced bronchiolitis obliterans in cystic fibrosis.

We report a 12-year-old boy with progressive bronchiolitis obliterans caused by Achromobacter xylosoxidans (Ax) colonization after liver transplantation, resulting in a steep decline in lung function.

Analysis of plasma surfactant protein D levels in lung transplant recipients.

In lung transplant recipients (LTRs), severe clinical complications, such as microbial infections of the lung or transplant rejection, may occur. Surfactant protein D (SP-D) is a C-type lectin that is mainly produced in alveolar type II cells. Plasma SP-D levels are usually low, but may increase when the lung-blood barrier is impaired. In this study, we analyzed whether plasma SP-D concentrations reflect rejection or infection of the lung allograft. An enzyme-linked immunosorbent assay was used to measure SP-D levels in plasma samples from 58 LTRs during intervals without pathologic respiratory findings and during episodes of acute cellular rejection (ACR), microbial colonization, and microbial pneumonia. Median plasma SP-D levels were significantly increased during episodes of microbial pneumonia, but not in the absence of pathologic respiratory findings, during microbial colonization, or during ACR up to grade A2-A3 (P < 0.05). During pneumonia, an increased plasma SP-D level was detected in 60% of LTRs and this was further associated with a significantly higher risk for the patients to develop stage III bronchiolitis obliterans syndrome (BOS III) or to die within the subsequent 6 months after pneumonia (P = 0.0093). All patients with a plasma SP-D level of >300 ng/mL during pneumonia developed BOS III and/or died within 6 months of follow-up (P = 0.001). The determination of SP-D levels in plasma during pneumonia in LTRs may be of prognostic value and warrants further evaluation.

Mold infections in lung transplant recipients.

Fungal infections continue to produce morbidity and mortality in lung transplant recipients despite the widespread use of antifungal prophylaxis. There has been a decline in Candida infections but Aspergillus species predominate. Other mold pathogens including Fusarium, Scedosporium, and Zygomycetes also cause infections in lung transplant recipients. Furthermore, the widespread use of antifungal prophylaxis has prompted a delay in onset of Aspergillus infection in lung transplant recipients. Pulmonary parenchymal disease has become the most common manifestation of invasive aspergillosis. Among the risk factors pre- or posttransplant Aspergillus colonization is the most important risk factor reported in several retrospective studies. Recently posttransplant colonization has been implicated in the development of bronchiolitis obliterans syndrome. Other factors that have been reported include preceding cytomegalovirus infections, hypogammaglobulinemia, and single-lung transplantation. The risk factors for other mold infections such as Scedosporium, Fusarium, and Zygomycetes are not well studied. The best antimold prophylaxis strategy and choice of drug remains to be elucidated. Most lung transplant centers use either voriconazole or inhaled amphotericin preparations. However, data have emerged regarding the increased risk of squamous cell cancer in lung transplant recipients on voriconazole prophylaxis. Advances in the diagnosis and treatment of invasive aspergillosis have resulted in a significant decrease in mortality.

Colonization with small conidia Aspergillus species is associated with bronchiolitis obliterans syndrome: a two-center validation study.

Aspergillus colonization after lung transplantation may increase the risk for bronchiolitis obliterans syndrome (BOS), a disease of small airways. We hypothesized that colonization with small conidia Aspergillus species would be associated with a greater risk of BOS, based upon an increased likelihood of deposition in small airways. We studied adult primary lung recipients from two large centers; 298 recipients at University of California, Los Angeles and 482 recipients at Duke University Medical Center. We grouped Aspergillus species by conidia diameter≤3.5 µm. We assessed the relationship of colonization with outcomes in Cox models. Pre-BOS colonization with small conidia Aspergillus species, but not large, was a risk factor for BOS (p=0.002, HR 1.44, 95% CI 1.14-1.82), along with acute rejection, single lung and Pseudomonas. Colonization with small conidia species also associated with risk of death (p=0.03, HR 1.30, 95% CI 1.03-1.64). Although other virulence traits besides conidia size may be important, we have demonstrated in two large independent cohorts that colonization with small conidia Aspergillus species increases the risk of BOS and death. Prospective evaluation of strategies to prevent Aspergillus colonization of small airways is warranted, with the goal of preserving lung allograft function as long as possible.

Reestablishment of recipient-associated microbiota in the lung allograft is linked to reduced risk of bronchiolitis obliterans syndrome.

RATIONALE: Bronchiolitis obliterans syndrome (BOS) is the primary limiting factor for long-term survival after lung transplantation, and has previously been associated with microbial infections. OBJECTIVES: To cross-sectionally and longitudinally characterize microbial communities in allografts from transplant recipients with and without BOS using a culture-independent method based on high-throughput sequencing. METHODS: Allografts were sampled by bronchoalveolar lavage, and microbial communities were profiled using 16S rRNA gene amplicon pyrosequencing. Community profiles were compared using the weighted Unifrac metric and the relationship between microbial populations, BOS, and other covariates was explored using PERMANOVA and logistic regression. MEASUREMENTS AND MAIN RESULTS: Microbial communities in transplant patients fell into two main groups: those dominated by Pseudomonas or those dominated by Streptococcus and Veillonella, which seem to be mutually exclusive lung microbiomes. Aspergillus culture was also negatively correlated with the Pseudomonas-dominated group. The reestablishment of dominant populations present in patients pretransplant, notably Pseudomonas in individuals with cystic fibrosis, was negatively correlated with BOS. CONCLUSIONS: Recolonization of the allograft by Pseudomonas in individuals with cystic fibrosis is not associated with BOS. In general, reestablishment of pretransplant lung populations in the allograft seems to have a protective effect against BOS, whereas de novo acquisition of microbial populations often belonging to the same genera may increase the risk of BOS.

Interaction between Pseudomonas and CXC chemokines increases risk of bronchiolitis obliterans syndrome and death in lung transplantation.

RATIONALE: Pseudomonas aeruginosa is the most commonly isolated gram-negative bacterium after lung transplantation and has been shown to up-regulate glutamic acid-leucine-arginine-positive (ELR(+)) CXC chemokines associated with bronchiolitis obliterans syndrome (BOS), but the effect of pseudomonas on BOS and death has not been well defined. OBJECTIVES: To determine if the influence of pseudomonas isolation and ELR(+) CXC chemokines on the subsequent development of BOS and the occurrence of death is time dependent. METHODS: A three-state model was developed to assess the likelihood of transitioning from lung transplant (state 1) to BOS (state 2), from transplant (state 1) to death (state 3), and from BOS (state 2) to death (state 3). This Cox semi-Markovian approach determines state survival rates and cause-specific hazards for movement from one state to another. MEASUREMENTS AND MAIN RESULTS: The likelihood of transition from transplant to BOS was increased by acute rejection, CXCL5, and the interaction between pseudomonas and CXCL1. The pseudomonas effect in this transition was due to infection rather than colonization. Movement from transplant to death was facilitated by pseudomonas infection and single lung transplant. Transition from BOS to death was affected by the length of time in state 1 and by the interactions between any pseudomonas isolation and CXCL5 and aspergillus, either independently or in combination. CONCLUSIONS: Our model demonstrates that common post-transplantation events drive movement from one post-transplantation state to another and influence outcomes differently depending upon when after transplantation they occur. Pseudomonas and the ELR(+) CXC chemokines may interact to negatively influence lung transplant outcomes.

Lung-enriched organisms and aberrant bacterial and fungal respiratory microbiota after lung transplant.

RATIONALE: Long-term survival after lung transplantation is limited by infectious complications and by bronchiolitis obliterans syndrome (BOS), a form of chronic rejection linked in part to microbial triggers. OBJECTIVES: To define microbial populations in the respiratory tract of transplant patients comprehensively using unbiased high-density sequencing. METHODS: Lung was sampled by bronchoalveolar lavage (BAL) and upper respiratory tract by oropharyngeal wash (OW). Bacterial 16S rDNA and fungal internal transcribed spacer sequencing was used to profile organisms present. Outlier analysis plots defining taxa enriched in lung relative to OW were used to identify bacteria enriched in lung against a background of oropharyngeal carryover. MEASUREMENTS AND MAIN RESULTS: Lung transplant recipients had higher bacterial burden in BAL than control subjects, frequent appearance of dominant organisms, greater distance between communities in BAL and OW indicating more distinct populations, and decreased respiratory tract microbial richness and diversity. Fungal populations were typically dominated by Candida in both sites or by Aspergillus in BAL but not OW. 16S outlier analysis identified lung-enriched taxa indicating bacteria replicating in the lower respiratory tract. In some cases this confirmed respiratory cultures but in others revealed enrichment by anaerobic organisms or mixed outgrowth of upper respiratory flora and provided quantitative data on relative abundances of bacteria found by culture. CONCLUSIONS: Respiratory tract microbial communities in lung transplant recipients differ in structure and composition from healthy subjects. Outlier analysis can identify specific bacteria replicating in lung. These findings provide novel approaches to address the relationship between microbial communities and transplant outcome and aid in assessing lung infections.