This article is part of Pulmonology Advisor’s coverage of the American Thoracic Society Virtual 2020 meeting.


Subclinical bacteria in the home environment likely influence the airway microbiome and contribute to poor asthma control in patients with refractory asthma, according to findings presented virtually at the American Thoracic Society (ATS) 2020 Virtual meeting, held from August 5 to 10, 2020.

Study investigators assessed the microbiome of bronchoalveolar lavage (BAL) and home dust samples from 5 patients with refractory asthma. These assessments were taken at 2 different time points 12 months apart. Custom extraction methods were used to extract DNA from dust and BAL. Researchers amplified, packaged, and sequenced the V4-V5 region of bacterial 16S rDNA using 2X300bp Illumina chemistry. Additionally, the investigators collected data on BAL cell differentials, bacterial cultures, Asthma Control Test (ACT), and forced expiratory volume in 1 second (FEV1).

Prevotella was present in the home environments of 4 patients and in the BAL of all patients. A total of 2 of the 4 patients with environmental Clostridia also had Clostridia in BAL and did not have improvements in clinical asthma outcomes. All patients had Staphylococcus DNA (1 +BAL DNA), Streptococcus (4 +BAL DNA), and Pseudomonas (3 +BAL DNA; 1 +BAL culture). There was 1 patient with Streptococcus who converted from -BAL to +BAL DNA.


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Only 1 patient with Pseudomonas +BAL DNA was treated with antibiotics. In this patient, there was a substantial BAL DNA burden of Pseudomonas with small amounts on culture. No clinical improvement was observed in patients with +BAL DNA and -BAL culture who did not receive antibiotics. Only 2 patients had positive clinical cultures for Pseudomonas and Mycobacterium. Both cultures featured low BAL genera diversity. The patient with Pseudomonas largely in the BAL microbiome showed a response responded to antibiotics. This response led to elimination of bacterial DNA and culture. Ultimately, there was increased BAL biodiversity and reduced environmental DNA burden in this patient, which correlated with clinical improvement.

The investigators noted, “Preliminary analysis of environment and airway microbiome suggests asthma control is dependent on treatment of microbes detected by culture and (possibly) by predominance in DNA profiling.” They added, “Microbial profiling by sequencing could complement standard clinical cultures of the airway in the management of asthma.”

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Reference

Guntur VP, Manka L, Epperson E, Strong M, Martin RJ. Examination of home environmental microbiome, airway microbiome, and clinical features of asthma control in refractory asthma. Presented at: American Thoracic Society 2020 Virtual; August 5-10, 2020. Abstract #P1327.