Table 4.

Main dysbiotic events that occur in GM during the onset and progression of pulmonary diseases.

Pulmonary Disease	Main Dysbiotic Events in GM	Reference
Asthma	-Deficiency in GM composition in early life is associated with childhood asthma development -Asthmatic patients have a higher abundance of Ruminococcus gnavus, Bacteroides plebeius, and Clostridium clostridioforme and a lower abundance of Roseburia inulinivorans and Clostridium disporicum -Alterations in GM composition are involved in the severity of asthma; mainly, a lower abundance of Acidaminococcaceae and a higher abundance of Veillonellaceae and Prevotellaceae was observed in severe asthma	[141,146,147,148,149]
Chronic obstructive pulmonary disease (COPD)	-In individuals with COPD compared to healthy subjects, there was a decrease in the proportion of Bacteroidetes and an increase in Firmicutes. Additionally, at the family level, there were notable differences in the relative abundances of Fusobacteriaceae, Prevotellaceae, and Bacteroidaceae, whereas Prevotella was more prevalent in the faecal samples of COPD patients -Specific Streptococci species and members of the Lachnospiraceae family were identified as distinguishing factors between COPD patients and healthy controls, and were also found to be correlated with impaired lung function -GM may be involved in the acute exacerbations of COPD, resulting in negative effects	[136,154,155,156]
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)	-The GM of COVID-19 patients appeared seriously dysbiotic, enriched in potential pathogens, with reduced diversity and loss of beneficial microorganisms, mainly Bacteroides, Blautia, Coprococcus, Dialister, Faecalibacterium, Lachnospira, Oscillospira, Prevotella, Roseburia, and Ruminococcus -GM dysbiosis of COVID-19 patients has been found to be correlated with disease severity -Gut dysbiosis persists even after recovery from COVID-19 and may contribute to long COVID-19	[167,169,171,172]
Lung cancer	-Augmented levels of Enterococcus in GM are associated with lung cancer, while Bifidobacterium and Enterococcus were found to be the highest potential biomarkers for lung carcinogens -GM dysbiosis may impact lung cancer treatment and prognosis	[177,178,179]