Species-Specific Interactions of Common Bacteria in COPD

Interspecies interactions, both positive and negative, between common pathogenic bacteria have been reported in patients with chronic obstructive pulmonary disease (COPD), which may offer novel therapeutic opportunities to alter the characteristics of the airway microbiota of these individuals.

Data from the Bacterial Infection in COPD study — a prospective cohort study of individuals with COPD who were recruited through an outpatient clinic in the Veterans Affair Medical Center in Buffalo, New York — were analyzed, and the results were published in the Journal of Clinical Microbiology.

The investigators sought to characterize the colonization of 4 bacterial species — Haemophilus influenzae, Moraxella catarrhalis, Streptococcus pneumoniae, and Pseudomonas aeruginosa — to determine species-specific interactions and to estimate the effect of host factors on bacterial colonization in patients with COPD.

The current study was conducted in veterans with COPD and involved monthly clinical assessments and sputum cultures, with an average follow-up duration of 4.5 years. The cultures were used for bacterial identification. Bacterial interactions were studied using generalized linear mixed models after controlling for demographic and clinical variables. The outcome of interest was the relationship among bacteria according to clinical status (ie, stable or exacerbation).

Overall, 181 study participants underwent a total of 8843 clinic visits, with 1 of the 4 above-named bacteria isolated in 30.8% of these visits. H influenzae, the most common bacterium isolated, was found in 14.4% of participants, followed by P aeruginosa in 8.1% of participants.

In adjusted models, S pneumoniae colonization was positively associated with H influenzae colonization (odds ratio [OR], 2.79; 95% CI, 2.03-3.73). In contrast, negative associations were reported between P aeruginosa and H influenzae (OR, 0.15; 95% CI, 0.10-0.22) and between P aeruginosa and M catarrhalis (OR, 0.51; 95% CI, 0.35-0.75).

Reported associations were similar during both stable and exacerbation visits. Moreover, recent antimicrobial therapy was linked to a lower prevalence of S pneumoniae, H influenza, and M catarrhalis, but not P aeruginosa.

The investigators concluded that the study findings support the existence of specific interspecies interactions between common bacteria in the lower respiratory tracts of patients with COPD. Additional research is warranted to clarify the mechanisms of these complex interactions that shift bacterial species, which may have important implications for the treatment of COPD.

Reference

Jacobs DM, Ochs-Balcom HM, Zhao J, Murphy TF, Sethi S. Lower airway bacterial colonization patterns and species-specific interactions in chronic obstructive pulmonary disease [published online July 25, 2018]. J Clin Microbiol. doi:10.1128/JCM.00330-18