New Biomarker May Enable Selective Antibiotic Use for COPD Exacerbation

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G:F ratio also has potential to be used an effective biomarker to implement selective antibiotic use in COPD exacerbations.
G:F ratio also has potential to be used an effective biomarker to implement selective antibiotic use in COPD exacerbations.

The selective use of antibiotics may be beneficial during an exacerbation of chronic obstructive pulmonary disease (COPD) in patients with a specific Gammaproteobacteria:Firmicutes (G:F) ratio present in their sputum, according to a study published in PLoS One.1

The researchers previously found that the sputum G:F ratio, determined by 16S genome sequencing, was increased at the time of COPD exacerbation and later returned to baseline after recovery.2 They hypothesized that this increased ratio may serve as a biomarker to guide antibiotic treatment.


A cohort of 58 individuals with a total of 66 exacerbation episodes was identified. Sputum samples were collected during a stable period (8 weeks after exacerbation), the day of exacerbation prior to initiation of antibiotic treatment (day 0), at day 14, and at day 42.

Three subgroups were identified: High Gammaproteobacteria (HG; n=20), High Firmicutes (HF; n=35), and Gammaproteobacteria Firmicutes (GF; n=9). The HG cluster demonstrated significantly higher G:F ratios at exacerbation that returned to baseline upon recovery (P <.00001). 

Additionally, a statically significant receiver-operator-characteristic curve (ROC) was identified in the HG group at the time of exacerbation (area under the curve [AUC] 0.90, P <.0001). 

An increase in G:F ratio was also positively associated with the increase in mean C-reactive protein levels during each visit (day 0>day 42>day 14>stable, P =.0002).


“Using an assay that assesses the balance between the two numerically dominant bacterial groups in COPD sputum samples, we have identified a subgroup of exacerbation events in which this balance is disturbed at exacerbation and returns to baseline with clinical recovery,” the researchers concluded.

The investigators surmised that the G:F ratio has potential to be used as an effective biomarker for implementing selective antibiotic use in the treatment of patients with COPD experiencing an exacerbation.


  1. Haldar K, Bafadhel M, Lau K, Berg A, Kwambana B, Kebadze T, et al.  Microbiome balance in sputum determined by PCR stratifies COPD exacerbations and shows potential for selective use of antibiotics [published online August 25, 2017]. PLoS One. 201712:e0182833. doi:10.1371/journal.pone.0182883
  2. Haldar K, Lau K, Bafadhel M, Brightling C, Barer M. S16 Molecular profiling of the airway microbiome in COPD. Thorax. 2011;66(Suppl 4):A10.

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