Causative Organisms and Empiric Therapy in Elderly COPD Smokers

Primary Bacterial Pathogens

The European Respiratory Society suggests that Haemophilus influenzae and Streptococcus pneumoniae are the two most common causative organisms of respiratory infections in elderly COPD smokers, with both being equally important and requiring empiric coverage 1, 2
Streptococcus pneumoniae remains predominant across all severity levels of COPD, according to the European Respiratory Society and Clinical Microbiology and Infection 1, 3, 4
Moraxella catarrhalis is the third most common organism, especially in patients with lower lung function, as reported by the European Respiratory Journal 1

In mild COPD, Streptococcus pneumoniae is predominant, followed by Haemophilus influenzae and Moraxella catarrhalis, as stated by the European Respiratory Journal 1
In moderate to severe COPD, Haemophilus influenzae and Moraxella catarrhalis become more frequent, according to the European Respiratory Journal 1
In very severe COPD or patients requiring mechanical ventilation, Enteric Gram-negative bacilli and Pseudomonas aeruginosa may appear, as reported by the European Respiratory Journal 1

Pseudomonas aeruginosa should be considered in patients with recent hospitalization, frequent antibiotic use, severe COPD, or previous isolation of P. aeruginosa, as suggested by the European Respiratory Journal 1
Chlamydia pneumoniae is found in 4-20% of exacerbations, often as co-infection, according to the European Respiratory Journal 1
Mycoplasma pneumoniae is less frequent than Chlamydia pneumoniae, as reported by the European Respiratory Journal 1

Viruses account for approximately one-third of acute exacerbations, with Rhinovirus and RSV being the most frequent viral causes, as stated by the European Respiratory Journal 1
Influenza A and B are common during seasonal outbreaks, according to Clinical Microbiology and Infection 3, 4

Polymicrobial infections occur in 6-26% of hospitalized patients, with the most frequent combinations including S. pneumoniae with H. influenzae, or bacteria with atypical organisms, as reported by Clinical Microbiology and Infection 3, 4
S. pneumoniae combined with influenza virus is a particularly common and severe combination, according to Clinical Microbiology and Infection 3, 4

First-line empiric therapy must cover both S. pneumoniae and H. influenzae, as recommended by the European Respiratory Society and Praxis Medical Insights 1, 2
The preferred antibiotic regimen is Amoxicillin-clavulanate 625 mg three times daily for 5-7 days, as suggested by Praxis Medical Insights 2, 5
Doxycycline is an alternative for β-lactam intolerance, according to Praxis Medical Insights 2
Respiratory fluoroquinolones, such as moxifloxacin or levofloxacin, may be considered for severe COPD with risk factors, as reported by the European Respiratory Journal 1