A Prospective Study on Bacterial and Atypical Etiology of Acute Exacerbation in Chronic Obstructive Pulmonary Disease

Alexandra Nakou; Joseph Papaparaskevas; Filia Diamantea; Nikoletta Skarmoutsou; Vlasis Polychronopoulos; Athanassios Tsakris


Future Microbiol. 2014;9(11):1251-1260. 

In This Article

Abstract and Introduction


Aim The bacterial and atypical etiology of acute exacerbations of chronic obstructive pulmonary disease was investigated and the diagnostic techniques used were compared among 92 hospitalized patients.

Materials & methods Sputum specimens were investigated using culture and PCR, serological status evaluation was performed and the inflammatory profile was associated with the microbiological results.

Results & conclusion The majority of the patients (65.2%) had very severe airway obstruction. The most common bacteria were Haemophilus influenzae and Pseudomonas aeruginosa (23.9 and 14.1%, respectively). Acinetobacter baumannii- and P. aeruginosa-positive cultures were associated with prolonged hospitalization and severe airway obstruction (p = 0.03 and 0.031, respectively). Chlamydia pneumoniae or Mycoplasma pneumoniae infection was diagnosed in four and two patients, respectively. Discrepant results were detected between PCR and serology, especially regarding C. pneumoniae.


Chronic obstructive pulmonary disease (COPD) is a progressive inflammatory airway disorder characterized by airflow limitation due to a mixture of small airway disease, chronic lung inflammation, parenchymal destruction and increased airways responsiveness.[1] Systemic implications and extrapulmonary effects may also contribute to its severity.[2] Although it is considered to be both preventable and treatable, it is also an increasing cause of morbidity and mortality and is projected to rank third among all causes of death by 2020 from fourth place currently.[3] None of the existing medication has been shown to modify the long-term decline in lung function.[4–6] The most important cause of COPD worldwide remains tobacco smoke;[7] other known risk factors are mainly environmental ones (dust, chemical, vapor and fume exposure) and infections.[8]

The chronic course of COPD is often accompanied by acute exacerbations (acute exacerbations of COPD [AECOPD]), due mainly to increased inflammation. Patients prone to frequent AECOPD have impaired health status, reduced physical activity levels, increased lower airway bacterial colonization and accelerated lung-function decline.[9–12] Published data suggest that in nearly 30% of AECOPD the etiology remains unclear, whereas the remaining cases are due to a respiratory tract infection (50–60%), or to environmental factors (10%).[13] Diagnosis of bacterial pathogens is culture based, whereas diagnosis of atypical pathogens is mainly serological and thus time consuming, and requires paired serum samples (acute and convalescence phase). Molecular techniques are used only complementary, while actual correlation of AECOPD etiology with serological status and PCR pathogen detection is unclear. Only a single major standardization initiative, regarding Chlamydophila pneumoniae, has been undertaken,[14] whereas no such endeavor has been initiated for Mycoplasma pneumoniae or Legionella spp. Although PCR is being used in the clinical laboratory, no clear guidelines exist regarding its true performance, drawbacks and limitations.

Reports have shown the association between AECOPD and the presence of bacterial, atypical or viral pathogens,[15–20] in most of the cases a single procedure has been used (serology or direct detection with culture or PCR),[21–27] and studies with combination of techniques are extremely scarce.[28] In addition, inflammatory indexes, like C-reactive protein (CRP) and fibrinogen (FBG) have rarely been included in these investigations.

The present prospective study was undertaken to determine the predominant bacterial and atypical pathogens in AECOPD using all three detection approaches in combination (serology, culture and PCR), implications of the pathogens in the inflammatory profile and functional impairment of the patients, possible discrepancies between the detection methods of atypical pathogens, and the parameters predicting positive sputum cultures.