Introduction Patients with lung cancer are at higher risk of pulmonary infection due to immunosuppression and impaired function of the natural protective mechanisms which can have an impact on oncological treatment and survival. Aims: To assess the proportion of potentially pathogenic microorganisms (PPM) that colonise the bronchial tree in patients with primary lung cancer.
Methods A bronchoscopic study of 165 patients (101 M and 64 F) aged from 31 to 96 (mean 69 years) with confirmed malignancy on bronchial sampling was conducted from January 2005 to July 2010. In all patients, bronchial washings (BW) were performed during bronchoscopy. Obtained BW fluid was subjected to microbiological examination and culture by the semi-quantitative method. A diagnostic level of >100 colony forming units (CFU) was set. Computed tomography thorax scans were also assessed for radiological signs of pneumonia.
Results In 27 (16.4%) of 165 patients, bronchial colonisation of PPM was >100 CFU. In 28 patients (17.0%), the culture of PPM was <100 CFU. The presence of fungi and upper respiratory tract flora was confirmed in 24 (14.5%) and 35 (21.2%) patients, respectively. Mycobacterium Tuberculosis was negative in the 159 patients that had been tested and Mycobacterium Fortuitum was isolated in one patient. Sixteen (9.7%) patients were colonised with Gram positive PPM. The most frequently isolated PPM was Coliform (n=9, 5.5%) followed by Staphylococcus aureus (n=8, 5%) and Streptococcus pneumoniae (n=5, 3.0%). Bronchial colonisation of PPM was highest in patients with small cell lung carcinoma (5/26, 19.2%) and similar between primary adenocarcinoma (4/30, 13.3%) and squamous cell carcinoma (12/82, 14.6%). Four multi-drug resistant strains of bacteria (2.4%) including MRSA (n=2) were isolated. In five patients (3.0%), the bronchial tree was colonised simultaneously by two or more types of PPM. A third (9/27) of patients with PPM also had radiological evidence of pneumonia.
Conclusions Less than 20% of patients with lung cancer had bronchial colonisation of microorganisms above the assumed diagnostic level. Approximately two-thirds had colonisation with Gram-positive bacteria in their distal airways. Bronchial bacterial colonisation appears to be slightly higher in patients with small cell lung cancer. The identification of potentially pathogenic microorganisms in the distal airways of lung cancer patients, especially at the time of diagnosis, is clinically important before deciding future management strategies. An empirical antibiotics policy would be useful in these patients.