Lower airway bacterial colonization in asymptomatic smokers and smokers with chronic bronchitis and recurrent exacerbations

Abstract

Bacterial colonization of the lower airways in patients with chronic bronchitis (CB) has been described mainly in patients with co-existing chronic obstructive pulmonary disease (COPD). Although smoking has been identified as a risk factor for bacterial colonization it is not known whether asymptomatic smokers (AS) can be colonized. The aim of this study was to study lower airway bacterial colonization in smokers with stable CB and recurrent exacerbations and compare with AS and healthy never-smokers (NS). Thirty-nine smokers with CB and recurrent exacerbations (median FEV1 85% of predicted normal), 10 AS and 10 NS, underwent bronchoscopy and a two-step bronchoalveolar lavage (BAL) procedure where the first portion (20 ml, 'pre-BAL') was recovered separately from the rest (140 ml, 'BAL'). The degree of oropharyngeal contamination of pre-BAL and BAL samples was evaluated by cytology. Semiquantitative bacterial cultures were performed on all samples. Higher bacterial numbers than 10(3) colony-forming units (cfu) x ml(-1) in BAL were found only in the two smoking groups. Using 10(3) cfu x ml(-1) as cut-off, 6/10 (60%) in the AS-, and 7/35 (20%) in the CB-group were colonized in the lower airways. In all, 29% of all smokers had bacterial colonization. Only bacteria belonging to the normal oropharyngeal flora were found. The proportion of samples with oropharyngeal contamination was significantly lower in BAL than in pre-BAL (5% vs. 21%, P=0.039). The proportion of sterile samples was significantly higher in BAL than in pre-BAL (49% vs. 26%, P=0.002). Lower airway bacterial colonization was found both in asymptomatic smokers and in patients with CB. Colonization with potential respiratory pathogens is uncommon in patients with CB and recurrent exacerbations without severe airflow obstruction. The two-step BAL procedure seems to decrease oropharyngeal contamination.

Topographical Continuity of Bacterial Populations in the Healthy Human Respiratory Tract

“…Unlike quantitative thresholds empirically determined for diagnosis of pneumonia, however, there are no validated criteria for defining colonization or identifying normal microbial populations of the lower airways. Some culture-based studies attempted to minimize URT carryover using the two-scope approach or separate analysis of BAL 1st Return (28)(29)(30)50). As we have shown, culture-independent characterization of LRT microflora does not obviate the need for similar careful sampling and interpretation.…”

“…One bronchoscope was inserted only to the level of the glottis, which provided samples approximating what a bronchoscope entering the LRT might carry down (28) (Scope #1 Tip and Post-wash). A second scope was then passed without suctioning, and sequential BAL done in two immediately adjacent regions of the right middle lobe (BAL-A and BAL-B), keeping the first aliquot of the initial BAL separate (BAL-A 1st and 2nd Returns) (29,30). The lower left lobe bronchial mucosa was then sampled by protected specimen brush (PSB).…”

Pseudomonal airway colonisation: risk factor for bronchiolitis obliterans syndrome after lung transplantation?

“…Even in the CF population, with a high prevalence of colonisation, there is no consensus on the appropriate definition [5,6]. To differentiate colonisation from infection, protected brush catheter cultures (regarded as the 'gold standard'), quantitative BAL and sputum cultures are being used, although not consistently in identical settings, making comparisons between studies difficult [2][3][4][5][28][29][30][31][32][33]. Regular BAL, which has a high diagnostic accuracy for the detection of lower airway inflammation, is also a generally accepted tool to assess airway inflammation [28][29][30][31][32][33].…”

“…Former Pseudomonas species have recently been reclassified and belong to other genera, such as Burkholderia (B. cepacia, Alcaligenes xylosoxidans), Xanthomonas (Stenothrophomonas), Aeromonas, etc., which are generally referred to as Pseudomonads [1]. Airway colonisation with Pseudomonads, especially P. aeruginosa, is common in patients with altered pulmonary defences [2][3][4][5][6], but also in immunocompromised lung transplant (LTx) recipients [7][8][9]. Colonisation with mucoid or multiple-antibiotic resistant P. aeruginosa or B. cepacia is associated with a worse prognosis, particularly in cystic fibrosis (CF) patients [10][11][12].…”

The Effect of Cigarette and Hookah Smoke on Oral Bacterial Growth, Streptococcus mutans and Streptococcus sanguis: An In vitro Study

“…Studying the subgingival microbiology assessment has identified Streptococcus (S.) mutans as the main cause of dental decay; S.s also plays a role in the oral plaque (16). The risk of respiratory infections also increases in smokers, possibly due to provision of an environment for bacterial colonization (17), especially in sterile sites, such as trachea and altered epithelial secretion and inflammation (18).…”