ORIGINAL ARTICLES

BACTERIOLOGY OF LOWER-RESPIRATORYTRACT SECRETIONS, SPUTUM, AND UPPER-RESPIRATORY-TRACT SECRETIONS IN " NORMALS " AND CHRONIC BRONCHITICS

Chronic obstructive pulmonary disease (COPD) is a common progressive respiratory disease that is associated with infective exacerbations that lead to worsening of symptoms. Many organisms are thought to trigger infective exacerbations, but Haemophilus influenzae is the most commonly isolated bacterium. The role of H. influenzae in infective exacerbations remains uncertain, mainly because the organism chronically colonises patients whose clinical condition is stable. H. influenzae may also comprise part of the normal nasopharyngeal flora in man, making the interpretation of positive cultures difficult in some cases.

The prolonged presence of aerobic Gram-negative bacilli (AGNB) in the oropharynx is termed ‘carriage’. AGNB carriage rates are low in populations of healthy individuals. Previously, severity of underlying disease has been positively correlated with oropharyngeal AGNB carriage rate. Overgrowth of AGNB at the oropharynx poses a significant risk of endogenous infection in end-stage chronic obstructive pulmonary disease (COPD) patients. The aims of this study were to undertake an epidemiological survey of the oropharyngeal flora of COPD patients and to correlate oropharyngeal carriage of AGNB with severity of disease.

Two oral rinses were obtained, within a 2-day interval, from 40 COPD patients comprising three disease severity groups: 1. mild, 2. moderate and 3. severe. Eighty oral rinses were quantitatively (1:10 dilution series) cultured for AGNB and yeasts using broth enrichment.

The mean AGNB carriage rate was 15%. AGNB carriage rates of 0, 7·7 and 29·4% were observed within the mild, moderate and severe disease groups, respectively. The mean yeast carriage rate was 33·3%. Yeast carriage rates of 33·3, 15·4 and 64·7% were observed within the mild, moderate and severe disease groups, respectively. Carriage of Staphylococcus aureus was 5%. Rates of oropharyngeal carriage of AGNB ($\text{1}\text{23}$ vs. $\text{5}\text{17}$) and yeasts ($\text{5}\text{23}$ vs. $\text{11}\text{17}$) were significantly higher within the severe disease group than in non-severe disease groups.

Oropharyngeal carriage of AGNB in end-stage COPD patients (forced expiratory volume in 1 sec, FEV₁ <50% predicted) presents a potential source of Gram-negative endogenous pneumonia. This outcome may be promoted by intubation and some flora-suppressing antibiotic therapies.

The presence of aerobic Gram-negative bacilli (AGNB) in the oropharynx can be either temporary or persistent. Prolonged colonization (ie, carriage) is distinguished from transient presence (ie, acquisition), which often occurs in healthy individuals but less frequently in those with underlying disease. Prevalence rates of up to 61.1% quoted previously for healthy individuals were obtained by using single sample surveys, which fail to differentiate acquisition from carriage.

To illustrate the need to distinguish carriage from acquisition in a healthy population at risk of acquisition of AGNB, and to show that although differing groups of healthy individuals may acquire oropharyngeal AGNB at differing frequencies, carriage is rare in healthy individuals.

Two oral rinses were obtained within a 2-day interval from 120 healthy individuals comprising 40 nurses, 40 students, and 40 laboratory-associated persons.

Two hundred forty oral rinses were quantitatively (1:10 dilution series) cultured for AGNB by using broth enrichment.

The rate of AGNB carriage based on two consecutive samples positive for the same AGNB was 6.6%; the rate of AGNB acquisition based on one positive sample was 35.8%. The concentrations of all carried and acquired AGNB were ≤ 103 cfu/mL. AGNB acquisition was significantly higher in students (52.5%) compared to nurses (32.5%) and laboratory-associated persons (22.5%; p < 0.05).

Healthy individuals rarely carry oropharyngeal AGNB, suggesting effective oropharyngeal clearance in a healthy population predisposed to acquisition. Apparently, the oropharyngeal mucosa in healthy individuals is not receptive to adhesins of AGNB, resulting in rapid elimination of these bacteria.

The prevalence of chronic bronchitis is between 3% and 17% in most developed countries. However, higher rates in the range of 13 to 27% are encountered in less developed areas of the world. Acute exacerbations of chronic bronchitis (AECB) have usually been defined as the presence of increases in cough/sputum, sputum purulence, and dyspnea. However, recent investigations suggest that the severity of AECB may be divided into three stages based on the history of the patient: (1) previously healthy individuals; (2) patients with chronic cough and sputum and infrequent exacerbations; and (3) persons with frequent exacerbations or more severe chronic airflow limitation. Therapy for patients with less severe AECB include older and less expensive broad-spectrum antibiotics, while newer agents are indicated for patients with the most severe stage of AECB.