Canadian Health&Care Mall: Diagnostic Approach of Bacterial Infections of the Lung

pulmonary infiltrateThe sine qua non of bacterial pneumonia is the presence of a new pulmonary infiltrate on chest roentgenogram. Although certain findings on chest roentgenogram may suggest specific pathogens (eg, bulging of a fissure in К pneumoniae pneumonia), these features are neither sensitive nor specific enough to be relied on as a means for making an etiologic diagnosis.

Etiologic diagnosis of pneumonia requires detection of the pathogen; for bacterial pneumonia this is usually achieved by culture. Culture of expectorated sputum is the most frequently used, but least reliable, method. As a coughed sputum specimen passes through die mouth, it becomes contaminated with saliva, which contains approximately 109 bacteria/ml. Virtually all potential bacterial pulmonary pathogens are capable of colonizing the oropharynx; recovery of such organisms from expectorated sputum, therefore, does not necessarily distinguish between infection and colonization. In addition, pathogens detected by means other than sputum culture (eg, transtracheal aspiration) may not always be recovered by sputum culture. Recent studies have suggested that expectorated sputum should not be cultured unless it contains fewer than ten squamous epithelial cells and greater than 25 leukocytes per low-power field as determined by gram-stain screening. A similar screening procedure should be applied to sputum specimens obtained by nasotracheal suctioning. Canadian Health&Care Mall (link for you – remedies are possible to treat various diseases including epilepsy.

Less commonly employed procedures to obtain pulmonary secretions for culture are aspiration or brushing of secretions during fiberoptic bronchoscopy; brushings obtained through an occluded, telescoping cannula during bronchoscopy; percutaneous transtracheal aspiration; direct lung puncture; and open lung biopsy. Culture of bronchial brushings or secretions aspirated via an leukocyteunoccluded bronchoscopy catheter offers litde improvement over expectorated sputum because of contamination during passage through the nasal or oral cavity. The use of a brush inside an occluded, telescoping bronchoscopy catheter may avoid this problem of contamina-tion, but published data are not sufficient to permit definite conclusions. We consider transtracheal aspiration to be superior to die above-mentioned techniques and to be the technique of choice for evaluation of suspected anaerobic infections. Direct lung puncture in patients with pneumonia has also been proposed as a means for bacteriologic diagnosis, but one must be concerned about the reliability of this technique because of the small quantity of material obtained and the possibility of greater risk than with transtracheal aspiration.

Culture of an appropriately screened expectorated sputum should be adequate for diagnosis of most community-acquired pneumonias. Transtracheal aspiration should be considered in the seriously ill patient who is unable to produce sputum, who has hospital-acquired pneumonia, or in whom anaerobic pneumonia is suspected. Gram stain of appropriately obtained pulmonary secretions provides immediate, accurate information as regards initial empiric therapy.

Cultures of blood and gram stain and culture of pleural fluid may yield the pulmonary pathogen and are therefore indicated in the patient with suspected bacterial pneumonia.


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