The bacteriology of obstructive pneumonitis: A prospective study using ultrasound-guided transthoracic needle aspiration

Obstructive pneumonitis, the opacity that develops distal to an obstructing endobronchial lesion or external compression, is actually a combination of atelectasis, bronchiectasis with mucus plugging, and true parenchymal inflammation. In the majority of cases, it is usually not possible to determine whether infection is present or not from the radiographic findings alone. The aim of this study was to evaluate the bacteriology of obstructive pneumonitis and the influence of this result on the treatment of patients. From March 1992 to February 1993, 26 consecutive patients (20 men and six women) with obstructive pneumonitis were investigated. The obstructive pneumonitis had been caused by malignant tumors in 24 and benign lesions in two. Chest ultrasound (US) and US-guided percutaneous transthoracic aspirations were undergone to obtain specimens for microbiologic examination. Microorganisms were isolated from seven of nine febrile patients and two of 17 nonfebrile patients. A total of 16 bacterial strains are detected in obstructive pneumonitis (Pseudomonas aeruginosa, Klebsiella pneumoniae, viridant streptococci, Bacteroides fragilis, two Peptostreptococcus species, Mycobacterium tuberculosis, Pseudomonas maltophilia, Streptococcus sanguis, Staphylococcus aureus, Bacteroides thetaiotamomicrons, Bacteroides intermedius, Bacteroides species, Veillonella species, aerobic gram-positive bacilli, and Escherichia coli). In five cases the isolates were monobacteriae, and in the remaining four cases, cultures yielded more than one bacteria. The results of aspirate cultures led to changes in the initial antibiotic trial in seven of nine patients, and fever subsided thereafter. Pneumothorax occurred in one case as the sole complication. The pathogen causing obstructive pneumonitis is very heterogeneous, and polymicrobial infection is common. Chest US and US-guided percutaneous transthoracic aspiration is helpful in identifying potential pathogens and selecting effective therapy for patients with obstructive pneumonitis.