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Comparison of Tracheal Aspirates and Protected Brush Catheter Specimens for Identifying Pathogenic Bacteria in Mechanically Ventilated Patients
Bacterial respiratory infections are common in patients undergoing prolonged mechanical Ventilation, and antibiotic selection often is based upon the results of smears and cultures of tracheal aspirates (TA). This study was designed to determine the reliability of gram stains, cultures and antibody-...
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Published in: | The American journal of the medical sciences 1989-06, Vol.297 (6), p.377-382 |
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Main Authors: | , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | Bacterial respiratory infections are common in patients undergoing prolonged mechanical Ventilation, and antibiotic selection often is based upon the results of smears and cultures of tracheal aspirates (TA). This study was designed to determine the reliability of gram stains, cultures and antibody-coating of bacteria in TA by comparing them with the results of quantitative cultures of specimens obtained by protected brush catheters (PBC) inserted into involved areas of lung parenchyma. Twenty-two patients on mechanical Ventilation for at least 72 hours, with new radiographic infiltrates and fever, were studied. Tracheal aspiration was performed in the usual manner using sterile disposable kits. Immediately thereafter, patients underwent fiberoptic bronchoscopy, and PBC specimens were obtained from the areas of new radiographic infiltrates. Tracheal aspirates were gram stained and cultured aerobically, and antibody coating of bacteria was determined by fluorescence microscopy. Quantitative culture of PBC specimens contained ≥103 colony forming units per brush in 16 of the 22 patients; a smaller number of organisms was present in two additional patients. In TA from all 22 patients, gram stains revealed polymorphonuclear neutrophils and bacteria. Cultures of TA revealed potential pathogens in 20 patients, and in 15, multiple pathogens were present. The bacteria isolated from PBC also were present in 14 of the 16 patients with ≥103 CFU in PBC cultures (88%). Antibody coating was present in TA from 12 patients, and antibody coating correlated poorly with cultures of PBC specimens. The authors conclude that while gram stains and cultures of TA are often nonspecific, organisms cultured from lung parenchyma using PBC usually also are present in TA. The presence of antibody-coating does not improve the specificity of gram stain results. |
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ISSN: | 0002-9629 1538-2990 |
DOI: | 10.1097/00000441-198906000-00009 |