Protected Specimen Brush Specimens Research Articles

Diagnosis of Ventilator‐Associated Pneumonia: Where Do We Go from Here?

Diagnosis of Ventilator‐Associated Pneumonia: Where Do We Go from Here?

The Significance of Distal Bronchial Samples with Commensals in Ventilator-Associated Pneumonia: Colonizer or Pathogen?

To investigate the role of oropharyngeal and cutaneous commensal microorganisms (OCCs) as a cause of ventilator-associated pneumonia (VAP). Retrospective analysis of the medical and microbiological records. One medical-surgical ICU. All VAP episodes recorded during a 10-year period were reviewed. All patients with suspected VAP underwent bronchoscopy with protected-specimen brush (PSB) sampling and BAL before any change in antibiotic therapy was made. OCC-VAP was defined as VAP with significant growth in quantitative cultures (PSB yielded > or = 10(3) cfu/mL and/or BAL yielded > or = 10(4) cfu/mL) of OCCs only. Three experts reviewed the episodes. Exposed patients (ie, those with OCC-VAP) and unexposed patients (ie, patients without VAP) matched on condition severity at ICU admission and mechanical ventilation duration were compared. Twenty-nine episodes in 28 patients with > or = 10(4) cfu/mL OCCs in BAL fluid and/or > or = 10(3) cfu/mL OCCs in PSB specimens were found. All patients in these episodes had new radiologic lung infiltrates, with 26 episodes involving purulent tracheal aspirates, 23 episodes involving temperatures > or = 38.5 degrees C, and 18 episodes involving > or = 11,000 leukocytes/ microL. The main OCCs found were non-beta-hemolytic Streptococcus spp (n = 12), Neisseria spp (n = 7), and coagulase-negative Staphylococcus spp (n = 6). Other possible reasons for fever and the presence of new chest infiltrates were found in 20 and 17 patients, respectively. Histologic evidence of pneumonia was found in 2 of the 10 patients who died. The three experts agreed on the diagnosis for 23 patients. In the OCC-VAP group only, the mean (+/- SD) logistic organ dysfunction (LOD) scores increased significantly (LOD score, 2 +/- 4; p = 0.008) during the 3 days before bronchoscopy, and ICU stay duration was longer than in the unexposed group. The exposed/unexposed study found no difference in mortality. OCCs may behave like classic nosocomial pathogens in critically ill patients.

Usefulness of Quantitative Cultures of BAL Fluid for Diagnosing Nosocomial Pneumonia in Ventilated Patients

To evaluate the role of quantitative cultures of BAL for diagnosing nosocomial pneumonia in mechanically ventilated patients. Cohort study. Medical ICU, Hôpital Bichat, Paris, France, an academic tertiary care center. A total of 141 episodes of suspected lung infection in 84 consecutive patients mechanically ventilated for 48 h or more. Microbiologic findings obtained using BAL were compared with those obtained with protected specimen brush (PSB) samples and their operating characteristics were determined. The level of qualitative agreement between BAL and PSB specimen cultures was high, with 83% of the organisms isolated in PSB specimens being recovered simultaneously from BAL fluid. In addition, the results of quantitative BAL and PSB cultures were significantly correlated (rho = 0.46, p < 0.0001). Fifty-seven cases of pneumonia were diagnosed based on the following criteria: PSB sample yielding > or = 10(3) cfu/mL of at least one microorganism and/or > or = 5% of cells containing intracellular bacteria on direct examination of BAL. The operating characteristics of BAL fluid cultures were determined using different ways to report the results and over a range of values. The discriminative value of 10(4) cfu/mL was found to be an optimal threshold, with a sensitivity of 82% (95% confidence interval [CI], 76 to 88) and a specificity of 84.5% (95% CI, 79 to 90). These results indicate that BAL fluid cultures can offer a sensitive and specific means to diagnose pneumonia in ventilated patients and may provide relevant information about the causative pathogens.

The Diagnostic Utility of Bronchoscopic Biopsy and Tissue Culture in Lower Respiratory Infections

Our objectives were (a) to determine if routinely sending bronchoscopic biopsy (BB) for histopathology (HP) and tissue culture (CUL) increases the diagnostic yield over that obtained by bronchoalveolar lavage (BAD) and protected specimen brush (PSB), (b) to identify subsets of patients who benefit from BB (CUL), and (c) to assess the morbidity associated with BB for suspected lower respiratory infection. We used a prospective design in a single tertiary care center. Our study patients were consecutive (N = 45) inpatients or outpatients with presumed lower respiratory infection in whom a BAL. PSB, and BB were planned as the standard of care. BAL, PSB, and BB specimens were obtained from each patient by flexible bronchoscopy. The initial two BB pieces were sent for BB (CUL) and subsequent specimens (three to six) were sent for routine BB (HP) analysis. Infectious pneumonia was identified in 34 (76%) study patients. Pathogens identified were cytomegalovirus (10), bacterial (10), Pneumocystis carinii (9), mycobacterial (3), fungi (1), and respiratory syncytial virus (1). BB (CUL) solely identified only one additional pathogen. However, BB (HP) provided additional diagnostic information over BAL and PSB in 13 of 45 (29%) patients. The addition of BB (HP) to BAL and PSB significantly increased the yield for making a specific diagnosis (either infectious or noninfectious) compared to BAL and PSB alone (p < 0.004). BB (HP) increased the diagnostic yield among patients with diffuse pulmonary infiltrates (p = 0.03). Pneumothorax (N = 3) and mild bleeding (N = 3) were the complications of biopsy. Our conclusions were as follows: (a) BB (HP) in addition to BAL and PSB significantly increased the likelihood for making a specific diagnosis (infectious or noninfectious) compared to BAL and PSB alone, especially among patients with diffuse pulmonary infiltrates: (b) routine CUL of BB had a limited incremental yield; and (c) sending BB routinely for both CUL and HP may be associated with a slight increase in morbidity.

A Comparison of Bronchoscopic vs Blind Protected Specimen Brush Sampling in Patients With Suspected Ventilator-Associated Pneumonia

Pneumonia is a common complication in patients undergoing mechanical ventilation and increases ICU mortality. The clinical diagnosis of ventilator-associated, however, pneumonia is unreliable, and many consider bronchoscopic-directed protected specimen brush sampling and quantitative culture the diagnostic method of choice. Bronchoscopy, however, is expensive and not readily available in many ICUs. To test the hypothesis that "blind" protected specimen brush (PSB) sampling may produce results similar to that of bronchoscopic-directed sampling. The medical ICU of a university-affiliated teaching hospital. Patients with suspected ventilator-associated pneumonia (VAP) who had not received antibiotics for at least 48 h underwent "blind" and bronchoscopic-directed PSB sampling with quantitative culture. Fifty-five paired PSB specimens were obtained from 53 patients. There was an 85% quantitative agreement between the blind and bronchoscopic-directed specimens. The agreement was independent of the bronchopulmonary segment from which the bronchoscopic sampling was directed. The results of this study are consistent with the notion that blind PSB sampling and quantitative culture may prove to be a useful, cost-effective, and minimally invasive method of diagnosing VAP.

Role of bronchoalveolar lavage in mechanically ventilated patients with suspected pneumonia

To determine the usefulness of samples obtained by bronchoalveolar lavage (BAL) in establishing the diagnosis of ventilator-associated pneumonia, quantitative cultures of BAL and protected specimen brush (PSB) samples obtained via fiberoptic bronchoscope were compared in 42 patients with suspected ventilator-associated pneumonia. Direct examination of BAL fluid was also used to identify cells with intracellular organisms. Ventilator-associated pneumonia was diagnosed in 18 patients; a total of 39 microorganisms were recovered from BAL fluid and 29 from PSB specimens. Cultures of 21 BAL and 23 PSB specimens were sterile. Quantitative BAL and PSB cultures coincided in 76% of cases. Sterile BAL and PSB cultures agreed in 87% of cases. Cultures were completely discordant in only three cases. The sensitivity of BAL for diagnosis of ventilator-associated pneumonia using bacterial counts of > or = 10(4) cfu/ml was 89%, and specificity was 100%. In 14 of the 18 patients with ventilator-associated pneumonia, the percentage of cells containing intracellular organisms in specimens recovered by BAL was 11.6% versus 0.45% in patients without pneumonia (p < 0.05). In the remaining four patients, all of whom had Pseudomonas aeruginosa pneumonia, no intracellular organisms could be detected. Using a cut-off point of > or = 5% of cells with intracellular organisms, the sensitivity and specificity for the early diagnosis of ventilator-associated pneumonia was 67% and 96%, respectively. The results confirm the usefulness of the quantitative BAL culture (with a cut-off at 10(4) cfu/ml) for the diagnosis of ventilator-associated pneumonia. The identification of intracellular organisms in BAL fluid is a good early indicator of pneumonia, but the sensitivity of this technique may be lower for Pseudomonas aeruginosa infections.

Quantitative cultures of protected brush specimens and bronchoalveolar lavage in ventilated patients without suspected pneumonia.

Quantitative bacterial cultures of protected specimen brush (PSB) and bronchoalveolar lavage (BAL) specimens were used to assess the presence of distal bronchial microflora in mechanically ventilated patients who were not suspected of having pneumonia. A total of 54 specimens from 32 ICU patients were obtained. In 10 patients, only PSB specimens were recovered, whereas in 22 patients both PSB and BAL specimens were obtained. Cultures demonstrated no growth in 10 (45%) of the 22 samples recovered by BAL and in 21 (66%) of the 32 samples recovered by the PSB method. Twenty-three specimens yielded microorganisms, but in only six patients was a significant growth in PSB and/or BAL cultures (> or = 10(3) and > or = 10(5) cfu/ml, respectively) detected. Four of these patients developed pneumonia on subsequent follow-up. In mechanically ventilated patients, the diagnostic thresholds of bacterial growth in PSB and BAL cultures may be misleading. A significant relationship was found between the ability of PSB to recover microorganisms and the duration of mechanical ventilation (p < 0.05). These findings may be a limitation present in all patients receiving prolonged mechanical ventilation.

Diagnostic value of direct examination of the protected specimen brush in ventilator-associated pneumonia.

Interpretation of the protected specimen brush (PSB) technique is based on quantitative bacterial cultures (QC), which unfortunately requires at least 24 h. We prospectively compared the diagnostic value of direct examination (DE) and QC of PSB specimens in 75 patients with suspected pneumonia. We also determined the optimal technique for DE. QC was performed using the serial dilution technique. From the original suspension, two cytospin slides were obtained and stained by the May-Grünwald Giemsa (MGG) and the Gram method for DE. If the prescreening on the MGG-stained slide was positive, the morphology and the Gram staining of the organisms were assessed on the Gram-stained slide. Using the 10(3) colony forming units (cfu.ml-1) threshold for defining PSB as positive or negative, DE had a sensitivity of 85% and a specificity of 94%. In a parallel in vitro study, 18 pairs of PSB specimens were collected from respiratory secretions inoculated with S. aureus. From each pair, one brush was processed as described above and the other was smeared on a glass slide prior to performance of QC. Using direct smear instead of cytocentrifuged preparation, slightly but significantly affected QC. Direct examination of cytospin slides is highly predictive of quantitative bacterial culture results, and provides rapid information regarding the Gram-stain morphology of the causative organisms. It may therefore guide initial therapy.

Protected Specimen Brush in the Assessment of Ventilator-Associated Pneumonia: Selection of a Certain Lung Segment for Bronchoscopic Sampling Is Unnecessary

The protected specimen brush (PSB) with quantitative cultures is one of the most reliable techniques for assessing pneumonia in mechanically ventilated (MV) patients. The need to select a certain lung segment for bronchoscopic sampling is still debated. We investigated whether the results of PSB specimens collected within an area radiographically involved with pneumonia (inv-PSB) differed from the results of PSB specimens collected within a lung area without radiographic abnormalities (non-inv-PSB) in 39 MV patients with suspected pneumonia. The comparison of bacterial titers of inv-PSB and non-inv-PSB cultures did not disclose significant differences. Agreement regarding the diagnosis of pneumonia according to recommended diagnostic threshold was observed in 34 of 39 patients (87.1 percent). These results which are in accordance with the pathophysiology of ventilator-associated pneumonia and histologic studies do not support the need to select a certain lung segment for bronchoscopic sampling in most MV patients with suspected pneumonia.

Nosocomial pneumonia in patients receiving continuous mechanical ventilation. Prospective analysis of 52 episodes with use of a protected specimen brush and quantitative culture techniques.

Epidemiologic studies of nosocomial bacterial pneumonia in patients requiring mechanical ventilation have been limited because of the poor reliability of diagnosis procedures in this setting. To determine prognostic and descriptive factors of ventilator-associated (V-A) pneumonia, we prospectively studied 567 patients who had been receiving mechanical ventilation for more than 3 days in our unit. Fiberoptic bronchoscopy using a protected specimen brush (PSB) was performed on each patient suspected of having pneumonia because of the presence of a new pulmonary infiltrate and purulent tracheal secretions. The diagnosis of V-A pneumonia was retained only if PSB specimens yielded greater than 10(3) cfu/ml of at least one microorganism, unless this result was established to be a false positive result on follow-up. V-A pneumonia developed in 49 patients for a total of 52 episodes (9%). The actuarial risk of V-A pneumonia was 6.5% at 10 days, 19% at 20 days, and 28% at 30 days of ventilation. Patients with pneumonia were significantly older (65 versus 57 yr of age, p less than 0.01) and more frequently had severe underlying illnesses (24 versus 10%, p less than 0.01) than did patients without pneumonia. A total of 84 microorganisms (51 gram-negative and 33 gram-positive) were isolated in significant concentrations from PSB specimens. Pseudomonas aeruginosa and Staphylococcus aureus were involved in 31 and 33% of these pneumonias, respectively. Forty percent of all specimens yielded a polymicrobial flora with more than one potential pathogen.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteriologic diagnosis of nosocomial pneumonia in primates. Usefulness of the protected specimen brush.

We evaluated the usefulness of a protected specimen brush (PSB) in obtaining uncontaminated lower respiratory tract material for bacteriologic examination in a primate model of oleic acid-induced acute diffuse lung injury and naturally occurring "nosocomial pneumonia." The bacterial cause of each pneumonia was established by either an immediate postmortem lung aspirate and/or antemortem blood culture. Bacterial pneumonia occurred in 12 of the 15 animals studied. The PSB cultures were sterile in 11 normal, intubated baboons and in 7 animals with non-pneumonic infiltrates by chest radiography. In each of these instances contamination of the specimen by proximal airway flora was avoided with the PSB. Among 10 baboons with bacteriologically documented pneumonias, the PSB cultures correctly identified the causative pathogen in 7 animals despite the presence of diffuse lung infiltrates radiographically, and multiple pathogenic bacteria in proximal airway secretions. Only 1 of 10 (10%) PSB specimens in these animals was contaminated with a possibly unrelated pathogen. The PSB largely avoided contamination of the culture specimen by proximal airway flora, and therefore should be useful in differentiating bacterial colonization of the airways from pneumonia in the presence of diffuse pulmonary infiltrates.