Protected Specimen Brush Samples Research Articles

Airway inflammation and bronchial microbial patterns in patients with stable chronic obstructive pulmonary disease.

The effect of bacterial colonization of the bronchi on the progress of airflow limitation is not well known. Therefore, the pattern of airway inflammation in smokers and patients with stable chronic obstructive pulmonary disease (COPD) and its relation to bronchial microbial colonization was assessed. Eight nonsmoking and 18 smoking controls as well as 52 patients with COPD (28 mild, 11 moderate and 13 severe) were studied. All subjects were investigated by means of flexible bronchoscopy including protected specimen brush and bronchoalveolar lavage (BAL) sampling. Differential cell counts, cytokine (interleukin (IL)-1beta, IL-6, IL-8, IL-10 and tumour necrosis factor-alpha(TNF-alpha) concentrations and microbial patterns were determined in BAL fluid. Forced expiratory volume in one second (FEV1) % of the predicted value was inversely correlated with pack-yrs of cigarette smoking (r=-0.47, p<0.0001), the percentage of neutrophil (p=-0.56, p<0.0001) and IL-6 (p=-0.37, p=0.01) and IL-8 concentration (p=-0.43, p=0.004) in BAL fluid. Accordingly, pk-yrs of cigarette smoking (p=0.39, p=0.01) and IL-8 (p=0.69, p<0.0001) and TNFalpha (p=0.4, p<0.005) were positively correlated with the percentage of neutrophils in BAL fluid. Smoking controls and COPD patients were mainly colonized in the bronchial tree (33%) by community endogenous potentially pathogenic micro-organisms (PPMs). Colonization rates and patterns of PPMs were not affected by severity of airflow obstruction. The presence of PPMs was significantly associated with higher percentages of neutrophils (33.2+/-10.4% versus 10.1+/-3.5%, p=0.02) and TNF-alpha concentration (29.9+/-10.8 versus 6.3+/-2.1 pg x mL(-1), p=0.01) in BAL fluid. In conclusion, bronchial neutrophilia is a key inflammatory pattern in chronic obstructive pulmonary disease patients. Bronchial colonization with potentially pathogenic micro-organisms may represent an independent stimulus for additional airway inflammation.

The Chest Radiograph in Critically Ill Surgical Patients is Inaccurate in Predicting Ventilator-Associated Pneumonia

Chest radiographs (CXRs) are frequently obtained in surgical intensive care unit (SICU) patients when a diagnosis of ventilator-associated pneumonia (VAP) is suspected. The purpose of this study was to determine if the interpretation of the CXR correlated with a diagnosis of VAP in SICU patients. Prospective evaluation of 20 SICU patients clinically suspected of VAP was performed from July 1997 through December 1998. All patients required mechanical ventilation for at least 48 hours, and antibiotic use was discontinued 24 hours before entry into the study. Bronchoscopy with protected specimen brush (PSB) sampling of secretions from the right and left lung was performed. A positive PSB was present if quantitative analysis yielded > or = 10(4) colony-forming units/mL of bacteria. VAP was diagnosed if either the right or left PSB was positive and ruled-out if both the right and left PSB yielded < 10(4) colony-forming units/mL. Twelve of 20 patients (60%) were diagnosed to have VAP by PSB criteria. Eight of 20 patients (40%) had CXRs interpreted as negative for infiltrates; four patients had VAP by PSB criteria. There were four patients with focal infiltrates; two patients had VAP. The remaining eight patients had radiographs interpreted as bilateral infiltrates (one) or pulmonary edema (seven); of these, six patients (75%) had VAP. The sensitivity of the CXR in determining the presence of VAP was 25 per cent, the specificity was 75 per cent, and the accuracy was 0.45. The CXR does not improve the clinician's ability to diagnose VAP: a normal CXR does not exclude the presence of VAP and the finding of a focal infiltrate does not confirm the diagnosis of VAP.

Bacterial colonization of central airways after stenting.

Airway stenting (AS) is increasingly used in the management of obstructive lesions of the central airways. Although retention of secretions and infection have been reported as complications of AS, the microbiological consequences of AS have not yet been evaluated. In this study, we prospectively performed protected specimen brush (PSB) sampling of the airways, before and 3 to 4 wk after AS, in 14 consecutive patients (65 +/- 17 yr), suffering from bronchial (5), extensive esophageal (2), thyroid (1), and adenocystic (1) carcinoma, stenotic tracheal burn lesions (2), postintubation stenosis (2), and Wegener's granulomatosis (1). A cutoff value of >/= 10(2) colony-forming units (cfu). ml(-)(1) was considered diagnostic for airway colonization (AC). PSB results were related to the presence and degree of secretion retention (SR) at the level of the stent. In five of the 14 patients, AC was present prior to AS; in three of these, potentially pathogenic microorganisms (PPM) were identified. After AS, AC was found in 11 (including seven patients without prior AC) of the 14 patients. In six of these patients, one or more PPM were present (Pseudomonas aeruginosa [4], Staphylococcus aureus [3], Streptococcus pneumoniae [1], Klebsiella spp. [1]). Although AC tended to be associated with the presence of SR (PSB >/= 10(2) cfu. ml(-)(1) in 10 of 12 SR-positive and in zero SR-negative cases; PSB < 10(2) cfu. ml(-)(1) in two SR-positive and in two SR-negative cases), statistical significance was not reached (Fisher exact test, p = 0.06). We conclude that AS is frequently followed by AC, the majority of which occurs in patients without AC prior to AS, and is caused by PPM. In no case, however, AC was associated with clinical signs of infection. AC tended to be associated with SR in the stent.

Viruses and bacteria in bronchial samples from patients with primary hypogammaglobulinemia.

Viruses and bacteria in bronchoalveolar lavage fluids, protected specimen brush samples, and bronchial biopsies from 14 patients with primary hypogammaglobulinemia (11 patients with common variable immunodeficiency [CVID] and three patients with X-linked agammaglobulinemia [XLA]) were analyzed. At the time of the study, the patients had no signs of acute respiratory infections, and no antibiotics were administered. In addition to routine bacterial and viral cultures, polymerase chain reaction tests were used for the detection of adenovirus, cytomegalovirus (CMV), herpes simplex virus 1, enterovirus, rhinovirus, Borrelia burgdorferi, Chlamydia pneumoniae, Legionella spp., Mycoplasma pneumoniae, Pneumocystis carinii, and Ureaplasma urealyticum. Viruses (four adenoviruses, one CMV, and one rhinovirus) were detected in four of the 11 (36%) CVID patients. No viruses were found in the three patients with XLA or in 13 control patients. Bacteria from the lower respiratory tract were detected in nine of the 14 (64%) patients with hypogammaglobulinemia and three of the 13 (23%) control patients. Haemophilus influenzae was the most prevalent bacterium (43%) in the hypogammaglobulinemia patients. The study shows that patients with CVID harbor viral and bacterial infections in the lower respiratory tract, which may predispose to the development of changes in the respiratory tract.

The Role of Anaerobes in Patients With Ventilator-associated Pneumonia and Aspiration Pneumonia: A Prospective Study

Aspiration of oropharyngeal material, with its high concentration of anaerobic bacteria, has been implicated in the pathogenesis of both ventilator-associated pneumonia (VAP) and aspiration pneumonitis (AP). Consequently, patients with these disorders are usually treated with antimicrobial agents with anaerobic activity. To determine the incidence of anaerobic bacteria in patients with VAP and AP. Prospective, nonrandomized, interventional study. University-affiliated community teaching hospital. We performed sequential blind protected specimen brush (PSB) sampling and mini-BAL in 143 patients with 185 episodes of suspected VAP and 25 patients with AP who required mechanical ventilation. Quantitative aerobic and anaerobic cultures were performed on all specimens. Pneumonia was considered to be present when either > 500 cfu/mL cultured from blind PSB sampling or > 5,000 cfu/mL cultured from mini-BAL were present. Using the predefined criteria, bacterial pneumonia was diagnosed in 63 of 185 suspected VAP episodes (34%) and 12 of 25 patients with AP (48%). At least one dose of an antibiotic was given in the 24 h prior to bacteriologic sampling in 106 suspected VAP episodes (57%) and in 12 patients with AP (48%). More than one pathogen was isolated from 11 VAP and four AP patients. Pseudomonas aeruginosa, Staphylococcus aureus, and enteric Gram-negative organisms were isolated most frequently from patients with VAP. In the patients with AP, enteric Gram-negative organisms were isolated in patients with GI disorders and Streptococcus pneumoniae and Haemophilus influenzae predominated in patients with "community-acquired" aspiration. Only one anaerobic organism was isolated from the entire group of patients; Veillonella paravula was isolated from a blind PSB specimen in a patient with suspected aspiration pneumonia. Despite painstaking effort, we were able to isolate only one anaerobic organism (nonpathogenic) from this group of patients. The spectrum of aerobes in patients with VAP was similar to that reported in the literature. The organisms found in patients with AP was a reflection of the organisms likely to colonize the oropharynx. The use of antibiotics with anaerobic coverage may not be necessary in patients with suspected VAP and AP. Furthermore, penicillin G and clindamycin may not be the antibiotics of choice in patients with AP.

Quality assessment of protected specimen brush samples by microscopic cell count.

Protected specimen brushing (PSB), combined with quantitative culture, is now recognized as one of the reference methods for diagnosis of nosocomial pneumonia. However, no criteria exist with which to assess the quality of the PSB sample. We studied numbers of inflammatory cells and bronchial cells per microscopic field (magnification: x500, objective x50) in cytospin preparations of PSB samples. Results of cell count and quantitative culture in a first study period were compared with those in a second study period, following adaptation of the PSB technique and collection of samples from more peripheral sites. The cellular content of samples from patients and controls was investigated. We examined 86 samples from patients with suspected nosocomial pneumonia and 15 samples from uninfected controls. The number of samples with a high cellular content was considerably greater in the second study period. No positive cultures were obtained from samples containing < 10 cells per field. The numbers of cells in samples from uninfected controls were comparable to the numbers in samples from patients. Our results indicate that absence of cells probably represents inadequate sampling. Negative PSB cultures with cytospin preparations containing < 10 cells per microscopic field should therefore be considered with caution, and resampling considered.

Oropharyngeal or gastric colonization and nosocomial pneumonia in adult intensive care unit patients. A prospective study based on genomic DNA analysis.

Colonization of the digestive tract has been supposed to be the source of many hospital-acquired infections, especially nosocomial pneumonia. To assess the relationship between oropharyngeal and gastric colonization and subsequent occurrence of nosocomial pneumonia, we prospectively studied 86 ventilated, intensive care unit (ICU) patients. Oropharyngeal or gastric colonizations were detected and quantified on admission and twice weekly during ICU stay. When nosocomial pneumonia was suspected on clinical grounds (new chest X-ray infiltrate and purulent tracheal secretions), diagnosis was assessed on fiberoptic bronchoscopy with quantitative cultures of a protected specimen brush sampling and/or a plugged telescoping catheter sampling yielding > or = 10(3) cfu/ml of at least one microorganism. Bacterial strains responsible for colonization and infection (Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacteriaceae, and Staphylococcus aureus) were compared using pulsed-field electrophoresis. A total of 31 cases (36%) of pneumonia were diagnosed. Oropharyngeal colonization, detected either on admission or from subsequent samples, was a predominant factor of nosocomial pneumonia as compared with gastric colonization. For instance, oropharyngeal colonization with A. baumannii yielded a 7.45-fold estimated increased risk of pneumonia as compared with patients not yet or not identically colonized (p = 0.0004). DNA genomic analysis demonstrated that an identical strain was isolated from oropharyngeal or gastric samples and bronchial samples in all but three cases of pneumonia, due to S. aureus. These findings provide better knowledge of the pathophysiology of nosocomial pneumonia in mechanically ventilated patients.

Bacterial colonization of distal airways in healthy subjects and chronic lung disease: a bronchoscopic study.

In contrast to the healthy population, distal airway bacterial colonization may occur in patients with chronic lung diseases, who often have altered pulmonary defences. However, the information dealing with this issue is insufficient and is based mainly on nonspecific samples, such as sputum cultures. Using quantitative cultures of bronchoscopic protected specimen brush (PSB) and bronchoalveolar lavage (BAL) samples, we studied the bacterial colonization of distal airways in 16 healthy subjects, 33 patients with bronchogenic carcinoma, 18 with chronic obstructive pulmonary disease (COPD), 17 with bronchiectasis, and 32 with a long-term tracheostomy due to laryngeal carcinoma. All patients were without exacerbation, and free from antibiotic treatment at least 1 month before the study protocol. Thresholds for quantitative cultures to define colonization were > or = 10(2) colony-forming units (cfu) x mL(-1) for PSB and > or = 10(3) cfu x mL(-1) for BAL. Only one healthy subject was colonized by a potential pathogenic microorganism (PPM) (Staphylococcus aureus 4x10(2) cfu x mL(-1) in a PSB culture). Colonization was observed in 14 (42%) bronchogenic carcinoma patients (19 non-PPMs, and 10 PPMs); in 15 (83%) COPD patients (22 non-PPMs and 7 PPMs); in 15 (88%) bronchiectasis patients (20 non-PPMs and 13 PPMs); and in 15 (47%) long-term tracheostomy patients (5 non-PPMs and 13 PPMs). The two most frequent non-PPMs isolated in all groups studied were Streptococcus viridans and Neisseria spp. Haemophilus spp., Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis were the most frequent PPMs isolated in bronchogenic carcinoma, COPD, bronchiectasis and long-term tracheostomized patients, respectively. Pseudomonas aeruginosa colonization was infrequent in all the groups. Our results show that distal airway bacterial colonization is a frequent feature in stable patients with chronic lung diseases and also in patients with long-term tracheostomy. However, the pattern of colonization differs among groups studied. The knowledge of different colonization patterns may be important for future antibiotic prophylactic strategies and for the empirical antibiotic regimens when exacerbations occur in these 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.

Effect of ventilator-associated pneumonia on mortality and morbidity.

The aim of this study was to evaluate the attributable mortality and excess intensive care unit (ICU) stay as linked to ventilator-associated pneumonia (VAP) in a medical-surgical ICU. We performed a matched cohort study. The diagnosis of VAP was established when clinical, biologic, and radiologic signs of VAP were associated with the presence of at least one microorganism at a concentration > or = 10(3) CFU/ml on the protected specimen brush sample. Each case patient with VAP was matched to one control patient on the basis of the following potential confounding factors: same diagnosis and same indication for mechanical ventilation, same age +/-5 yr, same sex, same APACHE II score +/-5 on admission. In addition, control patients had to be ventilated for at least as long as the case patient prior to the onset of VAP, and date of admission of the case and control patients had to be matched within 1 yr. In 85 of the 97 patients with VAP, we were able to match one case patient with one control patient. Mortality was similar in both case (40%) and control (38.8%) patients. The duration of mechanical ventilation was increased in survivor case patients (27.2 +/- 24.7 d) compared with survivor control patients (18.5 +/- 15.7 d) (p < 0.01). The duration of hospitalization in ICU was increased in survivor case patients (34.9 +/- 23.6 d) compared with survivor control patients (26.1 +/- 18.6 d) (p < 0.02). When confounding factors were controlled, VAP did not appear to increase mortality.

Comparison of Quantitative Cultures to Semiquantitative Loop Cultures of Bronchoscopic Protected Specimen Brush Samples

To compare quantitative growth from a calibrated loop to growth from the standard serial dilution technique of culturing bronchoscopic protected specimen brush (PSB) samples and to determine the effect of refrigeration of the PSB sample on subsequent quantitative growth. Laboratory stock cultures were sampled with a PSB and cultured by both standard 100-fold serial dilution as well as 1:100 mL and 1:1,000 mL calibrated loops. Stock cultures were also sampled with a PSB and growth before and after refrigeration for 24 h at 4 degrees C (both serial dilution and calibrated loops) was compared. Clinical PSB samples from seven patients suspected of having lower respiratory tract infections were cultured by both techniques as well. Clinical research laboratory and teaching hospital. PSB samples from inpatients and outpatients who had clinically indicated bronchoscopy. No interventions. Quantitative growth from the 1:1,000 mL calibrated loop was within 1 log10 of growth from the serial dilution technique for 20 of 21 organisms, including 2 yeasts. Except for Haemophilus influenzae (known to be cold intolerant), there were no important differences in growth of bacteria before and after 24 h at 4 degrees C. For quantitative bacterial growth, there was a significant correlation between serial dilution and the 1:1,000 mL loop cultures (r=0.86, p < 0.0001). In this study, quantitative growth from a single 1:1,000 mL loop culture of PSB samples was comparable to growth from the standard serial dilution technique. Our results also suggest that overnight refrigeration of PSB samples may be possible in certain clinical situations.

Outbreak of severe Pseudomonas aeruginosa respiratory infections due to contaminated nebulizers

During the six months from January–June 1994, 10 cases of severe and 11 of less severe pulmonary infection caused by Pseudomonas aeruginosa were diagnosed in patients with chronic obstructive airways disease. Possible sources were evaluated. P. aeruginosa was isolated from four of the 22 nebulizers tested. The relationship of isolates from the patients and nebulizers was confirmed by sero- and phage-typing, and by arbitrarilyprimed polymerase chain reaction (AP-PCR). Three types were identified and the distribution of types in patients with severe infection was as follows (one patient had a multiple infection). Type I was isolated from two nebulizers and from sputa, and/or blood and/or bronchial protected specimen brush samples or bronchial lavage fluid from four patients. Type II came from the sputa of three patients and a third nebulizer; and type III from sputa and/or blood of four further patients and another nebulizer. The data provided evidence for the relation between P. aeruginosa as a cause of infection and the contamination of the nebulizers. When nebulizer mouthpieces were changed every 24 h and sterilized between patients, no more contamination occurred, and the outbreak ceased.

Diagnosis of Infections in Intensive-Care Unit Patients

Fever is a frequent and nonspecific symptom after surgery. If appropriate cutoff values are chosen, C-reactive protein and interleukin-6 are useful parameters of infection in febrile postoperative intensive-care unit patients. The diagnostic workup of febrile critically ill patients should be guided by the underlying condition of the patient, and the clinical suspicion of a specific infection. For the diagnosis of intravascular catheter-related infections, a (semi)quantitative culture method should be used. There is no consensus about the ideal method to diagnose nosocomial pneumonia in ventilated patients. The best documented options are quantitative cultures of a protected specimen brush sample and of the bronchoalveolar lavage.

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.

Decision Making in Nosocomial Pneumonia: An Analytic Approach to the Interpretation of Quantitative Bronchoscopic Cultures

Quantitative cultures of specimens obtained at fiberoptic bronchoscopy have been used to diagnose nosocomial pneumonia in research settings, but their clinical role remains controversial. We reviewed the literature comparing these culture techniques with other accepted methods to diagnose pneumonia in mechanically ventilated patients and extracted data to describe the receiver operator characteristics (ROC) of quantitative cultures of protected specimen brush (PSB) and bronchoalveolar lavage (BAL) samples. Analysis of ROCs reveals that these tests have a discriminating power comparable or superior to that of many widely accepted routinely used tests. Current data do not suggest that either culture technique offers an advantage over the other. Since benefits of antibiotic therapy of pneumonia and risks of treatment of noninfected critically ill patients are not well quantified, universally applicable recommendations for appropriate values to define an abnormal test result cannot logically be made. Multiple decision analytic tools show that values lower than those previously recommended are more appropriate in patients suspected of having pneumonia unless the risk of antibiotic therapy is judged to be extreme. On the basis of these findings, we suggest guidelines for clinicians' interpretation of PSB and BAL quantitative culture results. Quantitative cultures of specimens obtained at fiberoptic bronchoscopy have been used to diagnose nosocomial pneumonia in research settings, but their clinical role remains controversial. We reviewed the literature comparing these culture techniques with other accepted methods to diagnose pneumonia in mechanically ventilated patients and extracted data to describe the receiver operator characteristics (ROC) of quantitative cultures of protected specimen brush (PSB) and bronchoalveolar lavage (BAL) samples. Analysis of ROCs reveals that these tests have a discriminating power comparable or superior to that of many widely accepted routinely used tests. Current data do not suggest that either culture technique offers an advantage over the other. Since benefits of antibiotic therapy of pneumonia and risks of treatment of noninfected critically ill patients are not well quantified, universally applicable recommendations for appropriate values to define an abnormal test result cannot logically be made. Multiple decision analytic tools show that values lower than those previously recommended are more appropriate in patients suspected of having pneumonia unless the risk of antibiotic therapy is judged to be extreme. On the basis of these findings, we suggest guidelines for clinicians' interpretation of PSB and BAL quantitative culture results.

Use of elastin fibre detection in the diagnosis of ventilator associated pneumonia.

Elastin fibre detection could be a simple and reliable marker of ventilator associated pneumonia. To confirm this, a prospective study was undertaken to evaluate the diagnostic yield of elastin fibre detection in the diagnosis of ventilator associated pneumonia. Seventy eight mechanically ventilated patients were evaluated by examining endotracheal aspirates for the presence of elastin fibres. All patients were previously treated with antibiotics. Quantitative bacterial cultures of endotracheal aspirates and protected specimen brush samples were also performed. Patients were classified into three diagnostic categories: group 1, definite pneumonia (n = 25); group 2, probable pneumonia (n = 35); and group 3, controls (n = 18). Patients with definite and probable pneumonia were grouped together. The presence of elastin fibres in endotracheal aspirate samples was more frequent in groups 1 and 2, being found in 19 of the 60 patients compared with five of the control group. Although the presence of elastin fibres had a low sensitivity (32%), it was a reasonably specific marker (72%) of pneumonia. This specificity increased to 86% and 81% respectively when only Gram negative bacilli and Pseudomonas aeruginosa pneumonia were considered. Again, calculated sensitivity was 43% and 44% when analysing cases infected by Gram negative bacilli and Ps aeruginosa, respectively. The negative predictive value of the detection of elastin fibres in pneumonia caused by Ps aeruginosa was 81%. Detection was more frequent with infection by Gram negative bacilli (14/19), particularly with Ps aeruginosa (8/14). By contrast, pneumonia due to Gram positive cocci or non-bacterial agents uncommonly resulted in positive elastin fibre preparations (4/19, 21%). When analysing patients with and without chronic obstructive pulmonary disease, the diagnostic value of elastin fibre detection did not change. Potassium hydroxide preparation of elastin fibres is a rapid and simple specific marker of ventilator associated pneumonia and may be a useful technique to help diagnose pulmonary infections in mechanically ventilated patients, although this assessment is at present limited to patients without adult respiratory distress syndrome.

Gastric and Pharyngeal Flora in Nosocomial Pneumonia Acquired during Mechanical Ventilation

We studied the interrelations between gastric, pharyngeal, proximal, and distal airway bacterial flora in ventilator-associated pneumonia (VAP) on 36 patients with nosocomial pneumonia acquired during mechanical ventilation (MV) and 27 mechanically ventilated control subjects without pulmonary infection. Gastric, pharyngeal, and endotracheal (EA) sampling for quantitative cultures were performed upon all patients, as well as fiberoptic bronchoscopy with protected specimen brush (PSB) sampling. Mean bacterial and fungi colony counts were significantly increased in pharyngeal, EA, and PSB samples in patients with VAP compared with control subjects. The overall increase in colonization was due to gram-positive cocci in all samples. In addition, gram-negative bacilli and fungi mean counts increased significantly in PSB pneumonia samples versus control samples. However, mean gastric colonization was similar in both patients with VAP and control subjects. In the former group there was an increase in coincident microorganisms isolated from gastric, pharyngeal, and EA samples in relation to PSB samples compared with control samples. Among the different quantitative cultures analyzed, only those obtained from EA significantly correlated with PSB cultures in patients with pneumonia (r = 0.67, p = 0.001). In summary, the present study shows that the coincidence between microorganisms isolated in PSB cultures and those from gastric and oropharynx increase in MV patients with pneumonia, indicating that both reservoirs play a key role in the pathogenesis of pneumonia. Conceivably, preventing both gastric and pharyngeal colonization may reduce the incidence of ventilator-associated pneumonia. From all the noninvasive samples studied only endotracheal aspirate cultures were useful for inferring the etiology of some VAP pneumonias.

Follow-up Protected Specimen Brushes to Assess Treatment in Nosocomial Pneumonia

To prospectively determine the bacteriologic and clinical efficacy of antimicrobial therapy for nosocomial bacterial pneumonia selected based upon information provided by cultures of protected specimen brush (PSB) samples obtained during bronchoscopy, 76 consecutive patients with ventilator-associated pneumonia were studied using follow-up quantitative PSB cultures obtained after 3 days of treatment. Of the 173 microorganisms initially present in the PSB samples, only 11 (6%) were not eradicated by antimicrobial therapy, including three recovered at high (> or = 10(3) cfu/ml) concentrations. Thirty-two emerging pathogens, including nine at high concentrations, were also detected; 26 of them (81%) were resistant to the initial antibiotics administered. Of the 76 patients included in the study, cultures of follow-up PSB samples identified 51 in whom the infection site in the lung was completely sterilized, 16 with low-grade infection, and only nine with persistent high-grade infection. Analysis of clinical outcome within the 15 days after the initiation of antimicrobial therapy demonstrated clinical improvement in 62 of 67 (93%) patients in whom the site of infection was contained by treatment as compared with four of 9 (44%) patients with persistent high-grade infection (p < 0.01). These data suggest that appropriate antimicrobial therapy for ventilator-associated pneumonia results in the control of the initial infection in 88% of the patients. However, an early superinfection caused by multiresistant pathogens can occur in a small subset of these patients. When follow-up PSB cultures were negative, an improved outcome was noted.

Diagnosis of pneumonia in mechanically ventilated patients. Repeatability of the protected specimen brush.

The repeatability (i.e., the variation in repeated measurements of the same quantity) of the protected specimen brush (PSB) with quantitative cultures was assessed in 22 consecutive mechanically ventilated (MV) patients with suspected nosocomial pneumonia. Five PSB samples were collected in the same lung area during the same bronchoscopic procedure and processed for bacteriologic identification and quantitative culture. A laboratory control was also performed in order to assess the in vitro repeatability of the quantitative culture technique. The five PSB always recovered the same microorganisms, indicating a 100% qualitative repeatability for the PSB. Conversely, the quantitative repeatability was somewhat lower since in 59% of the patients the quantitative results varied by more than one log10, which is the minimal precision affordable with quantitative cultures. The distinction between presence or absence of infection based on the 10(3) cfu/ml recommended diagnostic threshold was, however, only moderately affected by the variability of the quantitative results since only three of 22 patients (13.6%) displayed results spread out on each side of the 10(3) cfu/ml break point. Intrasubject variability of quantitative results was not explained by problems with the quantitative culture technique, which proved excellent repeatability in the laboratory. This study indicated that, although the PSB technique with quantitative cultures displays an acceptable level of repeatability, caution is advisable when interpreting PSB results in critically ill patients with suspected pneumonia, especially if one refers to the 10(3) cfu/ml recommended diagnostic threshold and if a decision to treat or to abstain from treating is to be made.

A Reappraisal of Blind Bronchial Sampling in the Microbiologic Diagnosis of Nosocomial Bronchopneumonia: A Comparative Study in Ventilated Patients

To assess the usefulness of fiberscopy for microbiologic diagnosis of nosocomial bronchopneumonia (NBP) in ventilated patients. Data were collected prospectively. We compared the results of semiquantitative cultures obtained by protected specimen brush (PSB), bronchoalveolar lavage (BAL) and blind bronchial sampling (BBS). Positive thresholds were 10(3) CFU ml-1 for PSB and BAL and 10(4) CFU ml-1 for BBS. We also evaluated the diagnostic performance of direct examination of samples obtained by BAL and BBS. We carried out this study in 64 ventilated patients admitted to a medico-surgical ICU. During the study, 85 sets of samplings were obtained. The concordance between the results of specimen cultures obtained with the three techniques was 87 percent. The concordance between BBS and PSB or between BBS and BAL was 91.8 percent. In two of seven patients with discordant results between BBS and PSB, the microorganisms isolated from blood cultures were found on BBS, but not on PSB samples. As for direct examination, the thresholds for the diagnosis of NBP using BBS were as follows: > or = 10 polymorphonuclear neutrophils (PMN)/high-power field (HPF), > or = 1 bacteria/oil immersion field (OIF), presence of intracellular bacterial inclusions. Using BAL, the thresholds were as follows: > or = 1 PMN/HPF, presence of bacteria/OIF, presence of intracellular bacterial inclusions. The specificity of the presence of bacterial inclusions was excellent regardless of the sampling technique, but the sensitivity of this criteria was mediocre (30.8 percent with BBS and 19.2 percent with BAL). Except for the number of PMN on BBS, all the other diagnostic criteria (PMN count on BAL, bacterial count, count of cells exhibiting inclusions) provide a similar prediction of NBP (correctly classified: 61.2 to 81.2 percent). No combination of criteria enabled significantly better classification regardless of the sampling technique. In view of these findings and the high cost and morbidity of fiberscopy, it is arguably better to use a simple, repeatable, and risk-free technique for obtaining culture specimens from mechanically ventilated patients. Obviously, protected brushing techniques remain the most effective for nonintubated patients.