Protected Specimen Brush Research Articles

The Effect of Blind-Protected Specimen Brush Sampling on Antibiotic Use in Patients with Suspected Ventilator-Associated Pneumonia

The diagnosis of pneumonia in ventilated patients is exceedingly difficult. Although culture of tracheal aspirates have poor diagnostic value they are frequently used to diagnose ventilator-associated pneumonia (VAP). Recently a number of studies have reported on the diagnostic value of “blind” protected specimen brush (B-PSB) sampling in the diagnosis of VAP. B-PSB sampling can readily and safely be performed by respiratory care practitioners (RCPs). The aim of this study was to determine the cost-effectiveness of B-PSB sampling performed by respiratory therapists in patients with suspected VAP. During a 3-month run-in period, patients in our medical intensive care unit (MICU) with suspected VAP were treated based on clinical criteria and tracheal aspirate culture. Following this run-in period the house staff, nurses, and RCPs were prevented from sending tracheal aspirates for culture. All patients suspected of having VAP underwent B-PSB sampling with quantitative culture. The B-PSB sampling was performe...

The Effect of Blind-Protected Specimen Brush Sampling on Antibiotic Use in Patients with Suspected Ventilator-Associated Pneumonia

The diagnosis of pneumonia in ventilated patients is exceedingly difficult. Although culture of tracheal aspirates have poor diagnostic value they are frequently used to diagnose ventilator-associated pneumonia (VAP). Recently a number of studies have reported on the diagnostic value of “blind” protected specimen brush (B-PSB) sampling in the diagnosis of VAP. B-PSB sampling can readily and safely be performed by respiratory care practitioners (RCPs). The aim of this study was to determine the cost-effectiveness of B-PSB sampling performed by respiratory therapists in patients with suspected VAP. During a 3-month run-in period, patients in our medical intensive care unit (MICU) with suspected VAP were treated based on clinical criteria and tracheal aspirate culture. Following this run-in period the house staff, nurses, and RCPs were prevented from sending tracheal aspirates for culture. All patients suspected of having VAP underwent B-PSB sampling with quantitative culture. The B-PSB sampling was performed by RCPs who had been trained to perform the technique. A PSB with a potential bacterial pathogen concentration greater than 500 CFU/ml was regarded as positive. During the 3-month run-in period 172 patients received mechanical ventilation with an average of 4.9 ±3.1 ventilator days/patient. During this period 79 patients were treated for VAP. During the 3-month study period 160 patients received mechanical ventilation, with an average of 5.1 ± 2.9 ventilator days/patient (NS). Fifty-eight B-PSB samplings were performed in 50 patients for suspected VAP. No complications related to the procedure were reported. No tracheal aspirates were cultured during this time period. Eight patients had positive PSB cultures. Antibiotics were changed in three of these patients based on the PSB results. Thirty-eight courses of antibiotics (in 36 patients) were stopped based on negative PSB results. Twelve cases of VAP were suspected in six patients receiving antibiotics for other reasons. No change in antibiotics were made in these cases based on the negative PSB results. The length of mechanical ventilation was 5.4 ± 3.2 days in the 38 culture-negative patients in whom antibiotics were stopped compared to 8.2 ± 4.7 days in the 8 patients with PSB-positive VAP (NS; p = 0.14). The direct cost savings as a result of discontinuing antibiotics was $9,500. There were additional cost savings due to the reduced number of culture specimens sent to the laboratory (approximately $3,000; taking the $23 cost of the PSB brush into account), with a projected annual cost savings of $50,000. B-PSB sampling is a simple and cost-efficient diagnostic test that can safely be performed by adequately trained RCPs. Furthermore, this study confirms that antibiotics may be safely discontinued in patients with negative quantitative culture results.

Surveillance tracheal aspirate in ventilator associated pneumonia (VAP)

VAP is associated with increased ICU stay and mortality, particularly when treatment is delayed or inappropriate [1]. When a clinical suspicion of VAP is justified, specific diagnostic tests are usually conducted: bronchoalveolar lavage (BAL), protected specimen brushing (PSB), diagnostic tracheal aspirate (dTA), blood cultures and pleural fluid. We evaluated the concordance between specific diagnostic tests and the surveillance tracheal aspirates (sTA).

Absence of bacterial colonization of the airways after therapeutic rigid bronchoscopy without stenting.

Following airway stenting, bacterial colonization of the airways with potentially pathogenic micro-organisms occurs within 4 weeks after treatment in the majority of patients. The objective of this study was to prospectively investigate whether nonstenting therapeutic rigid bronchoscopy (using laser, cryotherapy, mechanical dilatation or debridement) is followed by airway colonization or infection. Protected specimen brush sampling of the central airways and quantitative culture were performed immediately prior to, and 4 weeks after nonstenting therapeutic rigid bronchoscopy in 20 consecutive patients with central airway lesions. Prior to therapeutic bronchoscopy, airway colonization/infection was present in nine of 20 (45%) patients. In these nine patients, 10 different potential pathogens were identified: Streptococcus pneumoniae (four cases), Pseudomonas aeruginosa (three), Haemophilus influenzae (two), and Serratia marcescens (one). Eight of these nine patients had a history of postobstructive infections, of which three were currently being treated with antibiotics. Four weeks following therapeutic bronchoscopy, airway colonization/infection was present in five of 20 (25%) patients, each of whom had airway colonization/infection prior to bronchoscopy. In three of these five patients, the same organisms were found 4 weeks after bronchoscopy as at baseline bronchoscopy. In two of five patients new organisms were identified: one case of Streptococcus viridans and one case of Haemophilus parainfluenzae, both considered to be nonpathogens. In four of nine patients with airway colonization/infection prior to bronchoscopy, the airways were clear of micro-organisms after the procedure. The authors conclude that: 1) nonstenting therapeutic rigid bronchoscopy is not complicated by airway colonization or infection by new potential pathogens; and 2) therapeutic rigid bronchoscopy led to clearing of airway colonization/infection in almost half of the patients studied.

Gram staining of protected pulmonary specimens in the early diagnosis of ventilator-associated pneumonia

We evaluated prospectively the use of Gram staining of protected pulmonary specimens to allow the early diagnosis of ventilator-associated pneumonia (VAP), compared with the use of 60 bronchoscopic protected specimen brushes (PSB) and 126 blinded plugged telescopic catheters (PTC) obtained from 134 patients. Gram stains were from Cytospin slides; they were studied for the presence of microorganisms in 10 and 50 fields by two independent observers and classified according to their Gram stain morphology. Quantitative cultures were performed after serial dilution and plating on appropriate culture medium. A final diagnosis of VAP, based on a culture of > or = 10(3) c.f.u. ml-1, was established after 81 (44%) samplings. When 10 fields were analysed, a strong relationship was found between the presence of bacteria on Gram staining and the final diagnosis of VAP (for PSB and PTC respectively: sensitivity 74 and 81%, specificity 94 and 100%, positive predictive value 91 and 100%, negative predictive value 82 and 88%). The correlation was less when we compared the morphology of microorganisms observed on Gram staining with those of bacteria obtained from quantitative cultures (for PSB and PTC respectively: sensitivity 54 and 69%, specificity 86 and 89%, positive predictive value 72 and 78%, negative predictive value 74 and 84%). Increasing the number of fields read to 50 was associated with a slight decrease in specificity and positive predictive value of Gram staining, but with a small increase in its sensitivity and negative predictive value. The results obtained by the two observers were similar to each other for both numbers of fields analysed. Gram staining of protected pulmonary specimens performed on 10 fields predicted the presence of VAP and partially identified (using Gram stain morphology) the microorganisms growing at significant concentrations, and could help in the early choice of the treatment of VAP. Increasing the number of fields read or having the Gram stain analysed by two independent individuals did not improve the results.

Evaluation of Various Bronchoscopic Techniques to Diagnose the Cause of an Acute Exacerbation of Chronic Bronchitis

Bacterial infection is a common cause of acute exacerbation of chronic bronchitis (AECB). Interest in identifying the causative agent has led us to evaluate the role and efficacy of invasive diagnostic tests for culture in patients with AECB. We performed bronchoscopy on 10 patients with AECB. During bronchoscopy, four samples were obtained for semiquantitative culture: endotracheal aspirate, protected specimen brush, bronchial lavage, and bronchoalveolar lavage. All four techniques identified potential pathogens in some patients. The protected brush specimen had the highest yield, with at least one organism at >100 colony forming units/mL of sample from all 10 patients. Of the 10 patients, 6 had recognized pathogens recovered by protected brush, whereas only three of these were detected by endotracheal aspirate or bronchial lavage. In comparing various invasive diagnostic techniques, protected brush specimens had the highest diagnostic yield. Journal of Bronchology7:221-225, 2000 AECB, acute exacerbations of chronic bronchitis; PSB, protected specimen brush; BAL, bronchoalveolar lavage; CFU, colony-forming units; BronL, bronchial lavage

Blinded Invasive Diagnostic Procedures in Ventilator-Associated Pneumonia

Blinded Invasive Diagnostic Procedures in Ventilator-Associated Pneumonia

Protected-Specimen Brush Technique in the Diagnosis of Ventilator-Associated Pneumonia

The protected-specimen brush (PSB) technique has been used for almost 20 years in diagnosing pneumonia,1 and the technique has been refined for VAP. Of the many studies, those included in our analysis met certain criteria.

Evaluation of antimicrobial treatment in mechanically ventilated patients with severe chronic obstructive pulmonary disease exacerbations.

To study microbial and susceptibility patterns and antimicrobial treatment responses in patients with severe, acute exacerbations of chronic obstructive pulmonary disease requiring mechanical ventilation. Microbial investigation using tracheobronchial aspirates, bronchoscopy with a protected specimen brush, and bronchoalveolar lavage, as well as paired serologies. Evaluation of antimicrobial treatment by results of the initial investigation, susceptibility testing, and a repeated microbial investigation (tracheobronchial aspirates, bronchoscopy with a protected specimen brush, and bronchoalveolar lavage) after 72 hrs. A respiratory intensive care unit of a 1,000-bed teaching hospital. Fifty severely exacerbated and mechanically ventilated patients with chronic obstructive pulmonary disease. Initial empirical antimicrobial treatment according to clinical judgment. Overall, 36 of 50 patients (72%) had evidence of a microbial origin. Community-acquired endogenous pathogens were present in 70% of patients, and Gram-negative enteric bacilli and Pseudomonas/Stenotrophomonas species were present in 30%. All five isolates of Streptococcus pneumoniae were resistant to penicillin (three intermediately and two highly), and three were resistant to multiple antibiotics. Pseudomonas species revealed multiresistance in four of nine isolates (44%), and Stenotrophomonas maltophilia revealed multiresistance in one of two isolates. Antimicrobial treatment was modified according to diagnostic results in 11 of 31 patients (36%) with potentially pathogenic microorganisms. In patients who underwent a repeat investigation after 72 hrs, 24% of the initially present and potentially pathogenic microorganisms persisted. Inappropriate initial antimicrobial therapy was associated significantly with bacterial persistence (p < .002). Considering the diversity of microbial pathogens and the resistance rates especially to S. pneumoniae in this patient population, antimicrobial treatment should be based on the constant study of local microbial and susceptibility patterns along with routine microbial investigation of the individual patient.

Haemophilus influenzae in chronic bronchitis.

Colonization of the adult respiratory tract with nontypable Haemophilus influenzae is a dynamic process with new strains being acquired and replacing old strains periodically. The organism is a common cause of exacerbations of chronic bronchitis based on 3 lines of evidence: quantitative culture of the lower airways obtained by protected specimen brush, antibiotic trials, and serological studies. Nontypable H. influenzae expresses multiple adhesin molecules that mediate adherence to the respiratory tract mucosa. Recent studies have established that the bacterium penetrates the mucosal surface and survives intracellularly and in the interstitium of the submucosa. The organism shows a remarkable degree of antigenic diversity on its surface, including phase variation of lipooligosaccharide, antigenic heterogeneity of surface proteins, point mutations in genes encoding surface proteins and horizontal transfer of genes. These strategies facilitate evasion of the human immune response. Substantial progress has been made in identifying vaccine antigens to prevent infections caused by nontypable H. influenzae.

Etiology and Microbial Patterns of Pulmonary Infiltrates in Patients With Orthotopic Liver Transplantation

To evaluate the etiology and microbial patterns of pulmonary infiltrates in liver transplant patients using a bronchoscopic diagnostic approach and the impact of diagnostic results on antimicrobial treatment decisions. A prospective cohort study. A 1,000-bed tertiary-care university hospital. Fifty consecutive liver transplant patients with 60 episodes of pulmonary infiltrates (33 episodes during mechanical ventilation) were studied using flexible bronchoscopy with protected specimen brush (PSB) and BAL. A definite infectious etiology was confirmed in 29 episodes (48%). Eighteen episodes corresponded to probable pneumonia (30%), 10 episodes had noninfectious etiologies (17%), and 3 remained undetermined (5%). Opportunistic infections were the most frequent etiology (16/29, 55%, including 1 mixed etiology). Bacterial infections (mainly Gram-negative) accounted for 14 of 29 episodes (48%), including 1 of mixed etiology. The majority of bacterial pneumonia episodes (n = 10, 71%) occurred in period 1 (1 to 28 days posttransplant) during mechanical ventilation, whereas opportunistic episodes were predominant in periods 2 and 3 (29 to 180 days and > 180 days posttransplant, respectively; n = 14, 82%). Microbial treatment was changed according to diagnostic results in 21 episodes (35%). Microbial patterns in liver transplant patients with pulmonary infiltrates corresponded to nosocomial, mainly Gram-negative bacterial pneumonia in period 1, and to opportunistic infections in period 2 and, to a lesser extent, period 3. A comprehensive diagnostic evaluation including PSB and BAL fluid examination frequently guided specific antimicrobial therapy.

Multifactorial analyses in the diagnosis of pneumonia arising in the surgical intensive care unit

The diagnosis of ventilator-associated pneumonia in the surgical intensive care unit continues to be problematic. The majority of intensive care units use clinical criteria based on chest x-ray; fever; leukocytosis; alterations in the pulse oximeter observations; the need to alter modes and amounts of ventilatory support; and more specific microbiologic studies, such as appropriate sputum, Gram stain, and culture to identify pneumonia. Diagnosing pneumonia based on clinical criteria alone is often difficult and inaccurate, which may lead to inappropriate use and choice of antibiotics. Invasive diagnostic techniques, such as protected specimen brush and bronchoalveolar lavage, provide an important microbiologic diagnosis. However, the cost and inconvenience limit broad usage. Furthermore, those results that return positive are often too late to dictate the need for, or direction of, therapy. Our use of a “pneumonia grid” may help identify patients likely to have a poor outcome. Until a readily available and cost-effective diagnostic study for pneumonia is developed, clinical criteria remain vital in routine practice.

The diagnosis of ventilator-associated pneumonia using non-bronchoscopic, non-directed lung lavages.

(1)To assess the diagnostic utility of quantitative cultures of non-bronchoscopic lung lavage (NBL) in ventilator-associated pneumonia and evaluate the role of the Bacterial Index; (2) To assess the predictive value of NBL surveillance quantitative cultures in ventilated patients; (3) To evaluate the Clinical Pulmonary Infection Score (CPIS) system in ventilated patients. A prospective comparison of NBL with bronchoscopic bronchoalveolar lavage and protected specimen brush. Three intensive care units in academic tertiary care centres. 145 adults ventilated for 72 h, with and without clinical signs of pneumonia. Sampling of lower airway secretions by NBL, bronchoalveolar lavage and protected specimen brush. Diagnostic reliability of quantitative cultures, Bacterial Index and CPIS. 34 episodes of clinical ventilator-associated pneumonia were documented in 32 patients. 9 episodes were confirmed by concordant blood/pleural culture or post-mortem lung examination. Qualitative concordance of the predominant pathogen between sequential NBL: bronchoalveolar lavage and protected specimen brush was 83 %. Sensitivity and specificity of non-directed bronchial lavage at a threshold of 10(4) CFU/ml were 68 % and 70 % respectively (p = 0. 003) and were comparable with the bronchoscopic methods. However, the low positive predictive value of NBL indicates that quantitation in the absence of clinical signs is unlikely to be useful. Bacterial Index did not improve discriminatory power of quantitation compared with bacterial load of predominant organism. Mean CPIS for confirmed pneumonia cases was 8.4 +/- 1.01, significantly higher than for non-pneumonia observations (p = < 0.0001). NBL is a simple, safe, cheap, readily-available method of diagnosing ventilator-associated pneumonia with comparable diagnostic accuracy to bronchoscopic techniques. Quantitation of respiratory tract cultures can exclude pneumonia in patients with equivocal clinical signs. The diagnostic threshold should vary depending on the length of ventilation, likelihood of pneumonia and antibiotic administration. The Bacterial Index is a flawed mathematical device that has no contributory role in pneumonia diagnosis. The CPIS has some diagnostic role in selected cohorts of ventilated patients.

The Diagnosis of pneumoniae following bone marrow transplantation by bronchoscopy

Background : Pulmonary complications following bonemarrow transplantation (BMT) are common and associated with a high mortality rate. We investigated the yield, safety, and impact of fiberoptic bronchoscopy (FOB) for diagnosis of postBMT pneumoniae. Methods : From May 1997 to April 2000, 56 FOBs were performed in 52 post BMT patients for clinical pneumoniae. BMT patients with respiratory symptoms and/or pulmonary infiltrates had a thoracic HRCT(high resolution computed tomography) and bronchoscopic examination including BAL (bronchoalveolar lavage), TBLB (transbronchial lung biopsy), PSB (protected specimen brush). Results : The characteristics of the subjects were as follows : 37 males, 15 females, mean age of 31.3 years(l7-45), 35 sibling donor allogenic BMTs, 15 nonrelated donor allogenic BMTs, and 2 autologous BMTs. Fiftynine percent of FOBs (33 FOBs, 31 patients) were diagnostic. Isolated pathogens included the following : 12 cytomegalovirus (CMV) (21.4 %), 7 pneumocystis carinii (PC) (12.5 %), 11 CMV with PC (19.6 %), 2 Mycobacaterium tuberculosis (3.6%), and 1 streptococcus (1.8%). Most of the radiographic findings were diffuse interstitial lesions. CMV pneumoniae had mainly diffuse interstitial nodular lesion, and PC pneumoniae had diffuse, interstitial ground glass opacity(GGO). When CMV was accompanied by PC, a combined pattern of nodular and GGO was present. Of the 56 cases (23.2%), 13 died of CMV pneumoniae (n=2), PCP (n=2),mixed infection with CMV and PC (n=3), underlying GVHD (n=1), underlying leukemia progression (n=1), or respiratory failure of unknown origin (n=4). There was no major complication by bronchoscopy. Only 3 cases developed minor bleeding and 1 episode temporary hypoxemia. Conclusion : Based on our findings, CMV and PC are the major causes of postBMT pneumoniae. In addition, BAL can be considered a safe and accurate procedure for the evaluation of pulmonary complications after BMT.

Infections in Acute Exacerbation of Chronic Bronchitis: What Are They and How Do We Know?

Acute exacerbations of chronic bronchitis can be due to many factors. The most commonly recognized factor is infection, with bacterial infection being identified in about fifty percent of patients with chronic bronchitis. The causative agent can be detected by several different methods. The most common is sputum examination; however, more invasive techniques have been studied. These include transtracheal aspirates and bronchoscopic samples. The most widely studied bronchoscopic sample has been the protected brush specimen (PBS). Despite the wide array of sampling techniques, the pathogens which have been identified have been relatively consistent. The three most common pathogens have been H. influenzae, S. Pneumoniae, and B. catarrhalis. Other pathogens, including gram negative enteric organisms, are seen in patients with more advanced disease. The information obtained by the diagnostic studies has allowed clinicians to develop treatment strategies for AECB. These diagnostic studies will be needed to help upgrade treatment guidelines as new bacteria and bacterial resistance patterns change.

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.

Nosocomial pneumonia with isolation of anaerobic bacteria in ICU patients: Therapeutic considerations and outcome

Purpose: Evaluate the influence of the anti-anaerobic antimicrobial therapy in the outcome of patients with nosocomial pneumonia. Materials and Methods: The population study included 53 intensive care unit patients with nosocomial pneumonia in whom, using a protected specimen brush, anaerobic bacteria were isolated, which were associated or not with aerobes. Current and empirical anti-biotherapies were retrospectively analyzed, regarding their efficacy against anaerobic bacteria. Since it was debated, sensitivity to cefotaxime, ceftazidime, and ciprofloxacin was determined in 38 strains of Prevotella species. Outcome was evaluated 10 days after the day of protected specimen brushes. Improvement was defined as a decrease of Murray score or ventilator weaning. Results: The most frequently isolated bacteria were Prevotella species, which were more frequently resistant to cefotaxime (37%), ceftazidime (50%), and ciprofloxacine (32%) than usually reported in the literature. Sixty-six percent of these strains produced β-lactamase. The effect of empirical anti-anaerobic antibiotherapy on the outcome at day 10 was evaluable in 39 patients. Twenty-nine patients were improved and 10 patients worsened. Interestingly, patients who had received well-adapted antibiotics against anaerobes had a better outcome after 10 days ( P < .02). Conclusions: This study suggests that specific anti-anaerobic therapy may be considered in the choice of empirical antibiotherapy in patients with nosocomial pneumonia.

Etiology of community-acquired pneumonia: impact of age, comorbidity, and severity.

The aim of this study was to determine the etiology of community-acquired pneumonia (CAP) and the impact of age, comorbidity, and severity on microbial etiologies of such pneumonia. Overall, 395 consecutive patients with CAP were studied prospectively during a 15-mo period. Regular microbial investigation included examination of sputum, blood culture, and serology. Sampling of pleural fluid, transthoracic puncture, tracheobronchial aspiration, and protected specimen brush (PSB) sampling were performed in selected patients. The microbial etiology was determined in 182 of 395 (46%) cases, and 227 pathogens were detected. The five most frequent pathogens were Streptococcus pneumoniae (65 patients [29%]), Haemophilus influenzae (25 patients [11%]), Influenza virus A and B (23 patients [10%]), Legionella sp. (17 patients [8%]), and Chlamydia pneumoniae (15 patients [7%]). Gram-negative enteric bacilli (GNEB) accounted for 13 cases (6%) and Pseudomonas aeruginosa for 12 cases of pneumonia (5%). Patients aged < 60 yr were at risk for an "atypical" bacterial etiology (odds ratio [OR]: 2.3; 95% confidence interval [CI]: 1.2 to 4.5), especially Mycoplasma pneumoniae (OR: 5.3; 95% CI: 1.7 to 16.8). Comorbid pulmonary, hepatic, and central nervous illnesses, as well as current cigarette smoking and alcohol abuse, were all associated with distinct etiologic patterns. Pneumonia requiring admission to the intensive care unit was independently associated with the pathogens S. pneumoniae (OR: 2.5; 95% CI: 1.3 to 4.7), gram-negative enteric bacilli, and P. aeruginosa (OR: 2.5; 95% CI: 0.99 to 6.5). Clinical and radiographic features of "typical" pneumonia were neither sensitive nor specific for the differentiation of pneumococcal and nonpneumococcal etiologies. These results support a management approach based on the associations between etiology and age, comorbidity, and severity, instead of the traditional syndromic approach to CAP.

Role of Different Routes of Tracheal Colonization in the Development of Pneumonia in Patients Receiving Mechanical Ventilation

To evaluate the importance of the different pathogenic pathways involved in the development of ventilator-associated pneumonia (VAP). Prospective study. An 18-bed medical and surgical ICU. One hundred twenty-three patients receiving mechanical ventilation (MV). Tracheal, pharyngeal, and gastric samples were obtained simultaneously every 24 h. In cases where VAP was suspected clinically, bronchoscopy with protected specimen brush and BAL were performed. Semiquantitative cultures of pharyngeal samples and quantitative cultures for the remaining samples were obtained. Tracheal colonization at some time during MV was observed in 110 patients (89%). Eighty patients had initial colonization, 34 patients had primary colonization, and 50 patients had secondary colonization. Nineteen patients had VAP, and 25 organisms were isolated. For none of these organisms was the stomach the initial site of colonization. Gram-positive organisms colonized mainly in the trachea during the first 24 h of MV (p<0.001). On the contrary, enteric Gram-negative bacilli (p<0.001) and yeasts (p<0.002) colonized the trachea secondarily. Previous endotracheal intubation (p<0.005) and acute renal failure before admission to the ICU (p<0.001) were associated with colonization by Pseudomonas aeruginosa; prior antibiotics were associated with colonization by Acinetobacter baumanii (p<0.05) and yeasts (p<0.006); and cranial trauma was associated with Staphylococcus aureus colonization (p<0.035). Although the stomach can be a source of organisms that colonize the tracheobronchial tree, it is a much less common source of the bacteria that cause VAP. The pattern of colonization and risk factors may be different according to the type of organisms involved.