Evaluation of the protected brush catheter and bronchoalveolar lavage in the diagnosis of nosocomial pneumonia

Microbiological Status as a Factor of Airway Complications After Lung Transplantation

BACKGROUND

Lung transplantation (LTx) is the only treatment for patients with end-stage lung disease. This procedure is associated with a risk of complications related to airway stenosis, which can be treated by means of bronchoscopic interventions (BI). Microbiological colonization may have an impact on airway complications. The aim of the study was to investigate the effect of presence of microbiological pathogens in graft among lung recipients and frequency of BI, considered as the indicator of severe complications.

MATERIALS AND METHODS

The study design was single-center retrospective cohort research; cases of 116 patients with complete microbiological data who underwent LTx from April 2013 to June 2019 were reviewed (70.3% of transplanted patients). All statistical analyses were performed with SPSS version 25.0 and R 3.5.3. For analyses involving the number of bronchoscopy interventions, univariate and multivariate Poisson regression were used. Interaction effect of variables in multivariate Poisson regression was assessed with partial response plot.

RESULTS

The mean number of pathogens colonizing each patient was approximately 4.66 (range, 0 to 19) with Candida albicans (n = 42, 36.2%), Aspergillus spp. (n = 33, 28.4%), Pseudomonas aeruginosa (n = 32, 27.59%), and methicillin-sensitive Staphylococcus aureus (MSSA) (n = 29, 25%) being the most prominent. Microbiological agents causing the greatest increase in the risk of intervention are as follows: Proteus mirabilis by 3.84 times, Aspergillus spp. by 3.53 times, and Stenotrophomonas maltophilia by 3.09 times. Burkholderia multivorans, Enterococcus spp., and Klebsiella spp. do not have a statistically significant impact on the number of BI.

CONCLUSIONS

Some pathogens increase the frequency of complications, which are associated with deterioration of the general condition. Therefore, patients should be monitored for the presence of pathogens in the airways.

Bacterial Aetiologies of Lower Respiratory Tract Infections among Adults in Yaoundé, Cameroon

Lower respiratory tract infections (LRTIs) remain a challenge in African healthcare settings and only few data are available on their aetiology in Cameroon. The purpose of this study was to access the bacterial cause of LRTIs in patients in Cameroon by two methods. Methods. Participants with LRTIs were enrolled in the referral centre for respiratory diseases in Yaoundé city and its surroundings. To detect bacteria, specimens were tested by conventional bacterial culture and a commercial reverse-transcriptase real-time polymerase chain reaction (RT-PCR) assay. One hundred forty-one adult patients with LRTIs were enrolled in the study. Among the participants, 46.8% were positive for at least one bacterium. Streptococcus pneumoniae and Haemophilus influenzae were the most detected bacteria with 14.2% (20/141) followed by Klebsiella pneumoniae, 9.2% (13/141), Staphylococcus aureus, 7.1% (10/141), and Moraxella catarrhalis, 4.3% (6/141). Bacterial coinfection accounted for 23% (14/61) with Haemophilus influenzae being implicated in 19.7% (12/61). The diagnostic performance of RT-PCR for bacteria detection (43.3%) was significantly different from that of culture (17.7%) (p< 0.001). Only Streptococcus pneumoniae detection was associated with empyema by RT-PCR (p<0.001). These findings enhance understanding of bacterial aetiologies in order to improve respiratory infection management and treatment. It also highlights the need to implement molecular tools as part of the diagnosis of LRTIs.

The IRIDICA PCR/Electrospray Ionization-Mass Spectrometry Assay on Bronchoalveolar Lavage for Bacterial Etiology in Mechanically Ventilated Patients with Suspected Pneumonia

We studied the diagnostic performance of the IRIDICA PCR/electrospray ionization–mass spectrometry (PCR/ESI-MS) assay applied on bronchoalveolar lavage (BAL) samples, from 51 mechanically ventilated patients with suspected pneumonia, in a prospective study. In 32 patients with X-ray verified pneumonia, PCR/ESI-MS was positive in 66% and BAL culture was positive in 38% (p = 0.045), and either of the methods was positive in 69%. The following BAL result combinations were noted: PCR/ESI-MS+/culture+, 34%; PCR/ESI-MS+/culture-, 31%; PCR/ESI-MS-/culture+, 3.1%; PCR/ESI-MS-/culture-, 31%; kappa 0.36 (95% confidence interval (CI), 0.10–0.63). In pneumonia patients without prior antibiotic treatment, optimal agreement was noted with 88% PCR/ESI-MS+/culture+ and 12% PCR/ESI-MS-/culture- (kappa 1.0). However, in patients with prior antibiotic treatment, the test agreement was poor (kappa 0.16; 95% CI, -0.10–0.44), as 10 patients were PCR/ESI-MS+/culture-. In 8/10 patients the pathogens detected by PCR/ESI-MS could be detected by other conventional tests or PCR tests on BAL. Compared with BAL culture, PCR/ESI-MS showed specificities and negative predictive values of ≥87% for all individual pathogens, an overall sensitivity of 77% and positive predictive value (PPV) of 42%. When other conventional tests and PCR tests were added to the reference standard, the overall PPV increased to 87%. The PCR/ESI-MS semi-quantitative level tended to be higher for PCR/ESI-MS positive cases with pneumonia compared with cases without pneumonia (p = 0.074). In conclusion, PCR/ESI-MS applied on BAL showed a promising performance and has potential to be clinically useful in mechanically ventilated patients with suspected pneumonia. The usefulness of the method for establishment of pneumonia etiology and selection of antibiotic therapy should be further studied.

Transient airway colonization is associated with airway inflammation after lung transplantation

Lower airway tract colonization may trigger neutrophil-mediated airway inflammation. We investigated whether transient airway colonization influences airway inflammation and pulmonary function after lung transplantation (LTx). In this retrospective study, stable LTx patients with consecutive broncho-alveolar lavages (BAL), the first colonized and the second noncolonized, were included to create a Pooled group (P, n=32) and a Gram Negative (GN, n=14), Gram Positive (GP, n=9) and Fungi (F, n=9) subgroup. Similarly, LTx patients with consecutive, noncolonized BAL samples were included as Control group (C, n=19). BAL analysis (cell counts, IL6, IL8) and forced expiratory volume (FEV(1)) were compared between groups. In the P group and the GN subgroup, colonized BAL samples showed a significant increase in total cells, neutrophilia and IL8-concentration and a significant decrease in FEV(1), even when compared with the matched samples of the C group. A significant increase in neutrophilia was observed in the GP subgroup, but no other significant difference was found either in the GP and F subgroup or the C group. IL6 levels were not significantly different between groups. Transient airway colonization, especially with Pseudomonas-like GN bacteria, in stable LTx patients may be associated with IL8-dependent neutrophilic airway inflammation and a, albeit subtle, decrease in FEV(1).

Ventilator associated pneumonia

Hospital acquired or nosocomial infections continue to be an important cause of morbidity and mortality. The critically ill patient is at particular risk of developing intensive care unit acquired infection, with the lungs being especially vulnerable. Nosocomial bacterial pneumonia occurring after two days of mechanical ventilation is referred to as ventilator associated pneumonia, and is the most common nosocomial infection seen in the intensive care unit. Intubation of the trachea and mechanical ventilation is associated with a 7-fold to 21-fold increase in the incidence of pneumonia and up to 28% of patients receiving mechanical ventilation will develop this complication. Its development is associated with an attributable increase in morbidity and mortality. The establishment of an accurate diagnosis of ventilator associated pneumonia remains problematic and as yet there is still no accepted "gold standard" for diagnosis. The responsible pathogens vary according to case mix, local resistance patterns, and methodology of sampling. However, there is general agreement that rapid initiation of appropriate antimicrobial therapy improves outcome.

[Difficulties on diagnosis of ventilator associated pneumonia]

Ventilator associated pneumonia is associated with high morbidity and mortality. It is important a correct diagnosis in way to guide the antibiotic therapy in the most appropriate way. However, its diagnosis is difficult, because clinical and radiologic features are not specific and approaches to standard diagnosis, that allow its confirmation, are very invasive or not very frequent. Protected techniques and quantitative cultures have been trying to outline the problem of the contamination of the samples obtained by routine methods and to allow the distinction between colonization and infection. The author makes a revision on the different methods of diagnosis of this clinical entity.

A Prospective Assessment of Diagnostic Efficacy of Blind Protective Bronchial Brushings Compared to Bronchoscope-Assisted Lavage, Bronchoscope-Directed Brushings, and Blind Endotracheal Aspirates in Ventilator-Associated Pneumonia

BACKGROUND

The purpose of this study is to compare techniques for the diagnosis of suspected ventilator-associated pneumonia in the trauma patient. Per the literature, bronchoscope protected brushings and bronchoalveolar lavage were set as the standards for comparison because of their high specificity and sensitivity. We hypothesized that blind protected brushings were equivalent to bronchoscope-directed techniques and that endotracheal aspirates (ETA) were not.

METHODS

With informed consent, 90 trauma patients with two or more of the following were accepted into the study: 48 hours or more on the ventilator, new or increasing infiltrate on chest radiograph, excess or purulent secretions, suspected aspiration, temperature of 38.5 degrees C or above, white blood cell count greater than or equal to 12,000/mm3, and respiratory distress. Four samplings were performed on each patient using bronchoscope-assisted and nonbronchoscopic techniques. Each patient had cultures obtained by and significances quantified as follows: ETA, moderate/many/abundant; bronchoscope-directed protected brushings (BDPB), 103 colony-forming units [CFU]/mL; blind protected brushing via endotracheal tube (BPB), 103 CFU/mL; and bronchoscopic bronchoalveolar lavage (BAL), 104 CFU/mL. Quantitative cultures were obtained and compared for the following pathogens: gram-positive cocci, gram-positive rods, gram-negative cocci, gram-negative rods, anaerobic bacteria, and yeast. An assessment of agreement for cultured pathogens between the sampling modalities was completed using kappa (kappa) analysis, and significance was set at p < or = 0.05.

RESULTS

With patients used as their own controls, Gram's stain and pathogens cultured from the various sampling techniques were compared for agreement by kappa analysis. BDPB and BAL were set as the "gold standards" for comparison against each other and against the BPB and ETA. Kappa analysis was used to measure the strength of agreement for these findings; individual values from the comparisons of Gram's stain were then averaged for descriptive purposes of the data. Most kappa values were associated with a statistically significant value of p < 0.05. The greatest strength of agreement was found to be moderate comparing Gram's stain results of BPB and BDPB (kappa = 0.467), ETA and BAL (kappa = 0.535), and BPB and BAL (kappa = 0.547). Fair kappa values were shown in comparing Gram's stain results of ETA and BDPB (kappa = 0.382) and BAL and BDPB (kappa = 0.390).

CONCLUSION

A quantitative analysis of bacteriologic cultures obtained by four standard sampling techniques has demonstrated with statistical significance that no difference exists between modality of sampling in reliability or in obtaining clinically significant pathogens. In reviewing the literature, this study is the first assessment of agreement for cultured pathogens between the four different sampling modalities and the largest to assess the efficacy of the blind protected brush technique.

Quantitative culture of endotracheal aspirates in the diagnosis of ventilator-associated pneumonia in patients with treatment failure

STUDY OBJECTIVE

To study the correlation of bacteriology between quantitative cultures of protected specimen brush (PSB), BAL, and quantitative endotracheal aspirate (QEA) in ventilator-associated pneumonia (VAP) patients with treatment failure.

DESIGN

Prospective observational clinical study.

SETTING

A 15-bed medical ICU of tertiary medical center.

PATIENTS

Forty-eight patients receiving mechanical ventilation with clinical suspected VAP who had been treated with antibiotics for at least 72 h without improvement.

INTERVENTION

QEA, PSB, and BAL were performed with patients receiving antibiotics. The diagnostic thresholds for QEA, PSB, and BAL were 10(5), 10(3), and 10(4) cfu/mL, respectively.

MEASUREMENTS AND RESULTS

Microbial culture findings were positive in 24 BAL samples (50%), in 23 PSB samples (48%), and in 28 QEA samples (58%). The correlations between of QEA vs PSB and QEA vs BAL were significant (rho = 0.567 and rho = 0.620, p < 0.01, respectively). The most commonly isolated microorganisms were Acinetobacter baumannii (27%), Staphylococcus aureus (24%), Stenotrophomonas maltophilia (15%), and Pseudomonas aeruginosa (10%). Using the predetermined criteria, bacterial pneumonia was diagnosed in 28 of 48 suspected VAP episodes based on PSB and/or BAL results. The diagnostic efficiency of QEA at threshold of 10(5) cfu/mL had a sensitivity of 92.8% and a specificity of 80%.

CONCLUSIONS

QEA correlated with PSB and BAL in patients with suspected VAP who responded poorly to the existent antibiotic treatment. QEA missed only two cases of bacterial pneumonia diagnosed by invasive PSB and/or BAL with acceptable sensitivity and specificity. More importantly, QEA is noninvasive and easily repeatable. Early use of QEA is helpful to clinical physicians in decision making with regard to antibiotics use.

Ventilator-associated pneumonia. Prevention, diagnosis, and therapy

Ventilator-associated pneumonia remains the nosocomial ICU infection of greatest concern. The authors have summarized the clinical trials that have assessed specific strategies to prevent VAP and the current controversies regarding the diagnosis and therapeutic approach to this condition. Improvements in care of patients who are at risk for or who have developed VAP will depend on the judicious application of this information for individual patients.

Clinical aspiration-related practice patterns in the intensive care unit: a physician survey

OBJECTIVE

To characterize physician practice patterns regarding the clinical, microbiological, and antimicrobial-related events of suspected or documented aspiration and aspiration pneumonia within the intensive care unit.

DESIGN

National mail survey.

SETTING

University medical center.

STUDY POPULATION

Critical care physician members of the Society of Critical Care Medicine.

INTERVENTIONS

Survey questionnaire.

MEASUREMENTS AND MAIN RESULTS

The response rate was 645 (32%) of 2,000 mailed surveys; analysis of data represents completed questionnaires from 605 respondents. Intensivists (42.3%), pulmonologists (22.6%), and surgeons (21.6%) represent the majority of respondents. Altered level of consciousness (67.9%) in the intensive care unit was identified as the predominant predisposing factor for aspiration pneumonia. Sixty-four percent of physicians used sputum specimens, rather than protected specimen brushes or bronchoalveolar lavage, as the diagnostic source of bacterial cultures in cases of suspected aspiration pneumonia. Microbiological assessment of aspiration pneumonia revealed the absence of any predominant pathogen, although Staphylococcus aureus and Pseudomonas aeruginosa were cited in 40.1% of combined responses, whereas anaerobes represented the fifth most prevalent cultured bacteria. In cases of suspected and confirmed aspiration, 51.9% and 77.7% of respondents, respectively, would prescribe an antimicrobial agent in the absence of a definitive infectious process, with administration of dual antimicrobial therapy increasing from 28.9% to 46.0% in suspected vs. confirmed cases of aspiration. In the treatment of aspiration pneumonia, 27.6% of physicians preferred pathogen-specific therapy, whereas the remainder (72.4%) selected an empirical antibiotic regimen based on prior clinical experience. Overall, a beta-lactam/beta-lactamase inhibitor, followed by a cephalosporin, aminoglycoside in combination, or clindamycin, was most often selected for empirical therapy of all defined aspiration-related clinical diagnoses.

CONCLUSIONS

Our study revealed a divergent approach to antimicrobial treatment of cases of aspiration in the intensive care unit. Further investigation is warranted to determine why empirical antimicrobials are initiated frequently for noninfectious stages of aspiration.

Protected specimen brush or bronchoalveolar lavage to diagnose bacterial nosocomial pneumonia in ventilated adults: a meta-analysis

OBJECTIVE

We conducted a meta-analysis by using summary receiver operating characteristic curves to compare the diagnostic value for bacterial nosocomial pneumonia of the following: a) quantitative culture (colony-forming units per milliliter or CFU/mL) of respiratory secretions collected with a bronchoscopic protected specimen brush (PSB); b) quantitative culture of a bronchoscopic bronchoalveolar lavage (BAL); and c) the percentage of infected cells (IC) in BAL.

DATA SOURCES

All studies published in the English or the French language, through January 1, 1995, on the evaluation of PSB or BAL for the diagnosis of pneumonia were considered for analysis. The relevant literature was identified through computer and reference searching and by experts in the field.

STUDY SELECTION

A study was included if at least two of three independent readers regarded its purpose as the evaluation of CFU-PSB, CFU-BAL, or IC-BAL for the diagnosis in human beings of bacterial nosocomial pneumonia in ventilated adults and if the study was prospective and published in a peer-reviewed journal.

DATA EXTRACTION

Three readers reviewed all published articles and decided whether to include each study; consensus was defined as agreement by at least two readers. The authors of each original article included in the meta-analysis were asked to complete a questionnaire in which they were asked to check and to correct the data extracted by one of the independent readers.

DATA SYNTHESIS

Summary receiver operating characteristic curves were used to compare the efficacy of three diagnostic tests. Eighteen studies on CFU-PSB (795 patients) were included, as well as 11 studies on CFU-BAL (435 patients) and 11 on IC-BAL (766 patients). The accuracy of these tests was not different. However, it seems that administration of previous antibiotics markedly decreased accuracy of CFU-PSB (p = .0002) but not the accuracy of CFU-BAL and that of IC-BAL.

CONCLUSION

Both PSB and BAL are reliable to diagnose bacterial nosocomial pneumonia. Because CFU-BAL and IC-BAL seemed more resistant to the effects of antibiotics, we recommend BAL rather than PSB if the patient is already receiving antibiotics.

The clinical utility of invasive diagnostic techniques in the setting of ventilator-associated pneumonia. Canadian Critical Care Trials Group

OBJECTIVE

To evaluate the clinical utility of bronchoscopy with protected brush catheter (PBC) and BAL for patients with ventilator-associated pneumonia (VAP).

DESIGN

Prospective cohort study.

SETTING

Ten tertiary care ICUs in Canada.

PATIENTS

Ninety-two mechanically ventilated patients with a clinical suspicion of VAP who underwent bronchoscopy were compared with 49 patients with a clinical suspicion of pneumonia who did not.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

We compared antibiotic use, duration of mechanical ventilation, ICU stay, and mortality. In addition, for patients who received bronchoscopy, we administered a questionnaire (before and after bronchoscopy) to evaluate the effect of PBC or BAL on (1) physician perception of the probability of VAP, (2) physician confidence in the diagnosis of VAP, and (3) changes to antibiotic management. After bronchoscopy results became available, from the physician's perspective, the diagnosis of VAP was deemed much less likely (p < 0.001), confidence in the diagnosis increased (p = 0.03), and level of comfort with the management plan increased (p = 0.02). Following the results of invasive diagnostic tests, in the group that underwent bronchoscopy, patients were receiving fewer antibiotics (31/92 vs 9/49, p = 0.05) and more patients had treatment with all their antibiotics discontinued (18/92 vs 3/49, p = 0.04) compared with the group that did not undergo bronchoscopy. Duration of mechanical ventilation and ICU stay were similar between the two groups, but mortality was lower in the group that underwent bronchoscopy with PBC or BAL (18.5% vs 34.7%, p = 0.03).

CONCLUSIONS

Invasive diagnostic testing may increase physician confidence in the diagnosis and management of VAP and allows for greater ability to limit or discontinue antibiotic treatment. Whether performing PBC or BAL affects clinically important outcomes requires further study.

Invasive diagnostic techniques for pneumonia: protected specimen brush, bronchoalveolar lavage, and lung biopsy methods

We suggest the following strategy for managing patients with pneumonia. For nonventilated patients with either CAP or HAP, empiric antibiotic treatment should be started according to approved guidelines, and if the clinical evolution of the patient is not adequate, fiberoptic bronchoscopy including PSB and BAL could be considered, with modification of the antibiotic treatment accordingly. In ventilated patients with either CAP or HAP, respiratory secretion sampling using noninvasive techniques should be conducted upon clinical suspicion of VAP and before starting a new antibiotic treatment. Antibiotic therapy according to approved guidelines should be started as soon as possible and maintained during the first 48 hours if the patient's evolution is satisfactory and condition has stabilized. Then, initial antibiotic treatment should be adjusted according to cultures. If there is a clear diagnostic alternative to VAP and cultures are negative, this is the only case in which antibiotic treatment could be withdrawn. If the patient's clinical evolution is inadequate (persistence of fever, leukocytosis, increasing infiltrates, and respiratory failure), fiberoptic bronchoscopy with PSB and BAL and modification of the initial antibiotic regimen should be sought. Open lung biopsy may be indicated in patients with diffuse pulmonary infiltrates in whom a diagnosis has not been achieved by other methods, including bronchoscopy. Transbronchial lung biopsy should not be viewed as a diagnostic technique for pneumonia except in immunosuppressed patients with diffuse alveolar infiltrates.

Comparison of nonbronchoscopic techniques with bronchoscopic brushing in the diagnosis of ventilator-associated pneumonia

OBJECTIVE

To determine the diagnostic accuracy of quantitative cultures obtained via nonbronchoscopic protected specimen brushing (PSB) and nonbronchoscopic bronchoalveolar lavage (BAL) compared with quantitative cultures obtained by bronchoscopic PSB in surgical patients suspected of ventilator-associated pneumonia.

DESIGN

Prospective, crossover controlled study of 15 ventilated surgical intensive care unit patients in a university teaching hospital.

METHODS

Fifteen consecutive ventilated patients suspected of ventilator-associated pneumonia on the basis of leukocytosis, purulent sputum, and appearance of chest roentgenogram were enrolled. All patients underwent nonbronchoscopic PSB and BAL followed by bronchoscopic PSB. The duration of each procedure was noted. Culture results were considered positive only if greater than 10(4) colony forming units (CFU) per milliliter were present.

MAIN RESULTS

Perfect concordance was noted between bronchoscopic PSB and nonbronchoscopic BAL (kappa = 1.0). The concordance between bronchoscopic PSB and nonbronchoscopic PSB was 93% ((kappa = 0.86). The nonbronchoscopic procedures were performed in significantly less time than the bronchoscopic procedure.

CONCLUSION

Nonbronchoscopic PSB and BAL provide similar microbiologic data to bronchoscopic PSB in the diagnosis of ventilator-associated pneumonia while shortening procedure time significantly.

Ventilator-associated pneumonia due to Pseudomonas aeruginosa

OBJECTIVE

Ventilator-associated pneumonia (VAP) caused by Pseudomonas aeruginosa has been associated with higher case fatality rates than VAP caused by other bacterial etiologies. The causes of this excess mortality are unclear.

DESIGN

Retrospective review of 38 consecutive ventilated patients with Pseudomonas pneumonia, documented by highly reliable methods. Charts of five additional patients were unavailable for review.

SETTING

Medical ICUs of a university-affiliated Veterans Affairs Medical Center and a university-affiliated municipal hospital.

MEASUREMENTS

Prospectively collected hospital admission acute physiologic and chronic health examination (APACHE) II scores and cause of ICU admission. Retrospectively calculated organ failure and APACHE scores, VAP score. Clinical and microbiologic variables. Antibiotic treatment and outcome. Direct cause of death by standard definitions.

RESULTS

Overall mortality was 69% (26/38), significantly higher than the APACHE II predicted mortality of 42.6% (p=0.037). At least 38% (10/26) of deaths were directly attributable to Pseudomonas VAP. Multivariate analysis of factors associated with death found infectious cause for ICU admission (odds ratio [OR]=8.67; 95% confidence interval [CI], 0.86 to 85.94) and number of organ dysfunctions on the day of diagnosis (OR=1.73, 95% CI, 1.02 to 2.92) were significant. Septic shock from Pseudomonas VAP, septic shock from subsequent infection, and multiple organ dysfunction syndrome were the most common immediate causes of death. Mortality increased linearly with increasing APACHE III score on the day of diagnosis. Of initial antibiotic regimens, 67% (26/36) were considered failures. Persistent pneumonia occurred in 35% of patients while recurrent pneumonia was unusual (1/38).

CONCLUSIONS

Development of Pseudomonas pneumonia results in a mortality rate in excess of that due to the presenting illness. The attributable mortality determined by several means appears to approach 40%. The excess mortality appears to be related to the host defense response to the pneumonia rather than any characteristic of the pneumonia. Even standard antibiotic regimens fail frequently and do not prevent the excess mortality. Since at least 38% of deaths can be directly attributable to the Pseudomonas pneumonia, improvement in therapy is needed.

The role of bronchoalveolar lavage in the diagnosis of bacterial pneumonia

Bronchoalveolar lavage (BAL) has become an invaluable diagnostic tool with important clinical implications in both opportunistic infections and the pulmonary pathology of immunologic disease. Until recently, the use of BAL was limited primarily to two areas: the study of interstitial lung diseases and the diagnosis of lung infections by opportunistic microorganisms in severely immunocompromised patients with lung infiltrates. Over the past decade, the use of BAL has been expanded to include the conventional diagnosis of bacterial pneumonia in non-immunocompromised patients. In the past, different clinical studies proposed using BAL to quantify cultures in the sample obtained as a means of increasing the tool's effectiveness. Recent developments have led to a number of newer applications of BAL, such as bronchoscopic BAL, non-bronchoscopic BAL and protected BAL. The most important use of BAL in the non-immunocompromised patient is the diagnosis of pneumonia in the mechanically ventilated patient.

Bronchoscopic diagnosis of pneumonia

Lower respiratory tract infections are characterized by significant morbidity and mortality but also by a relative inability to establish a specific etiologic agent on clinical grounds alone. With the recognized shortcomings of expectorated or aspirated secretions toward establishing an etiologic diagnosis, clinicians have increasingly used bronchoscopy to obtain diagnostic samples. A variety of specimen types may be obtained, including bronchial washes or brushes, protected specimen brushings, bronchoalveolar lavage, and transbronchial biopsies. Bronchoscopy has been applied in three primary clinical settings, including the immunocompromised host, especially human immunodeficiency virus-infected and organ transplant patients; ventilator-associated pneumonia; and severe, nonresolving community- or hospital-acquired pneumonia in nonventilated patients. In each clinical setting, and for each specimen type, specific laboratory protocols are required to provide maximal information. These protocols should provide for the use of a variety of rapid microscopic and quantitative culture techniques and the use of a variety of specific stains and selective culture to detect unusual organism groups.

Diagnosing ventilator-associated pneumonia: the role of bronchoscopy

OBJECTIVE

To discuss the two diagnostic procedures used most frequently to obtain uncontaminated lower airway secretions during bronchoscopy.

DESIGN

This article reviews the contributing risk factors of ventilator-associated pneumonia (VAP) and the recent studies that have assessed the usefulness of the protected specimen brush (PSB) and bronchoalveolar lavage (BAL) in the nonimmunocompromised host.

RESULTS

A prompt, accurate diagnosis of VAP, including specific identification of the bacterial pathogen, remains a common challenge in the intensive-care unit. Standard clinical criteria are of suboptimal specificity for making decisions, including selecting antibiotic therapy. Bronchoscopic techniques of lung secretion sampling can be used in the intensive-care unit in an effort to overcome the effects of oropharyngeal contamination. The PSB and BAL, used appropriately, can help intensive-care clinicians formulate specific antimicrobial therapy. Evaluation of intracellular bacteria obtained by BAL has been reported to be useful in guiding empiric antibiotic therapy while the final results of cultures obtained with the PSB are pending. Prior antibiotic therapy, however, may confound the interpretation and clinical utility of results.

CONCLUSION

Currently, for a patient taking antibiotic therapy, no reliable technique nor quantitative culture threshold exists to help in diagnosing suspected VAP or in guiding antibiotic therapy. If the clinical situation allows, antibiotic therapy should be discontinued for 48 hours; then, the PSB, BAL, protected BAL, or endobronchial aspiration should be used. These contemporary modalities, however, necessitate further clinical trials before widespread use is warranted.

New approaches in the diagnosis of nosocomial pneumonia

We have presented a review of the present literature on new modalities to diagnose nosocomial pneumonia. Procedures are now available that, when correctly used, can establish a diagnosis of pneumonia with a high degree of reliability. In our institution, reliance on bronchoscopic modalities has simplified management of patients with suspected VAP, by eliminating confusion and rationalizing antibiotic treatment. Invasive procedures, however, should be performed only if the results of cultures are consistently applied to treatment. As this field rapidly evolves, we hope that this review will provide the reader with a foundation to understand new developments.

Pneumonia in the surgical intensive care unit: factors determining successful outcome

A review of 85 consecutive patients who acquired pneumonia in a surgical intensive care unit revealed several parameters associated with successful treatment. Fifty-five patients (65%) recovered after a single course of antimicrobial therapy. Statistical analysis demonstrated significant differences between those treated successfully and those whose therapy failed during the duration of intubation (7.2 +/- 1.5 days versus 29.3 +/- 4.3 days), duration of ventilation (6.7 +/- 1.4 days versus 14.8 +/- 3.2 days), and the alveolar-arterial oxygen gradient on the day of diagnosis (215 +/- 23 mm Hg versus 343 +/- 33 mm Hg, all p < 0.01). Multiple antimicrobial resistance was uncommon in bacteria isolated on initial culture but occurred in two thirds of patients with treatment failures. Pneumonia due to Pseudomonas aeruginosa and Staphylococcus aureus were associated with the highest rate of treatment failure, which were 56% and 45%, respectively.

Diagnostic efficiency of endotracheal aspirates with quantitative bacterial cultures in intubated patients with suspected pneumonia. Comparison with the protected specimen brush

The objectives of the study were to determine the agreement between the protected specimen brush technique (PSB) with quantitative cultures and endotracheal aspirates (EA) with quantitative cultures when using increasing interpretative cutoff points and to investigate the respective operating characteristics for the diagnosis of pneumonia of PSB and EA when using quantitative cultures. Consecutive sampling of respiratory secretions using these two techniques was conducted in the respiratory intensive care units in 52 mechanically ventilated patients with clinical and radiologic suspicion of pneumonia. Quantitative bacterial cultures of PSB and EA samples were obtained. The 10(6) cfu/ml cutoff point was the most accurate diagnostic threshold for the EA technique. When using this threshold, there was a high level of agreement (84.6%) between PSB and EA results. Among the few discrepancies, the EA result was always indicative of pneumonia, whereas the PSB result was nonindicative, thus permitting us to classify correctly five patients in whom pneumonia would have been erroneously excluded on the basis of the sole result of PSB. Conversely, there was no case where the PSB result was indicative of pneumonia when the EA result (at the 10(6) cfu/ml level) was not. The operating characteristics of the PSB technique for the diagnosis of pneumonia were in accordance with previously published studies. The operating characteristics of the EA technique (when taking the 10(6) cfu/ml of respiratory secretions as the interpretative cutoff point) compared favorably with those of the PSB technique. Diagnostic accuracy rates were similar. The specificity of EA was somewhat lower (83 versus 96%), but the sensitivity was higher (82 versus 64%).(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of antibiotic therapy on recovery of intracellular bacteria from bronchoalveolar lavage in suspected ventilator-associated nosocomial pneumonia

Intracellular bacteria (ICB) within recovered cells (> 7 percent) obtained via bronchoalveolar lavage (BAL) have been described as predictive of subsequent positive quantitative protected specimen brush (PSB) cultures in patients not receiving antibiotics. To determine the effect of prior or current antibiotic therapy on ICB relative to subsequent PSB culture, we prospectively evaluated 49 consecutive episodes of clinically suspected ventilator-associated pneumonia in 36 patients. Three patient groups were defined based on antibiotic administration: group 1 (current antibiotics), n = 31, samples obtained from patients currently receiving antibiotics; group 2 (recent antibiotics), n = 5, samples obtained from patients who received antibiotics > 48 h but < 72 h prior to sampling; and group 3 (no antibiotics), n = 13, samples from patients receiving no previous antibiotics within 7 days prior to sampling. Overall, PSB cultures (> or = 10(3) cfu/ml) were positive in 14 of 49 (29 percent) samples. In group 1, 2 of 31 (6 percent) samples were positive while 5 of 5 (100 percent) samples in group 2, and 7 of 13 (54 percent) in group 3 were positive. The presence or absence of ICB accurately predicted both positive and negative PSB cultures in 43 of 49 episodes. Of 43 correct predictions, 34 were negative predictions (negative ICB, negative PSB culture). The vast majority of these (29) were obtained from group 1, patients currently receiving antibiotics. In contrast, of nine positive predictions (+ICB, +PSB) virtually all (seven) occurred in group 3, patients receiving no antibiotics. In group 3, 13 of 13 PSB cultures were accurately predicted, either positive or negative, by the presence or absence of ICB. Of seven positive PSB cultures in groups 1 and 2, only 2 (28 percent) were accurately predicted by ICB. From both samples, the cultured organism was resistant to all administered antibiotics. These data suggest both prior and current antibiotic therapy reduces recovery of ICB from BAL and reduces predictive accuracy of ICB for subsequent positive PSB cultures. However, negative prediction by ICB for subsequent negative PSB cultures was good. In contrast, ICB obtained from patients not receiving antibiotics are highly predictive of subsequent PSB culture results, both positive and negative. We do not recommend BAL for evaluation of ICB in patients currently receiving antibiotics or with a recent history of antibiotic use.

Procedures for the diagnosis of pneumonia in ICU patients

The optimal technique for diagnosing nosocomial bacterial pneumonia in critically ill patients cared for in the intensive care unit remains unclear, especially in the subgroup of patients requiring mechanical ventilation. An important advance has been the development of the protected specimen brush technique. Secretions obtained using this technique and evaluated by quantitative cultures are useful in distinguishing patients with and without pneumonia. However, this procedure has important limitations in that results are not available immediately, and in that a few false negative of false positive results may occur. Bronchoalveolar lavage has been suggested to be of value in establishing the diagnosis of pneumonia, because the cells and liquid recovered can be examined microscopically immediately after the procedure and are also suitable for quantitative culture. Microscopic identification of bacteria within cells recovered by lavage may provide a sensitive and specific means for the early and rapid diagnosis of pneumonia in this setting. The lavage technique can also be conveniently incorporated into a protocol along with quantitative culture of samples obtained using the protected specimen brush. This combination will probably improve the overall accuracy of diagnosis while allowing the administration of prompt empiric antimicrobial therapy in most patients with pneumonia.