The significance of distal bronchial samples with commensals in ventilator-associated pneumonia: colonizer or pathogen?

Portable electronic bronchoscopy for clinical application: a multi-institutional randomized instrument validation study

OBJECTIVE

Electronic bronchoscopy is routinely used for the diagnosis and treatment of lung and bronchial disorders. However, the devices used are normally large and costly. Here, we evaluated the clinical effectiveness of a portable electronic bronchoscope produced by Zhejiang UE Medical Corp., the UE-EB.

METHODS

We conducted a multi-institutional, randomized, single-blind, non-inferiority and parallel-group controlled clinical trial. Participants were randomly assigned 1:1 to the experimental group or control group. The primary indicator was the effectiveness of the device. Safety indicators were assessed from enrollment to 3 days after the operation.

RESULTS

The UE-EB had good consistency between groups during the procedure, and the effective rate was 100.00% in both groups. The difference value (95% confidence interval) between the two groups was 0.00% (-5.45%, 5.45%), and the lower limit was greater than -10% (negative non-inferiority margin). There was also no difference between the two groups in terms safety indicators.

CONCLUSIONS

The portable electronic bronchoscope described in this study showed reliable effectiveness and safety. This device is worth promoting and applying in clinical practice.Research registry number: ZXLB20200295 (Zhejiang Medical Products Administration, China).

Identification of Potential Urinary Metabolite Biomarkers of Pseudomonas aeruginosa Ventilator-Associated Pneumonia

Introduction:

Ventilator-associated pneumonia (VAP) caused by Pseudomonas aeruginosa is a major cause of morbidity and mortality in hospital intensive care units (ICU). Rapid identification of P. aeruginosa-derived markers in easily accessible patients’ samples can enable an early detection of P. aeruginosa VAP (VAP-PA), thereby stewarding antibiotic use and improving clinical outcomes.

Methods:

Metabolites were analysed using liquid chromatography-mass spectrometry (LC-MS) in prospectively collected urine samples from mechanically ventilated patients admitted to the Antwerp University Hospital ICU. Patients were followed from the start of mechanical ventilation (n = 100 patients) till the time of clinical diagnosis of VAP (n = 13). Patients (n = 8) in whom diagnosis of VAP was further confirmed by culturing respiratory samples and urine samples were studied for semi-quantitative metabolomics.

Results:

We first show that multivariate analyses highly discriminated VAP-PA from VAP–non-PA as well as from the pre-infection groups (R² = .97 and .98, respectively). A further univariate analysis identified 58 metabolites that were significantly elevated or uniquely present in VAP-PA compared to the VAP–non-PA and pre-infection groups (P < .05). These comprised both a known metabolite of histidine as well as a novel nicotine metabolite. Most interestingly, we identified 3 metabolites that were not only highly upregulated for, but were also highly specific to, VAP-PA, as these metabolites were completely absent in all pre-infection timepoints and in VAP–non-PA group.

Conclusions:

Considerable differences exist between urine metabolites in VAP-PA compared to VAP due to other bacterial aetiologies as well to non-VAP (pre-infection) timepoints. The unique urinary metabolic biomarkers we describe here, if further validated, could serve as highly specific diagnostic biomarkers of VAP-PA.

Inoculation Pneumonia Caused by Coagulase Negative Staphylococcus

Rationale

Although frequently retrieved in tracheal secretions of critically ill patients on mechanical ventilation, the existence of pneumonia caused by coagulase-negative staphylococci (CoNS) remains controversial.

Objective

To assess whether Staphylococcus haemolyticus (S. haemolyticus) inoculated in mice’s trachea can infect normal lung parenchyma, increasing concentrations of S. haemolyticus were intratracheally administered in 221 immunocompetent mice.

Methods

Each animal received intratracheally phosphate-buffered saline (PBS) (n = 43) or live (n = 141) or inactivated (n = 37) S. haemolyticus at increasing load: 1.0 × 10⁶, 1.0 × 10⁷, and 1.0 × 10⁸ colony forming units (CFU). Forty-three animals were sacrificed at 12 h and 178 were sacrificed at 36 h; 64 served for post-mortem lung histology, 157 served for pre-mortem bronchoalveolar lavage (BAL) analysis, and 42 served for post-mortem quantitative bacteriology of lung tissue. The distribution of biofilm-associated genes was investigated in the S. haemolyticus strain used in our in vivo experiment as well as among 19 other clinical S. haemolyticus strains collected from hospitals or nursing houses.

Measurements and Main Results

Intratracheal inoculation of 1.0 × 10⁸ CFU live S. haemolyticus caused macroscopic and histological confluent pneumonia with significant increase in BAL white cell count, tumor necrosis factor-α (TNF-α), and macrophage inflammatory protein (MIP)-2. At 12 h, high concentrations of S. haemolyticus were identified in BAL. At 36 h, lung injury and BAL inflammation were less severe than at 12 h and moderate concentrations of species belonging to the oropharyngeal flora were identified in lung tissue. The inoculation of 1.0 × 10⁶ and 1.0 × 10⁷ CFU live S. haemolyticus caused histologic interstitial pneumonia and moderate BAL inflammation. Similar results were observed after inoculation of inactivated S. haemolyticus. Moreover, biofilm formation was a common phenotype in S. haemolyticus isolates. The low prevalence of the ica operon in our clinical S. haemolyticus strain collection indicated icaA and icaD independent-biofilm formation.

Conclusion

In immunocompetent spontaneously breathing mice, inoculation of S. haemolyticus causes concentration-dependent lung infection that spontaneously recovers over time. icaA and icaD independent biofilm formation is a common phenotype in S. haemolyticus isolates.

Multidimensional Assessment of the Host Response in Mechanically Ventilated Patients with Suspected Pneumonia

Rationale: The identification of informative elements of the host response to infection may improve the diagnosis and management of bacterial pneumonia. Objectives: To determine whether the absence of alveolar neutrophilia can exclude bacterial pneumonia in critically ill patients with suspected infection and to test whether signatures of bacterial pneumonia can be identified in the alveolar macrophage transcriptome. Methods: We determined the test characteristics of alveolar neutrophilia for the diagnosis of bacterial pneumonia in three cohorts of mechanically ventilated patients. In one cohort, we also isolated macrophages from alveolar lavage fluid and used the transcriptome to identify signatures of bacterial pneumonia. Finally, we developed a humanized mouse model of Pseudomonas aeruginosa pneumonia to determine if pathogen-specific signatures can be identified in human alveolar macrophages. Measurements and Main Results: An alveolar neutrophil percentage less than 50% had a negative predictive value of greater than 90% for bacterial pneumonia in both the retrospective (n = 851) and validation cohorts (n = 76 and n = 79). A transcriptional signature of bacterial pneumonia was present in both resident and recruited macrophages. Gene signatures from both cell types identified patients with bacterial pneumonia with test characteristics similar to alveolar neutrophilia. Conclusions: The absence of alveolar neutrophilia has a high negative predictive value for bacterial pneumonia in critically ill patients with suspected infection. Macrophages can be isolated from alveolar lavage fluid obtained during routine care and used for RNA-Seq analysis. This novel approach may facilitate a longitudinal and multidimensional assessment of the host response to bacterial pneumonia.

The endotracheal tube microbiome associated with Pseudomonas aeruginosa or Staphylococcus epidermidis

Ventilator-associated pneumonia (VAP) is one of the commonest hospital-acquired infections associated with high mortality. VAP pathogenesis is closely linked to organisms colonizing the endotracheal tube (ETT) such as Staphylococcus epidermidis and Pseudomonas aeruginosa, the former a common commensal with pathogenic potential and the latter a known VAP pathogen. However, recent gut microbiome studies show that pathogens rarely function alone. Hence, we determined the ETT microbial consortium co-colonizing with S. epidermidis or P. aeruginosa to understand its importance in the development of VAP and for patient prognosis. Using bacterial 16S rRNA and fungal ITS-II sequencing on ETT biomass showing presence of P. aeruginosa and/or S. epidermidis on culture, we found that presence of P. aeruginosa correlated inversely with patient survival and with bacterial species diversity. A decision tree, using 16S rRNA and patient parameters, to predict patient survival was generated. Patients with a relative abundance of Pseudomonadaceae <4.6% and of Staphylococcaceae <70.8% had the highest chance of survival. When Pseudomonadaceae were >4.6%, age of patient <66.5 years was the most important predictor of patient survival. These data indicate that the composition of the ETT microbiome correlates with patient prognosis, and presence of P. aeruginosa is an important predictor of patient outcome.

Analysis of Lung Microbiota in Bronchoalveolar Lavage, Protected Brush and Sputum Samples from Subjects with Mild-To-Moderate Cystic Fibrosis Lung Disease

Individuals with cystic fibrosis (CF) often acquire chronic lung infections that lead to irreversible damage. We sought to examine regional variation in the microbial communities in the lungs of individuals with mild-to-moderate CF lung disease, to examine the relationship between the local microbiota and local damage, and to determine the relationships between microbiota in samples taken directly from the lung and the microbiota in spontaneously expectorated sputum. In this initial study, nine stable, adult CF patients with an FEV₁>50% underwent regional sampling of different lobes of the right lung by bronchoalveolar lavage (BAL) and protected brush (PB) sampling of mucus plugs. Sputum samples were obtained from six of the nine subjects immediately prior to the procedure. Microbial community analysis was performed on DNA extracted from these samples and the extent of damage in each lobe was quantified from a recent CT scan. The extent of damage observed in regions of the right lung did not correlate with specific microbial genera, levels of community diversity or composition, or bacterial genome copies per ml of BAL fluid. In all subjects, BAL fluid from different regions of the lung contained similar microbial communities. In eight out of nine subjects, PB samples from different regions of the lung were also similar in microbial community composition, and were similar to microbial communities in BAL fluid from the same lobe. Microbial communities in PB samples were more diverse than those in BAL samples, suggesting enrichment of some taxa in mucus plugs. To our knowledge, this study is the first to examine the microbiota in different regions of the CF lung in clinically stable individuals with mild-to-moderate CF-related lung disease.

Understanding the Concept of Health Care-Associated Pneumonia in Lung Transplant Recipients

BACKGROUND

Limited data are available regarding the etiologic impact of health care-associated pneumonia (HCAP) in lung transplant recipients. Therefore, our aim was to evaluate the microbiologic differences between HCAP and hospital-acquired pneumonia (HAP)/ventilator-associated pneumonia (VAP) in lung transplant recipients with a radiographically confirmed diagnosis of pneumonia.

METHODS

We performed a retrospective cohort study of lung transplant recipients with pneumonia at one transplant center over a 7-year period. Eligible patients included lung transplant recipients who developed a first episode of radiographically confirmed pneumonia ≥ 48 h following transplantation. HCAP, HAP, and VAP were classified according to the American Thoracic Society/Infectious Diseases Society of America 2005 guidelines. χ² and Student t tests were used to compare categorical and continuous variables, respectively.

RESULTS

Sixty-eight lung transplant recipients developed at least one episode of pneumonia. HCAP (n = 42; 62%) was most common, followed by HAP/VAP (n = 26; 38%) stratified in HAP (n = 20; 77%) and VAP (n = 6; 23%). Pseudomonas aeruginosa was the predominantly isolated organism (n = 22; 32%), whereas invasive aspergillosis was uncommon (< 10%). Multiple-drug resistant (MDR) pathogens were less frequently isolated in patients with HCAP compared with HAP/VAP (5% vs 27%; P = .009). Opportunistic pathogens were less frequently identified in lung transplant recipients with HCAP than in those with HAP/VAP (7% vs 27%; P = .02). Lung transplant recipients with HCAP had a similar mortality at 90 days (n = 9 [21%] vs n = 4 [15%]; P = .3) compared with patients with HAP/VAP.

CONCLUSIONS

HCAP was the most frequent infection in lung transplant recipients. MDR pathogens and opportunistic pathogens were more frequently isolated in HAP/VAP. There were no differences in 30- and 90-day mortality between lung transplant recipients with HCAP and those with HAP/VAP.

Ventilator-associated Pneumonia caused by commensal oropharyngeal Flora; [corrected] a retrospective Analysis of a prospectively collected Database

Background

The significance of commensal oropharyngeal flora (COF) as a potential cause of ventilator-associated pneumonia (VAP) is scarcely investigated and consequently unknown. Therefore, the aim of this study was to explore whether COF may cause VAP.

Methods

Retrospective clinical, microbiological and radiographic analysis of all prospectively collected suspected VAP cases in which bronchoalveolar lavage fluid exclusively yielded ≥ 10⁴ cfu/ml COF during a 9.5-year period. Characteristics of 899 recent intensive care unit (ICU) admissions were used as a reference population.

Results

Out of the prospectively collected database containing 159 VAP cases, 23 patients were included. In these patients, VAP developed after a median of 8 days of mechanical ventilation. The patients faced a prolonged total ICU length of stay (35 days [P < .001]), hospital length of stay (45 days [P = .001]), and a trend to higher mortality (39 % vs. 26 %, [P = .158]; standardized mortality ratio 1.26 vs. 0.77, [P = .137]) compared to the reference population. After clinical, microbiological and radiographic analysis, COF was the most likely cause of respiratory deterioration in 15 patients (9.4 % of all VAP cases) and a possible cause in 2 patients.

Conclusion

Commensal oropharyngeal flora appears to be a potential cause of VAP in limited numbers of ICU patients as is probably associated with an increased length of stay in both ICU and hospital. As COF-VAP develops late in the course of ICU admission, it is possibly associated with the immunocompromised status of ICU patients.

Strategies to reduce curative antibiotic therapy in intensive care units (adult and paediatric)

Emerging resistance to antibiotics shows no signs of decline. At the same time, few new antibacterials are being discovered. There is a worldwide recognition regarding the danger of this situation. The urgency of the situation and the conviction that practices should change led the Société de Réanimation de Langue Française (SRLF) and the Société Française d'Anesthésie et de Réanimation (SFAR) to set up a panel of experts from various disciplines. These experts met for the first time at the end of 2012 and have since met regularly to issue the following 67 recommendations, according to the rigorous GRADE methodology. Five fields were explored: i) the link between the resistance of bacteria and the use of antibiotics in intensive care; ii) which microbiological data and how to use them to reduce antibiotic consumption; iii) how should antibiotic therapy be chosen to limit consumption of antibiotics; iv) how can antibiotic administration be optimized; v) review and duration of antibiotic treatments. In each institution, the appropriation of these recommendations should arouse multidisciplinary discussions resulting in better knowledge of local epidemiology, rate of antibiotic use, and finally protocols for improving the stewardship of antibiotics. These efforts should contribute to limit the emergence of resistant bacteria.

Changes in gastric and lung microflora with acid suppression: acid suppression and bacterial growth

IMPORTANCE

The use of acid suppression has been associated with an increased risk of upper and lower respiratory tract infections in the outpatient setting but the mechanism behind this increased risk is unknown. We hypothesize that this infection risk results from gastric bacterial overgrowth with subsequent seeding of the lungs.

OBJECTIVES

To determine if acid-suppression use results in gastric bacterial overgrowth, if there are changes in lung microflora associated with the use of acid suppression, and if changes in lung microflora are related to full-column nonacid gastroesophageal reflux.

DESIGN, SETTING, AND PARTICIPANTS

A 5-year prospective cohort study at a tertiary care center where children ages 1 to 18 years were undergoing bronchoscopy and endoscopy for the evaluation of chronic cough. Acid-suppression use was assessed through questionnaires with confirmation using an electronic medical record review.

MAIN OUTCOMES AND MEASURES

Our primary outcome was to compare differences in concentration and prevalence of gastric and lung bacteria between patients who were and were not receiving acid-suppression therapy. We compared medians using the Wilcoxon signed rank test and determined prevalence ratios using asymptotic standard errors and 95% confidence intervals. We determined correlations between continuous variables using Pearson correlation coefficients and compared categorical variables using the Fisher exact test.

RESULTS

Forty-six percent of patients taking acid-suppression medication had gastric bacterial growth compared with 18% of untreated patients (P = .003). Staphylococcus (prevalence ratio, 12.75 [95% CI, 1.72-94.36]), Streptococcus (prevalence ratio, 6.91 [95% CI, 1.64-29.02]), Veillonella (prevalence ratio, 9.56 [95% CI, 1.26-72.67]), Dermabacter (prevalence ratio, 4.78 [95% CI, 1.09-21.02]), and Rothia (prevalence ratio, 6.38 [95% CI, 1.50-27.02]) were found more commonly in the gastric fluid of treated patients. The median bacterial concentration was higher in treated patients than in untreated patients (P = .001). There was no difference in the prevalence (P > .23) of different bacterial genera or the median concentration of total bacteria (P = .85) in the lungs between treated and untreated patients. There were significant positive correlations between proximal nonacid reflux burden and lung concentrations of Bacillus (r = 0.47, P = .005), Dermabacter (r = 0.37, P = .008), Lactobacillus (r = 0.45, P = .001), Peptostreptococcus (r = 0.37, P = .008), and Capnocytophagia (r = 0.37, P = .008).

CONCLUSIONS AND RELEVANCE

Acid-suppression use results in gastric bacterial overgrowth of genera including Staphylococcus and Streptococcus. Full-column nonacid reflux is associated with greater concentrations of bacteria in the lung. Additional studies are needed to determine if acid suppression-related microflora changes predict clinical infection risk; these results suggest that acid suppression use may need to be limited in patients at risk for infections.

Endotracheal aspirate and bronchoalveolar lavage fluid analysis: interchangeable diagnostic modalities in suspected ventilator-associated pneumonia?

Authoritative guidelines state that the diagnosis of ventilator-associated pneumonia (VAP) can be established using either endotracheal aspirate (ETA) or bronchoalveolar lavage fluid (BALF) analysis, thereby suggesting that their results are considered to be in accordance. Therefore, the results of ETA Gram staining and semiquantitative cultures were compared to the results from a paired ETA-BALF analysis. Different thresholds for the positivity of ETAs were assessed. This was a prospective study of all patients who underwent bronchoalveolar lavage for suspected VAP in a 27-bed university intensive care unit during an 8-year period. VAP was diagnosed when ≥ 2% of the BALF cells contained intracellular organisms and/or when BALF quantitative culture revealed ≥ 10(4) CFU/ml of potentially pathogenic microorganisms. ETA Gram staining and semiquantitative cultures were compared to the results from paired BALF analysis by Cohen's kappa coefficients. VAP was suspected in 311 patients and diagnosed in 122 (39%) patients. In 288 (93%) patients, the results from the ETA analysis were available for comparison. Depending on the threshold used and the diagnostic modality, VAP incidences varied from 15% to 68%. For the diagnosis of VAP, the most accurate threshold for positivity of ETA semiquantitative cultures was moderate or heavy growth, whereas the optimal threshold for BALF Gram staining was ≥ 1 microorganisms per high power field. The Cohen's kappa coefficients were 0.22, 0.31, and 0.60 for ETA and paired BALF Gram stains, cultures, and BALF Gram stains, respectively. Since the ETA and BALF Gram stains and cultures agreed only fairly, they are probably not interchangeable for diagnosing VAP.

Significance of anaerobes and oral bacteria in community-acquired pneumonia

BACKGROUND

Molecular biological modalities with better detection rates have been applied to identify the bacteria causing infectious diseases. Approximately 10-48% of bacterial pathogens causing community-acquired pneumonia are not identified using conventional cultivation methods. This study evaluated the bacteriological causes of community-acquired pneumonia using a cultivation-independent clone library analysis of the 16S ribosomal RNA gene of bronchoalveolar lavage specimens, and compared the results with those of conventional cultivation methods.

METHODS

Patients with community-acquired pneumonia were enrolled based on their clinical and radiological findings. Bronchoalveolar lavage specimens were collected from pulmonary pathological lesions using bronchoscopy and evaluated by both a culture-independent molecular method and conventional cultivation methods. For the culture-independent molecular method, approximately 600 base pairs of 16S ribosomal RNA genes were amplified using polymerase chain reaction with universal primers, followed by the construction of clone libraries. The nucleotide sequences of 96 clones randomly chosen for each specimen were determined, and bacterial homology was searched. Conventional cultivation methods, including anaerobic cultures, were also performed using the same specimens.

RESULTS

In addition to known common pathogens of community-acquired pneumonia [Streptococcus pneumoniae (18.8%), Haemophilus influenzae (18.8%), Mycoplasma pneumoniae (17.2%)], molecular analysis of specimens from 64 patients with community-acquired pneumonia showed relatively higher rates of anaerobes (15.6%) and oral bacteria (15.6%) than previous reports.

CONCLUSION

Our findings suggest that anaerobes and oral bacteria are more frequently detected in patients with community-acquired pneumonia than previously believed. It is possible that these bacteria may play more important roles in community-acquired pneumonia.

Is the gram stain useful in the microbiologic diagnosis of VAP? A meta-analysis

In a meta-analysis examining respiratory specimen Gram stain for diagnosis of ventilator-associated pneumonia, absence of bacteria on Gram stain had a high negative predictive value, but a positive Gram stain correlated poorly with organisms recovered in culture. Rapid and accurate diagnosis of ventilator-associated pneumonia (VAP) is a major challenge and no generally accepted gold standard exists for VAP diagnosis. We conducted a meta-analysis to examine the role of respiratory specimen Gram stain to diagnose VAP, and the correlation with final culture results. In 21 studies, pooled sensitivity of Gram stain for VAP was 0.79 (95% confidence interval [CI], .77-0.81; P < .0001) and specificity was 0.75 (95% CI, .73-.78; P < .0001). Negative predictive value of Gram stain for a VAP prevalence of 20%-30% was 91%, suggesting that VAP is unlikely with a negative Gram stain but the positive predictive value of Gram stain was only 40%. Pooled kappa was 0.42 for gram-positive organisms and 0.34 for gram-negative organisms, suggesting fair concordance between organisms on Gram stain and recovery by culture. Therefore, a positive Gram stain should not be used to narrow anti-infective therapy until culture results become available.

Ventilator-associated pneumonia: a comprehensive review

Ventilator-associated pneumonia (VAP) is the most frequent and severe infection acquired in the intensive care unit, leading to prolonged mechanical ventilation and excess mortality. This article reviews the different aspects of VAP, such as risk factors, causative agents, and approaches to diagnosis, treatment, and prevention. Several aspects of VAP are still considered controversial.

Usefulness of quantitative endotracheal aspirate cultures in intensive care unit patients with suspected pneumonia

It is difficult to differentiate pathogens responsible for pneumonia or colonization in patients with an endotracheal tube or in patients that have undergone tracheostomy. We evaluated the clinical usefulness of quantitative endotracheal aspirates cultures and sought to determine the result threshold level for positivity. The authors performed this retrospective cohort study between December 1, 2004 and January 31, 2006. Forty-five suspected pneumonia patients admitted to an intensive care unit (ICU) with quantitative bronchoalveolar lavage (BAL) and endotracheal aspirate (EA) culture results were enrolled. Using a threshold of 10(5) cfu/mL, 10 of the 45 (22.2%) quantitative EA cultures were positive, as compared with 7 (15.6%) BAL cultures. When BAL culture findings were used as the reference, the sensitivity and specificity of quantitative EA cultures were 85.7% and 89.5%, respectively, at a threshold of 10(5) cfu/mL, and 85.7% and 94.7%, respectively, at a threshold of 10(6) cfu/mL. Of the 10 EA culture positive patients, 2 patients with a result of -10(5) cfu/mL were BAL culture negative. The quantitative EA culture is a useful non-invasive tool for the diagnosis of pneumonia pathogens. It is suggested that a threshold level of 10(6) cfu/mL is appropriate.

Usefulness of bronchoscopic microsampling to detect the pathogenic bacteria of respiratory infection

BACKGROUND

Bronchoscopic microsampling (BMS) is a method in which a device consisting of a wire with a polyester probe at the tip is used to collect bronchial epithelial lining fluid with bronchoscopy. In this study, we bacteriologically investigated sample collection using BMS to incorporate BMS into diagnosis of respiratory infection.

METHODS

Strains of Streptococcus pneumoniae, Haemophilus influenzae, Pseudomonas aeruginosa, and Mycobacterium avium complex (MAC), were used for experiments. In the standard sampling procedure using BMS, the probe coming out of the sheath was immersed in approximately 6 x 10(6) cfu/mL bacterial suspension for 30 s and cut into a tube containing 1 mL of normal saline solution. The tube was stirred for 1 min using a vortex. The sampling rate was calculated by the following equation: (actual amount of bacteria collected by BMS [colony forming units per milliliter])/(bacterial amount in suspension for sampling [colony forming units per milliliter]) x 100 (percentage).

RESULTS

The sampling rate of S pneumoniae, H influenzae, and MAC showed no significant difference among three bacteria, but the sampling rate of P aeruginosa was higher. The shortened time of sampling, stirring, and the reduced bacterial amount in the suspension (1/100) did not significantly affect the rates of standard procedure. In contrast, in comparison with a protected specimen brush (PSB), the recoveries of S pneumoniae, H influenzae, and MAC using PSB were significantly lower than those by BMS, but the recovery of P aeruginosa was not significantly different.

CONCLUSION

This in vitro study might suggested the usefulness of BMS as a new diagnostic technique capable of quantitative and stable sampling.

Prognosis and risk factors of early onset pneumonia in ventilated patients with Guillain–Barré syndrome

OBJECTIVE

Invasive mechanical ventilation is required in 30% of patients with Guillain-Barré syndrome (GBS) and is associated with pneumonia and increased mortality. Our objective was to determine the incidence, characteristics, outcomes, and risk factors of pneumonia in GBS patients receiving mechanical ventilation.

DESIGN AND SETTING

Study of a prospective database in an intensive care unit of a university hospital.

PATIENTS

The study included 81 patients who required intubation for GBS. Neurological findings, vital capacity, and signs of respiratory distress were recorded at admission and at intubation. A score predicting the risk of intubation (0-4) was calculated for each patient. Pneumonia was diagnosed based on predefined criteria and retrospectively confirmed by two observers. Early-onset pneumonia was defined as pneumonia diagnosed within 5 days after intubation.

MEASUREMENTS AND RESULTS

Mean vital capacity was 57 +/- 22% of predicted at admission and 33 +/- 11% at intubation. Pneumonia developed in 63 patients (78%), including 48 with early-onset pneumonia. Bacteria were consistent with aspiration. Of the 63 patients with pneumonia 11 (18%) had septic shock, 6 (10%) had acute respiratory distress syndrome, and 9 (14%) died. In the univariate analysis milder weakness, a lower risk of intubation (score < 2), and time from admission to intubation longer than 2 days were associated with early-onset pneumonia. Time from admission to intubation was the only independent predictor in the multivariate logistic regression model.

CONCLUSIONS

Early-onset pneumonia is a common and severe complication that is related to aspiration in patients with GBS. Delaying intubation may increase the risk of early-onset pneumonia.

Community-acquired bacteria frequently detected by means of quantitative polymerase chain reaction in nosocomial early-onset ventilator-associated pneumonia*

OBJECTIVE

To test whether real-time polymerase chain reaction allows for rapid quantitative detection of Streptococcus pneumoniae, Chlamydia pneumoniae, Mycoplasma pneumoniae, and Legionella pneumophila in bronchoalveolar lavage fluids and to determine the prevalence of these pathogens in nosocomial ventilator-associated pneumonia.

DESIGN

Prospective epidemiologic study applying a new molecular biology-based diagnostic tool during a 27-month period.

SETTING

Three medical intensive care units of a tertiary care university hospital.

PATIENTS

One hundred patients suffering from nosocomial ventilator-associated pneumonia, hospitalized for > or =14 days, intubated for reasons other than pneumonia, and mechanically ventilated for >48 hrs.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

S. pneumoniae, M. pneumoniae, and C. pneumoniae were detected in bronchoalveolar lavage fluids of 100 patients in 20 (20%), three (3%), and two (2%) cases, respectively. There of 17 (71%) revealed no growth or no significant growth by conventional culture. In one patient, S. pneumoniae and M. pneumoniae were detected simultaneously. Corresponding colony-forming units/mL were partly up to 10 CFU/mL with Gram stainings showing signs of acute inflammation in 80%. A significant temporary correlation between the number of days on ventilator, development of nosocomial pneumonia, and the frequency of detection of these pathogens was found for day 4.

CONCLUSIONS

S. pneumoniae, M. pneumoniae, and C. pneumoniae should be considered as causative agents in critically ill patients who develop early-onset nosocomial ventilator-associated pneumonia. Thus, empirical antimicrobial regimens should cover S. pneumoniae, Chlamydia, and Mycoplasma alike. Quantitative polymerase chain reaction is a fast diagnostic tool allowing for detection of these bacteria within 3 hrs in pretreated patients.

Endotracheal colonization at birth is associated with a pathogen-dependent pro- and antiinflammatory cytokine response in ventilated preterm infants: a prospective cohort study

The possible association between mediators of inflammation such as cytokines and perinatal colonization of the respiratory tract remains unclear. This prospective cohort study evaluated endotracheal colonization in 141 ventilated preterm infants at birth. The relation with cytokine response in the airways and C-reactive protein (CRP) in umbilical blood was investigated. Of the 141 preterm infants enrolled in this study, 37 (26%) were colonized. In addition to traditional pathogens (61%), commensal species (26%) and Mycoplasmataceae (13%) were isolated. Both the pro-inflammatory cytokines IL-1 beta, IL-6, IL-8, and tumor necrosis factor (TNF)-alpha as well as the antiinflammatory IL-10 are increased in colonized patients in a dose-dependent manner, with the strongest response in neonates colonized with Gram-negative organisms. There was no antimicrobial IL-12p70 response in colonized infants. Commensal flora is associated with the same inflammatory response as traditional pathogens. Although the umbilical cord blood CRP level was significantly higher in neonates with endotracheal colonization, it was highest in those colonized with Gram-negative organisms but still close to normal limits. Microorganisms in the endotracheal fluid of ventilated preterm infants are associated with a pathogen-specific and dose-dependent cytokine response in the airways and systemic CRP response.

Nosocomial lung infections in adult intensive care units

Nosocomial respiratory tract infections are the leading type of nosocomial infections. Despite the development of new antibiotic therapies, they are associated with an increased morbidity and mortality. Patients with comorbidities are especially predisposed to acquire these infections, as are patients exposed to respiratory therapy. Aspiration of colonized secretions from the oropharynx is the main mechanism of infection development. Barrier techniques to reduce aspiration and antimicrobial agents to alter bacterial flora are important in preventing pneumonia episodes. The initial institution of an adequate antibiotic regimen is a determinant of outcome. Nosocomial pneumonias are often difficult to treat due to antibiotic-resistant bacteria. Antibiotic policies are crucial in avoiding a progression in antibiotic resistance.

Variation of infected cell count in bronchoalveolar lavage and timing of ventilator-associated pneumonia

OBJECTIVES

The aim of this study was to evaluate and compare the accuracy of the percentage of infected cells (%IC) in bronchoalveolar lavage (BAL) for ventilator-associated pneumonia (VAP) diagnosis according to its onset from the initiation of mechanical ventilation.

PATIENTS

One hundred and eight patients admitted to a surgical ICU were retrospectively included (1999-2001). A total of 171 cases of VAP were diagnosed on clinical, biological, chest X-ray and BAL results (threshold >/=10(4 )cfu/ml).

RESULTS

The %IC significantly decreased with the timing of VAP diagnosis: 12.2+/-12.1% for VAP occurring less than 7 days after the initiation of mechanical ventilation, 7.4+/-9.2% for VAP occurring between 7 and 15 days and 4.8+/-6.4% for VAP after 15 days ( p=0.0002), despite the same number of elements and proportion of polymorphonuclear neutrophils in BAL. In addition, a relationship between the %IC and the pathogen responsible for VAP was observed for P. aeruginosa [higher for VAP <7 days than for VAP 7-15 days ( p=0.01) and VAP >15 days ( p=0.006)] and S. aureus [lower for VAP >15 days than VAP 7-15 days ( p=0.04) and VAP <7 days ( p=0.04)]. Furthermore, the %IC in BAL was lower in patients undergoing antimicrobial therapy than in patients without antibiotics ( p=0.04). Three factors were independently associated with the %IC: quantitative culture of BAL (beta=0.42, p<0.0001), ongoing antimicrobial therapy (beta= -0.21, p=0.003) and onset of VAP (beta= -0.17, p=0.01).

CONCLUSIONS

A relationship between the %IC in BAL, duration of ventilation, quantitative culture of BAL and ongoing antimicrobial therapy has been proved in this study. The %IC for VAP diagnosis may not be accurate in patients with ongoing antibiotics and late onset infections (>7 days).

Hospital-acquired pneumonia: etiologic considerations

The development of pneumonia requires the pathogen to reach the alveoli and the host defenses to be overwhelmed, either by microorganism virulence or by inoculums size. The endogenous sources of microorganisms are nasal carriers, sinusitis, mouth, oropharynx, gastric, or tracheal colonization, and hematogenous spread. The exogenous sources of microorganisms are biofilm of the tracheal tube, ventilator circuits, nebulizers, and humidifiers. Health care workers may also play a role in this setting. Different microorganisms can be found depending on the onset time of pneumonia and on the local pattern variation encountered between different institutions and countries. Healthy patients may be chronically colonized. A very important, unresolved issue is the definition of early and late-onset pneumonia; it still remains uncertain from the literature whether the given threshold refers to the number of days in hospital or to the number of days following intubation. Noninvasive ventilation is demonstrating that the term "ventilator-associated pneumonia" is perhaps inaccurate and should be referred to as "intubation-associated pneumonia."

Diagnosis of ventilator-associated pneumonia

PURPOSE OF REVIEW

This review examines the various techniques used to diagnose ventilator-associated pneumonia. The ideal diagnostic test not only helps the clinician to recognize whether pneumonia is present, but also to influence clinical outcome.

RECENT FINDINGS

Several studies have suggested that the clinical pulmonary infection score can be used to detect the onset of ventilator associated pneumonia. Serial clinical pulmonary infection scores have also been useful in helping to decide when to stop therapy. Semiquantitative culture methods have been used for nonbronchoscopic and bronchoscopic samples. Adequate initial empiric therapy for those organisms identified in these samples has been associated with improved survival. This supports the use of these culture techniques to diagnose patients with ventilator-associated pneumonia.

SUMMARY

Diagnostic testing for ventilator-associated pneumonia can identify those patients at risk for a poor clinical outcome.