Comparison between bronchoscopic BAL and non-bronchoscopic BAL in patients with VAP

Composition and diversity analysis of the lung microbiome in patients with suspected ventilator-associated pneumonia

Background

Ventilator-associated pneumonia (VAP) is associated with high morbidity and health care costs, yet diagnosis remains a challenge. Analysis of airway microbiota by amplicon sequencing provides a possible solution, as pneumonia is characterised by a disruption of the microbiome. However, studies evaluating the diagnostic capabilities of microbiome analysis are limited, with a lack of alignment on possible biomarkers. Using bronchoalveolar lavage fluid (BALF) from ventilated adult patients suspected of VAP, we aimed to explore how key characteristics of the microbiome differ between patients with positive and negative BALF cultures and whether any differences could have a clinically relevant role.

Methods

BALF from patients suspected of VAP was analysed using 16s rRNA sequencing in order to: (1) differentiate between patients with and without a positive culture; (2) determine if there was any association between microbiome diversity and local inflammatory response; and (3) correctly identify pathogens detected by conventional culture.

Results

Thirty-seven of 90 ICU patients with suspected VAP had positive cultures. Patients with a positive culture had significant microbiome dysbiosis with reduced alpha diversity. However, gross compositional variance was not strongly associated with culture positivity (AUROCC range 0.66–0.71). Patients with a positive culture had a significantly higher relative abundance of pathogenic bacteria compared to those without [0.45 (IQR 0.10–0.84), 0.02 (IQR 0.004–0.09), respectively], and an increased interleukin (IL)-1β was associated with reduced species evenness (r_s = − 0.33, p < 0.01) and increased pathogenic bacteria presence (r_s = 0.28, p = 0.013). Untargeted 16s rRNA pathogen detection was limited by false positives, while the use of pathogen-specific relative abundance thresholds showed better diagnostic accuracy (AUROCC range 0.89–0.998).

Conclusion

Patients with positive BALF culture had increased dysbiosis and genus dominance. An increased caspase-1-dependent IL-1b expression was associated with a reduced species evenness and increased pathogenic bacterial presence, providing a possible causal link between microbiome dysbiosis and lung injury development in VAP. However, measures of diversity were an unreliable predictor of culture positivity and 16s sequencing used agnostically could not usefully identify pathogens; this could be overcome if pathogen-specific relative abundance thresholds are used.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-022-04068-z.

Lower Respiratory Tract Coinfection in the ICU: Prevalence and Clinical Significance of Coinfection Detected via Microbiological Analysis of Bronchoalveolar Lavage Fluid With a Comparison of Invasive Methodologies

Pneumonia remains a significant cause of morbidity and mortality, with increasing interest in the detection and clinical significance of coinfection. Further investigation into the impact of bronchoalveolar lavage (BAL) sampling methodology and efficient clinical utilization of microbiological analyses is needed to guide the management of lower respiratory tract infection in the ICU.

Evaluation of the BioFire FilmArray Pneumonia Panel Plus to the Conventional Diagnostic Methods in Determining the Microbiological Etiology of Hospital-Acquired Pneumonia

Hospital-acquired pneumonia (HAP) is a substantial public health issue that is associated with high mortality rates and is complicated by an arsenal of microbial etiologies, expressing multidrug-resistant phenotypes, rendering relatively limited therapeutic options. BioFire FilmArray Pneumonia Panel plus (BFPP) is a simple multiplexed PCR system that integrates sample preparation, nucleic acid extraction, amplification, and analysis of microbial etiology, with a turnaround time of about one hour. In comparison to standard culture methods, BFPP is simpler, easier to perform, and can simultaneously detect the most common pathogens involved in lower respiratory tract infections (34 targets). Accordingly, we evaluated the diagnostic performance of the multiplexed BFPP for the rapid detection of 27 clinically relevant respiratory pathogens and 7 genetic markers among 50 HAP cases admitted to the intensive care unit (ICU), who submitted mini-bronchoalveolar (mBAL) specimens. In comparison to standard culture methods, BFPP showed an overall sensitivity of 100% [95% CI; 90-100] and overall specificity of 90% [95% CI; 87.4-92.5] among all the tested bacterial targets. BFPP identified 11 viral targets (22%) among the tested specimens. The BFPP semi-quantitative analysis showed a concordance rate of 47.4% among positive culture specimens. For the investigation of the antibiotic resistance genes, BFPP showed a positive percent agreement (PPA), a negative percent agreement (NPA), and an overall percent agreement (OPA), reaching 97% [95% CI; 90-100], 95% [95% CI; 91.5-97], and 95% [95% CI; 93-97], respectively, with standard antibiotic sensitivity testing. In conclusion, BFPP has the potential to enhance the rapid microbiological diagnosis of HAP cases, and could aid in tailoring appropriate antibiotic therapies.

A comparison of diagnostic algorithms and clinical parameters to diagnose ventilator-associated pneumonia: a prospective observational study

Background

Suspicion and clinical criteria continue to serve as the foundation for ventilator-associated pneumonia (VAP) diagnosis, however the criteria used to diagnose VAP vary widely. Data from head-to-head comparisons of clinical diagnostic algorithms is lacking, thus a prospective observational study was performed to determine the performance characteristics of the Johanson criteria, Clinical Pulmonary Infection Score (CPIS), and Centers for Disease Control and Prevention’s National Healthcare Safety Network (CDC/NHSN) criteria as compared to Hospital in Europe Link for Infection Control through Surveillance (HELICS) reference standard.

Methods

A prospective observational cohort study was performed in three mixed medical-surgical ICUs from one academic medical center from 1 October 2016 to 30 April 2018. VAP diagnostic criteria were applied to each patient including CDC/NHSN, CPIS, HELICS and Johanson criteria. Tracheal aspirate cultures (TAC) and serum procalcitonin values were obtained for each patient.

Results

Eighty-five patients were enrolled (VAP 45, controls 40). Using HELICS as the reference standard, the sensitivity and specificity for each of the assessed diagnostic algorithms were: CDC/NHSN (Sensitivity 54.2%; Specificity 100%), CPIS (Sensitivity 68.75%; Specificity 95.23%), Johanson (Sensitivity 67.69%; Specificity 95%). The positive TAC rate was 81.2%. The sensitivity for positive TAC with the serum procalcitonin level > 0.5 ng/ml was 51.8%.

Conclusion

VAP remains a considerable source of morbidity and mortality in modern intensive care units. The optimal diagnostic method remains unclear. Using HELICS criteria as the reference standard, CPIS had the greatest comparative diagnostic accuracy, whereas the sensitivity of the CDC/NHSN was only marginally better than a positive TAC plus serum procalcitonin > 0.5 ng/ml. Algorithm accuracy was improved by adding serum procalcitonin > 0.5 ng/ml, but not positive quantitative TAC.

Trial Registration: Not indicated for this study type.

The role of mini-bronchoalveolar lavage fluid in the diagnosis of pulmonary tuberculosis in critically ill patients

BACKGROUND

The detection of Mycobacterium tuberculosis (MTB) in the intensive care unit (ICU) presents several challenges, mainly associated to the clinical state of the patient. The presence of HIV infection further aggravates this scenario, requiring a reliable collection method, with better performance in the microbiological/molecular techniques to be used. We evaluated the performance of two methods for sample collection, mini bronchoalveolar lavage (Mini-BAL) and endotracheal aspirate (ETA), for diagnosis of pulmonary tuberculosis (PTB) in critically ill patients.

METHODS

This prospective study involved 26 HIV positive ICU internalized patients, with presumptive PTB who required mechanical ventilation. Two samples were obtained prospectively from 26 HIV ICU patients with presumptive PTB by Mini-BAL and ETA. The samples were processed for smear microscopy, Löwenstein-Jensen medium and the BACTEC Mycobacteria Growth Indicator Tube 960 system®. We define as confirmed PTB patients with positive MTB culture. Furthermore, all samples obtained through the Mini-BAL were analyzed by Xpert® MTB/RIF.

RESULTS

Our results demonstrated that the respiratory samples obtained by Mini-BAL were able to increase MTB detection in critically ill patients with presumptive PTB. The Mini-BAL allowed 30% increased recovery and guaranteed enough sample volume for processing in all methods. In addition, the larger volume of the samples obtained with this technique enabled the Xpert® MTB/RIF molecular test for diagnosis of TB.

CONCLUSIONS

The Mini-BAL showed be an acceptable alternative to ETA in this population, since these critically ill and often-immunocompromised patients are more likely to develop complications related to invasive procedures.

Safety profile of blind bronchial sampling-A prospective study in pediatric intensive care unit

OBJECTIVE

To study the safety profile of blind bronchial sampling in mechanically ventilated children.

DESIGN

Prospective interventional study.

SETTING

Tertiary level pediatric intensive care unit of a multispecialty hospital.

PATIENTS

Children aged 1 month to 16 years on mechanical ventilator for ≥48 h, were assessed by clinical pulmonary infection score for ventilator-associated pneumonia (VAP).

INTERVENTIONS

Blind bronchial sampling was performed following standard procedural guidelines. The hemodynamic, ventilation parameters, and arterial blood gases done before, and in next 24 h post procedure were recorded and compared.

MEASUREMENTS AND MAIN RESULTS

Among the 40 enrolled children, VAP was suspected at 5.8 ± 3.7 days post intubation with insignificant increase in median (IQR) PELOD score to 15 (11-23) from 13.5 (11-23) (P value 0.29). A statistically significant increase in mean blood pressure (75.5 ± 14.7 to 79.1 ± 14.2, P 0.04) and transient drop in SpO₂ (98.2 ± 2.3 to 92.2 ± 9.2, P < 0.001) were noted with insignificant change in heart rate (128.7 ± 25.6 vs 132.0 ± 30.8, P 0.52), though these variations were clinically not significant. There were no major complications like significant airway bleed, arrhythmia, air leaks, edema, and change in pulmonary infiltrates during the procedure. There were no significant (either clinical or statistical) effects of BBS procedure, whether transient or prolonged, on ventilatory requirements or gas exchange parameters.

CONCLUSIONS

Blind bronchial sampling is a safe procedure in children with no major adverse events related to hemodynamics, oxygenation, and ventilation parameters.