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

Preventive Effect of Probiotics on Ventilator-Associated Pneumonia: A Meta-analysis of 2428 Patients

BACKGROUND

Researchers had contradictory conclusions about the role of probiotics in preventing ventilator-associated pneumonia (VAP), which has led to the controversial use of probiotics in mechanically ventilated patients.

OBJECTIVE

To explore the efficacy and safety of probiotics in preventing VAP.

METHODS

A literature search was conducted in 7 medical databases. Two investigators assessed literature quality independently and collected data. The primary outcome was the incidence of VAP. Secondary outcomes included 16 measures. Sensitivity analysis and subgroup and meta-regression analyses were performed to analyze the source of heterogeneity. P values <0.05 were considered statistically significant, and CIs were set at 95%. A random-effects model was set when I² <50%, otherwise a fixed-effects model was used.

RESULTS

A total of 20 randomized controlled studies with a total of 2428 patients were analyzed. Pooled results showed positive effects of probiotics on the reduction of VAP incidence (risk ratio [RR] = 0.672; P < 0.001; I² = 11.3%), length of ICU stay (WMD = -1.417; P = 0.012; I² = 90.7%), oropharyngeal (RR = 0.866; P = 0.031; I² = 12.4%) and gastric (RR = 0.645; P < 0.001; I² = 30.2%) colonization.

CONCLUSIONS AND RELEVANCE

Probiotics can reduce the incidence of VAP and reduce oropharyngeal and gastric bacterial colonization. The results also suggest that probiotics do not cause adverse effects.

Effects of not monitoring gastric residual volume in intensive care patients: A meta-analysis

BACKGROUND

Monitoring gastric residual volume has been a common practice in intensive care patients receiving enteral feeding worldwide. Recent studies though, have challenged the reliability and necessity of this routine monitoring process. Several studies even reported improvements in the delivery of enteral feeding without monitoring gastric residual volume, while incurring no additional adverse events. However, the benefit of monitoring gastric residual volume remains controversial in intensive care patients.

OBJECTIVE

The aim of this review is to identify the effects of not monitoring gastric residual volume in intensive care patients through a meta-analysis of the data pooled from published studies that meet our inclusion criteria.

DESIGN

A systematic review DATA SOURCES: An electronic search of Embase, Pubmed, and the Cochrane Library was completed up to April 2018. The data included basic population characteristics, related complications, mortality, duration of mechanical ventilation and intensive care unit length of stay.

REVIEW METHODS

Eligibility and methodological quality of the studies were assessed by two researchers independently according to the Joanna Briggs Institute guidelines. The Review Manager Software was used to calculate the pooled risk ratio (RR), weighted mean difference, and the corresponding 95% confidential interval (95% CI). Sensitivity analyses were done by excluding each study. Publication bias analyses were conducted to avoid the exaggerated effect of the overall estimates.

RESULTS

Five studies involving 998 patients were included in this meta-analysis. Compared with monitoring gastric residual volume, not monitoring gastric residual volume decreased the rate of feeding intolerance in critically ill patients (RR = 0.61, 95%CI 0.51-0.72), and did not result in an increment in the rate of mortality (RR = 0.97, 95%CI 0.73-1.29, P = 0.84) or the rate of ventilator-associated pneumonia (RR = 1.03, 95%CI 0.74-1.44, P = 0.85). There were also no differences in the duration of mechanical ventilation (MD = 0.09, 95%CI, -0.99 to 1.16, P = 0.88) or intensive care unit length of stay (MD=-0.18, 95%CI, -1.52 to 1.17, P = 0.79).

CONCLUSION

Except for an increased risk of vomiting, the absence of monitoring gastric residual volume was not inferior to routine gastric residual volume monitoring in terms of feeding intolerance development, mortality, and ventilator-associated pneumonia in intensive care patients. There is encouraging evidence that not measuring gastric residual volume does not induce additional harm to the patients. More multicenter, randomized clinical trials are required to verify these findings.

Variations of the lung microbiome and immune response in mechanically ventilated surgical patients

Mechanically ventilated surgical patients have a variety of bacterial flora that are often undetectable by traditional culture methods. The source of infection in many of these patients remains unclear. To address this clinical problem, the microbiome profile and host inflammatory response in bronchoalveolar lavage samples from the surgical intensive care unit were examined relative to clinical pathology diagnoses. The hypothesis was tested that clinical diagnosis of respiratory tract flora were similar to culture positive lavage samples in both microbiome and inflammatory profile. Bronchoalveolar lavage samples were collected in the surgical intensive care unit as standard of care for intubated individuals with a clinical pulmonary infection score of >6 or who were expected to be intubated for >48 hours. Cytokine analysis was conducted with the Bioplex Pro Human Th17 cytokine panel. The microbiome of the samples was sequenced for the 16S rRNA region using the Ion Torrent. Microbiome diversity analysis showed the culture-positive samples had the lowest levels of diversity and culture negative with the highest based upon the Shannon-Wiener index (culture positive: 0.77 ± 0.36, respiratory tract flora: 2.06 ± 0.73, culture negative: 3.97 ± 0.65). Culture-negative samples were not dominated by a single bacterial genera. Lavages classified as respiratory tract flora were more similar to the culture-positive in the microbiome profile. A comparison of cytokine expression between groups showed increased levels of cytokines (IFN-g, IL-17F, IL-1B, IL-31, TNF-a) in culture-positive and respiratory tract flora groups. Culture-positive samples exhibited a more robust immune response and reduced diversity of bacterial genera. Lower cytokine levels in culture-negative samples, despite a greater number of bacterial species, suggest a resident nonpathogenic bacterial community may be indicative of a normal pulmonary environment. Respiratory tract flora samples were most similar to the culture-positive samples and may warrant classification as culture-positive when considering clinical treatment.

Host-Pathogen Interface: Progress in Understanding the Pathogenesis of Infection Due to Multidrug-Resistant Bacteria in the Intensive Care Unit

The diverse responses of critically ill patients to infection with multi-drug resistant (MDR) bacteria are determined by many complex factors. These include the nature of the immune response activated by specific organisms. Properties unique to each organism such as adherence proteins, microvesicle formation, toxin production and the propensity to form biofilms are important factors in pathogenesis. Equally important is the variability in the host immune response, whether due to genetic or iatrogenic factors, including the presence of major comorbidities, treatment with immunomodulatory therapy and disruption of the microbiome. Future approaches in treating infections caused by MDR bacteria will be heavily influenced by a precision medicine approach, with rapid diagnostic techniques of both bacterial and host factors and high throughput screening of novel therapeutics becoming the mainstay of treatment.