Effect of Probiotics on Incident Ventilator-Associated Pneumonia in Critically Ill Patients: A Randomized Clinical Trial

The role of bacterial translocation in sepsis: a new target for therapy

Sepsis is a leading cause of death in critically ill patients, primarily due to multiple organ failures. It is associated with a systemic inflammatory response that plays a role in the pathogenesis of the disease. Intestinal barrier dysfunction and bacterial translocation (BT) play pivotal roles in the pathogenesis of sepsis and associated organ failure. In this review, we describe recent advances in understanding the mechanisms by which the gut microbiome and BT contribute to the pathogenesis of sepsis. We also discuss several potential treatment modalities that target the microbiome as therapeutic tools for patients with sepsis.

Long-distance relationships - regulation of systemic host defense against infections by the gut microbiota

Despite compartmentalization within the lumen of the gastrointestinal tract, the gut microbiota has a far-reaching influence on immune cell development and function throughout the body. This long-distance relationship is crucial for immune homeostasis, including effective host defense against invading pathogens that cause systemic infections. Herein, we review new insights into how commensal microbes that are spatially restricted to the gut lumen can engage in long-distance relationships with innate and adaptive immune cells at systemic sites to fortify host defenses against infections. In addition, we explore the consequences of intestinal dysbiosis on impaired host defense and immune-mediated pathology during infections, including emerging evidence linking dysbiosis with aberrant systemic inflammation and immune-mediated organ damage in sepsis. As such, therapeutic modification of the gut microbiota is an emerging target for interventions to prevent and/or treat systemic infections and sepsis by harnessing the long-distance relationships between gut microbes and systemic immunity.

New, Useful Criteria for Assessing the Evidence of Infection in Sepsis Research

OBJECTIVES

The Sepsis-3 definition states the clinical criteria for sepsis but lacks clear definitions of the underlying infection. To address the lack of applicable definitions of infection for sepsis research, we propose new criteria, termed the Linder-Mellhammar criteria of infection (LMCI). The aim of this study was to validate these new infection criteria.

DESIGN

A multicenter cohort study of patients with suspected infection who were admitted to emergency departments or ICUs. Data were collected from medical records and from study investigators.

SETTING

Four academic hospitals in Sweden, Switzerland, the Netherlands, and Germany.

PATIENTS

A total of 934 adult patients with suspected infection or suspected sepsis.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Agreement of infection site classification was measured using the LMCI with Cohen κ coefficient, compared with the Calandra and Cohen definitions of infection and diagnosis on hospital discharge as references. In one of the cohorts, comparisons were also made to adjudications by an expert panel. A subset of patients was assessed for interobserver agreement.

MEASUREMENTS AND MAIN RESULTS

The precision of the LMCI varied according to the applied reference. LMCI performed better than the Calandra and Cohen definitions (κ = 0.62 [95% CI, 0.59-0.65] vs κ = 0.43 [95% CI, 0.39-0.47], respectively) and the diagnosis on hospital discharge (κ = 0.57 [95% CI, 0.53-0.61] vs κ = 0.43 [95% CI, 0.39-0.47], respectively). The interobserver agreement for the LMCI was evaluated in 91 patients, with agreement in 77%, κ = 0.72 (95% CI, 0.60-0.85). When tested with adjudication as the gold standard, the LMCI still outperformed the Calandra and Cohen definitions (κ = 0.65 [95% CI, 0.60-0.70] vs κ = 0.29 [95% CI, 0.24-0.33], respectively).

CONCLUSIONS

The LMCI is useful criterion of infection that is intended for sepsis research, in and outside of the ICU. Useful criteria for infection have the potential to facilitate more comparable sepsis research and exclude sepsis mimics from clinical studies, thus improving and simplifying sepsis research.

Probiotic in the prevention of ventilator-associated pneumonia in critically ill patients: evidence from meta-analysis and trial sequential analysis of randomized clinical trials

BACKGROUND

Probiotic might have a role in the prevention of ventilator-associated pneumonia (VAP) among mechanically ventilated patients, but the efficacy and safety remained inconsistent. The aim of this systematic review and meta-analysis was to evaluate the efficacy and safety of probiotic (prebiotic, synbiotic) versus placebo in preventing VAP in critically ill patients undergoing mechanical ventilation.

METHODS

PubMed, Embase and the Cochrane library databases were searched to 10 October 2021 without language restriction for randomized or semi-randomized controlled trials evaluating probiotic (prebiotic, synbiotic) vs. placebo in prevention of VAP in critically ill mechanically ventilated patients. The pooled relative risk (RR) along with 95% confidence intervals (CI) were combined using a random-effects model. Furthermore, the trial sequential analysis (TSA) and subgroup analyses were performed. Statistical significance was regarded as P < 0.05.

RESULTS

Twenty-three trials involving 5543 patients were eligible for this meta-analysis. The combined RR of decreasing the risk of VAP by probiotic was 0.67 (0.56, 0.81) for all eligible studies, 0.69 (n = 5136; 95% CI = 0.57 to 0.84; P < 0.01) for adults studies and 0.55 (n = 407; 95%CI = 0.31 to 0.99; P = 0.046) for neonates/children studies. Additionally, the above-mentioned positive finding in 20 adults studies was verified by the results of TSA, subgroup analyses and cumulative meta-analysis. Ample evidences demonstrated a 31% decrease in RR of incidence of VAP was noted when prophylactic probiotic therapy was administrated among adult patients. Finally, there were no effects on the ICU/hospital/28-/90-day mortality, bacteremia, CRBSI, diarrhea, ICU-acquired infections, infectious complications, pneumonia, UTI and wound infection between two groups (P > 0.05 for all).

CONCLUSIONS

Based on the results of our study, the current evidences suggested that prophylactic administration of probiotic might be utilized as a preventive method for VAP in neonates/children and adults patients who required mechanical ventilation. However, further large, high-quality RCTs are warranted to assess the efficacy and safety of probiotic treatment in critically ill patients, especially for the neonates/children studies and the long-term consequences of this therapy.

Probiotics for the Prevention of Ventilator-Associated Pneumonia: An Updated Systematic Review and Meta-Analysis of Randomised Controlled Trials

BACKGROUND

Presently, there is conflicting evidence regarding the efficacy of probiotics in the prevention of ventilator-associated pneumonia (VAP). This meta-analysis was conducted to update current clinical evidence and evaluate the efficacy and safety of probiotics for the prevention of VAP.

METHODS

We searched three databases and two trial registers to retrieve randomised controlled trials (RCTs) comparing probiotics or synbiotics with placebo or standard treatment for the prevention of VAP in adult patients receiving mechanical ventilation in the intensive care unit (ICU).

RESULTS

Our meta-analysis included 18 RCTs involving 4893 patients. Our results showed that probiotics may reduce the incidence of VAP (RR 0.68, 95% CI: 0.55-0.84; low certainty). However, in our subgroup and sensitivity analyses, the effect was not significant in double-blind studies, and in studies with a low risk of bias in the randomisation process. Probiotics reduced the length of ICU stay (MD -2.22 days, 95% CI: -4.17 to -0.28; moderate certainty) and the duration of antibiotic use (MD -1.25 days, 95% CI -1.86 to -0.64; moderate certainty).

CONCLUSIONS

Probiotics may reduce the incidence of VAP but due to the low quality of pooled evidence, the use of probiotics warrants caution. Further, large-scale, high-quality RCTs need to be conducted to provide conclusive evidence.

Efficacy of probiotics or synbiotics for critically ill adult patients: a systematic review and meta-analysis of randomized controlled trials

Background

Microbial dysbiosis in critically ill patients is a leading cause of mortality and septic complications. Probiotics and synbiotics have emerged as novel therapy on gut microbiota to prevent septic complications. However, current evidence on their effects is conflicting. This work aims to systematically review the impact of probiotics or synbiotics in critically ill adult patients.

Methods

A comprehensive search of the PubMed, CBM, Embase, CENTRAL, ISI, and CNKI databases was performed to identify randomized controlled trials that evaluate probiotics or synbiotics in critically ill patients. The quality assessment was based on the modified Jadad's score scale and the Cochrane Handbook for Systematic Reviews of Interventions Version 5.0.1. The major outcome measure was mortality. Secondary outcomes included incidence of septic complications, sepsis incidence, length of intensive care unit (ICU) stay, incidence of non-septic complication, and ventilator day. Data synthesis was conduct by Review Manager 5.4.

Results

A total of 25 randomized controlled trials reporting on 5049 critically ill patients were included. In the intervention group, 2520 participants received probiotics or synbiotics, whereas 2529 participants received standard care or placebo. Pooling data from randomized controlled trials demonstrated a significant reduction in the incidence of ventilator-associated pneumonia (VAP) in the treatment group [(risk ratio (RR) 0.86; 95% confidence interval (CI): 0.78–0.95; p < 0.003, I² = 85%)]. However, in the subgroup analysis, the reduction of incidence of VAP was only significant in patients receiving synbiotics (RR = 0.61, 95% CI: 0.47–0.80, p = 0.0004, I² = 40%) and not significant in those receiving only probiotics (RR = 0.91, 95% CI: 0.82–1.01, p = 0.07, I² = 65%). Moreover, sepsis incidence of critically ill patients was only significantly reduced by the addition of synbiotics (RR = 0.41; 95% CI: 0.22–0.72, p = 0.005, I² = 0%). The incidence of ICU-acquired infections was significantly reduced by the synbiotics therapy (RR = 0.72; 95% CI: 0.58–0.89, p = 0.0007, I² = 79%). There was no significant difference in mortality, diarrhea, or length of ICU stay between the treatment and control groups.

Conclusions

Synbiotics is an effective and safe nutrition therapy in reducing septic complications in critically ill patients. However, in such patients, administration of probiotics alone compared with placebo resulted in no difference in the septic complications.

Probiotics: Should We Use Them Proactively in Critical Illness?

Soni KD. Probiotics: Should We Use Them Proactively in Critical Illness? Indian J Crit Care Med 2022;26(3):266–267.

Probiotics in the Intensive Care Unit

The understanding of the gut microbiome in health and disease has shown tremendous progress in the last decade. Shaped and balanced throughout life, the gut microbiome is intricately related to the local and systemic immune system and a multitude of mechanisms through which the gut microbiome contributes to the host’s defense against pathogens have been revealed. Similarly, a plethora of negative consequences, such as superinfections and an increased rate of hospital re-admissions, have been identified when the gut microbiome is disturbed by disease or by the iatrogenic effects of antibiotic treatment and other interventions. In this review, we describe the role that probiotics may play in the intensive care unit (ICU). We discuss what is known about the gut microbiome of the critically ill, and the concept of probiotic intervention to positively modulate the gut microbiome. We summarize the evidence derived from randomized clinical trials in this context, with a focus on the prevention of ventilator-associated pneumonia. Finally, we consider what lessons we can learn in terms of the current challenges, efficacy and safety of probiotics in the ICU and what we may expect from the future. Throughout the review, we highlight studies that have provided conceptual advances to the field or have revealed a specific mechanism; this narrative review is not intended as a comprehensive summary of the literature.

Clinical Benefits From Administering Probiotics to Mechanical Ventilated Patients in Intensive Care Unit: A PRISMA-Guided Meta-Analysis

Background

The use of probiotics has been considered as a new intervention for ventilator-associated pneumonia (VAP) prevention in the intensive care unit (ICU). The aim of this meta-analysis was to evaluate the effect of probiotics on mechanical-ventilated patients in ICU.

Methods

PubMed, Embase, Scopus, and the Cochrane Library were searched for relevant randomized controlled trials (RCTs) from their respective inception through October 10, 2021. All studies meeting the inclusion criteria were selected to evaluate the effect of probiotics on patients receiving mechanical ventilation in ICU.

Results

A total of 15 studies involving 4,693 participants met our inclusion criterion and were included in this meta-analysis. The incidence of VAP in the probiotic group was significantly lower (odds ratio [OR] 0.58, 95% CI 0.41 to 0.81; p = 0.002; I² = 71%). However, a publication bias may be present as the test of asymmetry was significant (p = 0.007). The probiotic administration was associated with a significant reduction in the duration of mechanical ventilation (mean difference [MD] −1.57, 95% CI −3.12 to −0.03; p = 0.05; inconsistency [I]² = 80%), length of ICU stay (MD −1.87, 95% CI −3.45 to −0.28; p = 0.02; I² = 76%), and incidence of bacterial colonization (OR 0.59, 95% CI 0.45 to 0.78; p = 0.0001; I² = 34%). Moreover, no statistically significant differences were observed regarding the incidence of diarrhea (OR 0.90, 95% CI 0.65 to 1.25; p = 0.54; I² = 12%) and mortality (OR 0.91, 95% CI 0.80 to 1.05; p = 0.19; I² = 0%) between probiotics group and control group.

Conclusion

Our meta-analysis shows that probiotics are associated with a reduction in VAP, as well as the duration of mechanical ventilation, ICU length of stay, and bacterial colonization, but no significant effects on ICU mortality and occurrence of diarrhea. However, in consideration of the significant heterogeneity and publication bias, our findings need to be further validated.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/, identifier: CRD42020150770.

New Insights into the Prevention of Hospital-Acquired Pneumonia/Ventilator-Associated Pneumonia Caused by Viruses

A fifth or more of hospital-acquired pneumonias may be attributable to respiratory viruses. The SARS-CoV-2 pandemic has clearly demonstrated the potential morbidity and mortality of respiratory viruses and the constant threat of nosocomial transmission and hospital-based clusters. Data from before the pandemic suggest the same can be true of influenza, respiratory syncytial virus, and other respiratory viruses. The pandemic has also helped clarify the primary mechanisms and risk factors for viral transmission. Respiratory viruses are primarily transmitted by respiratory aerosols that are routinely emitted when people exhale, talk, and cough. Labored breathing and coughing increase aerosol generation to a much greater extent than intubation, extubation, positive pressure ventilation, and other so-called aerosol-generating procedures. Transmission risk is proportional to the amount of viral exposure. Most transmissions take place over short distances because respiratory emissions are densest immediately adjacent to the source but then rapidly dilute and diffuse with distance leading to less viral exposure. The primary risk factors for transmission then are high viral loads, proximity, sustained exposure, and poor ventilation as these all increase net viral exposure. Poor ventilation increases the risk of long-distance transmission by allowing aerosol-borne viruses to accumulate over time leading to higher levels of exposure throughout an enclosed space. Surgical and procedural masks reduce viral exposure but do not eradicate it and thus lower but do not eliminate transmission risk. Most hospital-based clusters have been attributed to delayed diagnoses, transmission between roommates, and staff-to-patient infections. Strategies to prevent nosocomial respiratory viral infections include testing all patients upon admission, preventing healthcare providers from working while sick, assuring adequate ventilation, universal masking, and vaccinating both patients and healthcare workers.

The role of the microbiota in the management of intensive care patients

The composition of the gut microbiota is highly dynamic and changes according to various conditions. The gut microbiota mainly includes difficult-to-cultivate anaerobic bacteria, hence knowledge about its composition has significantly arisen from culture-independent methods based on next-generation sequencing (NGS) such as 16S profiling and shotgun metagenomics. The gut microbiota of patients hospitalized in intensive care units (ICU) undergoes many alterations because of critical illness, antibiotics, and other ICU-specific medications. It is then characterized by lower richness and diversity, and dominated by opportunistic pathogens such as Clostridioides difficile and multidrug-resistant bacteria. These alterations are associated with an increased risk of infectious complications or death. Specifically, at the time of writing, it appears possible to identify distinct microbiota patterns associated with severity or infectivity in COVID-19 patients, paving the way for the potential use of dysbiosis markers to predict patient outcomes. Correcting the microbiota disturbances to avoid their consequences is now possible. Fecal microbiota transplantation is recommended in recurrent C. difficile infections and microbiota-protecting treatments such as antibiotic inactivators are currently being developed. The growing interest in the microbiota and microbiota-associated therapies suggests that the control of the dysbiosis could be a key factor in the management of critically ill patients. The present narrative review aims to provide a synthetic overview of microbiota, from healthy individuals to critically ill patients. After an introduction to the different techniques used for studying the microbiota, we review the determinants involved in the alteration of the microbiota in ICU patients and the latter's consequences. Last, we assess the means to prevent or correct microbiota alteration.

Probiotic prophylaxis to prevent ventilator-associated pneumonia in children on mechanical ventilation: A randomized double-blind clinical trial

PURPOSE

Ventilator-Associated Pneumonia (VAP) is one of the most common nosocomial infections in the Pediatric Intensive Care Unit (PICU). Using new strategies to prevent nosocomial infections is crucial to avoid antibiotic resistance. One of these strategies is the utilization of probiotics. This study aims to investigate the efficacy of probiotic prophylaxis in preventing VAP in mechanically ventilated children.

METHOD

This study was a randomized, double-blind clinical trial. The study included 72 children under 12 years of age under mechanical ventilation for more than 48 h in the Mofid Children's Hospital. Patients were randomly divided into Limosilactobacillus reuteri DSM 17938 probiotic recipients (n = 38) and placebo groups (n = 34). In addition to the standard treatment, both groups received a sachet containing probiotics or a placebo twice a day. Children were screened for VAP based on clinical and laboratory evidence.

RESULTS

The mean age of children in the intervention and placebo groups was 4.60 ± 4.84 and 3.38 ± 3.49 years, respectively. After adjusting the other variables, it was observed that chance of VAP among probiotics compared to the placebo group was significantly decreased (OR adjusted = 0.29; 95% CI: 0.09-0.95). Also, probiotic was associated with a significantly lower chance of diarrhea than the placebo group (OR adjusted = 0.09; 95% CI: 0.01-0.96).

CONCLUSION

Probiotic utilization is effective in preventing the incidence of VAP and diarrhea in children under mechanical ventilation in the PICU.

Sepsis and the Human Microbiome. Just Another Kind of Organ Failure? A Review

Next-generation sequencing (NGS) has been further optimised during the last years and has given us new insights into the human microbiome. The 16S rDNA sequencing, especially, is a cheap, fast, and reliable method that can reveal significantly more microorganisms compared to culture-based diagnostics. It might be a useful method for patients suffering from severe sepsis and at risk of organ failure because early detection and differentiation between healthy and harmful microorganisms are essential for effective therapy. In particular, the gut and lung microbiome in critically ill patients have been probed by NGS. For this review, an iterative approach was used. Current data suggest that an altered microbiome with a decreased alpha-diversity compared to healthy individuals could negatively influence the individual patient’s outcome. In the future, NGS may not only contribute to the diagnosis of complications. Patients at risk could also be identified before surgery or even during their stay in an intensive care unit. Unfortunately, there is still a lack of knowledge to make precise statements about what constitutes a healthy microbiome, which patients exactly have an increased perioperative risk, and what could be a possible therapy to strengthen the microbiome. This work is an iterative review that presents the current state of knowledge in this field.