The role of bacterial colonization of ventilator circuit in development of ventilator-associated pneumonia: a prospective observational cohort study

Effects of different frequencies of ventilator circuit changes on the incidence of ventilator-associated pneumonia: A network meta-analysis

OBJECTIVE

To investigate the effect of different frequencies of ventilator circuit changes on the occurrence of ventilation-associated pneumonia using network meta-analysis.

METHODS

Chinese and English databases were systematically searched to collect eligible studies on the relationship between ventilator circuit changes and ventilation-associated pneumonia. The incidence of pneumonia for each change frequency was pooled using R software, and network meta-analysis was performed using Stata software to determine the optimal change frequency.

RESULTS

A total of 23 studies were included, including nine ventilator circuit changes with different frequencies. The meta-analysis showed that the combined incidence of pneumonia was 25 %. Network meta-analysis showed 3-day circuit changes significantly reduced ventilation-associated pneumonia incidence compared with 1 day (odds ratio (OR) = 0.26, 95 % confidence interval (CI) [0.10, 0.69]), 2 days (OR = 0.41, 95 % CI [0.20, 0.87]), 4 days (OR = 0.17, 95 % CI [0.04, 0.72]), and 14 days (OR = 0.11, 95 % CI [0.02, 0.50]). Direct meta-analysis showed no significant difference in 3-day circuit changes versus 1 day, 3-day circuit changes versus 14 days, and 7-day circuit changes versus 14 days. The probability ranking indicated that a 3-day frequency of ventilator circuit changes had the greatest probability of being the optimal intervention, followed by 5 days and 7 days.

CONCLUSION

The meta-analysis showed that ventilator circuit changes every 3 days had the best effect, but once a week also showed a positive preventive effect, with no significant effect on ventilation-associated pneumonia occurrence. These findings combined with existing evidence indicate that high frequency changes in the ventilator circuit should be avoided.

Impact of Multifaceted Interventions Including Waterless Patient Care on Endemic Occurrence of Serratia marcescens in an Intensive Care Unit

Serratia marcescens acquisition is a common problem in intensive care units (ICUs). Following an initial outbreak in 2017 with ongoing endemicity, this study aimed to analyze the impact of behavioral interventions and sink removals on S. marcescens incidence in a tertiary-care ICU. We conducted a quasi-experimental, interventional study including patients with a positive screening or clinical culture for S. marcescens, from 48 h (D2) after ICU admission to 14 days after ICU discharge. A sub-analysis considered patients positive for S. marcescens from ICU admission (D0) to 14 days after ICU discharge. Multivariate Poisson regression analyses were performed. Between January 2014 and December 2022, 167 cases of S. marcescens infection or colonization were identified (respiratory samples, 71%). Despite the presence of an aquatic reservoir, we found that neither behavioral nor architectural interventions (sink removal) reduced significantly S. marcescens incidence, yielding incidence ratios of 1.02 [95%CI 0.33-3.11] and 4.25 [95%CI 0.59-30.56], respectively. However, an association was observed with administration of selective oral decontamination (SOD) in the sub-cohort (OR 1.01; 95%CI 1.00-1.03). Behavioral change interventions and transition to a waterless ICU did not control endemic, polyclonal S. marcescens occurrence. The selective pressure exercised by SOD may have reduced the effectiveness of waterless care.

Naso-intestinal versus gastric tube for enteral nutrition in patients undergoing mechanical ventilation: a systematic review and meta-analysis

BACKGROUND

A systematic appraisal of the comparative efficacy and safety profiles of naso-intestinal tube versus gastric tube feeding in the context of enteral nutrition for mechanically ventilated (MV) patients is imperative. Such an evaluation is essential to inform clinical practice, ensuring that the chosen method of nutritional support is both optimal and safe for this patient population.

METHODS

We executed an exhaustive search across PubMed et al. databases to identify randomized controlled trials (RCTs) that scrutinize the role of naso-intestinal and gastric tubes for mechanically ventilated (MV) patients up to May 30, 2024. The process of study selection, quality assessment, and data extraction was conducted independently by two researchers. RevMan 5.3 software was used for meta-analysis.

RESULTS

Our meta-analysis included 8 RCTs, published between 1992 and 2018, encompassing a total of 676 MV patients. The results indicated that naso-intestinal tube feeding, compared to gastric tube feeding, was associated with a significant reduction in the incidence of ventilator-associated pneumonia (VAP) [Risk Ratio (RR) = 0.69, 95% confidence interval (CI) (0.52, 0.92)] and gastric retention (RR = 0.11, 95% CI (0.04, 0.28)). No statistically significant differences were observed in the incidence of aspiration (RR = 0.93, 95% CI (0.35, 2.50)) vomiting (RR = 0.70, 95% CI (0.23, 2.08)), abdominal distension (RR = 0.87, 95% CI (0.29, 2.63)), or diarrhea (RR = 1.10, 95% CI (0.77, 1.55)).

CONCLUSIONS

The current evidence indicates that naso-intestinal tube feeding is efficacious in lowering the incidence of VAP and gastric retention among MV patients, without a corresponding escalation in the risk of adverse events, including aspiration, vomiting, abdominal distension, and diarrhea. These insights significantly augment the existing corpus of knowledge pertaining to the optimization of enteral nutrition strategies for patients on mechanical ventilation.

Can humidifier reservoir bacteria colonize the circuit during mechanical ventilation: An in vitro study

BACKGROUND

Although the circuit condensate, an ideal bacterial reservoir during mechanical ventilation, may flow into the humidifier reservoir, no studies have investigated if humidifier reservoir colonized bacteria colonize other circuit locations with airflow.

AIM

We aimed to prove whether the humidifier reservoir colonized bacteria colonize other circuit locations with airflow and provide some advice on the disposal of condensate in the clinical setting.

STUDY DESIGN

An in vitro experiment was conducted. Mechanical ventilation simulators (n = 90) were divided into sterile water group (n = 30) and broth group (n = 60). In the sterile water group, sterile water was used for humidification, either Acinetobacter baumannii or Pseudomonas aeruginosa were inoculated to humidifier water in the humidifier reservoir, each accounted for 50% of the simulators. The broth group was performed the same as the sterile water group except for the addition of broth into the humidified water. After 24, 72, and 168 h of continuous ventilation, the humidifier water and different locations of the circuits were sampled for bacterial culture.

RESULTS

All bacterial culture results of the sterile water group were negative. Bacteria in the humidifier water continued to proliferate in the broth group. With prolonged ventilation, the bacteria at the humidifier reservoir outlet increased. The bacteria at the humidifier reservoir outlet were much more in the Pseudomonas aeruginosa subgroup than in the Acinetobacter baumannii subgroup and the difference was statistically significant (p < .05). During continuous ventilation, no bacterial growth occurred at 10 cm from the humidifier reservoir outlet and the Y-piece of the ventilator circuits.

CONCLUSIONS

Sterile water in the humidifier reservoir was not conducive to bacterial growth. Even if bacteria grew in the humidifier reservoir and could reach the humidifier reservoir outlet, colonization of further circuit locations with the airflow was unlikely. During a certain mechanical ventilation time, the amount of bacteria reaching the outlet of the humidifier reservoir varied due to different mobility of bacteria.

RELEVANCE TO CLINICAL PRACTICE

In a clinical setting, nurses should not worry about a small amount of condensate backflow into the humidifier reservoir. Draining condensate into the humidifier reservoir can be used as a low risk and convenient method in clinical practice.

The cGAS-STING Pathway in Bacterial Infection and Bacterial Immunity

Cyclic guanosine monophosphate (GMP)-adenosine monophosphate (AMP) (cGAMP) synthase (cGAS), along with the adaptor stimulator of interferon genes (STING), are crucial components of the innate immune system, and their study has become a research hotspot in recent years. Many biochemical and structural studies that have collectively elucidated the mechanism of activation of the cGAS-STING pathway with atomic resolution have provided insights into the roles of the cGAS-STING pathway in innate immunity and clues to the origin and evolution of the modern cGAS-STING signaling pathway. The cGAS-STING pathway has been identified to protect the host against viral infection. After detecting viral dsDNA, cGAS synthesizes a second messenger to activate STING, eliciting antiviral immune responses by promoting the expression of interferons (IFNs) and hundreds of IFN-stimulated genes (ISGs). Recently, the cGAS-STING pathway has also been found to be involved in response to bacterial infections, including bacterial pneumonia, melioidosis, tuberculosis, and sepsis. However, compared with its functions in viral infection, the cGAS-STING signaling pathway in bacterial infection is more complex and diverse since the protective and detrimental effects of type I IFN (IFN-I) on the host depend on the bacterial species and infection mode. Besides, STING activation can also affect infection prognosis through other mechanisms in different bacterial infections, independent of the IFN-I response. Interestingly, the core protein components of the mammalian cGAS-STING signaling pathway have been found in the bacterial defense system, suggesting that this widespread signaling pathway may have originated in bacteria. Here, we review recent findings related to the structures of major molecules involved in the cGAS-STING pathway and the effects of the cGAS-STING pathway in various bacterial infections and bacterial immunity, which may pave the way for the development of new antibacterial drugs that specifically kill bacteria without harmful effects on the host.