In 2002, for the first time, the World Health Organization (WHO) described probiotics as live micro-organisms that, when administered in the necessary quantities, help to maintain the homeostasis of the intestinal flora. In fact, the microbiome is a collection of microorganisms that live in symbiosis with the human body and play a crucial role in regulating the response of the intestinal immune system through production of anti-inflammatory cytokines and inhibition of pro-inflammatory cytokines.
1. Overview
The use of probiotics in critically ill adult and children patients has been growing exponentially over the last 20 years. Numerous factors in pediatriac intensive care unit (PICU) patients may contribute to intestinal dysbiosis, which subsequently promotes the pathobiota’s growth. Currently, lactobacillus and bifidobacterium species are mainly used to prevent the development of systemic diseases due to the subverted microbiome, followed by streptococcus, enterococcus, propionibacterium, bacillus and Escherichia coli, Lactobacillus rhamnosus GG, and Lactobacillus reuteri DSM 17938. The aim of this article is to review the scientific literature for further confirmation of the importance of the usage of probiotics in intensive care unit (ICU) patients, especially in the pediatric population. A progressive increase in nosocomial infections, especially nosocomial bloodstream infections, has been observed over the last 30 years. The World Health Organization (WHO) reported that the incidence of nosocomial infections in PICUs was still high and ranged between 5% and 10%. Petrof et al. was one of the first to demonstrate the efficacy of probiotics for preventing systemic diseases in ICU patients. Recently, however, the use of probiotics with different lactobacillus spp. has been shown to cause a decrease of pro-inflammatory cytokines and an increase in anti-inflammatory cytokines. In addition, in some studies, the use of probiotics, in particular the mix of Lactobacillus and Bifidobacterium reduces the incidence of ventilator-associated pneumonia (VAP) in PICU patients requiring mechanical ventilation. In abdominal infections, there is no doubt at all about the usefulness of using Lactobacillus spp probiotics, which help to treat ICU-acquired diarrhoea episodes as well as in positive blood culture for candida spp. Despite the importance of using probiotics being supported by various studies, their use is not yet part of the standard protocols to which all doctors must adhere. In the meantime, while waiting for protocols to be drawn up as soon as possible for use in PICUs, routine use could certainly stimulate the intestine’s immune defences. Though it is still too early to say, they could be considered the drugs of the future.
2. Probiotics
Interest in the use of probiotics in critically ill patients in ICUs for adults or children has been growing exponentially over the last 20 years with numerous studies each year, but the first trials on the importance of probiotics were carried out about 30 years ago
[1].
In 2002, for the first time, the World Health Organization (WHO) described probiotics as live micro-organisms that, when administered in the necessary quantities, help to maintain the homeostasis of the intestinal flora
[2]. In fact, the microbiome is a collection of microorganisms that live in symbiosis with the human body and play a crucial role in regulating the response of the intestinal immune system through production of anti-inflammatory cytokines and inhibition of pro-inflammatory cytokines
[3][4][5][6].
In addition, the microbiota builds a physical barrier between the outside and inside of our bodies with the help of the caliciform cells, which produce mucus made up of proteins that strengthen the barrier of the intestinal wall
[7][8]. Moreover, the enterocytes produce antibacterial substances, such as bacteriocins and lactate, that can inhibit the growth of patho-biota
[9][10]. Studies conducted in the past have shown that the loss of normal intestinal flora and its replacement by the growth of pathogenic bacteria (dysbiosis) can lead to the development of critical illnesses
[11]. Sepsis has an important impact on the gastrointestinal function and the associated permeability alteration can become a source of systemic infection
[12].
The composition of the gut microbiome in ICU patients has previously been shown to play a major role in determining the outcome in those patients. Additionally, enteral nutrition and the use of various drugs, particularly antibiotics, can lead to alteration of the gut microbiome in ICU patients
[13][14][15].
Regrettably, despite this solid evidence, probiotics are not part of the standard protocols in the ICU
[16].
The most commonly used probiotics are lactobacillus and bifidobacterium species, followed by streptococcus, enterococcus, propionibacterium, bacillus, and
Escherichia coli [17]. In particular,
Lactobacillus rhamnosus GG [18] and
Limosilactobacillus reuteri [19] have been widely used in the treatment of infections of the gastrointestinal tract, inflammatory diseases, and drug-induced diarrhoea in the ICU in both adults and children. In addition to those, probiotics based on certain yeast species, such as
Saccharomyces boulardii [20] and
Saccharomyces cerevisiae [21][22], are also widely used, especially in the treatment of diseases of the gastrointestinal tract
[20][22].
3. Conclusions
The importance of using probiotics in the PICU is supported by various studies and their use is growing daily. Table 1 shows the most important studies supporting the use of probiotics mentioned in our article. Despite the scientific evidence, the use of probiotics in PICU patients is not yet part of the standard protocols. This is probably because, although they are safe and evidence confirms their importance in restoring the balance of the microbiota of pediatric and non-pediatric patients, and in assisting standard therapy in the course of even serious infectious diseases, these are the most fragile patients where the microbiota, although rarely, can induce bacteremia, fungemia, and sepsis. Well-designed multi-center RCTs are needed to address these issues before the routine use of probiotics is recommended in critically ill children.
Table 1. Summary of high-power studies supporting the benefit of probiotics in the pediatriac intensive care unit (PICU).