Table 1. Gut Microbiota Modulation as a Tool Against Antimicrobial Resistance.

Intervention	Mechanism of action	Advantages	Disadvantages	References
Diet and dietary supplements	-Wide variety, low fat and plant polysaccharide diet, low protein or high in fiber diets preserve the bacterial diversity of the gut microbiome and the colonization resistance. -Addition to the diet of substances such as konjac glucomannan, HMOs or some Chinese remedies protect the gut microbiome and promote its restoration. -Oral administration of IAP which maintains or even restores gut microbiota.	-Simple to apply. -Accessible to everyone. -Naturally derived components so fewer side effects.	-Lack of evidence in humans.	[53-57,59-61]
Prebiotics and probiotics	-Prebiotics stimulate, while probiotics serve as, lactobacilli or bifidobacterial that reduce the growth or interfere with the survival of pathogenic microorganisms in the gut. -Targeted eradication of pathogens by newly developed engineered probiotics.	-Easily accessible and administered.	-Difficult to find the most suitable probiotic for each dysbiosis condition. -Data mainly on ICU patients. -Conflicting results in protecting gut microbiota from MDROs, especially gram(-) pathogens. -Reports of bacteremias in ICU patients.	[65,66,71,73]
Fecal Microbiota Transplantation (FMT)	-Infusion of donor feces into patient’s gut (administered mainly orally) in order to repopulate it with a healthy and balanced microbiota as a weapon against C. difficile infections (especially recurrent), as a “barrier” to colonization by multi-drug resistant bacteria, and as a method of reducing the load of antibiotic resistance genes. -Enhancing host responses.	-Successful against difficult-to-treat situations. -High rates of effectiveness.	-Lack of large randomized clinical trials. -Incidents of serious adverse events.	[9,88-90,92,93,95-97,103,108,111-113]
Antimicrobial compounds	-Use of bacteriocins to inhibit the growth of pathogenic bacteria and preservation of gut microbiota.	-Targeted therapy. -Avoidance of using broad-spectrum antibiotics.	-Lack of scientific data. -No available clinical trials.	[119]
Selective Digestive Decontamination (SDD) and Selective Oropharyngeal Decontamination (SOD)	-Prophylactic use of antibiotics to reduce the gut colonization with MDROs.	-Successful into wards with low rates of resistant bacteria.	-Lack of data in centers with high rates of resistance. -Need for rigorous surveillance of patients.	[122-124,124,126,127]

HMOs: human milk oligosaccharides, IAP: intestinal alkaline phosphatase, ICU: intensive care unit, MDRO: multi-drug resistant organism