Probiotics are widely consumed for their potential health benefits, particularly in promoting gastrointestinal health and treating functional gastrointestinal disorders (FGIDs). However, recent studies have raised concerns about the potential association between probiotic use and brain fog, a cognitive dysfunction characterized by confusion, impaired judgment, and lack of focus. A 47-year-old male commercial airline captain with over 10000 flight hours presented with a two-month history of bloating, abdominal distension, and irregular bowel habits following a period of occupational stress and irregular dietary habits. The pilot\'s previous medical history was largely uneventful, with the exception of a long-standing gastritis diagnosis. To manage this condition, he had been on a daily regimen of 20 mg of pantoprazole for approximately eight years. After a telemedicine consultation, he began taking an over-the-counter probiotic supplement containing 16 strains. Within five days, he experienced a significant exacerbation of abdominal symptoms, accompanied by somnolence, difficulty concentrating, and mental fatigue, raising safety concerns given his profession. Functional gastrointestinal examination revealed a distended abdomen with increased bowel sounds. Probiotic-associated brain fogginess was suspected, and the patient was advised to discontinue the supplements. Rifaximin therapy was initiated, resulting in rapid resolution of both gastrointestinal and cognitive symptoms. The clear temporal association between probiotic intake and symptom onset, followed by resolution after antibiotic treatment, suggests a causal relationship. This case highlights the potential risks of unsupervised probiotic use, particularly in safety-sensitive professions such as commercial aviation. Occupational health physicians and aeromedical examiners should be aware of the potential for probiotic-induced brain fog in airline pilots (APs). Prompt recognition and appropriate antibiotic treatment can result in complete symptom resolution and prevent occupational hazards.

Irritable bowel syndrome (IBS) is a prevalent disorder of gut-brain interaction without a reliable cure. Evidence suggests that an alteration of the gut microbiome may contribute to IBS pathogenesis, motivating the development of microbiome-targeted therapies to alleviate IBS symptoms. However, IBS-specific microbiome signatures are variable across cohorts. A total of 9204 datasets were meta-analyzed, derived from fourteen IBS microbiome discovery cohorts, three validation cohorts for diet-microbiome interactions, and five rifaximin therapy cohorts. The consistent bacterial species and functional signatures associated with IBS were identified. Network analysis revealed two distinct IBS-enriched microbiota clusters; obligate anaerobes that are found commonly in the gut, and facultative anaerobes typically present in the mouth, implying a possible association between oral bacterial translocation to gut and IBS pathogenesis. By analyzing diet-microbiome interactions, microbiota-targeted diets that can potentially modulate the altered gut microbiota of IBS subjects toward a healthy status were identified. Furthermore, rifaximin treatment of IBS subjects was linked with a reduction in the abundance of facultatively anaerobic pathobionts. Gut microbiome signatures were identified across IBS cohorts that may inform the development of therapies for microbiome modulation in IBS. The microbiota-targeted diet patterns described may enable nutritional intervention trials in IBS and for assisting dietary management.

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) pneumonia is one of the leading causes of death and an immense financial burden on healthcare systems. Rifaximin (RFX) has good antibacterial activity against MRSA, but its clinical application is limited due to its poor oral absorption. Solid lipid nanoparticles have good biocompatibility, high drug loading, sustained release performance, and the inertia of lipids in gastric acid, which facilitates oral drug delivery.
OBJECTIVE: In order to improve the oral bioavailability of rifaximin and expand the clinical application of RFX for MRSA pneumonia, this study developed RFX-loaded myristic acid solid lipid nanoparticles (RFX-SLNs).
METHODS: This study first prepared RFX-SLNs through hot melt emulsification and ultrasonic methods and selected the optimal formula of RFX-SLNs through single-factor screening. Afterward, the particle size, zeta potential, and polydispersity index (PDI) of the RFX-SLNs were measured, the morphology of RFX-SLNs was observed by transmission electron microscopy, and the encapsulation efficiency (EE) and drug loading capacity (LC) of RFX-SLNs were detected by high-performance liquid chromatography. Then, the sustained release ability and oral bioavailability of RFX-SLNs were studied through in vitro release and pharmacokinetics. Finally, the therapeutic effect of RFX-SLNs on MRSA pneumonia infection was studied by using a mouse MRSA pneumonia infection model.
RESULTS: The optimal formulation of RFX-SLNs was 1% RFX with water (3% PVA) and oil (myristic acid) ratio of 1:19. RFX-SLNs were spherical in shape with a smooth surface and uniform size. The EE and LC of three different batches of RFX-SLNs were 89.35±2.47%, 90.45±3.69%, 88.72±1.18%, and 9.50 ± 0.01%, 10.09±0.01%, and 9.68±0.00%, respectively. In vitro release and pharmacokinetic studies showed that the myristic acid solid lipid nanoparticles showed excellent sustained release as expected and increased the oral bioavailability of RFX by 2.18 times. This indicates that RFX-SLNs can be used for the oral treatment of bacterial infections. Compared to RFX, RFX-SLNs showed good therapeutic effects in a mouse MRSA pneumonia infection model.
CONCLUSIONS: This study indicates that the myristic acid solid lipid nanoparticles might be an effective way to enhance the oral absorption and therapy effects of RFX and other insoluble drugs. This not only opens up avenues for the clinical application of RFX but also provides a way for the development of new dosage forms of water-soluble drugs and the expansion of their clinical application scope.

Rifaximin, derived from rifamycin, is a broad-spectrum antibiotic by inhibiting bacterial RNA synthesis. Rifaximin has a very low intestinal absorption and exerts its antimicrobial activity primarily in the intestinal tract. It regulates the gut microbiota with limited side effects systemically. Rifaximin has been recommended for the treatment of hepatic encephalopathy but some studies shed light on its medicinal effects in many other diseases. For instance, rifaximin may suppress the progression of liver fibrosis and its related complications, and ameliorate metabolic dysfunction-associated steatotic liver disease and alcohol-associated liver disease, etc. Rifaximin can also mediate anti-inflammation, antiproliferation, and proapoptotic events by activating pregnane X receptor, which is efficious in cancers such as colon cancer. In addition, some investigations have shown rifaximin may play a therapeutic role in various autoimmune and neurological disorders. However, these findings still need more real-world practices and in-depth investigations to obtain more precise indications and fully elucidate the multifaceted potentials of rifaximin.

Rifaximin is FDA-approved for treatment of irritable bowel syndrome with diarrhea (IBS-D), but poor solubility may limit its efficacy against microbes in the mucus layer, e.g. Escherichia coli. Here we evaluate adding the mucolytic N-acetylcysteine (NAC) to improve rifaximin efficacy. In a resazurin checkerboard assay, combining rifaximin with NAC had significant synergistic effects in reducing E. coli levels. The optimal rifaximin + NAC combination was then tested in a validated rat model of IBS-D (induced by cytolethal distending toxin [CdtB] inoculation). Rats were inoculated with vehicle and treated with placebo (Control-PBS) or rifaximin + NAC (Control-Rif + NAC, safety), or inoculated with CdtB and treated with placebo (CdtB-PBS), rifaximin (CdtB-Rifaximin), or rifaximin + NAC (CdtB-Rif + NAC) for 10 days. CdtB-inoculated rats (CdtB-PBS) developed wide variability in stool consistency (P = 0.0014) vs. controls (Control-PBS). Stool variability normalized in rats treated with rifaximin + NAC (CdtB-Rif + NAC) but not rifaximin alone (CdtB-Rifaximin). Small bowel bacterial levels were elevated in CdtB-PBS rats but normalized in CdtB-Rif + NAC but not CdtB-Rifaximin rats. E. coli and Desulfovibrio spp levels (each associated with different IBS-D microtypes) were also elevated in CdtB-inoculated (CdtB-PBS) but normalized in CdtB-Rif + NAC rats. Cytokine levels normalized only in CdtB-Rif + NAC rats, in a manner predicted to be associated with reduced diarrhea driven by reduced E. coli. These findings suggest that combining rifaximin with NAC may improve the percentage of IBS-D patients responding to treatment.

In this study, a new analytical method was developed using magnetic molecularly imprinted polymers (MMIPs) by employing eco-friendly supramolecular ternary deep eutectic solvents to synthesize these MMIPs for selective extraction of rifaximin. The characterization analysis and adsorption affinity investigation were conducted. The results showed fast adsorption (15 min) with high adsorption capacity (43.20 mg g-1) and selectivity for rifaximin. Various extraction parameters were optimized, achieving recoveries ranging from 86.67% to 99.47% in spiked milk samples using high-performance liquid chromatography (HPLC). The detection and quantification limits were 0.01 mg L-1 and 0.03 mg L-1, respectively. The method exhibited low RSDs (<4.70%) and excellent selectivity, with MMIPs reusable up to seven times with only a 10% performance loss. This study proposes a convenient and reliable method for trace-level rifaximin extraction from milk using eco-friendly MMIPs.

Rifaximin, a broad-spectrum antibiotic, boasts a unique chemical composition and pharmacokinetic profile, rendering it highly effective in treating irritable bowel syndrome (IBS). Its minimal systemic absorption confines its impact to the gastrointestinal (GI) tract, where it yields significant therapeutic benefits. This review examines rifaximin\'s physico-chemical attributes and its role in managing IBS symptoms. Its molecular structure facilitates intestinal lumen retention postoral administration, minimizing systemic exposure and adverse effects. This targeted action is crucial in addressing the gut microbiota\'s role in IBS pathophysiology. By modifying microbial populations and their metabolite production, rifaximin mitigates symptoms like bloating, irregular bowel habits, and abdominal pain associated with IBS. It achieves this by reducing pathogenic bacteria and altering bacterial metabolism, enhancing mucosal and immune function. Clinical trials affirm rifaximin\'s superiority over placebo and conventional therapies in alleviating overall IBS symptoms and addressing small intestine bacterial overgrowth (SIBO). Despite its promising efficacy and sustained symptom relief, further research is essential to optimize long-term effectiveness and dosing regimens. Rifaximin stands as a vital treatment option for IBS due to its distinctive properties and clinical utility; yet, ongoing investigation is imperative for maximizing its therapeutic benefits.

BACKGROUND: The regulatory role of gut microbiota and gut-derived metabolites through the gut-liver axis in the development of cirrhotic portal hypertension (PH) has received increasing attention.
METHODS: The review summarized a series of investigations on effects of metabolites derived from microbiota and medicines targeting microbiome including rifaximin, VSL#3, statins, propranolol, FXR agonists as well as drugs derived from bile acids (BAs) on PH progression.
RESULTS: Patients with PH exhibit alterations in gut microbial richness and differential overall microbiota community, and several results clearly displayed the correlation of PH with enrichment of Veillonella dispar or depletion of Clostridiales, Peptostreptococcaceae, Alistipes putredinis, Roseburia faecis and Clostridium cluster IV. The gut-derived metabolites including hydrogen sulfide, tryptophan metabolites, butyric acid, secondary BAs and phenylacetic acid (PAA) participate in a range of pathophysiology process of PH through modulating intrahepatic vascular resistance and portal blood flow associated with the formation and progression of PH. Established and emerging drugs targeting on bacterial translocation and intestinal eubiosis are gradually identified as potential strategies for treatments of liver cirrhosis and PH by modulating intestinal inflammation, splanchnic arterial vasodilation and endothelial dysfunction.
CONCLUSIONS: Future explorations should further characterize the alteration of the fecal microbiome and metabolite profiles in PH and elucidate the regulatory mechanism of the intestinal microbiome, gut-derived metabolites and gut microbiota targeted pharmaceutical treatments involved in PH.

BACKGROUND: Vasodilatation and bacterial dislocation are the main contributors to the catastrophic events in patients with decompensated liver cirrhosis (DLC).
OBJECTIVE: The aim of this study was to evaluate the impacts of adding midodrine and rifaximin on morbidity, mortality, and quality of life in patients with DLC.
METHODS: This interventional clinical study included 100 consecutively enrolled DLC patients randomized 1 : 1 into two groups. Group A received oral midodrine (5 mg/8 h) and rifaximin (550 mg/12 h) with standard diuretic therapy, while group B received only standard diuretic therapy. Clinical and laboratory data, including the McGill Quality of Life Questionnaire, were evaluated over a 3-month treatment period.
RESULTS: In the study group, there was a significant reduction in Child-Pugh and Model for End-Stage Liver Disease scores, international normalized ratio, and mean arterial blood pressure at 2, 6, and 12 weeks (P < 0.05). Ascites, spontaneous bacterial peritonitis incidence, hematemesis, paracentesis need, and hepatic encephalopathy showed improvement after 12 weeks compared with the control group. McGill Quality of Life Questionnaire significantly improved after 6 and 12 weeks (P < 0.05). Survival rates demonstrated a noteworthy improvement (P = 0.014), substantiated by evidence in both univariate and multivariate regression analyses.
CONCLUSIONS: Combined midodrine with rifaximin represents an endowment to patients with DLC with spectacular improvements in synthetic liver functions, along with improved quality of life, and survival.

BACKGROUND: Hepatic encephalopathy (HE) is a severe neuropsychiatric complication of liver diseases characterized by neuroinflammation. The efficacies of nonabsorbable rifaximin (RIF) and lactulose (LAC) have been well documented in the treatment of HE. [18F]PBR146 is a translocator protein (TSPO) radiotracer used for in vivo neuroinflammation imaging. This study investigated anti-neuroinflammation effect of RIF or/and LAC in chronic HE rats by [18F]PBR146 micro-PET/CT.
METHODS: Bile duct ligation (BDL) operation induced chronic HE models, and this study included Sham+normal saline (NS), BDL+NS, BDL+RIF, BDL+LAC, and BDL+RIF+LAC groups. Behavioral assessment was performed to analyze the motor function, and fecal samples were collected after successfully established the chronic HE model (more than 28 days post-surgery). In addition, fecal samples collection and micro-PET/CT scans were performed sequentially. And we also collected the blood plasma, liver, intestinal, and brain samples after sacrificing the rats for further biochemical and pathological analyses.
RESULTS: The RIF- and/or LAC-treated BDL rats showed similar behavioral results with Sham+NS group, while the treatment could not reverse the biliary obstruction resulting in sustained liver injury. The RIF or/and LAC treatments can inhibit IFN-γ and IL-10 productions. The global brain uptake values of [18F]PBR146 in BDL+NS group was significantly higher than other groups (p < .0001). The brain regions analysis showed that the basal ganglia, hippocampus, and cingulate cortex had radiotracer uptake differences among groups (all p < .05), which were consistent with the brain immunohistochemistry results. Sham+NS group was mainly enriched in Christensenella, Coprobacillus, and Pseudoflavonifractor. BDL+NS group was mainly enriched in Barnesiella, Alloprevotella, Enterococcus, and Enterorhabdus. BDL+RIF+LAC group was enriched in Parabacteroides, Bacteroides, Allobaculum, Bifidobacterium, and Parasutterella.
CONCLUSIONS: RIF or/and LAC had anti-neuroinflammation in BDL-induced chronic HE rats with gut microbiota alterations. The [18F]PBR146 could be used for monitoring RIF or/and LAC treatment efficacy of chronic HE rats.