Prospective study on the impact of BEAM versus FEAM conditioning on occurrence of neutropenic enterocolitis and on transplant outcome in lymphoma patients.

Introduction: Carmustine (BCNU), etoposide, cytarabine, and melphalan (BEAM) are a widely used high-dose chemotherapy regimen for autologous stem cell transplantation transplant (ASCT) in lymphoid malignancies. During BCNU shortages, some centers switched to fotemustine-substituted BEAM (FEAM). Neutropenic enterocolitis (NEC) is a life-threatening complication occurring after intestinal mucosa damage related to intensive chemotherapy. NEC mortality may be up to 30%-50%. In our study, we compared NEC incidence, symptoms, mortality, and transplant outcome in terms of overall survival (OS) and progression-free survival (PFS) in the BEAM vs. FEAM groups. Furthermore, we compared the cost of hospitalization of patients who did vs. patients who did not experience a NEC episode (NECe). Methods: A total of 191 patients were enrolled in this study (N = 129 and N = 62 were conditioned with BEAM and FEAM, respectively). All patients received bed-side high-resolution ultrasound (US) for NEC diagnosis. Results and discussion: NEC incidence and NEC-related mortality were similar in the BEAM and FEAM groups (31% and 40.3%, p = 0.653, and 5% and 8%, p = 0.627, respectively). At a median follow-up of 116 months, no difference was noted between BEAM vs. FEAM groups in terms of OS and PFS (p = 0.181 and p = 0.978, respectively). BEAM appeared equivalent to FEAM in terms of NEC incidence and efficacy. The high incidence of NEC and the low mortality is related to a timely US diagnosis and prompt treatment. US knowledge in NEC diagnosis allows to have comparable days of hospitalization of patients NECpos vs. patients NECneg. The cost analysis of NECpos vs. NECneg has been also performed.

Evaluation of Circulating Endothelial Cells as Direct Marker of Endothelial Damage in Allo-Transplant Recipients at High Risk of Hepatic Veno-Occlusive Disease/Sinusoidal Obstruction Syndrome.

Sinusoidal obstruction syndrome (SOS), also known as veno-occlusive disease (VOD), is a rare but potentially fatal complication following allogenic hematopoietic cell transplantation (allo-HCT). Timely identification of SOS/VOD to allow for prompt treatment is critical, but identifying a VOD-predictive biomarker remains challenging. Given the pivotal role of endothelial dysfunction in SOS/VOD pathophysiology, the CECinVOD study prospectively evaluated levels of circulating endothelial cells (CECs) in patients undergoing allo-HCT with a myeloablative conditioning (MAC) regimen to investigate the potential of CEC level in predicting and diagnosing SOS/VOD. A total of 150 patients from 11 Italian bone marrow transplantation units were enrolled. All participants were age >18 years and received a MAC regimen, putting them at elevated risk of developing SOS/VOD. Overall, 6 cases of SOS/VOD (4%) were recorded. CECs were detected using the Food and Drug Administration-approved CellSearch system, an immunomagnetic selection-based platform incorporating ferrofluid nanoparticles and fluorescent-labeled antibodies, and were defined as CD146+, CD105+, DAPI+, or CD45-. Blood samples were collected at the following time points: before (T0) and at the end of conditioning treatment (T1), at neutrophil engraftment (T2), and at 7 to 10 days postengraftment (T3). For patients who developed VOD, additional samples were collected at any suspected or proven VOD onset (T4) and weekly during defibrotide treatment (T5 to T8). A baseline CEC count >17/mL was associated with an elevated risk of SOS/VOD (P = .04), along with bilirubin level >1.5 mg/mL and a haploidentical donor hematopoietic stem cell source. Postconditioning regimen (T1) CEC levels were elevated (P = .02), and levels were further increased at engraftment (P < .0001). Additionally, patients developing SOS/VOD after engraftment, especially those with late-onset SOS/VOD, showed a markedly higher relative increase (>150%) in CEC count. Multivariate analysis supported these findings, along with a high Endothelial Activation and Stress Index (EASIX) score at engraftment (T2). Finally, CEC kinetics corresponded with defibrotide treatment. After the start of therapy (T4), CEC levels showed an initial increase in the first week (T5), followed by a progressive decrease during VOD treatment (T6 and T7) and a return to pre-SOS/VOD onset levels at resolution of the complication. This prospective multicenter study reveals a low incidence of SOS/VOD in high-risk patients compared to historical data, in line with recent reports. The results from the CECinVOD study collectively confirm the endothelial injury in allo-HCT and its role in in the development of SOS/VOD, suggesting that CEC level can be a valuable biomarker for diagnosing SOS/VOD and identifying patients at greater risk of this complication, especially late-onset SOS/VOD. Furthermore, CEC kinetics may support treatment strategies by providing insight into the optimal timing for discontinuing defibrotide treatment.

Real-life diagnostic and therapeutic approach to CLL: a 2022 update from an expert panel in Tuscany.

A panel of chronic lymphocytic leukemia (CLL) experts from Tuscany propose a real-life diagnostic and therapeutic approach CLL that considers the role of genomic and somatic prognostic factors in risk stratification and treatment decisions. Safety and efficacy of new agents has been demonstrated now not only in clinical trials but also in many real-world series. The BTK inhibitors, ibrutinib and acalabrutinib, and BH3 mimetic venetoclax are now indicated as first-line therapy and chemoimmunotherapy can be spared to the majority of CLL patients, thus preventing unnecessary hematological and non-hematological toxicity and second primary tumors. For treatment, FISH for 17 p and P53 mutational status are essential. IGHV mutation can be done at diagnosis or before treatment. Echography is the gold standard radiological investigation in CLL, at both diagnosis and response evaluation. Chemotherapy is virtually abandoned. Age, genetic risk, and patient comorbidities have to be carefully evaluated for treatment decision. With the availability of different drugs, there is a need for a uniform and shared approach in daily therapeutic choice. The proposed approach is based on current evidence and guidelines as well as results from clinical trials and daily clinical experience.

Impact of different chemotherapy regimens on intestinal mucosal injury assessed with bedside ultrasound: a study in 213 AML patients.

Introduction: Neutropenic enterocolitis (NEC) is a life-threatening complication reported in patients with acute myeloid leukemia (AML) following chemotherapy (CHT). Intensive induction and consolidation CHT may damage intestinal mucosa leading to a NEC episode (NECe). NEC reported mortality may be up to 30-60%. Early US-guided bed-side diagnosis and prompt treatment may substantially improve the survival. An emerging worldwide concern is the intestinal colonization by multi-drug-resistant bacteria especially when patients are exposed to chemotherapy regimens potentially correlated to mucosal damage. Methods: In our study we prospectively enrolled all AML patients admitted in our leukemia unit to receive intensive induction and consolidation chemotherapy and experiencing chemotherapy-induced-neutropenia (CHTN). Results and discussion: Overall, we enrolled N=213 patients from 2007 to March 2023. We recorded N=465 CHTN, and N=42 NECe (9.0% incidence). The aim of our study was to assess which chemotherapy regimens are more associated with NEC. We found that ALM1310, followed by 7 + 3 (daunorubicin), 7 + 3 (idarubicin), 5 + 3 + 3 (cytarabine, etoposide, idarubicin), and AML1310 (consolidation) were associated with a statistically higher incidence of NEC. We did not detect NEC episodes in patients treated with CPX-351, 5 + 2 (cytarabine, idarubicine), and high-dose cytarabine. Thus, we found that cytarabine could determine mucosal damage when associated with an anthracycline but not if delivered either alone or as dual-drug liposomal encapsulation of daunorubicin/cytarabine. We also describe NEC mortality, symptoms at diagnosis, intestinal sites involvement, and prognostic significance of bowel wall thickening.

The Role of the Preanalytical Step for Human Saliva Analysis via Vibrational Spectroscopy.

Saliva is an easily sampled matrix containing a variety of biochemical information, which can be correlated with the individual health status. The fast, straightforward analysis of saliva by vibrational (ATR-FTIR and Raman) spectroscopy is a good premise for large-scale preclinical studies to aid translation into clinics. In this work, the effects of saliva collection (spitting/swab) and processing (two different deproteinization procedures) were explored by principal component analysis (PCA) of ATR-FTIR and Raman data and by investigating the effects on the main saliva metabolites by reversed-phase chromatography (RPC-HPLC-DAD). Our results show that, depending on the bioanalytical information needed, special care must be taken when saliva is collected with swabs because the polymeric material significantly interacts with some saliva components. Moreover, the analysis of saliva before and after deproteinization by FTIR and Raman spectroscopy allows to obtain complementary biological information.

Relapsed/Refractory Chronic Lymphocytic Leukemia Patients Treated with Fixed Duration Venetoclax-Rituximab: Assessment of Response with Ultrasound, and Relationship with Minimal Residual Disease.

A fixed duration of venetoclax-rituximab (VenR) resulted in a significant benefit of both PFS and in the attainment of an undetectable minimal residual disease (uMRD) compared with bendamustine-rituximab in relapsed/refractory (R/R) chronic lymphocytic leukemia (CLL) patients. The 2018 International Workshop on CLL guidelines, outside the context of clinical trials, suggested ultrasonography (US) as a possible imaging technique to evaluate visceral involvement, and palpation to evaluate superficial lymph nodes (SupLNs). In this real-life study we prospectively enrolled N = 22 patients. Patients were assessed by US, to determine nodal and splenic response in R/R CLL patients treated with a fixed duration VenR. We found an overall response rate, complete remission, partial remission, and stable disease, of 95.4%, 68%, 27.3%, and 4.5%, respectively. Responses were also correlated with risk categories. The time to response, and the time to clearance of the disease in the spleen, in abdominal LN (AbdLNs), and in SupLNs were discussed. Responses were independent from LN size. The correlation between response rate with MRD were also investigated. US allowed to detect a substantial CR rate correlated with uMRD.

A Prospective Cross-Sectional Study on the Comparison of Ultrasound Assessment vs. Palpation in Chronic Lymphocytic Leukemia Patients in the Era of Targeted Therapy.

Background. In IWCLL guidelines, progressive splenomegaly and lymphadenopathy are signs of active disease. In this study, we have tested the hypotheses if US could be a reliable tool for both superficial lymphnodes (SupLNs) and splenic assessment in chronic lymphocytic leukemia (CLL) patients. Methods. We enrolled N = 75 patients. SupLN and the spleen were assessed by two independent physicians (M1 and M2) by palpation and by a third physician (M3) with ultrasound sonography (US) using two different sonographers (US1 and US2). The results of M1 vs. M2 assessment, US1 vs. US2, palpation vs. US were compared. The echostructure of N = 1037 SupLN and of the spleen was also investigated. Results. The dimensions of SupLNs assessed by MD1 vs. MD2 were statistically discordant. Splenic size was concordant. There was concordance between US1 and US2 SupLN and splenic assessment. US found a higher number of pathological SupLN (Cohen's Kappa < 0.1) than palpation, which misses remarkable-sized SupLNs. LN echostructure and splenic involvement patterns were described. Conclusions. US is a reliable, radiation-free tool useful in clinical practice to assess SupLN and splenic involvement in CLL.

Fast, Direct Dihydrouracil Quantitation in Human Saliva: Method Development, Validation, and Application.

Background. Salivary metabolomics is garnering increasing attention in the health field because of easy, minimally invasive saliva sampling. Dihydrouracil (DHU) is a metabolite of pyrimidine metabolism present in urine, plasma, and saliva and of fluoropyrimidines-based chemotherapeutics. Its fast quantification would help in the identification of patients with higher risk of fluoropyrimidine-induced toxicity and inborn errors of pyrimidine metabolism. Few studies consider DHU as the main salivary metabolite, but reports of its concentration levels in saliva are scarce. We propose the direct determination of DHU in saliva by reversed-phase high-performance liquid chromatography (RP-HPLC-UV detector) as a simple, rapid procedure for non-invasive screening. Methods. The method used was validated and applied to 176 saliva samples collected from 21 nominally healthy volunteers and 4 saliva samples from metastatic colorectal cancer patients before and after receiving 5-fluorouracil chemotherapy. Results. DHU levels in all samples analyzed were in the µmol L-1 range or below proving that DHU is not the main metabolite in saliva and confirming the results found in the literature with LC-MS/MS instrumentation. Any increase of DHU due to metabolism dysfunctions can be suggestive of disease and easily monitored in saliva using common, low-cost instrumentation available also for population screening.

Time-dependent influence of high glucose environment on the metabolism of neuronal immortalized cells.

Mitochondria are organelles of bacterial origin historically identified as the cell power plant. In addition to energy, mitochondria produce reactive oxygen species and they have been found to have a key role in cell defense regulation, cell stress and damage. All the investigations regarding the nature of the molecules mediating these processes include compounds from mammalian cell metabolism. We hypothesize that the bacterial origin of mitochondria brings them to produce small fermentation products when cell is subjected to stress. In this work we studied the effect of hyperglycemia on the metabolome of hippocampal HN9.10e neurons, an in vitro model of one of the most vulnerable regions of central nervous system. Targeted metabolites were analyzed in the cell culture medium by liquid chromatography - diode array detection and headspace - gas chromatography - mass spectrometry. Twenty-two low molecular weight metabolites were identified and quantified in the growth medium of the cells, treated with 25, 50 or 75 mM glucose, sampled along 8 days to mimic a prolonged hyperglycemia. The results of statistical analysis showed the clear impairment of neuronal metabolism already after 48 h, represented by a significant reduction of the metabolic activity, together with the production of typical fermentative compounds.

Joint Pain and Arthritis as First Clinical Manifestation of Systemic Amyloidosis and Multiple Myeloma: Case Report and Brief Literature Review.

Amyloidosis is a rare disease that is often seen in conjunction with multiple myeloma (MM). Its damage varies depending on the anatomical site affected; however, it is believed that many cases of amyloidosis are misrecognized due to the fact that its signs and symptoms are nonspecific. Joint amyloidosis, in particular, may be confused with degenerative or autoimmune diseases. When it is associated with MM, it can significantly precede the diagnosis of the latter. We describe a case report of a woman of Nigerian heritage diagnosed with MM with widespread joint manifestations compatible with a diagnosis of amyloidosis, which had preceded the diagnosis of MM and benefited from MM treatment. Faced with the suspicion of amyloidosis, if confirmed, this can be used to anticipate the diagnosis of MM, and at a more advanced stage, it can benefit from the treatment of the MM.

Early Diagnosis of Neutropenic Enterocolitis by Bedside Ultrasound in Hematological Malignancies: A Prospective Study.

(1) Background: Neutropenic enterocolitis (NEC) is a life-threatening complication following chemotherapy with high mortality rates. Early diagnosis is crucial to improve outcomes. We designed a large prospective study employing bedside ultrasonography (US) as a novel approach to allow early diagnosis and prompt treatment to reduce mortality. (2) Methods: NEC was defined as US or computed tomography (CT)-proven bowel wall thickness ≥ 4 mm at the onset of at least one of the following symptoms: fever and/or abdominal pain and/or diarrhea during neutropenia. From 2007 to 2018, 1754 consecutive patients underwent baseline bedside US that was invariably repeated within 12 h from the onset of symptom(s) suggestive of NEC. (3) Results: Overall, 117 episodes of NEC were observed, and overall mortality was 9.4%. Bowel wall thickening was invariably absent in the negative control group. Abdominal pain associated with one or more symptoms correlated with the highest relative risk (17.33), sensitivity (89.7%), specificity (100%), and accuracy (96.2%) for diagnosis. The combination of abdominal pain and fever at onset significantly correlated with worse survival (p < 0.0001, OR 13.85). BWT (p = 0.046), type of therapy (p = 0.049) and blood culture positivity (p = 0.003) correlated with worse survival. (4) Conclusions: Bedside ultrasound is a non-invasive and radiation free imaging technique for early diagnosis of NEC and its prompt treatment significantly reduced mortality.

Unraveling the Extracellular Metabolism of Immortalized Hippocampal Neurons Under Normal Growth Conditions.

Metabolomic profiling of cell lines has shown many potential applications and advantages compared to animal models and human subjects, and an accurate cellular metabolite analysis is critical to understanding both the intracellular and extracellular environments in cell culture. This study provides a fast protocol to investigate in vitro metabolites of immortalized hippocampal neurons HN9.10e with minimal perturbation of the cell system using a targeted approach. HN9.10e neurons represent a reliable model of one of the most vulnerable regions of the central nervous system. Here, the assessment of their extracellular metabolic profile was performed by studying the cell culture medium before and after cell growth under standard conditions. The targeted analysis was performed by a direct, easy, high-throughput reversed-phase liquid chromatography with diode array detector (RP-HPLC-DAD) method and by headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) for the study of volatile organic compounds (VOCs). The analysis of six different batches of cells has allowed to investigate the metabolic reproducibility of neuronal cells and to describe the metabolic "starting" conditions that are mandatory for a well-grounded interpretation of the results of any following cellular treatment. An accurate study of the metabolic profile of the HN9.10e cell line has never been performed before, and it could represent a quality parameter before any other targeting assay or further exploration.

Validation and Application of a Derivatization-Free RP-HPLC-DAD Method for the Determination of Low Molecular Weight Salivary Metabolites.

Saliva is an interesting, non-conventional, valuable diagnostic fluid. It can be collected using standardized sampling device; thus, its sampling is easy and non-invasive, it contains a variety of organic metabolites that reflect blood composition. The aim of this study was to validate a user-friendly method for the simultaneous determination of low molecular weight metabolites in saliva. We have optimized and validated a high throughput, direct, low-cost reversed phase liquid chromatographic method with diode array detection method without any pre- or post-column derivatization. We indexed salivary biomolecules in 35 whole non-stimulated saliva samples collected in 8 individuals in different days, including organic acids and amino acids and other carbonyl compounds. Among these, 16 whole saliva samples were collected by a single individual over three weeks before, during and after treatment with antibiotic in order to investigate the dynamics of metabolites. The concentrations of the metabolites were compared with the literature data. The multianalyte method here proposed requires a minimal sample handling and it is cost-effectiveness as it makes possible to analyze a high number of samples with basic instrumentation. The identification and quantitation of salivary metabolites may allow the definition of potential biomarkers for non-invasive "personal monitoring" during drug treatments, work out, or life habits over time.

Organ Stiffness in the Work-Up of Myelofibrosis and Philadelphia-Negative Chronic Myeloproliferative Neoplasms.

To define the role of spleen stiffness (SS) and liver stiffness (LS) in myelofibrosis and other Philadelphia (Ph)-negative myeloproliferative neoplasms (MPNs), we studied, by ultrasonography (US) and elastography (ES), 70 consecutive patients with myelofibrosis (MF) (no.43), essential thrombocythemia (ET) (no.10), and polycythemia vera (PV) (no.17). Overall, the median SS was not different between patients with MF and PV (p = 0.9); however, both MF and PV groups had significantly higher SS than the ET group (p = 0.011 and p = 0.035, respectively) and healthy controls (p < 0.0001 and p = 0.002, respectively). In patients with MF, SS values above 40 kPa were significantly associated with worse progression-free survival (PFS) (p = 0.012; HR = 3.2). SS also correlated with the extension of bone marrow fibrosis (BMF) (p < 0.0001). SS was higher in advanced fibrotic stages MF-2, MF-3 (W.H.O. criteria) than in pre-fibrotic/early fibrotic stages (MF-0, MF-1) (p < 0.0001) and PFS was significantly different in the two cohorts, with values of 63% and 85%, respectively (p = 0.038; HR = 2.61). LS significantly differed between the patient cohort with MF and healthy controls (p = 0.001), but not between the patient cohorts with ET and PV and healthy controls (p = 0.999 and p = 0.101, respectively). We can conclude that organ stiffness adds valuable information to the clinical work-up of MPNs and could be employed to define patients at a higher risk of progression.

The CoV-2 outbreak: how hematologists could help to fight Covid-19.

COVID-19 is a medical emergency, with 20 % of patients presenting with severe clinical manifestations. From the pathogenetic point of view, COVID-19 mimics two other well-known diseases characterized by cytokine storm and hyper-activation of the immune response, with consequent organ damage: acute graft-versus-host disease (aGVHD) and macrophage activation syndrome (MAS). Hematologists are confident with these situations requiring a prompt therapeutic approach for switching off the uncontrolled cytokine release; here, we discuss pros and cons of drugs that are already employed in hematology in the light of their possible application in COVID-19. The most promising drugs might be: Ruxolitinib, a JAK1/2 inhibitor, with a rapid and powerful anti-cytokine effect, tyrosine kinase inhibitors (TKIs), with their good anti-inflammatory properties, and perhaps the anti-Cd26 antibody Begelomab. We also present immunological data from gene expression experiments where TKIs resulted effective anti-inflammatory and pro-immune drugs. A possible combined treatment algorithm for COVID-19 is here proposed.

Treatment of steroid resistant acute graft versus host disease with an anti-CD26 monoclonal antibody-Begelomab.

We have treated 69 patients with steroid refractory acute graft versus host disease (SR-aGvHD), with an anti-CD26 monoclonal antibody (Begelomab): 28 patients in two prospective studies (EudraCT No. 2007-005809-21; EudraCT No. 2012-001353-19), and 41 patients on a compassionate use study. The median age of patients was 42 and 44 years; the severity of GvHD was as follows: grade II in 8 patients, grade III in 33, and grade IV in 28 patients. There were no adverse events directly attributable to the antibody. Day 28 response was 75% in the prospective studies and 61% in the compassionate use patients, with complete response rates of 11 and 12%. Response for grade III GvHD was 83 and 73% in the two groups; response in grade IV GvHD was 66 and 56% in the two groups. Non relapse mortality (NRM) at 6 months was 28 and 38%. Overall there were 64, 56, 68% responses for skin, liver, and gut stage 3-4 GvHD. The overall survival at 1 year was 50% for the prospective studies and 33% for the compassionate use patients. In conclusion, Begelomab induces over 60% responses in SR-aGvHD, including patients with severe gut and liver GvHD, having failed one or more lines of treatment.

Temporal trends in latecomer STEMI patients: insights from the AMIS Plus registry 1997-2017.

INTRODUCTION AND OBJECTIVES: A substantial proportion of patients experiencing ST-segment elevation myocardial infarction (STEMI) have a late presentation. There is a lack of temporal trends drawn from large real-word scenarios in these patients. METHODS: All STEMI patients included in the AMIS Plus registry from January 1997 to December 2017 were screened and patient-related delay was assessed. STEMI patients were classified as early or latecomers according to patient-related delay (≤ or> 12hours, respectively). RESULTS: A total of 27 231 STEMI patients were available for the analysis. During the study period, the prevalence of late presentation decreased from 22% to 12.3% (P <.001). In latecomer STEMI patients, there was a gradual uptake of evidence-based pharmacological treatments (rate of P2Y12 inhibitors at discharge, from 6% to 90.6%, P <.001) and a marked increase in the use of percutaneous coronary intervention (PCI), particularly in 12- to 48-hour latecomers (from 11.9%-87.9%; P <.001). In-hospital mortality was reduced from 12.4% to 4.5% (P <.001). On multivariate analysis, PCI had a strong independent protective effect on in-hospital mortality in 12- to 48-hour latecomers (OR, 0.29; 95%CI, 0.15-0.55). CONCLUSIONS: During the 20-year study period, there was a progressive reduction in the prevalence of late presentation, a gradual uptake of main evidence-based pharmacological treatments, and a marked increase in PCI rate in latecomer STEMI patients. In-hospital mortality was reduced to a third (to an absolute rate of 4.5%); in 12- to 48-hour latecomers, this reduction seemed to be mainly associated with the increasing implementation of PCI.

Toxicity of Thallium at Low Doses: A Review.

A mini review of the toxicity of Thallium (Tl) at low doses is herein presented. Thallium has severe toxicity. Although its acute biological effects have been widely investigated and are well known, its biological effects on human health and in cell cultures at low doses (<100 µg/L) due, for example, to Tl chronic exposure via consumption of contaminated water or foods, have often been overlooked or underestimated. Relatively few papers have been published on this topic and are herein reviewed to provide a focused scientific opinion in the light of current worldwide regulatory issues.

HS-SPME-GC-MS approach for the analysis of volatile salivary metabolites and application in a case study for the indirect assessment of gut microbiota.

In this work, a straightforward analytical approach based on headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry was developed for the analysis of salivary volatile organic compounds without any prior derivatization step. With a sample volume of 500 µL, optimal conditions were achieved by allowing the sample to equilibrate for 10 min at 50 °C and then extracting the samples for 10 min at the same temperature, using a carboxen/polydimethylsiloxane fibre. The method allowed the simultaneous identification and quantification of 20 compounds in sample headspace, including short-chain fatty acids and their derivatives which are commonly analysed after analyte derivatization. The proof of applicability of the methodology was performed with a case study regarding the analysis of the dynamics of volatile metabolites in saliva of a single subject undergoing 5-day treatment with rifaximin antibiotic. Non-stimulated saliva samples were collected over 3 weeks from a nominally healthy volunteer before, during, and after antibiotic treatment. The variations of some metabolites, known to be produced by the microbiota and by bacteria that are susceptible to antibiotics, suggest that the study of the dynamics of salivary metabolites can be an excellent indirect method for analysing the gut microbiota. This approach is novel from an analytical standpoint, and it encourages further studies combining saliva metabolite profiles and gut microbiota dynamics. Graphical abstract.