High-throughput anaerobic screening for identifying compounds acting against gut bacteria in monocultures or communities.

The human gut microbiome is a key contributor to health, and its perturbations are linked to many diseases. Small-molecule xenobiotics such as drugs, chemical pollutants and food additives can alter the microbiota composition and are now recognized as one of the main factors underlying microbiome diversity. Mapping the effects of such compounds on the gut microbiome is challenging because of the complexity of the community, anaerobic growth requirements of individual species and the large number of interactions that need to be quantitatively assessed. High-throughput screening setups offer a promising solution for probing the direct inhibitory effects of hundreds of xenobiotics on tens of anaerobic gut bacteria. When automated, such assays enable the cost-effective investigation of a wide range of compound-microbe combinations. We have developed an experimental setup and protocol that enables testing of up to 5,000 compounds on a target gut species under strict anaerobic conditions within 5 d. In addition, with minor modifications to the protocol, drug effects can be tested on microbial communities either assembled from isolates or obtained from stool samples. Experience in working in an anaerobic chamber, especially in performing delicate work with thick chamber gloves, is required for implementing this protocol. We anticipate that this protocol will accelerate the study of interactions between small molecules and the gut microbiome and provide a deeper understanding of this microbial ecosystem, which is intimately intertwined with human health.

Association of intraindividual tacrolimus variability with de novo donor-specific HLA antibody development and allograft rejection in pediatric kidney transplant recipients with low immunological risk.

BACKGROUND: Tacrolimus (Tac) intraindividual variability (TacIPV) in pediatric kidney transplant patients is only poorly understood. We investigated the impact of TacIPV on de novo donor-specific HLA antibodies (dnDSA) development and allograft rejection in Caucasian pediatric recipients of a living or deceased donor kidney with low immunological risk. METHODS: This was a single-center retrospective study including 48 pediatric kidney transplant recipients. TacIPV was calculated based on coefficient of variation (CV%) 6-12 months posttransplant. TacIPV cutoff was set at the median (25%). Outcome parameters were dnDSA development and rejection episodes. RESULTS: In total, 566 Tac levels were measured with median 11.0 (6.0-17.0) measurements per patient. The cutoff of 25% corresponded to the median CV% in our study cohort (25%, IQR 18-35%) and was comparable to cutoffs determined by receiver operating characteristic (ROC) curve analysis. High TacIPV was associated with higher risk of dnDSA development (HR 3.4, 95% CI 1.0-11.1, P = 0.047; Kaplan-Meier analysis P = 0.018) and any kind of rejection episodes (HR 4.1, 95% CI 1.1-14.8, P = 0.033; Kaplan-Meier analysis P = 0.010). There was a clear trend towards higher TacIPV below the age of 6 years. TacIPV (CV%) was stable over time. A TacIPV (CV%) cutoff of 30% or IPV quantification by mean absolute deviation (MAD) showed comparable results. CONCLUSIONS: High TacIPV is associated with an increased risk of dnDSA development and rejection episodes > year 1 posttransplant even in patients with low immunological risk profile. Therefore, in patients with high TacIPV, potential causes should be addressed, and if not resolved, changes in immunosuppressive therapy should be considered. A higher resolution version of the Graphical abstract is available as Supplementary information.

The gut microbiome in solid organ transplantation.

Despite ground-breaking advances in allogeneic transplantation, allograft rejection and immunosuppressant-specific complications remain a major challenge in transplant medicine. Growing evidence suggests the human gut microbiome as a potential contributor to transplant outcome and patient health. After breakthrough findings in haematopoietic stem cell transplantation (HSCT), the relevance of the microbiome in solid organ transplantation (SOT) is becoming increasingly clear. Here, we review the role of the microbiome in SOT focusing on its significance for transplant-associated complications such as allograft rejection and infections, and highlight its potential impact on immunosuppressive treatment. Moreover, we shed light on the emerging role of the microbiome as a diagnostic biomarker and therapeutic target and discuss current microbial intervention strategies. In addition, this review includes some practical considerations in designing clinical microbiome trials and offers some advice for the interpretation of the resulting data. Further investigation of the gut microbiome harbours countless clinical application possibilities and holds great promise of having a lasting impact on transplant medicine.