The Burden and Impact of Early Post-transplant Multidrug-Resistant Organism Detection Among Renal Transplant Recipients, 2005-2021.

Background: Reducing the burden of multidrug-resistant organism (MDRO) colonization and infection among renal transplant recipients (RTRs) may improve patient outcomes. We aimed to assess whether the detection of an MDRO or a comparable antibiotic-susceptible organism (CSO) during the early post-transplant (EPT) period was associated with graft loss and mortality among RTRs. Methods: We conducted a retrospective cohort study of RTRs transplanted between 2005 and 2021. EPT positivity was defined as a positive bacterial culture within 30 days of transplant. The incidence and prevalence of EPT MDRO detection were calculated. The primary outcome was a composite of 1-year allograft loss or mortality following transplant. Multivariable Cox hazard regression, competing risk, propensity score-weighted sensitivity, and subgroup analyses were performed. Results: Among 3507 RTRs, the prevalence of EPT MDRO detection was 1.3% (95% CI, 0.91%-1.69%) with an incidence rate per 1000 EPT-days at risk of 0.42 (95% CI, 0.31-0.57). Among RTRs who met survival analysis inclusion criteria (n = 3432), 91% (3138/3432) had no positive EPT cultures and were designated as negative controls, 8% (263/3432) had a CSO detected, and 1% (31/3432) had an MDRO detected in the EPT period. EPT MDRO detection was associated with the composite outcome (adjusted hazard ratio [aHR], 3.29; 95% CI, 1.21-8.92) and death-censored allograft loss (cause-specific aHR, 7.15; 95% CI, 0.92-55.5; subdistribution aHR, 7.15; 95% CI, 0.95-53.7). A similar trend was seen in the subgroup and sensitivity analyses. Conclusions: MDRO detection during the EPT period was associated with allograft loss, suggesting the need for increased strategies to optimize prevention of MDRO colonization and infection.

Advancing cytomegalovirus prevention in solid organ transplant recipients: The promise of cell-mediated immune assays.

Cytomegalovirus (CMV) infections are a major source of morbidity and mortality in solid organ transplant recipients. Prophylactic, preemptive, and hybrid prevention strategies have traditionally been the mainstay of CMV prevention but there is growing interest in the use of CMV cell-mediated immune assays to inform novel approaches to risk stratification. Recent evidence suggests that CMV interferon-gamma release assays can offer predictive insights into the risk for CMV-related illnesses, raising the potential for tailored CMV prevention strategies anchored to each individual's unique CMV immune profile. However, the predictive capacity of these assays for CMV-related illnesses can be profoundly influenced by when they are performed relative to transplant, and the induction immunosuppressive regimen the patient has received. In this review, we explore the relevant literature shaping our understanding of the optimal use of these assays. Furthermore, we also highlight the benefits of quantifying the CD4+ and CD8+ T-Cell responses to CMV, which is offered by some interferon-gamma release assays utilizing intracellular cytokine staining, for providing a holistic assessment of the recovery of cell-mediated immunity post-induction immunosuppression.

Impact of an ultrasensitive Cytomegalovirus quantitative nucleic acid test on Cytomegalovirus detection and therapy in renal transplant recipients.

BACKGROUND: Cytomegalovirus (CMV) infection has broad implications for morbidity and mortality in renal transplant recipients (RTR). Routine surveillance for CMV replication with PCR-based quantitative nucleic acid testing (qNAT) assays is standard practice in most transplant centers, but the impact of assay sensitivity on antiviral decision-making and virologic outcomes has not been studied. We investigated the effects of an ultrasensitive CMV qNAT assay on multiple clinical outcomes, including time to detection and duration of CMV DNAemia. METHODS: We conducted a single-center cohort study contrasting RTRs monitored with a qNAT with a higher lower limit of quantification (LLOQ >300 IU/mL) with those monitored with a more sensitive qNAT (LLOQ >35 IU/mL). Patients were stratified by donor (D)/recipient (R) CMV serostatus (D+/R-: high risk; any R+: moderate risk). CMV viral load monitoring was performed monthly post transplantation, with the primary outcomes being time to CMV DNAemia and its duration. RESULTS: Total 1382 patients were analyzed from 2014 to 2016 and 2019 to 2021. Moderate-risk RTRs monitored with the more sensitive assay experienced a greater hazard for the development of a first episode of CMV DNAemia (aHR: 1.95, 95% confidence interval [CI]: 1.55-2.46) and an average of 24 (95% CI: 16.40-31.98) additional days of DNAemia. There was no difference in CMV end-organ disease or 1-year all-cause mortality between moderate-risk RTRs. CONCLUSIONS: The more sensitive assay was associated with earlier detection and extended durations of CMV DNAemia in moderate-risk RTRs, without altering clinical outcomes. These findings inform optimal use of these assays and antiviral stewardship in RTRs. KEY SUMMARY: The use of ultrasensitive CMV qNAT assays in moderate-risk CMV renal transplant recipients is associated with earlier detection and longer durations of CMV DNAemia without impacting CMV end-organ disease or 1-year mortality.

Fecal microbiota transplantation promotes reduction of antimicrobial resistance by strain replacement.

Multidrug-resistant organism (MDRO) colonization is a fundamental challenge in antimicrobial resistance. Limited studies have shown that fecal microbiota transplantation (FMT) can reduce MDRO colonization, but its mechanisms are poorly understood. We conducted a randomized, controlled trial of FMT for MDRO decolonization in renal transplant recipients called PREMIX (NCT02922816). Eleven participants were enrolled and randomized 1:1 to FMT or an observation period followed by delayed FMT if stool cultures were MDRO positive at day 36. Participants who were MDRO positive after one FMT were treated with a second FMT. At last visit, eight of nine patients who completed all treatments were MDRO culture negative. FMT-treated participants had longer time to recurrent MDRO infection versus PREMIX-eligible controls who were not treated with FMT. Key taxa (Akkermansia muciniphila, Alistipes putredinis, Phocaeicola dorei, Phascolarctobacterium faecium, Alistipes species, Mesosutterella massiliensis, Barnesiella intestinihominis, and Faecalibacterium prausnitzii) from the single feces donor used in the study that engrafted in recipients and metabolites such as short-chain fatty acids and bile acids in FMT-responding participants uncovered leads for rational microbiome therapeutic and diagnostic development. Metagenomic analyses revealed a previously unobserved mechanism of MDRO eradication by conspecific strain competition in an FMT-treated subset. Susceptible Enterobacterales strains that replaced baseline extended-spectrum ß-lactamase-producing strains were not detectable in donor microbiota manufactured as FMT doses but in one case were detectable in the recipient before FMT. These data suggest that FMT may provide a path to exploit strain competition to reduce MDRO colonization.

Enteric Populations of Escherichia coli are Likely to be Resistant to Phages Due to O Antigen Production.

Bioinformatic and experimental data show that bacteriophages are ubiquitous in human enteric microbiomes. However, there are gaps in understanding the contribution of these viruses in shaping the bacterial strain and species composition of the gut microbiome and how these phages are maintained over time. To address these questions, we adapted and analyzed the properties of a mathematical model of the population and evolutionary dynamics of bacteria and phage and performed experiments with Escherichia coli and phages isolated from four fecal microbiota transplantation (FMT) doses as representative samples of non-dysbiotic enteric microbiota. Our models predict and experiments confirm that due to production of the O antigen, E. coli in the enteric microbiome are likely to be resistant to infection with co-occurring phages. However, phages can be maintained in these populations in high densities due to high rates of transition between resistant and sensitive states, which we call leaky resistance. Based on these models and observations, we postulate that the phages found in the human gut are likely to play little role in shaping the composition of E. coli in the enteric microbiome in healthy individuals. How general this is for other species of bacteria in enteric microbiota is not yet clear, although O antigen production is broadly conserved across many taxa.

Clinical and Genomic Epidemiology of mcr-9-Carrying Carbapenem-Resistant Enterobacterales Isolates in Metropolitan Atlanta, 2012 to 2017.

Colistin is a last-resort antibiotic for multidrug-resistant Gram-negative infections. Recently, the ninth allele of the mobile colistin resistance (mcr) gene family, designated mcr-9, was reported. However, its clinical and public health significance remains unclear. We queried genomes of carbapenem-resistant Enterobacterales (CRE) for mcr-9 from a convenience sample of clinical isolates collected between 2012 and 2017 through the Georgia Emerging Infections Program, a population- and laboratory-based surveillance program. Isolates underwent phenotypic characterization and whole-genome sequencing. Phenotypic characteristics, genomic features, and clinical outcomes of mcr-9-positive and -negative CRE cases were then compared. Among 235 sequenced CRE genomes, 13 (6%) were found to harbor mcr-9, all of which were Enterobacter cloacae complex. The median MIC and rates of heteroresistance and inducible resistance to colistin were similar between mcr-9-positive and -negative isolates. However, rates of resistance were higher among mcr-9-positive isolates across most antibiotic classes. All cases had significant health care exposures. The 90-day mortality was similarly high in both mcr-9-positive (31%) and -negative (7%) CRE cases. Nucleotide identity and phylogenetic analysis did not reveal geotemporal clustering. mcr-9-positive isolates had a significantly higher number of median [range] antimicrobial resistance (AMR) genes (16 [4 to 22] versus 6 [2 to 15]; P < 0.001) than did mcr-9-negative isolates. Pangenome tests confirmed a significant association of mcr-9 detection with mobile genetic element and heavy metal resistance genes. Overall, the presence of mcr-9 was not associated with significant changes in colistin resistance or clinical outcomes, but continued genomic surveillance to monitor for emergence of AMR genes is warranted. IMPORTANCE Colistin is a last-resort antibiotic for multidrug-resistant Gram-negative infections. A recently described allele of the mobile colistin resistance (mcr) gene family, designated mcr-9, has been widely reported among Enterobacterales species. However, its clinical and public health significance remains unclear. We compared characteristics and outcomes of mcr-9-positive and -negative CRE cases. All cases were acquired in the health care setting and associated with a high rate of mortality. The presence of mcr-9 was not associated with significant changes in colistin resistance, heteroresistance, or inducible resistance but was associated with resistance to other antimicrobials and antimicrobial resistance (AMR), virulence, and heavy metal resistance (HMR) genes. Overall, the presence of mcr-9 was not associated with significant phenotypic changes or clinical outcomes. However, given the increase in AMR and HMR gene content and potential clinical impact, continued genomic surveillance of multidrug-resistant organisms to monitor for emergence of AMR genes is warranted.

Haemophagocytic lymphohistiocytosis associated with bartonella peliosis hepatis following kidney transplantation in a patient with HIV.

Bacillary peliosis hepatis is a well recognised manifestation of disseminated Bartonella henselae infection that can occur in immunocompromised individuals. Haemophagocytic lymphohistiocytosis is an immune-mediated condition with features that can overlap with a severe primary infection such as disseminated Bartonella spp infection. We report a case of bacillary peliosis hepatis and secondary haemophagocytic lymphohistiocytosis due to disseminated Bartonella spp infection in a kidney-transplant recipient with well controlled HIV. The patient reported 2 weeks of fever and abdominal pain and was found to have hepatomegaly. He recalled exposure to a sick dog but reported no cat exposures. Laboratory evaluation was notable for pancytopenia and cholestatic injury. The patient met more than five of eight clinical criteria for haemophagocytic lymphohistiocytosis. Pathology review of a bone marrow core biopsy identified haemophagocytosis. A transjugular liver biopsy was done, and histopathology review identified peliosis hepatis. Warthin-Starry staining of the bone marrow showed pleiomorphic coccobacillary organisms. The B henselae IgG titre was 1:512, and Bartonella-specific DNA targets were detected by peripheral blood PCR. Treatment with doxycycline, increased prednisone, and pausing the mycophenolate component of his transplant immunosuppression regimen resulted in an excellent clinical response. Secondary haemophagocytic lymphohistiocytosis can be difficult to distinguish from severe systemic infection. A high index of suspicion can support the diagnosis of systemic Bartonella spp infection in those who present with haemophagocytic lymphohistiocytosis, especially in patients with hepatomegaly, immunosuppression, and germane animal exposures.

Fecal Microbiota Transplantation Donor Screening Updates and Research Gaps for Solid Organ Transplant Recipients.

In this review, we discuss stool donor screening considerations to mitigate potential risks of pathogen transmission through fecal microbiota transplant (FMT) in solid organ transplant (SOT) recipients. SOT recipients have a higher risk for Clostridioides difficile infection (CDI) and are more likely to have severe CDI. FMT has been shown to be a valuable tool in the treatment of recurrent CDI (RCDI); however, guidelines for screening for opportunistic infections transmitted through FMT are underdeveloped. We review reported adverse effects of FMT as they pertain to an immunocompromised population and discuss the current understanding and recommendations for screening found in the literature while noting gaps in research. We conclude that while FMT is being performed in the SOT population, typically with positive results, there remain many unanswered questions which may have major safety implications and warrant further study.

Microbial metabolite delta-valerobetaine is a diet-dependent obesogen.

Obesity and obesity-related metabolic disorders are linked to the intestinal microbiome. However, the causality of changes in the microbiome-host interaction affecting energy metabolism remains controversial. Here, we show the microbiome-derived metabolite δ-valerobetaine (VB) is a diet-dependent obesogen that is increased with phenotypic obesity and is correlated with visceral adipose tissue mass in humans. VB is absent in germ-free mice and their mitochondria but present in ex-germ-free conventionalized mice and their mitochondria. Mechanistic studies in vivo and in vitro show VB is produced by diverse bacterial species and inhibits mitochondrial fatty acid oxidation through decreasing cellular carnitine and mitochondrial long-chain acyl-coenzyme As. VB administration to germ-free and conventional mice increases visceral fat mass and exacerbates hepatic steatosis with a western diet but not control diet. Thus, VB provides a molecular target to understand and potentially manage microbiome-host symbiosis or dysbiosis in diet-dependent obesity.

Large scale enzyme based xenobiotic identification for exposomics.

Advances in genomics have revealed many of the genetic underpinnings of human disease, but exposomics methods are currently inadequate to obtain a similar level of understanding of environmental contributions to human disease. Exposomics methods are limited by low abundance of xenobiotic metabolites and lack of authentic standards, which precludes identification using solely mass spectrometry-based criteria. Here, we develop and validate a method for enzymatic generation of xenobiotic metabolites for use with high-resolution mass spectrometry (HRMS) for chemical identification. Generated xenobiotic metabolites were used to confirm identities of respective metabolites in mice and human samples based upon accurate mass, retention time and co-occurrence with related xenobiotic metabolites. The results establish a generally applicable enzyme-based identification (EBI) for mass spectrometry identification of xenobiotic metabolites and could complement existing criteria for chemical identification.

Validation of High-Sensitivity Severe Acute Respiratory Syndrome Coronavirus 2 Testing for Stool-Toward the New Normal for Fecal Microbiota Transplantation.

INTRODUCTION: Mounting evidence demonstrates potential for fecal-oral transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The US Food and Drug Administration now requires SARS-CoV-2 testing of potential feces donors before the use of stool manufactured for fecal microbiota transplantation. We sought to develop and validate a high-sensitivity SARS-CoV-2 reverse transcriptase polymerase chain reaction (RT-PCR) procedure for testing stool specimens. METHODS: A modified extraction method was used with an RT-PCR assay adapted from the Centers for Disease Control and Prevention PCR protocol for respiratory specimens. Contrived specimens were created using pre-COVID-19 banked stool specimens and spiking in known concentrations of SARS-CoV-2-specific nucleic acid. The highest transcript concentration at which 2/2 or 1/2 SARS-CoV-2 targets were detected in 9/10 replicates was defined as the dual-target limit and single-target limit of detection, respectively. The clinical performance of the assay was evaluated with stool samples collected from 17 nasopharyngeal swab RT-PCR-positive patients and 14 nasopharyngeal RT-PCR-negative patients. RESULTS: The dual-target and single-target limit of detection were 56 copies/µL and 3 copies/µL, respectively. SARS-CoV-2 was detected at concentrations as low as 0.6 copies/µL. Clinical stool samples from known COVID-19-positive patients demonstrated the detection of SARS-CoV-2 in stool up to 29 days from symptom onset with a high agreement with nasopharyngeal swab tests (kappa statistic of 0.95, P value < 0.001). DISCUSSION: The described RT-PCR test is a sensitive and flexible approach for the detection of SARS-CoV-2 in stool specimens. We propose an integrated screening approach that incorporates this stool test to support continuation of fecal microbiota transplantation programs.

Clinical characteristics and outcomes of toxoplasmosis among transplant recipients at two US academic medical centers.

Toxoplasma gondii can cause severe opportunistic infection in immunocompromised individuals, but diagnosis is often delayed. We conducted a retrospective review of solid organ transplant (SOT) and hematopoietic stem cell transplant (HSCT) recipients with toxoplasmosis between 2002 and 2018 at two large US academic transplant centers. Patients were identified by ICD-9 or ICD-10 toxoplasmosis codes, positive Toxoplasma polymerase chain reaction test result, or pathologic diagnosis. Data were collected regarding transplant type, time from transplant to toxoplasmosis diagnosis, clinical and radiographic features, and mortality at 30 and 90 days. Twenty patients were identified: 10 HSCT recipients (80% allogeneic HSCT) and 10 SOT recipients (60% deceased donor renal transplants). Rejection among SOT recipients (70%) and graft-versus-host disease (GVHD) prophylaxis among HSCT recipients (50%) were frequent. Median time from transplant to toxoplasmosis diagnosis was longer for SOT than HSCT (1385 vs. 5 days, P-value .002). Clinical manifestations most commonly were encephalitis (65%), respiratory failure (40%), renal failure (40%), and distributive shock (40%). Cohort 30-day mortality was 45%, and 90-day mortality was 55%. Diagnosis was postmortem in 25% of the cohort. Further evaluation of toxoplasmosis screening is needed for noncardiac SOT recipients, HSCT recipients with GVHD, and periods of increased net immunosuppression.

Changes in treatment of community-onset Clostridioides difficile infection after release of updated guidelines, Atlanta, Georgia, 2018.

Updated Clostridioides difficile infection (CDI) guidelines published in 2018 recommend vancomycin as first-line treatment. Of 833 community-onset CDI cases in metropolitan Atlanta, Georgia in 2018, over half did not receive first-line treatment, although guideline adherence increased over the year. Second-line treatment was more common in patients treated in ambulatory settings.

Fecal Microbiota Transplantation Is Safe and Effective in Patients With Clostridioides difficile Infection and Cirrhosis.

BACKGROUND & AIMS: Clostridioides difficile infection (CDI) harms a large proportion of patients with cirrhosis. Fecal microbiota transplantation (FMT) is recommended for recurrent CDI, but its effects in patients with cirrhosis have not been established. We performed a multicenter observational study to evaluate the efficacy and safety of FMT for CDI in patients with cirrhosis. METHODS: We performed a retrospective study of 63 adults with cirrhosis (median model for end-stage liver disease score, 14.5; 24 patients with decompensated cirrhosis) who underwent FMT for CDI from January 2012 through November 2018 at 8 academic centers in the United States, Canada, and Italy. We collected data on patient demographics and characteristics of cirrhosis, CDI, and FMT from medical records and compared differences among patients with different severities of cirrhosis, and FMT successes vs failures at the 8-week follow-up evaluation. We also obtained data on adverse events (AEs) and severe AEs within 12 weeks of FMT. RESULTS: Patients underwent FMT for recurrent CDI (55 of 63; 87.3%), severe CDI (6 of 63; 9.5%), or fulminant CDI (2 of 63; 3.2%) primarily via colonoscopy (59 of 63; 93.7%) as outpatients (47 of 63; 76.8%). FMT success was achieved for 54 patients (85.7%). Among FMT failures, a higher proportion used non-CDI antibiotics at the time of FMT (44.4% vs 5.6%; P < .001), had Child-Pugh scores of B or C (100% vs 37.7%; P < .001), used probiotics (77.8% vs 24.1%; P = .003), had pseudomembranes (22.2% vs 0; P = .018), and underwent FMT as inpatients (45.5% vs 19%; P = .039), compared with FMT successes. In multivariable analysis, use of non-CDI antibiotics at the time of FMT (odds ratio, 17.43; 95% CI, 2.00-152.03; P = .01) and use of probiotics (odds ratio, 11.9; 95% CI, 1.81-78.3; P = .01) were associated with a greater risk of FMT failure. FMT-related AEs occurred in 33.3% of patients (21 of 63)-most were self-limited abdominal cramps or diarrhea. There were only 5 severe AEs that possibly were related to FMT; none involved infection or death. CONCLUSIONS: In a retrospective study, we found FMT to be safe and effective for the treatment of CDI in patients with cirrhosis.

Current Capabilities of Gut Microbiome-Based Diagnostics and the Promise of Clinical Application.

There is increasing evidence for the importance of the gut microbiome in human health and disease. Traditional and modern technologies - from cell culture to next generation sequencing - have facilitated these advances in knowledge. Each of the tools employed in measuring the microbiome exhibits unique capabilities that may be leveraged for clinical diagnostics. However, much still needs to be done to standardize the language and metrics by which a microbiome is characterized. Here we review the capabilities of gut microbiome-based diagnostics, review selected examples, and discuss the outlook towards clinical application.

Critical Care Management of the Patient with Clostridioides difficile.

OBJECTIVES: To review published clinical evidence on management of Clostridioides difficile infection in critically ill patients. DATA SOURCES: We obtained relevant studies from a PubMed literature review and bibliographies of reviewed articles. STUDY SELECTION: We selected English-language studies addressing aspects of C. difficile infection relevant to critical care clinicians including epidemiology, risk factors, diagnosis, treatment, and prevention, with a focus on high-quality clinical evidence. DATA EXTRACTION: We reviewed potentially relevant studies and abstracted information on study design, methods, patient selection, and results of relevant studies. This is a synthetic (i.e., not systematic) review. DATA SYNTHESIS: C. difficile infection is the most common healthcare-associated infection in the United States. Antibiotics are the most significant C. difficile infection risk factor, and among antibiotics, cephalosporins, clindamycin, carbapenems, fluoroquinolones, and piperacillin-tazobactam confer the highest risk. Age, diabetes mellitus, inflammatory bowel disease, and end-stage renal disease are risk factors for C. difficile infection development and mortality. C. difficile infection diagnosis is based on testing appropriately selected patients with diarrhea or on clinical suspicion for patients with ileus. Patients with fulminant disease (C. difficile infection with hypotension, shock, ileus, or megacolon) should be treated with oral vancomycin and IV metronidazole, as well as rectal vancomycin in case of ileus. Patients who do not respond to initial therapy should be considered for fecal microbiota transplant or surgery. Proper infection prevention practices decrease C. difficile infection risk. CONCLUSIONS: Strong clinical evidence supports limiting antibiotics when possible to decrease C. difficile infection risk. For patients with fulminant C. difficile infection, oral vancomycin reduces mortality, and adjunctive therapies (including IV metronidazole) and interventions (including fecal microbiota transplant) may benefit select patients. Several important questions remain regarding fulminant C. difficile infection management, including which patients benefit from fecal microbiota transplant or surgery.