Infections in Solid-Organ Transplant Recipients

The American Association of Tissue Banks tissue donor screening for Mycobacterium tuberculosis-Recommended criteria and literature review

After two multistate outbreaks of allograft tissue-transmitted tuberculosis (TB) due to viable bone, evidence-based donor screening criteria were developed to decrease the risk of transmission to recipients. Exclusionary criteria, commentary, and references supporting the criteria are provided, based on literature search and expert opinion. Both exposure and reactivation risk factors were considered, either for absolute exclusion or for exclusion in combination with multiple risk factors. A criteria subset was devised for tissues containing viable cells. Risk factors for consideration included exposure (e.g., geographic birth and residence, travel, homelessness, incarceration, healthcare, and workplace) and reactivation (e.g., kidney disease, liver disease, history of transplantation, immunosuppressive medications, and age). Additional donor considerations include the possibility of sepsis and chronic illness. Donor screening criteria represent minimal criteria for exclusion and do not completely exclude all possible donor TB risks. Additional measures to reduce transmission risk, such as donor and product testing, are discussed but not included in the recommendations. Careful donor evaluation is critical to tissue safety.

An Unexpectedly High Incidence of Invasive Fungal Diseases in Solid Organ Transplant Recipients Taking Belatacept for Organ Rejection Prophylaxis: A Single-Center Retrospective Cohort Study

Among solid organ transplant recipients taking belatacept, 15% developed invasive fungal diseases. The most common invasive fungal diseases were aspergillosis (56%) and candidiasis (22%). The infected cohort was more likely to receive basiliximab, undergo lung transplantation, or identify as White. Higher rates of aspergillosis were seen in this lung cohort than previously reported.

Mucormycosis during COVID-19 era: A retrospective assessment

In a retrospective view, this review examines the impact of mucormycosis on health workers and researchers during the COVID era. The diagnostic and treatment challenges arising from unestablished underlying pathology and limited case studies add strain to healthcare systems. Mucormycosis, caused by environmental molds, poses a significant threat to COVID-19 patients, particularly those with comorbidities and compromised immune systems. Due to a variety of infectious Mucorales causes and regionally related risk factors, the disease's incidence is rising globally. Data on mucormycosis remains scarce in many countries, highlighting the urgent need for more extensive research on its epidemiology and prevalence. This review explores the associations between COVID-19 disease and mucormycosis pathology, shedding light on potential future diagnostic techniques based on the fungal agent's biochemical components. Medications used in ICUs and for life support in ventilated patients have been reported, revealing the challenge of managing this dual onslaught. To develop more effective treatment strategies, it is crucial to identify novel pharmacological targets through "pragmatic" multicenter trials and registries. In the absence of positive mycology culture data, early clinical detection, prompt treatment, and tissue biopsy are essential to confirm the specific morphologic features of the fungal agent. This review delves into the history, pathogens, and pathogenesis of mucormycosis, its opportunistic nature in COVID or immunocompromised individuals, and the latest advancements in therapeutics. Additionally, it offers a forward-looking perspective on potential pharmacological targets for future drug development.

Epidemiology and Management of Infections in Liver Transplant Recipients

Background: Improvements in liver transplant (LT) outcomes are attributed to advances in surgical techniques, use of potent immunosuppressants, and rigorous pre-LT testing. Despite these improvements, post-LT infections remain the most common complication in this population. Bacteria constitute the most common infectious agents, while fungal and viral infections are also frequently encountered. Multi-drug-resistant bacterial infections develop because of polymicrobial overuse and prolonged hospital stays. Immediate post-LT infections are commonly caused by viruses. Conclusions: Appropriate vaccination, screening of both donor and recipients before LT and antiviral prophylaxis in high-risk individuals are recommended. Antimicrobial drug resistance is common in high-risk LT and associated with poor outcomes; epidemiology and management of these cases is discussed. Additionally, we also discuss the effect of coronavirus disease 2019 (COVID-19) infection and monkeypox in the LT population.

Third-party virus-specific T cells for the treatment of double-stranded DNA viral reactivation and posttransplant lymphoproliferative disease after solid organ transplant

Reactivation or primary infection with double-stranded DNA viruses is common in recipients of solid organ transplants (SOTs) and is associated with significant morbidity and mortality. Treatment with conventional antiviral medications is limited by toxicities, resistance, and a lack of effective options for adenovirus (ADV) and BK polyomavirus (BKPyV). Virus-specific T cells (VSTs) have been shown to be an effective treatment for infections with ADV, BKPyV, cytomegalovirus (CMV), and Epstein-Barr virus (EBV). Most of these studies have been conducted in stem cell recipients, and no large studies have been published in the SOT population to date. In this study, we report on the outcome of quadrivalent third-party VST infusions in 98 recipients of SOTs in the context of an open-label phase 2 trial. The 98 patients received a total of 181 infusions, with a median of 2 infusions per patient. The overall response rate was 45% for BKPyV, 65% for cytomegalovirus, 68% for ADV, and 61% for Epstein-Barr virus. Twenty percent of patients with posttransplant lymphoproliferative disorder had a complete response and 40% of patients had a partial response. All the VST infusions were well tolerated. We conclude that VSTs are safe and effective in the treatment of viral infections in SOT recipients.

Barriers toward xenotransplantation in Arab World

Organ transplant is a crucial therapeutic strategy offering a life-saving and transformative medical intervention. It provides an opportunity to improve their quality of life and increase their lifespan. The shortage of organs remains a critical global challenge, leading to a prolonged waiting times for organ receivers, which contributes to an increase in morbidity and mortality rates. Hence, xenotransplantation offered a promising solution to the global shortage of organs through the use of animal organs, leading to an increase in donor availability, reducing waiting times, minimizing organ trafficking, improving genetic engineering advancements, and driving scientific innovation. Even though xenotransplantation has many benefits in the clinical setting, it has many barriers that are hindering its achievements and constraining its occurrence. Some barriers to xenotransplant are general, such as the immunological barrier, while others are specific to certain regions due to local causes. The Arab region exhibits disparities in clinical settings compared to the global context, marked by the huge economic crisis and a shortage of trained healthcare professionals. Considering the huge resources and advancements needed in the field of xenotransplantation, this review aims to explore the specific barriers toward xenotransplantation in the Arab countries, highlighting the challenges to overcome these barriers.

Solid organ transplantation and gut microbiota: a review of the potential immunomodulatory properties of short-chain fatty acids in graft maintenance

Transplantation is the treatment of choice for several end-stage organ defects: it considerably improves patient survival and quality of life. However, post-transplant recipients may experience episodes of rejection that can favor or ultimately lead to graft loss. Graft maintenance requires a complex and life-long immunosuppressive treatment. Different immunosuppressive drugs (i.e., calcineurin inhibitors, glucocorticoids, biological immunosuppressive agents, mammalian target of rapamycin inhibitors, and antiproliferative or antimetabolic agents) are used in combination to mitigate the immune response against the allograft. Unfortunately, the use of these antirejection agents may lead to opportunistic infections, metabolic (e.g., post-transplant diabetes mellitus) or cardiovascular (e.g., arterial hypertension) disorders, cancer (e.g., non-Hodgkin lymphoma) and other adverse effects. Lately, immunosuppressive drugs have also been associated with gut microbiome alterations, known as dysbiosis, and were shown to affect gut microbiota-derived short-chain fatty acids (SCFA) production. SCFA play a key immunomodulatory role in physiological conditions, and their impairment in transplant patients could partly counterbalance the effect of immunosuppressive drugs leading to the activation of deleterious pathways and graft rejection. In this review, we will first present an overview of the mechanisms of graft rejection that are prevented by the immunosuppressive protocol. Next, we will explain the dynamic changes of the gut microbiota during transplantation, focusing on SCFA. Finally, we will describe the known functions of SCFA in regulating immune-inflammatory reactions and discuss the impact of SCFA impairment in immunosuppressive drug treated patients.

Physical Exercise After Solid Organ Transplantation: A Cautionary Tale

An increasing body of randomized controlled trials suggests the safety of engaging in moderate to vigorous intensity exercise training following solid organ transplantation. Fueled by emerging sport events designed for transplant recipients and the ever-growing body of research highlighting the diverse health benefits of physical activity, transplant recipients are now increasingly participating in strenuous and occasionally competitive physical endeavors that largely surpass those evaluated in controlled research settings. This viewpoint article adopts a cautionary stance to counterbalance the prevalent one-sided optimistic perspective regarding posttransplant physical activity. While discussing methodological limitations, we explore plausible adverse impacts on the cardiovascular, immunological, and musculoskeletal systems. We also examine the physiological consequences of exercising in the heat, at high altitude, and in areas with high air pollution. Risks associated with employing performance-enhancing strategies and the conceivable psychological implications regarding physical activity as a tribute to the 'gift of life' are discussed. With a deliberate focus on the potential adverse outcomes of strenuous posttransplant physical activity, this viewpoint aims to restore a balanced dialogue on our comprehension of both beneficial and potentially detrimental outcomes of physical activity that ultimately underscores the imperative of well-informed decision-making and tailored exercise regimens in the realm of posttransplant care.

Detrimental impact of immunosuppressive burden on clinical course in patients with Cytomegalovirus infection after liver transplantation

INTRODUCTION

Cytomegalovirus (CMV)-infection and reactivation remain a relevant complication after liver transplantation (LT). The recipient and donor serum CMV-IgG-status has been established for risk stratification when choosing various pharmaceutical regimens for CMV-prophylaxis in the last two decades. However, factors influencing course of CMV-infection in LT remain largely unknown. In this study, the impact of immunosuppressive regimen was examined in a large cohort of patients.

METHODS

All patients that underwent primary LT between 2006 and 2018 at the Charité-Universitaetsmedizin, Berlin, were included. Clinical course as well as histological and laboratory findings of patients were analyzed our prospectively maintained database. Univariate and multivariate regression analysis for impact of variables on CMV-occurrence was conducted, and survival was examined using Kaplan-Meier analysis.

RESULTS

Overall, 867 patients were included in the final analysis. CMV-infection was diagnosed in 325 (37.5%) patients after transplantation. Significantly improved overall survival was observed in these patients (Log rank = 0.03). As shown by correlation and regression tree classification and regression tree analysis, the recipient/donor CMV-IgG-status with either positivity had the largest influence on CMV-occurrence. Analysis of immunosuppressive burden did not reveal statistical impact on CMV-infection, but statistically significant inverse correlation of cumulative tacrolimus trough levels and survival was found (Log rank < .001). Multivariate analysis confirmed these findings (p = .02).

DISCUSSION

CMV-infection remains of clinical importance after LT. Undergone CMV-infection of either recipient or donor requires prophylactic treatment. Additionally, we found a highly significant, dosage-dependent impact of immunosuppression (IS) on long-term outcomes for these patients, underlying the importance of minimization of IS in liver transplant recipients.

A metagenomic prospective cohort study on gut microbiome composition and clinical infection in small bowel transplantation

Two-thirds of small-bowel transplantation (SBT) recipients develop bacteremia, with the majority of infections occurring within 3 months post-transplant. Sepsis-related mortality occurs in 31% of patients and is commonly caused by bacteria of gut origin, which are thought to translocate across the implanted organ. Serial post-transplant surveillance endoscopies provide an opportunity to study whether the composition of the ileal and colonic microbiota can predict the emergence as well as the pathogen of subsequent clinical infections in the SBT patient population. Five participants serially underwent aspiration of ileal and colonic bowel effluents at transplantation and during follow-up endoscopy either until death or for up to 3 months post-SBT. We performed whole-metagenome sequencing (WMS) of 40 bowel effluent samples and compared the results with clinical infection episodes. Microbiome composition was concordant between participants and timepoint-matched ileal and colonic samples. Four out of five (4/5) participants had clinically significant infections thought to be of gut origin. Bacterial translocation from the gut was observed in 3/5 patients with bacterial infectious etiologies. In all three cases, the pathogens had demonstrably colonized the gut between 1-10 days prior to invasive clinical infection. Recipients with better outcomes received donor grafts with higher alpha diversity. There was an increase in the number of antimicrobial resistance genes associated with longer hospital stay for all participants. This metagenomic study provides preliminary evidence to support the pathogen translocation hypothesis of gut-origin sepsis in the SBT cohort. Ileal and colonic microbiome compositions were concordant; therefore, fecal metagenomic analysis could be a useful surveillance tool for impeding infection with specific gut-residing pathogens.

Non-meningeal, non-pulmonary cryptococcosis with limited posterior uveitis in a kidney organ transplant recipient with antibody-mediated rejection: a case report

BACKGROUND

Cryptococcosis is one of the most frequent fungal eye infections in patients with immunosuppression. Currently, treatment approaches for non-meningeal, non-pulmonary cryptococcosis are based on those used for cryptococcal meningitis or pneumonia.

CASE PRESENTATION

We present a rare case of non-meningeal, non-pulmonary cryptococcosis with clinical manifestations limited to one eye of a cadaveric kidney transplant recipient with chronic-active antibody-mediated rejection. Typical manifestations, diagnosis, and treatments, including antifungal therapies, adjunctive therapies, and immunosuppression reduction, are discussed. After timely diagnosis and treatment, her visual acuity recovered to baseline without recurrence or sequelae of cryptococcosis.

CONCLUSIONS

Clinicians should be aware of rare presentations of fungal infections, especially when a kidney transplant recipient with rejection has been treated with intensive immunosuppressants. Early diagnosis with individualized therapies may have a favorable prognosis.

Invasive Pulmonary Aspergillosis After Sars-CoV-2 Infection as Limitation of Contemporary Transplantology: A Case Report

Invasive fungal infections are uncommon in pediatric heart transplant recipients. Risk and mortality are highest in the first 6 months post-transplant, especially in patients with previous surgery and those requiring mechanical support. There is a possibility that prior SARS-CoV-2 infection may cause a more severe course of pulmonary aspergillosis, especially in immunosuppressed individuals. This report describes a female patient, eight years of age, who was admitted to the pediatric cardiac surgery department with symptoms of end-stage heart failure in urgent need of mechanical circulatory support (MCS). A left ventricular assist device (LVAD) was implanted as a bridge to transplantation. During over a year on the waiting list, LVAD was replaced twice due to the presence of fibrin on the inlet valve. While staying in the ward, the patient underwent SARS-CoV-2 infection. An orthotopic heart transplant was successfully performed after 372 days of MCS with LVAD. One month after transplantation, the girl developed severe pulmonary aspergillosis complicated by sudden cardiac arrest and implantation of venovenous extracorporeal membrane oxygenation (VV ECMO) used for 25 days. Unfortunately, a few days after weaning from VV ECMO, the patient died due to intracerebral bleeding.

Human cytomegalovirus and Epstein-Barr virus infections occurring early after transplantation are risk factors for antibody-mediated rejection in heart transplant recipients

Background

Antibody-mediated rejection (AMR) is a serious complication affecting the survival of patients receiving transplantation. Human cytomegalovirus (CMV) and Epstein-Barr virus (EBV) are common viral infections that occur after transplantation, frequently emerging as viral reactivation in donor grafts or transplant recipients. The present study aimed to investigate the association between CMV and EBV infections and early-onset AMR.

Materials and methods

This study was conducted at the Heart Transplantation Center of Padova General Hospital and included a cohort of 47 heart transplant recipients (HTxs), including 24 HTxs diagnosed with AMR and 23 control HTxs with no episodes of AMR. Only early cases of CMV and/or EBV infections (1-90 days after transplantation) were considered. Fisher's exact test and logistic regression analysis were used to statistically analyze the correlation and association between AMR and CMV or EBV infection.

Results

We observed a positive statistical association between CMV and EBV infections (two-sided Fisher's exact test, p = 0.0136) and between EBV infection and AMR (two-sided Fisher's exact test, p = 0.0034). Logistic regression analysis revealed a direct statistical association between CMV and EBV infections and AMR risk (p = 0.037 and 0.006 and odds ratio = 1.72 and 2.19, respectively). AMR occurrence was associated with increased viral loads of both CMV and EBV early after transplantation.

Discussion

These findings suggest the role of CMV and EBV infections as relevant risk factors for AMR in HTxs for the first time.

Mechanisms and strategies to promote cardiac xenotransplantation

End stage heart failure is a terminal disease, and the only curative therapy is orthotopic heart transplantation. Due to limited organ availability, alternative strategies have received intense interest for treatment of patients with advanced heart failure. Recent studies using gene-edited porcine organs suggest that cardiac xenotransplantation may provide a future source of organs. In this review, we highlight the historical milestones for cardiac xenotransplantation and the gene editing strategies designed to overcome immunological barriers, which have culminated in a recent cardiac pig-to-human xenotransplant. We also discuss recent results of studies on the engineering of human-porcine chimeric organs that may provide an alternative and complementary strategy to overcome some of the major immunological barriers to producing a new source of transplantable organs.

Vaccination Against SARS-CoV-2 in Lung Transplant Recipients: Immunogenicity, Efficacy and Safety

Lung transplant (LuTx) recipients are considered to be at higher risk of developing serious illness from COVID-19. COVID-19 vaccines were shown in randomized clinical trials to substantially reduce the severity of COVID-19, however, patients receiving immunosuppressants were excluded from these trials. Observational studies report a proportion of solid organ transplant (SOT) recipients being able to mount sufficient titers of SARS-CoV-2 specific IgG antibodies, however, other studies demonstrate that more than 90% of the SOT recipients elicit neither humoral nor cellular immune response after vaccination. Currently, the third booster dose of the COVID-19 vaccines was shown to elicit strong immune responses and may, thus, represent a potent tool in the prevention of severe COVID-19 infection in SOT recipients, including patients after lung transplantation. To address the main challenges of SARS-CoV-2 vaccination in LuTx recipients in the era of COVID-19, we have closely collected all available data on the immunogenicity, efficacy and safety of COVID-19 vaccines in LuTx recipients.

COVID-19 infection in pediatric solid organ transplant patients

BACKGROUND

Adult SOT recipients with COVID-19 have higher mortality rates when compared to general population. There is paucity of data on outcomes in pediatric SOT recipients.

METHODS

This is a cross-sectional study investigating the prevalence of COVID-19 infection and outcomes in pediatric SOT (heart, liver, and kidney) recipients. We extracted demographic and clinical characteristics and COVID-19 testing (PCR or [Ab] test) results from medical records. Clinical characteristics were compared between patients who were positive for COVID-19 (PCR or Ab) and those who did not, using Mann-Whitney, Student's t test, or chi-square test. p value <.05 was statistically significant.

RESULTS

A total of 108 SOT recipients with a median age of 13.1 (8.4, 17.8) years and median 4.2 (2.7, 7.9) years from transplant were checked for COVID-19 via a PCR or Ab test. A positive PCR was confirmed in 10 patients (9.3%), while 12 patients (11.1%) were positive for COVID-19 Ab. The patients who tested positive in our cohort were 9/50 (18%) heart, 6/68 (8.8%) kidney, and 7/50 (14%) liver transplant recipients. There were no differences in the clinical characteristics between patients with and without COVID-19 infection. All patients were either asymptomatic (50%) or had self-limiting symptoms. No changes were made to the immunosuppressive regimen. Only one patient was hospitalized and none had an oxygen requirement.

CONCLUSIONS

In our cohort of pediatric SOT recipients, COVID-19 infection was asymptomatic or mild. This data may aid clinicians in counseling patients and families in this increased-risk population.

Prevalence of Multidrug-Resistant Klebsiella pneumoniae Clinical Isolates in Nepal

Background

Multidrug-resistant Klebsiella pneumoniae (MDR-KP) are becoming increasingly common over the world. The focus of this research was to get a quantitative assessment of K. pneumoniae and their multidrug resistance (MDR) profile in Nepal.

Methods

Three electronic databases: PubMed, Google Scholar, and Research4Life were used to search publications specifying K. pneumoniae infections and/or their MDR status from January 2015 to October 2021. Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines was followed for the review, and R language 4.1.1 was used for analysis. Depending upon heterogeneity of data, we used random model for pooled data to examine the prevalence of the organism and the multidrug resistance.

Results

Evaluation included 16 studies, and the pooled estimation of K. pneumoniae in total clinical samples was 3% (95% CI; 0.01–0.05). In the meta-analysis, 14 studies were combined for determining the prevalence of K. pneumoniae in total positive clinical isolates which was 16% (95% CI: 0.11–0.20), while from 12 research studies, MDR status in the pathogen was found to be 64% (95% CI, 0.53–0.74).

Conclusion

The MDR status of K. pneumoniae as well as the prevalence of the bacteria in Nepal was analyzed which showed alarming situation about administration of antibiotics and indicated choosing and developing reliable antibiotic strategies.

Noninfectious and Infectious Complications and Their Related Characteristics in Heart Transplant Recipients at a National Institute

OBJECTIVES

Complications, which affect the morbidity and mortality of patients after heart transplant, can be divided into infectious and noninfections com-plications. Here, we analyzed both infectious and noninfectious complications and their relation to clinical, laboratory, and surgical characteristics in a Latin American heart transplant population.

MATERIALS AND METHODS

Data were obtained from records of 35 heart transplant patients in the period from 2010 to 2015. Noninfectious and infectious complications were divided into 3 time intervals: within the first month, from month 2 to 6, and after month 6. Relations between complications and clinical, laboratory and surgical variables in different interval times were analyzed.

RESULTS

In our patient group, 70 infectious and 133 noninfectious complications were reported after heart transplant. Infectious complications occurred more often between months 2 and 6 after heart transplant, whereas noninfectious complications occurred more often during the first month. Bacteria were the most common microorganism, and acute graft rejection was the most common noninfectious complication. Moreover, infectious complications were statistically related to 5 factors at month 1 (intraoperative bleeding, normal postsurgery leukocyte level, mild malnutrition, severe malnutrition, and graft rejection), to 3 factors between months 2 and 6 (diabetes mellitus, stage 2 chronic kidney disease, and cryoprecipitate trans-fusions), and to 2 factors after month 6 (prothrombin time and psychologic diagnosis).

CONCLUSIONS

Our results demonstrated that noninfectious complications should be anticipated first in patients after heart transplant. In addition, there are characteristics associated with infectious complications that can be seen during a specific time period.

Morphology-Independent Virulence of Candida Species during Polymicrobial Intra-abdominal Infections with Staphylococcus aureus

Intra-abdominal polymicrobial infections cause significant morbidity and mortality. An experimental mouse model of Candida albicans-Staphylococcus aureus intra-abdominal infection (IAI) results in 100% mortality by 48 to 72 h postinoculation, while monomicrobial infections are avirulent. Mortality is associated with robust local and systemic inflammation without a requirement for C. albicans morphogenesis. However, the contribution of virulence factors coregulated during the yeast-to-hypha transition is unknown. This also raised the question of whether other Candida species that are unable to form hyphae are as virulent as C. albicans during polymicrobial IAI. Therefore, the purpose of this study was to evaluate the ability of non-albicans Candida (NAC) species with various morphologies and C. albicans transcription factor mutants (efg1/efg1 and cph1/cph1) to induce synergistic mortality and the accompanying inflammation. Results showed that S. aureus coinoculated with C. krusei or C. tropicalis was highly lethal, similar to C. albicans, while S. aureus-C. dubliniensis, S. aureus-C. parapsilosis, and S. aureus-C. glabrata coinoculations resulted in little to no mortality. Local and systemic interleukin-6 (IL-6) and prostaglandin E2 (PGE2) levels were significantly elevated during symptomatic and/or lethal coinfections, and hypothermia strongly correlated with mortality. Coinoculation with C. albicans strains deficient in the transcription factor Efg1 but not Cph1 reversed the lethal outcome. These results support previous findings and demonstrate that select Candida species, without reference to any morphological requirement, induce synergistic mortality, with IL-6 and PGE2 acting as key inflammatory factors. Mechanistically, signaling pathways controlled by Efg1 are critical for the ability of C. albicans to induce mortality from an intra-abdominal polymicrobial infection.