Editor's Note: Infection remains a major challenge for recipients of solid organ transplants (SOT), leading to serious risks of mortality and transplant failure. Previous research has primarily focused on the characteristics and prevention of infections within the first year post-surgery, with limited data on long-term infections beyond one year post-surgery. At the recent 34th European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Global 2024 Annual Meeting, a large-scale follow-up study from Switzerland reported that SOT recipients still face a high incidence of infections and disease burden beyond one year post-surgery. Professor ChunRong Ju from The First Affiliated Hospital of Guangzhou Medical University provides an introduction and commentary on this study as follows:Study Overview
Infection Burden During Long-Term Follow-Up of Solid Organ Transplant Recipients (Abstract No: O0150)
Background
Over the past three decades, significant progress has been made in solid organ transplantation, with increased graft survival rates and significantly extended survival periods for transplant recipients (SOTr). However, infection remains a major complication affecting SOTr survival. Previous studies have mainly focused on the impact of infections in the early postoperative period (≤12 months), with limited understanding of their long-term effects (>12 months post-surgery). The Swiss Transplant Cohort Study (STCS) aimed to investigate the epidemiological characteristics and disease burden of long-term (>12 months post-surgery) infections following transplantation.
Methods
This was a retrospective observational study, including all SOTr who underwent transplantation between May 1, 2008, and December 31, 2020. The STCS systematically registers over 95% of SOTr in Switzerland, including heart, liver, lung, kidney, and pancreas-kidney transplant recipients. The study collected clinical data related to infections, including the timing of infection occurrence, types of pathogens involved, and outcomes of infection events. The level of evidence for collected infection cases included both confirmed and clinically diagnosed infections. Pathogens causing infections included common clinical pathogens as well as rare pathogens such as bacteria, fungi, viruses, parasites, mycobacteria, and rare/uncommon pathogens.
Results
The study included a total of 4,378 SOTr (330 heart, 980 liver, 448 lung, 2,514 kidney, and 106 pancreas-kidney transplant recipients), with a median follow-up time of 6.3 years. Among them, 2,840 patients (64.9%) experienced at least one clinically relevant infection. Classified by organ transplant type, lung transplant recipients and pancreas-kidney transplant recipients had the highest incidence rates of long-term infections, at 1.45, 0.76, and 0.7 cases per 1000 transplant-days, respectively. Among 5,948 clinically relevant infections, 3,436 (57.8%) were bacterial, 2,366 (39.8%) were viral, 264 (4.4%) were fungal, and 52 (0.9%) were parasitic. Enterobacteriaceae bacteria and respiratory viruses were the most common pathogens. Only 34 cases of opportunistic infections occurred. Viruses were the main pathogens causing infections in heart and lung transplant recipients, while bacteria were the main pathogens causing infections in kidney, liver, and pancreas-kidney transplant recipients. These infection incidence rates remained consistently high throughout the entire study observation period.
Conclusion
The data from this study provide evidence of the continued high burden of long-term infectious diseases in solid organ transplant recipients.
Expert Commentary
In the field of solid organ transplantation (SOT), infection remains an “evergreen topic” and one of the most concerning postoperative complications due to its impact on the “life and death” of transplant recipients, leading to graft loss and threatening patient lives. Previous research has focused more on perioperative or early postoperative (within the first year) infections. For instance, surgical site infections (SSI) are common during the perioperative period, predominantly caused by multidrug-resistant bacteria. Beyond 2 to 3 months postoperatively, viral infections gradually become predominant, followed by various community-acquired or opportunistic infections, including bacterial community-acquired pneumonia (CAP) caused by Enterobacteriaceae bacteria such as Streptococcus pneumoniae, Haemophilus influenzae, Klebsiella pneumoniae, and atypical pathogens, as well as viral pneumonia caused by coronaviruses, adenoviruses, influenza viruses, parainfluenza viruses, and opportunistic infections such as cytomegalovirus (CMV) and Pneumocystis jirovecii pneumonia.
Infections within the first year post-transplantation are one of the most common causes of mortality and the most common postoperative complications for SOT recipients. However, after the first year, with the rebuilding of the transplant recipient’s immune balance and the reduction in the intensity of immunosuppression, the incidence of infections significantly decreases. Therefore, there has been little focus from scholars on infections occurring beyond one year post-transplantation. This large-scale, long-term follow-up study from Switzerland [1] summarized the epidemiological characteristics and disease burden of long-term infections in SOT recipients, providing a fresh perspective on observing infections post-SOT.
From the study results, two main points should be emphasized. Firstly, the long-term infection risk or burden for SOT recipients remains high, with 64.9% of patients experiencing at least one clinically relevant infection. Although the study did not provide comparative data on infection disease burden with the general population, it is important to note that for immunosuppressed populations like SOT recipients, each infection could potentially result in a “disastrous blow.” This study observed consistently high incidence rates of infectious diseases throughout the entire follow-up period.
Secondly, among the 4,378 enrolled SOT recipients, 5,948 infections were observed, indicating that patients can experience multiple infections, and the cumulative incidence of infections increases with postoperative time. Among all SOTr, lung transplant recipients and pancreas-kidney transplant recipients had the highest incidence rates of long-term infections. The study revealed that bacteria (57.8%) were the leading infectious pathogens overall, followed by viruses (39.8%), fungi, and parasites. Enterobacteriaceae bacteria and respiratory viruses were the most common. However, for thoracic organ transplant recipients such as lung, heart, and heart-lung transplant recipients, viral infections were most common, while for abdominal organ transplants such as liver, kidney, and pancreas-kidney transplants, bacterial infections were common. These infection characteristics provide valuable epidemiological reference for the prevention and treatment strategies of long-term infections in SOT recipients.
In conclusion, this study provides a new perspective for understanding the infection risk of SOT recipients: from primarily observing early infections within the first year post-transplantation to long-term infections beyond one year post-transplantation. After the first year post-transplantation, SOT recipients enter a relatively stable period in terms of immune status and transplant organ function, with a decreased risk of infection compared to the early postoperative period, but the risk of infection still persists. The data from this large-scale survey from Switzerland, with its long observation period and comprehensive epidemiological data, show the characteristics of long-term infections post-SOT, including infection sites, pathogens, and the incidence among recipients of different organ transplants, providing valuable reference for the diagnosis and treatment strategies of long-term infections in SOT recipients.
Professor ChunRong Ju
First Affiliated Hospital of Guangzhou Medical University
Professor, Chief Physician, PhD Supervisor, Postdoctoral Cooperative Supervisor
Deputy Chair, Fourth Committee of Organ Transplantation Branch, Guangdong Medical Association
Chair, Immunodeficiency Special Committee, Guangdong Provincial Primary Medical Association
Deputy Chair, Youth Committee of Respiratory Diseases Branch, Guangdong Provincial Medical Association
Member, Lung Transplantation Group, Organ Transplantation Branch, Chinese Medical Association
Member, Perioperative Group, Organ Transplantation Branch, Chinese Medical Association
Quality Control Member, China Lung Transplantation Quality Control Center, National Health Commission
Deputy Leader, Internal Medicine Quality Control Committee, China Lung Transplantation Quality Control Center, National Health Commission
Member, Organ Recipient Health Management Committee, China Organ Transplantation Development Foundation
Standing Committee Member, Heart-Lung Transplantation Professional Committee, Guangdong Provincial Chest Diseases Society
Deputy Chair, Diffuse Parenchymal Lung Disease Professional Committee, Guangdong Provincial Chest Diseases Society
Member, Critical Illness and Infection Group, Guangdong Provincial Medical Association
Visiting Scholar, Organ Transplantation Center, University of Toronto, Canada
One of the First Batch of Leading Medical Young Talents in Guangdong Province
