Infections Connected with Organ and Tissue Transplantation

Organ transplantation (or grafting) amongst humans has developed over the past 70 years (Giwa et al. 2017). The first successful transplantation of the human kidney between identical twins was performed by dr. Joseph E. Murray in 1954 (Merrill et al. 1956). In 1990, Murray and E. Donnall Thomas were awarded with Nobel Prize in Physiology or Medicine for “their discoveries that have enabled the development of organ and cell transplantation into a method for the treatment of human disease” (The Nobel Prize, 1990). Currently, transplantation is the only effective therapy for patients with end-stage disease. So, transplants can save lives, but they can also restore function in patients with vital organ failure, thus improving their quality of life. Several factors are responsible for therapeutic success: selection of the right donor with a high-quality and efficacious organ; preservation of the organ to ensure it is in a good condition for transplantation; ensuring there is enough time to organize staff, facilities, and equipment, and to perform the tests and the actual procedure; appropriate immunosuppressive medication; and post-transplant care of the organ recipient (Jing et al. 2018).

European Committee (Partial Agreement) on Organ Transplantation of the Council of Europe developed special guide for specialists, intended to ensure the quality and safety of the donation and transplantation of organs, tissues and cells as well as technical guidance to ensure the safety and quality of human organs intended for transplantation (European Committee (Partial Agreement) on Organ Transplantation of the CE, Guide 2022). The chapter 8 of this guide draws attention to risk of transmission of microbial diseases, especially viral infections. The issues related to infections of people – potential organ donors, are also discussed. Moreover attention is paid to geographic distribution, endemic zones and risks of infectious diseases, that can be transmitted by solid organ transplantation.

Considering the data collected during the collaboration between the World Health Organization (WHO) and the Spanish Transplant Organization (Organización Nacional de Transplantes [ONT]), the most frequently transplanted solid organs (grafts) regardless of geographical region, are, in order: kidney, liver, heart, lung and pancreas (ONT-WHO Global Observatory on Donation and Transplantation, 2022). Over 150,000 these organs were transplanted in 2022 (Table I). According to Finger et al. (2023), the percentage of patients from the United States who survived with an implanted organ for 1 and 5 years is 90.9% and 78.6%, respectively, for heart transplants; 86.7% and 47.3%, respectively, for a single lung transplant; 87.7% and 58.6%, respectively, for a double-lung transplant; 80.9% and 50.2%, respectively, for a heart-lung transplant; 92.3% and 83.3%, respectively, for a liver transplant from a living donor; 91.2% and 75%, respectively, for a liver transplant from a deceased donor; 98.8% and 92.1%, respectively, for a kidney transplant from a living donor; 96.3% and 83.3%, respectively, for a kidney transplant from a deceased donor; and 90.9% and 79.6%, respectively, for a pancreas transplant. In addition to the above mentioned solid organs, small bowel, eyes and cornea, bones, and soft tissues/skin called vascularized composite allotransplant, are also grafted.

The aim of this review is to draw attention to the infections of organ recipients and to recognize the severity of the microbiological problem connected with the use of preservation fluid (PF) for organs before transplantation. PF contains substances that protect cells against degradation, but does not contain antimicrobial agents. Thus, it is interesting to investigate how often infections occur in organ recipients due to contaminated PF. Attention should also be paid to latent infections, mainly viruses, that develop in immunosuppressed organ recipients, as well as to parasites that may be transmitted along with the transplanted organ and that may cause infection in the organ recipient. This review provides information for microbiologists working in transplantation units, as well as medical staff directly involved in the transplantation process.

There are four types of transplants based on the genetic relationship between the donor and the recipient: xenotransplant, where the donor is an animal and the recipient is a human; allotransplant, where the donor and recipient are from the same species; isotransplant, where the donor and recipient are identical twins; and autotransplant, where the donor and recipient are the same person. The chance of organ rejection decreases in the order given above (Oli et al. 2022). Transplanted organs, either the whole organ or segments/fragments, may be recovered from either living or deceased donors (for the latter, donors who have been declared brain dead or after cardiac death). Living donor donation often takes place between related people; however, there are also anonymous and altruistic donors.

In the initial period of transplantation, organs were preserved at room temperature with the use of blood-based perfusates. Chemically defined cell culture media were developed in the 1950s (Jing et al. 2018). The use of blood-based perfusates versus chemically defined preservative solutions is still a concern. There are unfavorable phenomena related to blood, including hemolysis, thrombus formation, immune-mediated responses, and blood-borne infectious transmission, mainly of a viral origin (Jing et al. 2018). During the development of transplantology, researchers found that lowering the temperature of PF reduces biological deterioration of organs, attenuates ischemia/reperfusion-induced cell/tissue injury, and protects organs from damage. Cooling reduces cellular metabolism and the oxygen requirements. The aspects of cellular injury and microvascular dysfunction in the pathogenesis of ischemia/reperfusion during organ preservation have been discussed elsewhere (Petrenko et al. 2019: Datta et al. 2021). Renal preservation by ice cooling was first used during kidney transplantation (Calne et al. 1963).

Currently, there are two ways to preserve organs: static cold storage (0–8°C) and dynamic storage based on machine perfusion (Jing et al. 2018; Guibert et al. 2011). Using perfusion equipment, which provide enhanced nutrient and oxygen delivery, various procedures have been developed depending on the temperature (Jing et al. 2018; Petrenko et al. 2019): hypothermic machine perfusion (0–12°C), midthermic machine perfusion (13–24°C), subnormothermic machine perfusion (25–34°C), and normothermic machine perfusion (35–38°C). Besides, controlled oxygenated rewarming (8–20°C) has been used to preserve kidneys and livers. In this method, the perfusate temperature rises gradually to weaken ischemia/reperfusion injury (Jing et al. 2018). PF continuously pumped by machine perfusion systems through the organ (e.g., kidney) provides nutrients and oxygen, carries away toxic waste products, and delivers buffers that absorb metabolites produced by the organ (e.g., lactic acid and adenosine monophosphate). The use of an ultra-low temperature to protect tissues and organs has also been considered.

It should be underline, that PF in unopen containers must be sterile (European Pharmacopoeia 11, 2023, 2.6.1. Sterility). These preparations are prepared by specialized manufacturers that meet the requirements of Good Manufacturing Practice (GMP). The microbiological quality of these fluids should be similar to fluids used for cell culture.

Many chemically defined solutions that can replace blood have been evaluated and used to preserve tissues and organs before transplantation (Guibert et al. 2011; Latchana et al. 2015; Jing et al. 2018; Petrenko et al. 2019; Datta et al. 2021; Finger et al. 2023). However there is no consensus among transplantation centers as to which of PFs is the best (Salehi et al. 2018). The compositions of several PFs are listed in Table II. These solutions are intended to provide appropriate physiological and biochemical conditions, oxygenation, and temperature to ensure cell survival and to reduce damage associated with ischemia/reperfusion injury. The most known and frequently used PFs in solid organ transplantation are EC or Euro-EC (Collins et al. 1969) and UW (Belzer et al. 1968; Southard and Belzer 1995). Generally, PFs contain electrolytes, buffers, antioxidants, and pharmacological agents. Importantly, PFs do not contain antimicrobial agent, except for the modified UW liquid listed in Table II (Guibert et al. 2011), which contains penicillin G (200,000 IU/L). PFs can be differentiated based on the Na⁺/K⁺ ratio. High Na⁺ and low K⁺ concentrations correspond to extracellular solutions, whereas high K⁺ and low Na⁺ concentrations correspond to intracellular solutions, which are intended to prevent cellular edema by maintaining intracellular ion concentrations upon cold-induced dysfunction of Na⁺/K⁺ pumps (Jing et al. 2018; Datta et al. 2021).

Taking into account the risk of infection of the organ recipient through contaminated PF, it is recommended to perform a microbiological examination of a PF sample taken from the container in which the organ was stored just after removing the organ to transplantation process. The test should be performed in accordance with the procedures applicable in a given microbiological laboratory for clinical samples taken from the patient. Public Health England (PHE) in partnership with the NHS described in UK standards for microbiology investigations (UKSMIs) Document “Abdominal organ transport fluid testing” (UK Standards for Microbiology Investigations, B62, 2020). According to these recommendations, the sample of specimen from fluid surrounding the organ should be taken immediately after the organ has been lifted from the transport bag for implantation. Volume of transport fluid to submit for analysis differs depending on the size of organ being transplanted. A minimum of approximately 5% of the total volume in the organ transport bag should be used for analysis (ideally a minimum of 20 mL). PF fluid should be centrifuged at 1200 × g for 5 min. and spread on appropriate media such as blood agar, Sabouraud agar and CLED agar (for Enterobacterales). All cultured microorganisms should be identified to species level. A separate issue is transplantation of corneas, the most commonly transplanted human tissue (Fabre et al. 2021). Corneal disease is the second major cause of blindness worldwide (Li et al. 2019). Corneal transplantation, also known as keratoplasty, involves replacing part of the recipient’s corneal tissue with tissue taken from a deceased donor. The first recorded therapeutic corneal transplantation on a human, unfortunately unsuccessful, was reported in 1838; the first successful human corneal transplant was performed by Zirm in 1905 (Crawford et al. 2013). Currently, donor tissue is routinely retrieved by eye banks either through in situ excision of the cornea or enucleation of a complete eyeball. Of note, these tissues still carry ocular surface microbiota upon arrival at the eye bank, and these microorganisms may be a source of infection. Eye tissues are stored either in hypothermic storage at 4°C for 5–10 days (an approach mainly used in the United States) or in organ culture at 31–37°C for up to 35 days (an approach mainly used in Europe) (Li et al. 2019; Gibbons et al. 2020; Fabre et al. 2021). The mission, history, and tasks of the European Eye Bank Association and Eye Bank Association of America (EBAA) have been presented elsewhere (Jones et al. 2012; EBAA 2021).

In a systematic review, Gimenes et al. (2022) compared several specially developed corneal storage media with Optisol-GS, the most widely used medium to preserve corneas for transplantation. All of them contain antibiotics, most often gentamicin and streptomycin. However, considering the incidence of devastating fungal infection, most often caused by Candida sp., amphotericin and voriconazole have sometimes been added to Optisol-GS (Layer et al. 2014; Mistò et al. 2020; Gimenes et al. 2022). There are also objections to supplementation of hypothermic corneal storage media with amphotericin, mainly due to the high cost and low effectiveness of this antifungal chemotherapeutic at low concentrations (Tu 2021). On the other hand, Gibbons et al. (2020) concluded that the use of the fungicidal amphotericin B for endothelial keratoplasty was more cost-effective than the use of the fungistatic voriconazole or caspofungin. While the opinions are divided, cost-effectiveness also plays a role in developing treatments.

To minimize the risk of infections in organ recipients caused by microorganisms that contaminate tissues, a special monograph was introduced into the European Pharmacopoeia in 2023: “Microbiological Examination of Human Tissues” (Ph. Eur. 2023). An example of the content included in this source is a microbiological control strategy for cornea. This example was elaborated because the preservation of ocular tissue and corneal transplantation deserves special attention due to the large number of grafts performed (Chu 2000; Jones et al. 2012). In addition, to ensure long-term storage of corneas, Chaurasia et al. (2020) suggested their sterilization by gamma irradiation (17–23 kGy from a cobalt-60 source). This strategy effectively stabilizes tissue grafts and eradicates contaminating microorganisms, including viruses.

In addition to the above-mentioned preservation methods, cryopreservation has also been developed (Whaley et al. 2021). It requires freezing the tissue/organ to a temperature below 0°C to slow deterioration by reducing the rate of metabolism. Such preserved material, like bone marrow, blood components, and gametes, can be stored for many weeks (Datta et al. 2021; Ozgur et al. 2023). However, problems arise when large organs and other three-dimensional structures are cooled below 0°C, because ice crystals can form immediately inside cells and cause severe mechanic destruction. Cryoprotective agents (CPAs) are crucial for cryobiology (Elliott et al. 2017; Jang et al. 2017; Whaley et al. 2021). Solutions containing alcohols (e.g., methanol, ethanol, glycerol, ethylene glycol, and propylene glycol), sugars (e.g., trehalose, sucrose, mannitol, and raffinose), polymers (e.g., polyethylene glycol, dextrans, and hydroxyethyl starch), dimethyl sulfoxide, dimethyl acetamide, and glutamine, among other components, are commonly used for cryopreservation of microorganisms and cells. CPAs can mitigate cryoinjury caused by ice nucleation, crystal growth, and cellular dehydration during freezing, all of which influence post-thaw survival (Elliott et al. 2017; Ozgur et al. 2023). Considering the penetration of CPA into solid organs, it is necessary to use hypothermic perfusion with CPAs at a temperature of 10°C prior to cooling the material to -80°C (Elliott et al. 2017). Microorganisms that contaminate tissues or organs do not multiply at such a low temperature. Supercooling (to about -10°C) in the presence of CPAs largely protects cells against the negative impact of ice crystal formation (Ozgur et al. 2023). Experimental results concerning vitrification – rapid cooling to below -100°C to form a noncrystalline glassy phase in animal, rabbit, and rat organs (e.g., heart, liver, kidney), are promising (Ozgur et al. 2023; Berendsen et al. 2014), based on the successful cryopreservation of hepatocytes, pancreatic islets, gametes, and stern cells (Whaley et al. 2021). However, rewarming vitrified material and preserving functionality and viability are notable challenges. A thorough understanding of the chemical and biological processes behind freezing and thawing will be necessary for the future development of a safe and effective cryopreservation method (Weissenbacher et al. 2019).

There are a myriad of sources of infections in organ recipients (Oriol et al. 2019; European Committee (Partial Agreement) on Organ Transplantation of the CE 2022; Li et al. 2022; Manuel et al. 2023). Endogenous pathogens, mainly viruses and less often parasites, may be present in the transplanted organ and transmitted to the recipient. The donor might be unaware of their infection or be asymptomatic, especially when latent viruses become virulent in a recipient subjected to immunosuppression due to the risk of transplant rejection. Exogenous microorganisms in PF may occur during the procurement process – for example, they may come from the surface of the donor’s body or from the environment. Most often, infections in organ recipients occur due to unhygienic organ collection, improper handling and transport, and inappropriate preservation conditions, especially contamination of the PF used for perfusion and storage. Antibiotic therapy in recipients before transplantation reduces the risk of developing infection in case a contaminated organ is transplanted.

Besides, some potential organ recipients often travel abroad, mainly to Asian countries, to reduce costs and to shorten the waiting time for transplantation. In some geographic regions, there is limited medical and microbiological screening of donors. Furthermore, in countries where payment for organ donation is legal, donors typically come from lower socioeconomic areas where endemic infections such as tuberculosis and malaria may occur (Len et al. 2014).

Len et al. (2014) developed and proposed recommendations for screening donors and recipients prior to organ transplantation to minimize transmission of donor-derived infections. The authors considered latent and acute bacterial, fungal, viral, and protozoal infections. In addition, the Infectious Diseases Community of Practice of the American Society of Transplantation has published guidelines concerning screening of donors and candidate prior to solid organ transplantation (Malinis et al. 2019). Moreover, the online medical portal emedicine.medscape.com provides current information on transplantation of the kidney (Collins 2021), liver (Manzarbeitia and Arvelakis 2022), pancreas (Rao and Finger 2022), intestines (Andacoglu and Greenstein 2021), lung (Whitson 2022), and heart (Botta and Mancini 2023), as well as post-transplantation complications and infections accompanying the transplantation of these organs.

Although immunosuppressive therapies are involved at the time of transplantation, the early post-transplant period (up to 1 month) is notable for hospital-acquired infections, especially related to surgical procedures including implant placement and the use of medical devices like intravenous and urinary tract catheters. The intermediate post-transplant period (months 1–6) is the time where there is the greatest risk for opportunistic infections. In stable recipients, infections are less frequent 6 months after transplantation (Fishman 2017; Sawinski and Blumberg 2019). Transmission of infection during transplantation of solid organs grafts is uncommon but potentially life threating. Fishman (2017) provided a comprehensive overview of the epidemiology of infections during organ transplantation, diagnosis, and therapy. Regardless of whether infections are directly related to the process of organ transplantation, one should remember that these severely ill and immunosuppressed patients are also exposed to nosocomial pathogenic microorganisms in their environment. For this reason, some microorganisms isolated from infected patients may differ from microorganisms found in contaminated PF.

Microbiological contamination of PF is a potential source of post-transplantation infections and requires patients to be treated with antibiotics or antimicrobial chemotherapeutics. The most frequently isolated microorganisms from these fluids are staphylococci, Gram-negative rods, and Candida spp. strains (Sotiropoulos et al. 2018). An important issue that requires microbiological and clinical analysis is whether all isolated microorganisms should be treated as actual pathogens and antimicrobial therapy should be implemented in recipients (Manuel et al. 2023). Moreover, the protocols for screening organ or tissue donors for infectious risks are inconsistent and vary according to the type of graft, national standards, and the availability of the screening tests.

A number of publications have focused on PF contamination or infections in solid organ recipients. Mattner et al. (2008) investigated the extent to which bacterial and fungal donor organ contamination caused post-transplant nosocomial infections in solid organ transplant recipients. Out of 282 organ recipients (140 lung, 71 liver, 51 heart, and 16 heart-lung recipients), 150 (53.2%) received contaminated organs. The lung and heart-lung transplants were the most contaminated based on PF or organ swab microbiological examination. In the lung transplant group, 126 Grampositive bacteria, 102 Gram-negative rods, and 57 fungi were isolated, whereas in the heart-lung transplant group, 18 Gram-positive bacteria, 5 Gram-negative rods, and 6 fungi were cultured. Of note, polymicrobial contamination was frequent.

Colvara Mattana et al. (2011), analyzed 136 PF samples used to store kidneys and pancreas. The contamination rate of these samples was 27.9%, mainly by coagulase-negative staphylococci, Bacillus spp., and Enterococcus spp. (representing 55% of contaminated PF samples). The authors concluded that infections of the organ recipients were not associated with contaminated PF. Sotioropoulos et al. (2019) reviewed 19 studies published from 2000 to 2016 regarding bacterial and fungal contamination of PF samples used to store solid organs before transplantation. Of 5647 patients, 1428 (25.3%) had positive microbial cultures. The bacteremia data showed a wide range (0%–69%), which precluded the authors for drawing conclusions or making recommendations.

Peghin et al. (2024) recently described skin and soft tissue infections in solid organ transplants. The authors drew attention to the possibility of infections caused by staphylococci and streptococci, as well as microorganisms that are rare in such a situation, including Nocardia sp., Bartonella sp., and Mycobacteria. Some of these infections may be related to the patient’s hospital stay and the environmental contamination there.

Isabel Oriol together with a group of Spanish researchers (Oriol et al. 2016; Oriol et al. 2018; Oriol et al. 2019) have conducted multicenter investigations, systematic reviews, and meta-analysis on the impact of culture-positive PF on solid organ transplantation for several years. In one study, they found that 46 out of 50 liver grafts had been stored in contaminated PF, but only in 14 cases were there pathogenic microorganisms. They mainly isolated coagulasenegative staphylococci. There was no infection among the recipients (Oriol et al. 2016). The authors also emphasized that the examination of PF immediately before implantation has the greatest diagnostic value. In another large multicenter cohort study, out of 622 transplanted organs (362 kidneys, 166 livers, 51 lungs, 32 hearts, and 11 multiple organs) and PF samples, as many as 389 (62.5%) were microbiologically contaminated, but only one fourth of positive samples contained “high risk” pathogens; Staphylococcus aureus, Escherichia coli, Enterococcus faecalis, and Enterobacter cloacae dominated (Oriol et al. 2019). PF contamination could be directly linked to the development of infection in only five patients. The authors concluded that clinical monitoring of solid organ recipients infected with microorganisms present in contaminated PF, regardless of their species, is important to make the proper diagnosis and to determine whether the situation requires the treatment of infections associated with PF (Oriol et al. 2018). Yahav and Manuel (2019), in a commentary on the publication of Oriol (Oriol et al. 2019), and Yu et al. (2019) also called for an increase in evidence, especially in terms of precise characterization of contaminating microorganisms, to limit the use of antibiotics in the prevention and treatment of infections.

What is important, Cervera et al. (2014) described recommendations for the management of multi-drugresistant (MDR) bacteria in solid organ transplant patients, considering infections with methicillinresistant S. aureus (MRSA); vancomycin resistant enterococci; and extended-spectrum beta-lactamase (ESBL)-, AmpC-, and carbapenemase-producing Gram-negative rods. Recently, Pilmis et al. (2023) analyzed MDR Enterobacterales infections in the context of abdominal solid organ transplantation, paying attention to donor screening for gastrointestinal tract colonization by these MDR Gram-negative bacteria. The authors also considered the prevalence of bacterial infections, including those caused by MDR Gram-negative bacteria, in kidney and liver recipients. The prevalence of infections was up to 65%, and the prevalence of MDR pathogens was up to 20%. While Bodro et al. (2013) analyzed the outcomes of bacteremia caused by drug resistant Enterococcus faecium, S. aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and E. cloacae (ESKAPE pathogens) in solid organ transplant recipients. In the 6-year study, there were 276 bacteremia cases among 190 recipients, of which 54 (19.6%) cases were caused by drug-resistant ESKAPE strains. These strains were found in 24 kidney recipients, 21 liver recipients, and 9 heart recipients. Carbapenem- and quinolone-resistant P. aeruginosa strains predominated in the above recipient groups – 13, 9, and 5, respectively – followed by ESBL-producing K. pneumoniae −7, 3, and 1 cases respectively.

Complications related to organ and tissue transplantation and PF contamination are primarily caused by bacteria that grow aerobically. Anaerobic bacteria generally do not pose a significant threat to transplant recipients, with the exception of Clostridioides difficile, a common nosocomial pathogen in hospital wards that causes infections especially in immunocompromised patients, such as organ recipients. The American Society of Transplantation Infectious Diseases Community of Practice (Mullane et al. 2019) developed guidelines to address the prevention and management of C. difficile infections in solid organ transplant recipients. The incidence of C. difficile infections varies by the type and number or organs transplanted. The prevalence of these infections in the solid organ transplant population ranges from a low of 3.2% in the pancreatic transplant population to 12.7% in those receiving multiple organ transplants (Mullane et al. 2019). It should be mentioned that Audet et al. (2011) examined PF contamination in the context of liver transplantation. Apart from a number of aerobic bacteria (mainly coagulase-negative staphylococci), they isolated anaerobes, four strains of Propionibacterium sp., and a strain of Veillonella sp. These bacteria did not cause infection in organ recipients.

Bacterial infections are generally connected with organ storage and surgical procedures and are not latent in nature, with the exception of Mycobacterium spp. infections. Transplant recipients are immunocompromised and vulnerable to developing tuberculosis. There have been a number of cases of tuberculosis reactivation in recipients of organs contaminated with Mycobacterium tuberculosis (Sidhu et al. 2014; Abad et al. 2019; Nguyen Van et al. 2024; Hyun et al. 2024). Screening of latent tuberculosis infection in donors is the cornerstone of the tuberculosis preventive strategy in recipients (Malinis and Koff 2021).

The use of antibiotics to decontaminate grafts has been evaluated (Paolin et al. 2018). The authors examined bacterial contamination profiles of 11,129 tissue samples as allografts retrieved from multi-tissue donors. The tissues were incubated twice at 4°C for 24–28 hours in a decontamination solution containing ceftazidime (24 mg/L), lincomycin (120 mg/L), polymyxin B (100 mg/L), and vancomycin (50 mg/L). The samples were analyzed microbiologically. Immediately after tissue retrieval, 6130 (55%) of the samples were contaminated. Using subsequent decontamination, the number of bacteria decreased – to 1955 samples after the first decontamination step and to 113 samples after the second decontamination step. Coagulase-negative staphylococci were the dominant bacterial group.

Louart et al. (2019) drew some interesting conclusions when considering the risk of contamination of organ procurement in different locations. Their multivariate statistical analysis of 2535 grafts indicated that 285 (11%) were microbiologically contaminated, of which 20% were skin grafts, 12% were arterial grafts, 9% were heart valves, and 7% were corneal grafts. Regarding the location of organ retrieval, 47% were collected in standard operating rooms, 39% in dedicated non-operating rooms (hospital mortuaries), and 14% in intensive care units. The authors concluded that although standard operating rooms provide the best place to procure grafts, dedicated non-operating rooms led to a lower risk of tissue microbial contamination. This may be related to the fact that corneal samples, which constituted approximately 60% of the analyzed grafts, were mainly recovered from deceased patients stored in a cooled room. The authors reported that the percentage of contaminating microorganisms varied depending on the place of tissue collection. For tissues collected in standard operating rooms, 65.5% of the microbes were Gram-positive bacteria, 17.2% were Gram-negative rods, and 14.8% were fungi isolated. In dedicated non-operating rooms, 26.4% of the isolated microbes were Gram-positive bacteria, 39% were Gram-negative rods, and 20.7% were fungi. Finally, for the tissues collected in intensive care units, 64.3% of the microbes were Gram-positive bacteria, 24.3% were Gram-negative rods, and 5.7% were fungi (Louart et al. 2019).

In many cases, it is quite difficult to locate a proper organ donor. Sometimes, there is not enough time to find one and a patient qualified to receive a transplant dies. Kieslichova et al. (2019) presented a case report in which both kidneys, the liver, pancreatic islets, and the heart were transplanted to five organ recipients from a deceased patient with antibiotic-sensitive K. pneumoniae and E. coli in her sputum. Appropriate antibiotic prophylaxis and antibiotic therapy were administered to four of the five patients who developed ESBL-producing K. pneumoniae and ESBL-producing E. coli infections. It turned out that these strains were present in the transport medium in which the organs were stored during organ procurement. The two kidney recipients died, but the remaining three patients survived the operations with good graft function.

In addition to bacterial infections, organ recipients may experience fungal infections. Peghin et al. (2024) analyzed several skin and soft tissue fungal infections in solid organ transplant recipients. Infections in recipients were caused by strains from the following genera: Candida spp., Cryptococcus spp., Aspergillus spp., Mucor spp., Fusarium spp., Histoplasma spp., Blastomyces spp., and Coccidioides spp. It is extremely important to use appropriate diagnostic tests to detect the etiological factor of the infection. In addition, Sawinski and Blumberg (2019) reported that kidney transplant patients are at increased risk for opportunistic fungal infections, including Candida, Aspergillus, Cryptococcus, and Pneumocystis. Candidemia is most often an early post-transplant nosocomial infection of surgical drains or vascular access catheters. Candida infections may be observed in liver recipients with cholangitis, hematomas, or bile leaks (Fishman 2017). Invasive Aspergillus infections occur most often in debilitated or immunosuppressed organ recipients. Within 1-year after organ transplantation, opportunistic infections emerge, including by Pneumocystis jirovecii, which causes pneumonia, and by endemic fungi such as Histoplasma capsulatum, which causes Darling’s disease (Fishman 2017).

Contamination of PF with yeasts during solid organ recovery can lead to life-threatening complications in the recipients. Fungal infections constitute a significant clinical problem in liver and kidney recipients. Botterel et al. (2010) analyzed 650 PF samples collected during a 5-year period in terms of fungal contamination using standardized procedures for systematic mycological culture. The yeast contamination rate was 4.1% and 3.1% for liver and kidney transplants, respectively. Strains belonging to the following species were identified: C. albicans, Candida glabrata, Candida krusei, Candida tropicalis, Candida valida, Pichia etchelsii, and Rhodotorula sp. Audet et al. (2011) analyzed 91 PF samples used in liver transplantation and detected 4 C. albicans strains, 1 Aspergillus fumigatus strain, and 1 Saccharomyces sp. strain. Stern et al. (2022) analyzed the PF of 1248 hepatic and 1273 renal transplants. They found that fungal contamination in the PF of hepatic and renal grafts was 1.2% and 0.86%, respectively. Although the incidence of fungal contamination was low, contaminated PF was associated with high mortality of organ recipients. C. albicans was the most common organism (70.4%), followed by C. krusei and C. glabrata. The above observations are consistent with those reported by Levesque et al. (2015) in a 5-year multicenter study of PF contamination after liver transplantation. Among 2107 PF samples, 28 (1.33%) were contaminated with Candida strains, 64% of which were C. albicans. Eight recipients developed yeast-related complications and 1-year after transplantation, the mortality rate among this group of patients was 62.5%. Bachellier et al. (2014) mentioned C. albicans arteritis transmitted by PF after liver transplantation.

Ten years ago, the EBAA (Aldave et al. 2013) reported that from 2005 to 2010, the incidence of fungal infections after corneal transplantation showed an increasing trend. Thirty-one cases of culture-proven fungal keratitis (n = 14) and endophthalmitis (n = 17) were reported out of 221,664 corneal transplants performed using corneal tissue distributed by domestic eye banks.

Thareja et al. (2020) noticed that in post-keratoplasty infections, the main fungal pathogen is C. albicans, followed by C. glabrata. Besides, Alternaria sp. and Cladosporium sp. may also cause infections. Based on the findings, the authors proposed antifungal supplementation of PF to eliminate contaminated fungi. The arguments for and against supplementation of PF with voriconazole, caspofungin, amphotericin B, and betadine have been discussed. Malinis and Boucher (2019) provided recommendations regarding screening of solid organ donors for histoplasmosis, coccidioides, and cryptococcosis.

The laboratory serological tests to detect viral infections, especially latent ones, should be performed in both organ donors and recipients (Grossi 2018; Malinis and Boucher 2019; Sawinski and Blumberg 2019). The risk of infection for recipients may be associated with the following viruses: herpes viruses (e.g. human herpes virus [HHV]6, HHV7, and HHV8); Kaposi sarcoma herpesvirus; cytomegalovirus (CMV); herpes simplex virus (HSV); varicella zoster virus (VZV); Epstein-Barr virus (EBV); retroviruses, including human immunodeficiency virus (HIV) and human T cell lymphotropic virus-1 and 2; and hepatitis viruses, including hepatitis A virus (HAV), hepatitis B virus (HBV), hepatitis C virus (HCV), and hepatitis E virus (HEV). Other rare viruses may also pose a threat: West Nile virus, Chikungunya virus, Zika virus, dengue virus, lymphocytic choriomeningitis virus, and rabies virus (Fishman 2017; Peghin et al. 2024). Saad et al. (2020) analyzed infections in the first year after renal transplant and found that the most frequent viral infections were caused by CMV (21.8%) 31–180 days after transplantation.

The U.S. Public Health Service has published recommendations on how to reduce the risk for transmission of several viruses through solid organ transplantation (Jones et al. 2020). In 2021, the Centers for Disease Control and Prevention realized that this recommendation might be unnecessary for pediatric organ transplant candidates. Thus, a year later the guidelines were updated to specify that solid organ transplant candidates aged < 12 years at the time of transplantation who have received postnatal infectious disease testing are exempt from the recommendation for HIV, HBV, and HCV testing during hospital admission for transplantation (Free et al. 2022).

In addition to bacteria, fungi, and viruses, parasites including Toxoplasma gondii, Trypanosoma cruzi, Strongyloides stercoralis and Leishmania spp., and amoebas including Balamuthia spp. and Naegleria spp. can cause infections related to transplants (Fishman 2017; Grossi 2018; Malinis and Boucher 2019; Peghin et al. 2024). Toxoplasmosis constitutes a significant danger in heart transplant recipients, when a Toxoplasma seropositive heart is transplanted into a Toxoplasma seronegative recipient. Toxoplasmosis has also been transmitted to liver and kidney recipients (Malinis and Boucher 2019). Transmission of Strongyloides spp., an intestinal nematode endemic to the tropics and subtropics, via transplantation hs been described with significant mortality and morbidity (Malinis and Boucher 2019; CDC 2012; Peghin et al. 2024).

Implantology is a field of medicine that has recently shown quite dynamic development. The number of people receiving solid organ and tissue transplants has increased markedly. After successful organ transplantation, many people with end-stage organ failure can live for a long period of time. The surgical process of transplantation involves the risk of infections, primarily with bacteria and fungi. This is facilitated by the contamination of PF in which an organs is stored, as well as non-compliance with hygiene procedures. The published data regarding the extent of contaminated PF and the bacterial and fungal strains are very diverse and largely depend on the level of the transplantation centers and the procedures they follow. The second area of microbiological danger for transplant recipients is related to the possibility of transmitting mainly viruses and parasites with the transplanted organ. Latent microorganisms like Mycobacteria and viruses may be reactivated in the body of a patient subjected to immunosuppression after transplantation. Opinions on the scope and method of antibiotic prophylaxis for organ donors and recipients are divided. Contamination of PF with essentially non-pathogenic microorganisms and their transfer to the organ recipient rarely results in severe infection. However, post-transplantation infections caused by MDR bacteria should undoubtedly be detected quickly and treated with the appropriate antibiotics.