Candida kefyr/Kluyveromyces marxianus infection of aortic endograft

Sir, Candida kefyr (Kluyveromyces marxianus) is an uncommon pathogen in immunocompromised patients. Although it is usually associated with food sources (e.g., dairy products), its role in prosthetic infections is poorly documented [1]. When it affects a graft, infection frequently necessitates graft removal owing to biofilm formation and the need to eradicate the infectious focus to prevent systemic complications or graft failure. A 65-year-old man presented to the emergency department with a fever >38°C, left lower back pain, and profuse sweating. In 2022, the patient underwent surgery with placement of a vascular endograft (EG) for an abdominal aortic aneurysm. After positron emission tomography–computed tomography (PET-CT) findings were consistent with infection of the abdominal aortic EG, the patient was admitted to Vascular Surgery service (VS) for substitution of the infected EG (Figure 1). Peritoneal fluid and the explanted EG were sent to microbiology for culture. After 24 hours of incubation at 37^oC, yeast growth was observed on Sabouraud dextrose agar; isolates were identified as Candida kefyr using MALDI-TOF MS (Bruker Daltonics^®, Germany). Based on CLSI epidemiological cutoff values (ECVs), the isolate was wild-type for echinocandins but non–wild–type for amphotericin B; however, by Etest, it was classified as wild-type for amphotericin B. To confirm these results, the isolate was sent to a reference center, which classified it as wild-type for amphotericin B using the CLSI broth microdilution method, as well as identification by ITS sequencing. Considering these results, we decided to repeat the Sensititre YeastOne^® (SYO) test to further confirm the discrepancy between the reference method and SYO. Once identification and susceptibility were confirmed, treatment with micafungin and meropenem was started. The patient was discharged three weeks after surgery in a clinically stable condition, afebrile, and without signs of persistent infection, and was prescribed oral fluconazole for six months. From an infectious diseases standpoint, the patient remained clinically stable throughout mid- and long-term follow-up, with no febrile episodes or laboratory findings suggestive of infection reactivation. One of the most feared complications of an endovascular aneurysm repair (EVAR) is aortic endograft infection. This infection is rare, with incidence ranging from 0.2 to 5% according to different published series [2–5], but its overall mortality is close to 50% [5,6]. Staphylococcus spp. are the most common bacterial genera involved in this type of infection [7,8]. Fungal endograft infections are rare, with most of the few reported cases being caused by Candida albicans [8,9]. One series reports fungi being involved in up to 14% of endograft infections [10]. In the 1997-2016 SENTRY Programme, C. kefyr was listed as a rare finding even among invasive candidiasis, accounting for 0.45% of invasive Candida isolates [11].  In epidemiological surveillance studies conducted in Spain, such as the population-based CANDIPOP study and the regional multicenter CANDIMAD study, uncommon species, including C. kefyr, represented less than 7% of isolates from blood and intra-abdominal samples. Approximately 40%-50% of intra-abdominal isolates were C. albicans. [12,13]. Another study evaluating and comparing the outcome of aortic graft infections associated and not associated with Candida spp. found 21 infections caused by fungi, and in only one case was the aetiology C. kefyr [14].  Our discrepancy in susceptibility may be attributed to limitations of SYO testing. However, reduced susceptibility to amphotericin B (rs-AMB) in C. kefyr has been described previously. Asadzadeh et al. studied 81 C. kefyr isolates, eight of which were rs-AMB by Etest. SYO correctly identified all eight rs-AMB isolates, but this reduced susceptibility was not corroborated by a reference method [15] . In conclusion, C. kefyr has garnered attention as a rare pathogen in graft infections. Fungal infections of vascular devices are a therapeutic challenge due to biofilm formation, which contributes to virulence and potential resistance to antifungal treatment, as well as the frequent need for surgery [16]. This case highlights the importance of microbiological cultures for the management of prosthetic infections. Diagnosis requires a combination of clinical, radiological, and microbiological criteria, as well as a multidisciplinary approach (vascular surgery and microbiology). Funding No funding was received for the research, authorship, and/or publication of this article. Author contributions Conceptualization, JLMB; investigation and resources, LGB, BBR, SVG; writing—original draft preparation, LGB and BBR; writing—review and editing, JLMB; supervision, JLMB. All authors have read and agreed to the published version of the manuscript. Conflict of interest No commercial, financial, or personal conflicts of interest were identified in relation to the research, authorship, and/or publication of this article. AI statement No artificial intelligence tools were used in the writing, analysis, interpretation, or review of this article. References

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