Clinical characteristics, healthcare-associated exposures, and antifungal susceptibility patterns of Candida auris colonization and invasive infections: a retrospective observational study at a single center in Turkey

Abstract

Background

Candida auris (Candidozyma auris) differs from other yeast species by its ability to persist for prolonged periods on environmental surfaces and human skin. This feature facilitates person-to-person transmission and contributes to healthcare-associated infections and outbreaks. In this study, both invasive C. auris infections and colonization were evaluated together. We aimed to compare clinical characteristics and healthcare-associated exposures between invasive and colonized cases and to assess antifungal susceptibility patterns in invasive infections.

Methods

A total of 79 patients with C. auris isolation between December 2022 and April 2025 were retrospectively analyzed. Species identification was confirmed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Patients with C. auris isolated from invasive specimens, such as blood or tissue, were classified as having invasive infection, whereas those with isolation from non-invasive specimens such as axilla/groin swabs, nasal swabs, urine, catheters, and sputum, without concurrent invasive positivity, were classified as colonized. Patients with both screening and invasive positivity were included in the invasive infection group for comparative analyses. Antifungal susceptibility to amphotericin B, fluconazole, micafungin, and anidulafungin was determined on invasive isolates using the Sensititre YeastOne colorimetric microdilution method. Interpretation of results was based on the tentative breakpoints defined by the United States Centers for Disease Control and Prevention and the epidemiological cutoff values established by the European Committee on Antimicrobial Susceptibility Testing. Demographic characteristics, clinical variables, and healthcare-associated exposures were compared between the invasive infection and colonization groups.

Results

A total of 91 C. auris isolates from 79 patients were evaluated. Invasive infection was detected in 41 patients (52%) and colonization in 38 patients (48%). Most cases were observed in intensive care and palliative care units. Among screening sites, axilla/groin swabs showed the highest positivity rate. Central venous catheter use, intubation, surgical history, and decubitus ulcer were numerically more frequent among invasive cases; however, none of these differences reached statistical significance. Echinocandin resistance developed in two patients during follow-up. The median age was significantly higher in the invasive group than in the colonized group (74 vs. 64.5 years; p = 0.002).

Conclusion

Accurate identification of C. auris and continuous antifungal susceptibility surveillance are essential for infection control. Older age was the only variable significantly associated with invasive infection, while other clinical and healthcare-associated exposures were common in both groups but did not differ significantly. All isolates were resistant to fluconazole, and echinocandin resistance emerged in two isolates. Amphotericin B susceptibility findings should be interpreted cautiously, as the use of Sensititre YeastOne without confirmatory reference testing may have overestimated resistance. Larger multicenter studies are needed to better define factors independently associated with invasive infection.

Background

Candida auris (Candidozyma auris) was first isolated in 2009 from the external ear canal of a patient in a hospital in Japan [1]. The clinical importance of this fungal species has increased due to its frequent resistance to multiple antifungal classes and its potential for healthcare-associated transmission [2]. Unlike other yeast species, C. auris can survive on the skin and environmental surfaces for extended periods. Its prolonged survival on these surfaces facilitates person-to-person transmission, leading to hospital-acquired infections and outbreaks [3].

The World Health Organization (WHO) and the U.S. Centers for Disease Control and Prevention (CDC) have classified C. auris as a critical public health concern requiring coordinated containment measures [4, 5]. C. auris is an important cause of nosocomial infections, particularly among elderly patients and those with multiple risk factors who require prolonged hospitalization. In a systematic review that included 37 studies, the overall mortality rates associated with C. auris candidemia ranged from 29% to 62%, while 30-day mortality rates ranged from 23% to 67%. Identification of C. auris infections can be challenging, often leading to delays in diagnosis and treatment. Accurate identification is achieved when using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) using the Bruker Microflex LT/SH system (Bruker Daltonics, Bremen, Germany) or polymerase chain reaction (PCR)–based assays [6]. According to previous studies, C. auris infections frequently exhibit reduced susceptibility to fluconazole, whereas susceptibility to echinocandins generally remains relatively preserved [2, 3]. However, resistance to this antifungal class may also develop following echinocandin use.

In this single-center study from Turkey, we evaluated patients with invasive C. auris infection and colonization. We aimed to compare clinical characteristics and healthcare-associated exposures between invasive infection and colonization and to assess the antifungal susceptibility profiles of invasive isolates.

Methods

This retrospective observational study included hospitalized patients aged ≥ 18 years who had at least one C. auris-positive culture confirmed by MALDI-TOF MS at Bursa City Hospital between December 2022 and April 2025. A total of 79 patients were included. Patients from whom any C. auris isolate was obtained from invasive specimens (e.g., blood or tissue) were classified as the invasive infection group (n = 41). In only two patients, acquired echinocandin resistance was detected after prolonged and recurrent positive cultures, and resistant isolates from these patients were also included in the antifungal susceptibility and laboratory analyses. Therefore, antifungal susceptibility as well as neutrophil count, C-reactive protein (CRP), and procalcitonin levels were evaluated based on a total of 43 isolates from 41 patients. Thirty-eight patients in whom C. auris was isolated from non-invasive specimens, such as axilla/groin swabs, nasal swabs, urine, catheters, and sputum, and who did not have concurrent invasive positivity were classified as colonized. Ten patients with both screening and invasive positivity were classified in the invasive infection group for comparative analyses, as invasive positivity was considered to reflect progression beyond colonization and thus the more clinically relevant presentation. The distribution of colonization and invasive cases across hospital units from the time of the first C. auris detection is presented in Figs. 1 and 2.

Fig. 1.

Monthly distribution of screening and invasive Candida auris detection episodes recorded between 2022 and 2025. Detection episodes refer to the first positive screening sample and the first positive invasive sample per patient. “Screening + invasive” indicates patients with both detection episodes recorded within the same month

Fig. 2.

Distribution of Candida auris detection episodes by hospital units between 2022 and 2025. Screening, invasive, and screening + invasive detection episodes are shown. Hospital units are presented on the x-axis, and detection episodes are grouped by year [2022–2025]. Anesth Reanim, anesthesiology and reanimation; CV Surg Svc, cardiovascular surgery service; Chest Diseases Svc, chest diseases service; Chest Diseases ICU, chest diseases intensive care unit; Gen Surg Svc, general surgery service; ICU, intensive care unit; Int Med ICU, internal medicine intensive care unit; Palliative Svc, palliative care service; Surg ICU, surgical intensive care unit; Urology Svc, urology service

Invasive specimens (blood and tissue) and non-invasive clinical specimens, including sputum, urine, catheters, and wound samples, were inoculated onto 5% sheep blood agar (RTA Laboratories, Gebze, Turkey) and incubated at 37 °C for 24–48 h. Isolates identified as C. auris by the VITEK^® 2 system (bioMérieux, Marcy-l’Étoile, France), as well as those identified as other yeast species but considered suspicious based on colony morphology, were evaluated by MALDI-TOF MS. To support identification, invasive isolates were additionally subcultured onto CHROMagar™ Candida and cornmeal agar at 30 °C, and onto Sabouraud dextrose agar (SDA) at 37 °C for antifungal susceptibility testing, whereas non-invasive clinical isolates were subcultured onto cornmeal agar and incubated at 30 °C for 24–48 h (all media: RTA Laboratories, Gebze, Turkey). Pure growth obtained on SDA was used for antifungal susceptibility testing.

For active surveillance, nasal and axilla/groin swab samples were inoculated onto CHROMagar™ Candida and incubated at 30 °C for 24–48 h. Suspicious colonies were evaluated by MALDI-TOF MS and additionally subcultured onto cornmeal agar and incubated at 30 °C for 24–48 h to support identification. All isolates included in the study were confirmed using MALDI-TOF MS.

Minimum inhibitory concentrations (MICs) for amphotericin B, fluconazole, micafungin, and anidulafungin were determined using the Sensititre YeastOne colorimetric microdilution method (Thermo Fisher Scientific, Waltham, MA, USA), and the panels were read after 24 h of incubation at 37 °C. The CDC has defined tentative breakpoints for amphotericin B, fluconazole, and echinocandins, whereas the European Committee on Antimicrobial Susceptibility Testing (EUCAST) has not established clinical breakpoints for C. auris but provides epidemiological cutoff values (ECOFFs) [7, 8]. Quality control was performed using the reference strains Candida parapsilosis ATCC 22,019 and Candida krusei ATCC 6258. It should be noted that the Sensititre YeastOne system is a commercial colorimetric method and not the EUCAST reference broth microdilution method. No confirmatory testing using the EUCAST or CLSI reference method was performed for MIC values of amphotericin B, fluconazole, and echinocandins. MIC50, MIC90, and MIC ranges were calculated to summarize antifungal susceptibility profiles, and resistance rates were interpreted according to CDC tentative breakpoints and EUCAST epidemiological cutoff values (ECOFFs). Laboratory parameters, including neutrophil count, CRP, and procalcitonin levels, were summarized using descriptive statistics. These laboratory analyses were limited to invasive cases, were based on 43 invasive C. auris isolates obtained from 41 patients, and were intended to describe the laboratory profile of patients with invasive C. auris infection.

Epidemiological analyses were performed on 79 patients, including 41 patients with invasive infection and 38 patients with colonization. Data extracted from the medical records included age, sex, hospital unit, specimen type, ICU stay within the previous 30 days, duration of hospital and ICU stay, central venous catheter use, endotracheal intubation, tracheostomy, urinary catheter use, decubitus ulcer, previous surgery, tracheal stent, percutaneous endoscopic gastrostomy (PEG), comorbidities, and, for invasive cases, available laboratory parameters such as neutrophil count, CRP, and procalcitonin. Age, sex, clinical variables, and healthcare-associated exposures were compared between invasive and colonized patients. Laboratory parameters and antifungal susceptibility analyses were limited to 43 invasive C. auris isolates obtained from 41 patients.

Statistical analysis

The data were analyzed using SPSS version 26.0 (IBM Corp., Armonk, NY, USA). Continuous variables were given as mean ± standard deviation (SD) or median (min–max, interquartile range, IQR), and categorical variables were shown as numbers and percentages. The Mann–Whitney U test was used for continuous variables, and the chi-square or Fisher’s exact test was used for categorical variables to compare invasive and colonized groups. Results with a p < 0.05 were considered statistically significant. Because of the limited sample size and the distribution of the available variables, multivariable analysis was not considered sufficiently statistically robust for reliable interpretation.

Results

Between December 2022 and April 2025, 91 C. auris isolates obtained from 79 patients hospitalized at Bursa City Hospital were included in the study. The distribution of samples was as follows: blood [n = 40 (two samples from the same patient)], tissue (n = 3), and non-invasive samples [n = 48; surveillance swabs (axilla/groin and/or nasal, n = 42), wound (n = 1), urine (n = 2), catheter (n = 2), and sputum (n = 1)]. C. auris was isolated from invasive specimens in 41 patients (51.9%) and from non-invasive specimens in 38 patients (48.1%). Epidemiological characteristics were evaluated in 79 patients, comprising 41 invasive and 38 colonized cases. Laboratory and antifungal susceptibility comparisons were performed on 43 invasive isolates recovered from 41 patients.

The number of invasive and colonized patients from the beginning of the study period is shown in Fig. 1.

When screening samples from patients in the same rooms as C. auris-positive cases were examined, detection in axilla/groin swabs was higher than in nasal swabs. C. auris was detected in 26 patients from axilla/groin samples, in 6 patients from nasal samples, and in 10 patients from both sites. In nine patients, C. auris was first detected in screening samples and later recovered from blood cultures. In our study, bloodstream infection developed in 9 patients (11.4%) with documented colonization, occurring 2–57 days after the first positive screening swab. In one patient, C. auris was detected in screening samples shortly after bloodstream isolation.

The annual distribution of invasive and screening C. auris detection episodes by hospital unit is shown in Fig. 2.

When patients with both colonization and invasive episodes were evaluated according to the hospital unit in which the first detected episode occurred, most patients were managed in intensive care units (60 [75.9%]) and palliative care units (13 [16.5%]). However, in the table analyses, the additional episodes of these patients were also evaluated separately under the corresponding hospital units. When all patients were evaluated together, 44 males (55.7%) and 35 females (44,3%) were aged 18 years or older. Fifty-six patients (70.9%) were aged 60 years or older. No C. auris isolates were detected in the pediatric department.

Demographic characteristics, clinical variables, and healthcare-associated exposures of invasive and colonized patients are compared in Table 1.

Table 1.

Comparison of demographic characteristics, clinical variables, and healthcare-associated exposures between invasive and colonized Candida auris cases

Variable	Invasive (n = 41) n (%)	Colonized (n = 38) n (%)	p-value
Gender			0.02*
Male	18 (43.9%)	26 (68.4%)
Female	23 (56.1%)	12 (31.6%)
Age (years)	74 (60–80)	64.5 (52.3–71.0)	0.002*
Clinical variables and healthcare-associated exposures
CVC	39 (95.1%)	33 (86.8%)	0.252
Endotracheal Intubation	35 (85.4%)	28 (73.7%)	0.197
Tracheostomy	18 (43.9%)	19 (50.0%)	0.587
Urinary catheter	40 (97.6%)	36 (94.7%)	0.606
Decubitus ulcer	32 (78%)	26 (68.4%)	0.231
Surgery	27 (65.9%)	19 (50.0%)	0.153
Tracheal stent	3 (7.3%)	0 (0.0%)	0.241
PEG	10 (24.4%)	14 (36.8%)	0.229
ICU stay (past 30 days)	41 (100%)	37 (97.4%)	0.472

CVC, central venous catheter; PEG, percutaneous endoscopic gastrostomy; Values are expressed as n (%) or Median (IQR); p < 0.05 was considered statistically significant; Patients with both screening and invasive positivity were counted only once and classified under the invasive group for comparative analyses

The presence of a central venous catheter (CVC), intubation, surgical procedures, and decubitus ulcers was numerically slightly higher in invasive cases compared with colonized cases. However, no statistically significant differences were found between the invasive infection and colonization groups in terms of the assessed clinical variables. In general, the rates of CVC, urinary catheterization, surgery, intubation, tracheostomy, PEG, and decubitus ulcers were high across all patients. There was no significant difference between invasive and colonized groups in terms of underlying diseases. The most common underlying conditions were a history of surgical procedures (46 [58.2%]), hypertension (36 [45.6%]), and neurological disorders (35 [44.3%]). The proportion of male patients was significantly higher in the colonized group compared with the invasive group (p = 0.02). The median age of invasive cases was higher than that of colonized cases (74 vs. 64.5 years), and this difference was statistically significant according to the Mann–Whitney U test (p = 0.002).

Antifungal susceptibility results, MIC₅₀, MIC₉₀, and MIC ranges evaluated according to CDC tentative breakpoints are presented in Table 2, whereas the evaluation based on EUCAST epidemiological cutoff values (ECOFFs) is shown in Table 3. According to CDC tentative breakpoints, 42 isolates (97.7%) were categorized as resistant to amphotericin B, whereas 9 isolates (21%) were categorized as resistant according to EUCAST ECOFF-based interpretation.

Table 2.

Antifungal susceptibility profile of Candida auris isolates evaluated according to CDC tentative breakpoints [7]

Antifungal agent	MIC₅₀	MIC₉₀	MIC range	CDC tentative breakpoint	Resistant n (%)
Fluconazole	128	256	32–256	≥ 32	43 (100%)
Amphotericin B	2	4	1–4	≥ 2	42 (97.7%)
Anidulafungin	0.12	0.12	0.06–4	≥ 4	2 (4.7%)
Micafungin	0.06	0.12	0.03–8	≥ 4	2 (4.7%)

MIC₅₀, MIC₉₀, and MIC range represent the distribution of measured minimum inhibitory concentrations (MICs) among the isolates. MIC values are expressed in mg/L

Table 3.

Antifungal susceptibility profile of Candida auris isolates evaluated according to EUCAST epidemiological cutoff values (ECOFFs) [8]

Antifungal agent	MIC₅₀	MIC₉₀	MIC range	EUCAST ECOFF	Resistant n (%)
Fluconazole	128	256	32–256	Not defined	Not defined
Amphotericin B	2	4	1–4	> 2	9 (21%)
Anidulafungin	0.12	0.12	0.06–4	> 0.25	2 (4.7%)
Micafungin	0.06	0.12	0.03–8	> 0.25	2 (4.7%)

MIC₅₀, MIC₉₀, and MIC range represent the distribution of measured minimum inhibitory concentrations (MICs) among the isolates. MIC values are expressed in mg/L. Although EUCAST has not established clinical breakpoints or ECOFFs for Fluconazole in C. auris, the vast majority of C. auris isolates are considered to be resistant to Fluconazole

In two patients, C. auris isolates from follow-up blood cultures developed resistance to echinocandins. These two isolates were considered pan-resistant C. auris according to CDC tentative resistance thresholds and EUCAST epidemiological cutoff values (ECOFFs). Laboratory findings of these patients were also included in the evaluation. For invasive cases, the mean, median, and range values of neutrophil counts, C-reactive protein (CRP), and procalcitonin levels are summarized in Table 4.

Table 4.

Laboratory parameters of invasive Candida auris cases

Variable	Mean ± SD	Median (IQR)	Min–Max	n
Neutrophil count (×10^3/µL)	8.54 ± 5.32	6.43 (4.56–10.87)	2.06–23.92	43
CRP (mg/L)	113.63 ± 70.83	113.40 (57.95–147.90)	10.70–347.40	43
Procalcitonin (ng/mL)	3.43 ± 8.56	0.79 (0.30–2.40)	0.05–44.00	43

SD, standard deviation; IQR, interquartile range

Discussion

C. auris is an emerging pathogen that continues to attract attention worldwide because of its increasing number of cases, its ability to cause outbreaks, and its resistance to multiple antifungal agents. Considering its resistance profile, C. auris is expected to remain a persistent challenge for healthcare systems. Early and accurate identification of C. auris can play a key role in limiting its spread.

On CHROMagar™ Candida medium, C. auris colonies appear in white to pink tones, while on CHROMagar™ Candida Plus medium, they form light blue colonies surrounded by a blue halo, making identification easier [9]. C. auris is generally known not to produce filamentous forms on cornmeal agar. However, under stress conditions such as DNA damage or exposure to antifungal treatment, filamentous growth may occur [10]. In our study, rudimentary pseudohyphae or pseudohyphae-like extensions were also observed in some C. auris isolates. Because of the difficulties in identification, commercial identification systems used in many laboratories may give incorrect results. Therefore, confirmation by MALDI-TOF MS is essential in suspicious cases. Previous studies have shown that MALDI-TOF MS provides highly accurate results [11]. In our study, this system was also used as the main identification method. Internal transcribed spacer (ITS) sequencing gives precise results but is expensive and time-consuming [12]. For this reason, rapid and accurate identification is very important for controlling the spread of C. auris infections.

In studies from Turkey and other countries, C. auris has also been detected in blood cultures of pediatric patients [13, 14]. In our study, no C. auris cases were identified in the pediatric department. However, routine screening was not performed in this unit. The absence of C. auris detection was therefore based solely on the lack of growth in clinical samples submitted for microbiological analysis rather than on systematic surveillance.

Previous studies have reported Fluconazole resistance rates ranging from 87% to 100% and echinocandin resistance rates ranging from 0% to 8% among C. auris isolates [15–18]. As shown in Tables 2 and 3, the resistance rates to fluconazole, amphotericin B, and echinocandins observed in our study are consistent with those reported in the literature, supporting the recommendation that echinocandins should be considered the first-line treatment option [11]. Some studies have reported Amphotericin B resistance rates of 4% to 35% [15–17], while others from the United States have reported rates up to 61% [18, 19]. In our study, Amphotericin B resistance was found to be 97.7% according to the CDC tentative breakpoints and 21% according to the EUCAST criteria. This marked discrepancy should primarily be regarded as a methodological issue related to different interpretive thresholds rather than as direct evidence for conflicting clinical resistance patterns. While the CDC considers isolates with an MIC value of ≥ 2 mg/L as resistant, EUCAST classifies only those with MIC values > 2 mg/L as resistant. Therefore, isolates with an MIC value exactly equal to 2 mg/L are interpreted as resistant according to the CDC but as susceptible according to EUCAST. Since the majority of our isolates had an MIC value of 2 mg/L, this difference in interpretation led to markedly different resistance rates between the two guidelines. Accordingly, amphotericin B susceptibility findings in our study should be interpreted cautiously, particularly because MICs were determined using Sensititre YeastOne without confirmation by a reference broth microdilution method. A study comparing different testing methods demonstrated that the Sensititre YeastOne method may overestimate amphotericin B resistance in C. auris isolates [20]. As our study relied exclusively on the Sensititre YeastOne method without confirmatory testing using a reference method, the high amphotericin B resistance rate observed according to CDC criteria may represent an overestimate. Further methodological comparisons using reference methods are warranted to clarify the true resistance rate in our isolates.Although echinocandin resistance was initially absent, several studies have demonstrated that resistance can emerge during therapy. In our investigation, echinocandin resistance developed in two patients who had received prolonged echinocandin therapy. Both patients had recurrent positive blood cultures over extended periods, and resistance emerged after several weeks of antifungal exposure. These patients subsequently had limited therapeutic options and experienced poor clinical outcomes [18, 21].

Treatment options for pan-resistant C. auris remain extremely limited, underscoring the need for novel therapeutic approaches. Rezafungin, one of the newer antifungal agents, has shown promising efficacy against multidrug-resistant C. auris infections, as highlighted in a recent review, offering hope for patients with limited treatment options [22]. In addition, newer antifungal agents such as ibrexafungerp and fosmanogepix have demonstrated promising activity against these highly resistant infections. Although not yet in widespread clinical use, these agents are considered potential alternatives in cases where conventional antifungal therapies fail to achieve an adequate response [12, 23].

One study reported that nasal colonization was more common than axilla or groin colonization [19]. In our study, C. auris was detected in 26 patients from axilla/groin swab samples, in 6 patients from nasal swabs, and in 6 patients from other non-blood clinical specimens, while 10 patients had positive results from both axilla/groin and nasal samples. According to the CDC, swabs obtained from the axilla and groin are considered the most consistent and reliable sampling sites for detecting C. auris colonization [24]. Our findings support this recommendation and may contribute to the appropriate selection of screening sites.

The predominance of surgical history, hypertension, and neurological disorders in our cohort provides insight into the clinical profile of patients with C. auris isolation. Previous studies have emphasized that C. auris primarily affects patients with substantial healthcare exposure and underlying chronic conditions [11, 25]. Progression from colonization to invasive infection has also been reported in patients with substantial healthcare exposure and underlying chronic conditions [26, 27]. In our study, these conditions were common in the overall cohort and likely reflect the high burden of comorbidity, prolonged healthcare contact, and critical care exposure in this patient population. However, most clinical variables did not differ significantly between invasive and colonized patients. Therefore, these findings should not be interpreted as evidence of independent predictors of invasive disease. Larger multicenter studies with sufficient sample sizes and multivariable analyses are needed to identify factors associated with progression from colonization to invasive C. auris infection.

In our study, blood culture positivity developed in 19% of patients with documented colonization 2–57 days after the first positive swab. This finding indicates that the risk of progression from colonization to infection is not negligible. Similarly, in the report of the Florida outbreak published in the CDC’s Morbidity and Mortality Weekly Report, the mean age of colonized patients was 69 years, 60% were male, and 23% of colonized individuals later had C. auris isolated from clinical cultures [28]. The concurrent increase in invasive infections during periods of high colonization rates highlights the importance of colonization detection in predicting the development of invasive disease.

As shown in Fig. 1, the rise in C. auris detections in early 2025 was largely driven by screening-positive results. This points to a higher colonization burden and increased transmission pressure, rather than a sudden surge in invasive disease. Similar trends have been reported elsewhere, where growing colonization/screening positivity is followed by improved infection prevention and control practices and a subsequent decline in detections [12, 29].

In our study, the median age of patients with invasive disease was significantly higher than that of colonized patients (74 vs. 64.5 years, p = 0.002). Interestingly, a significantly higher proportion of male patients was observed in the colonized group compared with the invasive group. A similar male predominance among colonized patients has also been reported in a COVID-19 unit outbreak in Florida [28]. However, no significant difference in sex distribution between candidemia and colonized patients was observed in another outbreak study [30]. These findings suggest that sex-related differences may be associated more with colonization dynamics than with progression to invasive infection. Larger studies are needed to clarify this relationship.

In our study, CRP levels were markedly elevated in all patients, neutrophil counts showed a heterogeneous distribution but were increased in most cases, and procalcitonin levels reached the range of bacterial sepsis in some patients. This pattern suggests that the elevation of inflammatory biomarkers in our cohort reflects the overall clinical severity and concomitant infections rather than a pathogen-specific response to C. auris. These laboratory findings should therefore be interpreted as descriptive indicators of overall clinical severity rather than as comparative markers distinguishing invasive infection from colonization. A similar observation has been previously reported [17]. Previous studies have reported that intensive care unit stay and central venous catheter (CVC) use are common among patients with C. auris colonization or infection [15, 17, 31, 32]. In our cohort, most patients were managed in intensive care (60 [75.9%]) or palliative care units (13 [16.5%]), and CVC use was very frequent (72 [91.1%]). Invasive devices and other healthcare-associated exposures were common in both invasive and colonized patients. CVC use, endotracheal intubation, surgical history, and decubitus ulcers were numerically more frequent in invasive cases; however, these differences were not statistically significant. Therefore, these findings should be considered descriptive of a severely ill patient population with substantial healthcare exposure, rather than evidence of independent risk factors for invasive infection. The mean hospital stay (50.7 ± 32.1 days) and ICU stay (42.5 ± 29.2 days) also support the prolonged healthcare exposure in this cohort. Larger multicenter studies are needed to determine whether these variables independently contribute to progression from colonization to invasive disease.

By evaluating both colonization and invasive infection due to C. auris within the same cohort, our study provides a more integrated perspective on colonization-to-infection progression, healthcare-associated exposure patterns, and clinically relevant antifungal susceptibility findings.

This study has some limitations. Its single-center, retrospective design and relatively small sample size may limit the generalizability of the findings and the statistical power to detect significant differences between invasive and colonized groups. Moreover, the classification of patients with both screening and invasive positivity into the invasive group for comparative analyses may have influenced the comparisons between invasive infection and colonization. In addition, MICs were determined using the Sensititre YeastOne system instead of the EUCAST or CLSI reference broth microdilution method; therefore, amphotericin B resistance results should be interpreted with caution. Finally, the absence of molecular epidemiological analyses, including clade characterization, limited the evaluation of clade distribution and phylogenetic relationships among the isolates.

Conclusions

Our study provides important insight into the clinical and healthcare-associated factors observed in patients with C. auris colonization and invasive infection. Understanding these factors and identifying and monitoring colonized patients are essential for effective infection control. A key strength of our study is the simultaneous evaluation of colonization and invasive infection within the same cohort, which enabled a more comprehensive assessment of progression risk, healthcare-associated exposures, and antifungal susceptibility patterns. All isolates were resistant to fluconazole, and echinocandin resistance was detected in two isolates. Amphotericin B susceptibility findings should be interpreted cautiously, as testing was performed using Sensititre YeastOne without confirmation by a reference method and resistance may therefore have been overestimated. Older age was the only variable significantly associated with invasive infection in this cohort. Invasive procedures and prolonged ICU exposure were frequently observed in both invasive and colonized patients, but they did not differ significantly between groups and should therefore be interpreted descriptively. Further multicenter studies with larger sample sizes and molecular epidemiological analyses are needed to better define factors independently associated with invasive C. auris infection and to support evidence-based infection control strategies.

Abbreviations

ATCC

American Type Culture Collection

CDC

Centers for Disease Control and Prevention

COVID-19

Coronavirus disease 2019

CRP

C-reactive protein

CVC

Central venous catheter

DNA

Deoxyribonucleic acid

ECOFF

Epidemiological cut-off value

EUCAST

European Committee on Antimicrobial Susceptibility Testing

ICU

Intensive care unit

IQR

Interquartile range

ITS

Internal transcribed spacer

MALDI-TOF MS

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

MIC

Minimum inhibitory concentration

MIC₅₀

Minimum inhibitory concentration inhibiting 50% of isolates

MIC₉₀

Minimum inhibitory concentration inhibiting 90% of isolates

MMWR

Morbidity and Mortality Weekly Report

PCR

Polymerase chain reaction

PEG

Percutaneous endoscopic gastrostomy

SD

Standard deviation

SPSS

Statistical Package for the Social Sciences

WHO

World Health Organization

Author contributions

Demet Timur conceived the study, collected the laboratory data, analyzed and interpreted the clinical data, and wrote the manuscript. Canan Demir collected the clinical data and analyzed and interpreted them together with the laboratory findings.

Funding

No funding was received for this study.

Data availability

Individual patient-level data are not publicly available because they may contain information that could compromise patient confidentiality. A de-identified dataset may be made available by the corresponding author upon reasonable request, subject to approval by the institution and the ethics committee.

Declarations

Ethics approval and consent to participate

Ethical approval for this study was obtained from the Bursa City Hospital Clinical Research Ethics Committee (14.05.2025, decision no: 2025-10/19). Owing to the retrospective study design and the use of anonymized data, the requirement for informed consent was waived by the committee. The study was conducted in accordance with the Declaration of Helsinki.

Consent for publication

Not Applicable. This study does not include any identifying images or other personal or clinical details of participants that could compromise anonymity.

Large language model use

We did not use large language models (such as ChatGPT) for writing the manuscript or for data analysis/interpretation.

Competing interests

The authors declare no competing interests.