Distribution and antifungal resistance patterns of clinical Candida isolates in a hospital setting

Authors

Abstract

AimCandida species are an example of opportunistic fungal pathogens that are frequently associated with nosocomial infections, particularly among immunocompromised and hospitalized patients. Specific distribution variations and rising antifungal resistance pose significant clinical challenges.
MethodsThis retrospective study aimed to evaluate the distribution of Candida species isolated from hospitalized and outpatient populations in Near East University Hospital between September 2020 and February 2022, and to determine their antifungal susceptibility patterns against voriconazole, flucytosine, and amphotericin B. A total of 202 Candida isolates collected from different clinical samples, including yeast cultures, urine, sputum, aspirates, wound samples, blood, genital specimens, and catheter tips, were analyzed.
ResultsIdentification of species and antifungal susceptibility testing (AFST) were performed by following the VITEK 2 Compact system, following European Committee on Antimicrobial Susceptibility Testing guidelines. Clinical and demographic data such as gender, age, hospitalization department, and inpatient/outpatient status were also evaluated. The majority of isolates originated from inpatients (96%) (p = 0.037) and principally from the intensive care unit (72%). Candida albicans was the most common species (68.8%), followed by C. parapsilosis (11.4%), C. tropicalis (6.9%), and C. glabrata (6.4%). Overall, Amphotericin B showed 93.1% sensitivity, while voriconazole and flucytosine exhibited sensitivity rates of 88.1% and 94.6%, respectively.
ConclusionResistance was low but present across non-albicans species. Although Candida albicans remains the main cause of candidiasis, non-albicans Candida species highlight the need for routine susceptibility testing and accurate species identification. The findings emphasize targeted infection control and antifungal stewardship.

Keywords

Introduction

Candida species are ubiquitous eukaryotic fungi that colonize mucosal surfaces, the skin, gastrointestinal tract, and genitourinary regions, and they are part of the normal human microbiota. Although they are typically commensal organisms, they can become opportunistic pathogens under conditions of immune suppression, catheterization, disruption of normal flora, prolonged hospitalization, leading to oropharyngeal candidiasis, candiduria, superficial infections, disruption of normal flora and life-threatening invasive candidiasis. These infections are among the most common hospital-acquired fungal diseases and present a substantial global health problem.^1,2
Although more than 150 Candida species have been identified, only a limited number, including C. albicans, C. krusei, C. parapsilosis, and C. glabrata, are responsible for most clinical infections. C. albicans remains the most common species, partly due to its ability to undergo biofilm formation and morphological switching, which enhance its virulence, resistance to host immune defenses, and environmental adaptability.^1,3 Non-albicans Candida (NCAC) species have recently gained particular attention in hospital environments, where their prevalence is rising due to increased use of invasive medical devices, extensive antifungal exposure, and improved detection methods.^4,5
Nosocomial Candida infections occur through both exogenous and endogenous routes. Exogenous transmission may occur via colonized catheters, contaminated hospital equipment, or the hands of healthcare workers, while endogenous infections frequently arise from overgrowth of commensal Candida spp. Studies report frequent isolation of C. albicans and C. parapsilosis from healthcare workers’ hands, highlighting the importance of infection control practices.^6,7
Antifungal resistance has appeared as a significant challenge, driven by incorrect dosing regimens, prolonged therapy, and broad-spectrum antifungal use. Resistance mechanisms, particularly among flucytosine and azoles, are well documented, involving alterations in reduced drug uptake, efflux pump upregulation, and target enzymes. Considering the limited availability of effective antifungals, routine antifungal susceptibility testing (AFST) and early species identification are now essential components of clinical management.^8,9
Based on the evidence presented, this study aimed to evaluate the distribution of Candida species isolated from hospitalized and outpatient populations in Near East University Hospital and to determine their resistance and susceptibility patterns to Voriconazole, Flucytosine, and Amphotericin B. Understanding antifungal response profiles and local epidemiology is essential for strengthening infection control measures, guiding targeted therapeutic strategies, and informing antifungal stewardship programs.

Materials and Methods

Study Design and SettingThis retrospective study was conducted at the Microbiology Laboratory of Near East University Hospital and included clinical Candida isolates collected between 15 September 2020 and 28 February 2022. In total, 702 samples obtained from outpatient and hospitalized individuals were evaluated. All culture conditions, laboratory procedures, and identification methods followed the standard clinical microbiology protocols used at the institution. Since the study was designed as a retrospective laboratory-based analysis and all patient data were analyzed anonymously, formal ethical committee approval was not required in accordance with local and institutional regulations.
Study Population and Inclusion CriteriaClinical specimens from patients aged 0-95 years were included without restriction to gender or age. Duplicate isolates and cultures not identified as Candida species were excluded from the dataset. Samples considered infection sources for Candida species, such as abscess materials, yeast culture specimens, urine, sputum, aspirates, wound scrapings, blood cultures, catheter tips, genital tract specimens, and potential colonizers, were analyzed.
Specimen Collection and ProcessingOnce the samples were delivered to the microbiology laboratory, each specimen was recorded both in the electronic microbiology database and in a laboratory logbook, including patient identifiers, date, sample type, and department.
Primary inoculation was performed on eosin methylene blue agar (EMB) (Becton, Dickinson and Company, France) and Blood agar (Becton, Dickinson and Company, France). If Candida species were detected on primary media or if the clinician specifically requested a yeast culture, isolates were sub-cultured onto Sabouraud dextrose agar (SDA) without cycloheximide (Becton, Dickinson and Company, France) to obtain pure colonies.
A sterile inoculating loop previously flamed to redness and cooled was used to streak urine specimens onto EMB and blood agar. Plates were incubated at 35 °C for 24–48 hours. Suspected yeasts were further sub-cultured onto SDA to obtain pure isolates for identification.
Aspirates were primarily used to prepare smears for Gram staining, followed by inoculation onto EMB and Blood agar plates. Gram-stained slides and cultures were incubated at 35 °C for 24–48 hours. Positive cultures were consequently processed for yeast identification.
Blood samples were collected in two BD BACTEC bottles: one from each arm, 15 minutes apart. Adults provided 8–10 mL per bottle; pediatric patients 1–3 mL. Afterwards, bottles were scanned into the BD BACTEC 9120 automated system. Negative cultures remained in the system for 7 days, and positive signals (indicative of candida or bacteria) were typically detected within 24 hours, or sooner in severe infections. Positive bottles were sub-cultured onto EMB and blood agar, incubated at 35 °C for 24–48 hours, followed by SDA subculture to obtain pure Candida isolates.
Identification of Candida Species and AFSTColony morphology, Gram staining, microscopy, and VITEK 2 Compact System (BioMérieux) were performed to identify species. Pure colonies (2–3 colonies) were suspended in saline to prepare the standardized inoculum for the identification of the VITEK 2 card.
VITEK 2 Compact automated system used to perform AFST. Two test tubes were prepared for each isolate in order to identify the inoculum and antifungal susceptibility. The McFarland turbidity standard range for Candida species was adjusted to 1.80–2.20. For susceptibility testing, 2.8 μL of the inoculated suspension (for Candida species and Gram-positive organisms) was added to the second tube. Amphotericin B, Flucytosine, and Voriconazole were the antifungal agents assessed in this study. European Committee on Antimicrobial Susceptibility Testing standards were used to interpret the results.
The staining was performed by applying crystal violet for 1 minute, followed by a water rinse. Gram’s iodine was then applied for 1 minute and rinsed. Decolorization was carried out using alcohol for 5-10 seconds with immediate rinsing, followed by safranin counterstain for 1 minute. After rinsing and blotting dry, the slides were examined under oil immersion using an electronic microscope (x40). Gram-positive cells, including yeasts, appeared purple/blue, while Gram-negative cells appeared pink/red.
The VITEK 2 Compact system was used to automatically generate the biochemical profiles required for yeast identification.
Ethical ApprovalThis study did not require ethical approval according to the relevant guidelines.
Statistical AnalysisSPSS Demo Version 22 was used to perform all statistical analyses. Fisher’s exact test and Pearson’s chi-square test were applied where appropriate. A p-value < 0.05 was considered statistically significant.
Reporting GuidelinesThis study is reported in accordance with the STROBE guidelines.

Results

A total of 202 clinical Candida isolates obtained between September 2020 and February 2022 were included in this study. Isolates originated from multiple hospital departments and from patients of varying ages, with both outpatients and inpatients represented. The majority of isolates were recovered from inpatients, particularly those admitted to the intensive care unit (ICU). Antifungal susceptibility testing and species identification revealed a predominance of Candida albicans, followed by several non-albicans species. No statistically significant difference was found between genders (Male: 57.4%, Female: 42.6%, p = 0.553). Isolates were predominantly recovered from yeast cultures (57.9%), followed by sputum (15.3%) and aspiration materials (11.4%). Detailed distributions of patient demographics, clinical sample types, species frequencies, departmental origins, and antifungal susceptibility patterns are demonstrated in the tables below (Table 1 and Table 2).

Discussion

Candida species are important opportunistic pathogens capable of causing a wide spectrum of diseases ranging from superficial infections to invasive candidiasis, particularly among immunocompromised and hospitalized individuals. The findings of this study confirm the continued clinical importance of Candida spp. in the hospital setting and further emphasize the predominance of C. albicans and the emerging significance of NCAC species. These findings align with earlier regional surveillance and global studies showing similar epidemiological patterns.^6,10
The predominance of C. albicans (68.8%) in this study is in alignment with previous reports, including Pfaller and Diekema6, who indicated that C. albicans remains the leading cause of mucosal candidiasis and candidemia in spite of the increasing detection of NCAC species in healthcare settings. However, the significant prevalence of C. parapsilosis (11.4%) in our findings is especially important, as this species is shown to colonize the hands of healthcare workers and hospital surfaces, facilitating nosocomial transmission. This observation supports earlier studies, which underlined the frequent isolation of C. parapsilosis from the hands of clinical personnel, highlighting its role in catheter-related and device-associated infections.^6,11,12 In this study, yeast cultures constituted the majority of isolates (57.9%), implying that the highest burden of Candida spp. was detected in non-blood samples. Our finding is in alignment with previous studies showing that Candida species are more commonly recovered from urine, wound secretions, respiratory aspirates, and mucosal surfaces than from bloodstream samples, particularly in ICU and hospitalized settings.^6,13 Similarly, different studies from tertiary-care hospitals have shown high recovery rates from urine and tracheal aspirates reflecting early infection and colonization, while candidemia accounted for only a small proportion of isolates (~ <5%).¹⁴ These similar findings highlight that the predominance of non-sterile site isolates in our dataset is in accordance with global epidemiologic data, further emphasizing the importance of species-level identification across diverse clinical specimen types and continuous surveillance.
Moreover, in a different study, a five-year evaluation (2020-2024) of Candida spp. isolates was performed on bloodstream infections. The antifungal susceptibility profiles of Candida spp. strains of recovered patients were documented in the study. Similar to our study, ICU, cardiology, and pneumology units reported systemic Candida spp. isolation.¹⁵
Importantly, as the frequency of isolates from inpatients (96%) is significantly higher than that of outpatients (4%), this further highlights the nosocomial nature of these infections. Hospitalized individuals, specifically those admitted to ICUs are exposed to well-defined risk factors including invasive procedures, parenteral nutrition, central venous catheters, immunosuppression, and broad-spectrum antimicrobial therapy. This trend is in agreement with surveillance data emphasizing that ICU admissions are a major cause of candidemia incidence globally.^14,16,17
The antifungal susceptibility observed in this study provides important insights into contemporary resistance trends. Amphotericin B proved high sensitivity (93.1%) among isolates, which verifies earlier findings suggesting that resistance to polyenes in C. albicans is not common due to the drug’s mechanism of binding to ergosterol in fungal membranes.8 Nevertheless, reduced susceptibility in certain species, especially NCAC such as C. krusei and C. glabrata, has been reported in previous studies, underscoring the need for continuous local surveillance.^10,18,19
The highest sensitivity (94.6%) was exhibited by Flucytosine, consistent with previous studies reporting the high intrinsic susceptibility of Candida spp. to 5-FC. Nevertheless, resistance can develop rapidly during monotherapy due to mutations in FCY2 and FUR1 genes affecting metabolism and drug uptake. Hence, although the observed high sensitivity is in agreement with the literature, it highlights the well-documented recommendation to avoid 5-FC monotherapy, except in selected cases.^15,20
Furthermore, the sensitivity of Voriconazole (88.1%) observed in this study is in agreement with previous global epidemiological data indicating increased azole resistance, particularly in NCAC species. Previous studies demonstrated that azole resistance mechanisms involve formation of biofilm, especially in C. albicans, which significantly reduces the efficacy of azole, overexpression of efflux pump, and mutations in ERG11.²¹ Importantly, biofilm formation is extensively discussed in the literature,^22,23 and contributes to therapeutic failure and persistent colonization, especially in catheter-associated infections, further validating the clinical significance of our findings.
In previous studies, Candida has been shown to be the most commonly detected in elderly patients, and advanced age has been shown as a key predisposing factor. Frequent hospitalization, immunosenescence and multiple comorbidities have been shown to increase fungal infection risk. However, in our study, patients ages ranged from 0 to 95 years; age-based statistical analysis was not performed. Additionally ,the high rate of isolates from ICU departments and catheterized patients supports previous studies’ findings that highlight the role of biofilm formation on medical devices in mortality and morbidity.^24,25 These findings emphasize the importance of hand hygiene, strict infection control measures, and surveillance protocols in reducing nosocomial transmission.
In general, the results of the study regarding the susceptibility profile concluded that high sensitivity to Flucytosine and Amphotericin B and relatively lower sensitivity to Voriconazole, which suggests a similar pattern in a global sense of shift in antifungal effectiveness patterns. The main causes in the shift are likely directed by the extensive use of azoles, elevated reliance on empirical therapy, and the emergence of resistant NCAC species. In optimization of treatment outcomes, the cornerstone still relies on the continuous monitoring, species-level identification, and routine AFST.
Overall, the results corroborate global surveillance data highlighting predominance of C. albicans, the growing clinical implications of non-Candida species, and dynamic antifungal presentations. These findings highlight the urgent need for antifungal management, directed interventions, and improved infection control practises to manage the growing threat posed by the Candida infections, especially in environments where vulnerable populations are at heightened risk, such as hospitals.

Limitations

This study has several limitations that should also be addressed. Firstly, although patient ages ranged from 0 to 95 years, age-based statistical comparisons were not performed, preventing conclusions regarding age-related susceptibility. Secondly, the retrospective design depended on existing laboratory records, such as catheterization status, prior antifungal exposure, or comorbidities. Thirdly, molecular identification methods were not used; therefore, cryptic or rare Candida species may not have been detected. Finally, antifungal susceptibility testing was limited to Flucytosine, Voriconazole, and Amphotericin B, and the absence of echinocandin testing restricts the broader interpretation of resistance patterns.

Conclusion

This study showed that while non-albicans Candida species, particularly C. parapsilosis, are emerging as clinically significant pathogens, Candida albicans remains the prevalent species isolated from hospitalized patients. The significantly higher number of isolates from inpatients highlights the need for strict infection control practices and the persistent role of nosocomial transmission. Antifungal susceptibility testing demonstrated high sensitivity to Amphotericin B (93.1%) and Flucytosine (94.6%), whereas Voriconazole showed comparatively lower sensitivity (88.1%). These findings emphasize the necessity of routine susceptibility testing due to the potential for azole resistance and underline the continued relevance of flucytosine and polyenes in clinical management. To conclude, the results emphasize the importance of regular antifungal susceptibility monitoring, early species identification, and strengthened infection prevention strategies to effectively handle Candida infections in hospital settings.

Declarations

Abbreviations

AFST: antifungal susceptibility testing
BD: Becton, Dickinson and Company
C.: Candida
EMB: eosin methylene blue agar
EUCAST: European Committee on Antimicrobial Susceptibility Testing
ICU: intensive care unit
NCAC: non-albicans Candida
SDA: Sabouraud dextrose agar
SPSS: Statistical Package for the Social Sciences
STROBE: Strengthening the Reporting of Observational Studies in Epidemiology

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About This Article

Received:

February 4, 2026

Accepted:

April 3, 2026

Published Online:

April 8, 2026