Introduction
The genus Candida comprises over 150 species, with approximately 20 known to cause infections in humans.1 Candida albicans is traditionally recognized as the most common opportunistic fungal pathogen responsible for a variety of infections, including urinary tract infections (UTIs).2 Candiduria, the presence of Candida species in urine, is frequently encountered in both hospital and community settings, with reported prevalence ranging from 1% to 10% among all urine samples processed in clinical microbiology laboratories.3, 4
Differentiating between colonization and true infection is a significant clinical challenge. While candiduria may represent mere colonization or contamination, it can also indicate invasive disease, particularly in high-risk populations such as critically ill patients, those with indwelling urinary catheters, diabetics, and individuals receiving broad-spectrum antibiotics.5, 6 Accurate identification of Candida species and determination of their pathogenic role are essential for effective patient management.
In recent years, there has been a notable shift in the epidemiology of candiduria, with non-albicans Candida species emerging as significant pathogens.7 These species often exhibit reduced susceptibility or inherent resistance to commonly used antifungal agents, particularly azoles, complicating treatment decisions.8, 9, 10, 11, 12 Therefore, Antifungal sensitivity testing plays a critical role in guiding appropriate therapy and improving patient outcomes.
This study aims to elucidate the microbial profile of candiduria in a tertiary care hospital in Vadodara, Gujarat, distinguish between uropathogenic and commensal isolates based on clinical and microbiological criteria, and assess their Antifungal sensitivity patterns to inform effective treatment strategies.
Aim
To determine the microbial profile of candiduria, differentiate between uropathogenic and commensal isolates, and assess their antifungal sensitivity patterns in a tertiary care hospital in Vadodara, Gujarat.
Objectives
To identify and quantify the Candida species in urine specimen from patients with suspected UTIs.
To classify the Candida isolates as uropathogens or commensals based on clinical data, colony counts, and patient symptoms.
To evaluate the antifungal sensitivity of Candida by standard testing methods.
Materials and Methods
Study design and setting
This study employed a retrospective cross-sectional approach, spanning from January 1, 2022, to December 31, 2022, at a tertiary care facility located in Vadodara, Gujarat. The Institutional Ethics Committee approved the study.
Sample collection
We collected a total of 9,227 urine samples from patients of various ages and genders who presented with suspected urinary tract infections across different hospital departments, including both inpatient and outpatient settings.
Inclusion criteria
Patients exhibiting clinical symptoms indicative of a urinary tract infection (e.g., dysuria, frequent urination, urgency, suprapubic discomfort, fever).
Patients with identified risk factors such as indwelling urinary catheters, diabetes mellitus, immunosuppression, recent antibiotic usage, or extended hospital stays.
Sample processing
Microscopic examination
Uncentrifuged urine samples were analyzed under a microscope using wet mounts and Gram staining to identify yeast cells and pseudohyphae.
Culture techniques
Samples were plated onto Cysteine Lactose Electrolyte Deficient (CLED) agar and Sabouraud Dextrose Agar (SDA) using a calibrated loop to deliver 0.001 mL of urine.
The plates were incubated aerobically at 37°C for 24-48 hours.
Colony counts were assessed, with ≥104 CFU/mL for catheterized patients and ≥105 CFU/mL for non-catheterized patients considered significant.
Identification of candida species
Preliminary identification
Yeast colonies were examined for morphological traits on SDA and Chromogenic Candida Agar (HiCrome Candida Differential Agar, HiMedia, India), which allowed presumptive identification based on colony color:
Germ tube test
Suspected yeast colonies were inoculated into human serum and incubated at 37°C for 2 hours to test for germ tube formation, indicating C. albicans or C. dubliniensis.
Cornmeal agar morphology
Chlamydospore formation was evaluated by culturing isolates on Cornmeal Agar with Tween 80 and incubating at 25°C for 48-72 hours.
Automated identification
Final species identification was verified using the VITEK 2 Compact System (BioMérieux, France) with the YST identification card, adhering to the manufacturer's guidelines.
Quality control was conducted using standard reference strains (C. albicans ATCC 90028, C. tropicalis ATCC 750, C. glabrata ATCC 2001, and C. krusei ATCC 6258).
Antifungal sensitivity Testing
Methodology
Antifungal sensitivity was assessed using the CLSI M27-A3 broth microdilution method.
The antifungal agents tested included:
Procedure
Yeast suspensions were adjusted to match a 0.5 McFarland standard and diluted to 0.5 x 10^3 to 2.5 x 10^3 CFU/mL.
Antifungal agents were prepared in RPMI 1640 medium with MOPS buffer at the required concentrations.
Microdilution plates were incubated at 35°C and assessed visually after 24 and 48 hours.
Minimum Inhibitory Concentrations (MICs) were determined:
Differentiation between Uropathogenic and commensal candida isolates
Criteria for uropathogenicity
Significant colony counts (≥105 CFU/mL for non-catheterized and ≥104 CFU/mL for catheterized patients).
Presence of urinary symptoms (e.g., dysuria, urgency, frequency, hematuria, suprapubic pain).
Risk factors for candiduria (e.g., indwelling urinary catheter, recent antibiotic use, diabetes mellitus, immunosuppression).
Results
Microbial profile of candiduria
We identified 67 Candida isolates from the 9,227 urine samples, representing a candiduria prevalence of 2.43%. Among these, Candida albicans was isolated in 24 cases (35.82%), while non-albicans species predominated, accounting for 43 cases (64.18%).
The distribution of non-albicans Candida species was as follows
C. tropicalis: 17 cases (25.37%)
C. parapsilosis: 14 cases (20.90%)
C. glabrata: 8 cases (11.94%)
C. krusei: 4 cases (5.97%)
Table 1
Antifungal Susceptibility Patterns of Candida Isolates
Table 2
Criteria for differentiation between uropathogenic and commensal Candida Isolates
Differentiation between uropathogenic and commensal isolates
Based on clinical and microbiological criteria, 45 isolates (67.16%) were classified as uropathogens, while 22 isolates (32.84%) were considered commensals. C. albicans was more frequently associated with uropathogenicity (16/24, 66.67%), whereas non-albicans species were more commonly isolated as commensals.
Antifungal sensitivity patterns
Antifungal sensitivity testing revealed the following patterns:
C. albicans isolates were highly susceptible to fluconazole (95.83%) and caspofungin (100%), with no resistance to amphotericin B observed.
Among non-albicans species, C. tropicalis showed 70.59% susceptibility to fluconazole and 94.12% susceptibility to caspofungin, while 100% of isolates were susceptible to micafungin.
C. parapsilosis isolates exhibited variable resistance to azoles, with 78.57% susceptible to voriconazole and 85.71% susceptible to caspofungin.
C. glabrata and C. krusei demonstrated inherent resistance to fluconazole and were fully susceptible to echinocandins.
Discussion
Candiduria, though often perceived as benign colonization, can represent invasive infection in certain patient populations. 13 The clinical significance of candiduria, therefore, depends on various factors, including colony counts, patient symptoms, and underlying risk factors. 14
The present study demonstrates a predominance of non-albicans Candida species in candiduria cases, consistent with recent epidemiological trends worldwide. 15 The high isolation rate of C. tropicalis and C. parapsilosis highlights the shifting landscape of candiduria, with these species increasingly recognized as important Uropathogens. 16, 17
Antifungal sensitivity testing remains a critical tool in managing candiduria, particularly given the rising incidence of antifungal resistance.18 In our study, echinocandins demonstrated the highest efficacy against Candida isolates, while azole resistance was notably higher among non-albicans species, particularly C. glabrata and C. krusei. 19, 20
The study underscores the importance of distinguishing between uropathogenic and commensal Candida isolates. Clinical and microbiological criteria, including colony counts and patient symptoms, are essential in guiding appropriate management decisions.21 While echinocandins may offer a robust treatment option for invasive candiduria, the use of azoles should be guided by susceptibility results, particularly in the context of non-albicans species.
Continuous surveillance of antifungal resistance patterns in candiduria is imperative to inform empirical therapy and improve patient outcomes.
Conclusion
The study highlights a significant shift in the microbial profile of candiduria, with non-albicans Candida species emerging as predominant pathogens. Differentiating between uropathogenic and commensal isolates based on clinical and microbiological criteria is crucial for appropriate management. Antifungal sensitivity testing remains essential, particularly in the context of rising resistance to azoles. Ongoing surveillance and tailored treatment protocols are necessary to address the evolving landscape of candiduria.
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