Molecular Identification and Antifungal Susceptibility Patterns of Candida Species in Pediatric Patients at Tabriz Children's Hospital.

Candida species are significant opportunistic pathogens, particularly in immunocompromised pediatric populations. With the increasing incidence of invasive candidiasis in neonatal and pediatric intensive care units, accurate species identification and antifungal susceptibility profiling have become critical for effective treatment. This dual-phase study is aimed at: (1) identifying Candida species from clinical samples using conventional and molecular methods (rDNA-ITS sequencing), and (2) evaluating antifungal susceptibility patterns against fluconazole, itraconazole, amphotericin B, and caspofungin. A total of 97 clinical isolates were obtained from pediatric patients for molecular identification, with 67 isolates successfully subcultured and evaluated for antifungal susceptibility testing. Species identification involved culture on selective media, microscopic examination, DNA extraction, and ITS region sequencing. Antifungal susceptibility testing was performed using the broth microdilution method (CLSI M27 standard) with RPMI-1640 medium, incubating at 35°C for 48 h. Minimum inhibitory concentration (MIC) endpoints were determined visually. Molecular identification revealed the following distribution: C. glabrata (50 isolates, 51.5%), C. albicans/dubliniensis complex (34, 35.1%), C. kefyr (5, 5.2%), C. krusei (6, 6.2%), and C. tropicalis (2, 2.1%). Susceptibility testing showed widespread resistance to fluconazole (particularly in C. glabrata, C. albicans, and C. krusei) and amphotericin B; variable resistance to itraconazole (with 100% susceptibility in C. kefyr); and universal susceptibility to caspofungin (97.4%-100% across species). Our findings highlight a concerning epidemiological shift toward nonalbicans species, predominantly C. glabrata, with distinct resistance profiles. While caspofungin remains highly effective, the observed resistance patterns underscore the necessity of routine antifungal susceptibility testing to guide therapy and prevent treatment failure in pediatric candidiasis.