Candida tropicalis is one of the major candidaemia agents, associated with the highest mortality rates among Candida species, and developing resistance to azoles. Little is known about the molecular mechanisms of azole resistance, genotypic diversity, and the clinical background of C. tropicalis infections. Consequently, this study was designed to address those questions. Sixty-four C. tropicalis bloodstream isolates from 62 patients from three cities in Iran (2014–2019) were analyzed. Strain identification, antifungal susceptibility testing, and genotypic diversity analysis were performed by MALDI-TOF MS, CLSI-M27 A3/S4 protocol, and amplified fragment length polymorphism (AFLP) fingerprinting, respectively. Genes related to drug resistance (ERG11, MRR1, TAC1, UPC2, and FKS1 hotspot9s) were sequenced. The overall mortality rate was 59.6% (37/62). Strains were resistant to micafungin [minimum inhibitory concentration (MIC) ≥1 μg/ml, 2/64], itraconazole (MIC > 0.5 μg/ml, 2/64), fluconazole (FLZ; MIC ≥ 8 μg/ml, 4/64), and voriconazole (MIC ≥ 1 μg/ml, 7/64). Pan-azole and FLZ + VRZ resistance were observed in one and two isolates, respectively, while none of the patients were exposed to azoles. MRR1 (T255P, 647S), TAC1 (N164I, R47Q), and UPC2 (T241A, Q340H, T381S) mutations were exclusively identified in FLZ-resistant isolates. AFLP fingerprinting revealed five major and seven minor genotypes; genotype G4 was predominant in all centers. The increasing number of FLZ-R C. tropicalis blood isolates and acquiring FLZ-R in FLZ-naive patients limit the efficiency of FLZ, especially in developing countries. The high mortality rate warrants reaching a consensus regarding the nosocomial mode of C. tropicalis transmission.

Despite the increasing occurrence of Candida orthopsilosis and Candida metapsilosis in clinical settings, little is known about their microbiological and clinical properties. Herein, we conducted a national retrospective study (2014–2019) from multiple centers in Iran. Among the 1,770 Candida isolates collected, we identified 600 Candida parapsilosis species complex isolates. Isolate identification was performed by 9-plex PCR, matrix-assisted laser desorption-time of flight mass spectrometry (MALDI-TOF MS), and rDNA sequencing, and antifungal susceptibility testing (AFST) followed CLSI M27-A3/S4; genotyping was performed by amplified fragment length polymorphism (AFLP) analysis; and clinical information was mined. Thirty-one isolates of C. orthopsilosis from various clinical sources, one mixed sample (blood) concurrently containing C. orthopsilosis and C. parapsilosis and one isolate of C. metapsilosis from a nail sample were identified. Although both 9-plex PCR and MALDI-TOF successfully identified all isolates, only 9-plex PCR could identify the agents in a mixed sample. For the C. orthopsilosis isolates, resistance (non-wild type) was noted only for itraconazole ( n = 4; 12.5%). Anidulafungin and fluconazole showed the highest and voriconazole had the lowest geometric mean values. AFLP analysis showed three main and four minor genotypes. Interestingly, 90% of nail isolates clustered with 80% of the blood isolates within two clusters, and four blood isolates recovered from four patients admitted to a hospital clustered into two genotypes and showed a high degree of similarity (>99.2%), which suggests that C. orthopsilosis disseminates horizontally. Supported by our data and published case studies, C. orthopsilosis and C. metapsilosis can be linked to challenging clinical failures, and successful outcomes are not always mirrored by in vitro susceptibility. Accordingly, conducting nationwide studies may provide more comprehensive data, which is required for a better prognosis and clinical management of patients.

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Background: The aspects of the epidemiology of bloodstream Candida infections including clinical features, the causal agents, underlying conditions, and risk factors have not been well-defined in Iranian pediatric patients. The aim of this observational study was to identify uncommon Candida species isolated from blood and other normally sterile specimens of the neonates and children admitted to intensive care units at Children's medical center, Tehran, Iran. Methods: The study was carried out prospectively on patients < 16 years, who were hospitalized in Children's medical center, Tehran, Iran, during 25 months, from June 2014 to July 2016. Blood and other normally sterile specimens were collected from 6,075 pediatric patients and only pure growth of yeasts were included the study. The yeast isolates were subjected to DNA extraction, PCR of ITSregion, and sequencing followed by Blast analysis to accurately identify the species. Results: A total of 16 out of 136 isolates were recognized as uncommon or rare Candida species. According to the sequence analysis, these isolates were identified as C. orthopsilosis (N = 5, 3.7%), C. glabrate (n = 4, 2.5%), C. dubliniensis (n = 2, 1.5%), C. lusitaniae (n = 2, 1.5%), C. kefyr (n = 2, 1.5%), and C. intermedia (n = 1, 0.75%) Conclusions: Candida species, which were once considered harmless, have now been recognized as causative agents of candidemia. It is essential to consider, manage, and control the conditions that lead to the development of these unusual but severe cases of candidemia.

Four isolates of C. nivariensis were deposited in the culture collection of Westerdijk Fungal Biodiversity Institute (accession numbers CBS 15642-15645). Sequences of the large subunit and internal transcribed sequences of rDNA and hotspot 1 of FKS1 and FKS2 were deposited in GenBank under the accession numbers, MK503934-MK503937, MK503955-MK503958, and MK509355-MK509362. †These authors contributed equally to this work Two supplementary tables are available with the online version of this article.

This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

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Background: Candida species originating from either endogenous or exogenous sources are one of the main causes of opportunistic infections. Colonization is an important independent risk factor for invasive candidiasis, and many patients admitted to neonatal intensive care unit (NICU) and pediatric intensive care unit (PICU) are colonized with Candida species that may result in invasive candidiasis. Awareness among clinicians about various aspects of colonization is critical to optimal management. The aim of this study was to determine the frequency and species distribution of Candida strains isolated from predisposed patients hospitalized at Children's Medical Center (CMC), Tehran, Iran. Methods: From June 2014 to June 2016, 347 Candida isolates were collected from 341 patients either hospitalized in different wards or referred as outpatients. The yeasts were identified by colony color characteristics using CHROMagar Candida medium and by amplification of the ITS1-5.8S rDNA-ITS2 region in DNA extracted from each isolate followed by analysis of species specific electrophoretic patterns of PCR products digested with the restriction enzyme MspI. Results: Of the 341 patients, 213 were males and 128 were females. Most samples were obtained from the 1 -12-month age group, and the majority of samples represented urine (n = 182), throat swabs (n = 57), and stool samples (n = 53), respectively. The samples were mostly from patients in general wards. The most commonly isolated species was C. albicans (77%), followed by C. tropicalis (8.4%), C. parapsilosis (7.5%), C. glabrata (2.3%), C. kefyr (1.7%), C. krusei (1.1%), C. lusitaniae (0.6%), C. guilliermondii (0.3%), C. albicans + C. parapsilosis (1.4%), and C. albicans + C. glabrata (0.3%). Conclusions: C. albicans is the most common species isolated from children in Iran, followed by C. tropicalis and C. parapsilosis, a prevalence pattern that is relatively different from studies in other countries. Neonates and infants 1 -12 months of age hospitalized in ICU, were more colonized by Candida species than other groups.