Detection and Molecular Identification of Eight Candida Species in Clinical Samples by Simplex PCR

Experimental study of specific and nonspecific blood culture bottles for the diagnosis of candidemia

BACKGROUND

Early diagnosis of candidemia is critical for the correct management and treatment of patients.

AIMS

To test the efficacy of different blood culture bottles in the growth of Candida strains.

METHODS

We compared the performance of BD BACTEC™ Plus Aerobic/F (Aero) culture bottles with the specific BD BACTEC™ Mycosis IC/F Lytic (Myco) culture bottles using the BD BACTEC™ FX 40 automated blood culture system to determine the mean time-to-detection (TTD) in Candida species. One isolate each of six Candida species was inoculated into blood culture bottles (final concentration, 1-5CFUml-1) and incubated at 37°C until automated growth detection.

RESULTS

Candida albicans and Nakaseomyces glabratus (Candida glabrata) were detected earlier in the specific culture bottle, whereas Candida tropicalis was detected earlier in the nonspecific bottle; Candida parapsilosis, Pichia kudriavzevii (Candida krusei), and Meyerozyma guilliermondii (Candida guilliermondii) presented similar TTD in both bottles.

CONCLUSIONS

Our study suggests the suitability of using both bottles in clinical laboratories for a faster diagnosis and prompt starting of any treatment.

Fungal Spectrum and Susceptibility Against Nine Antifungal Agents in 525 Deep Fungal Infected Cases

Background

Deep fungal infection has become an important cause of infection and death in hospitalized patients, and this has worsened with increasing antifungal drug resistance.

Objective

A 3-year retrospective study was conducted to investigate the clinical characteristics, pathogen spectrum, and drug resistance of deep fungal infection in a regional hospital of Guangzhou, China.

Methods

Non-duplicate fungi isolates recovered from blood and other sterile body fluids of in-patients of the clinical department were identified using biochemical tests of pure culture with the API20C AUX and CHROMagar medium. Antifungal susceptibilities were determined by Sensititre YeastOne^® panel trays.

Results

In this study, 525 patients (283 female, 242 male) with deep fungal infection were included, half of them were elderly patients (≥60 years) (54.67%, n=286). A total of 605 non-repetitive fungi were finally isolated from sterile samples, of which urine specimens accounted for 66.12% (n=400). Surgery, ICU, and internal medicine were the top three departments that fungi were frequently detected. The mainly isolated fungal species were Candida albicans (43.97%, n=266), Candida glabrata (20.00%, n=121), and Candida tropicalis (17.02%, n=103), which contributed to over 80% of fungal infection. The susceptibility of the Candida spp. to echinocandins, 5-fluorocytosine, and amphotericin B remained above 95%, while C. glabrata and C. tropicalis to itraconazole were about 95%, and the dose-dependent susceptibility of C. glabrata to fluconazole was more than 90%. The echinocandins had no antifungal activity against Trichosporon asahi in vitro (MIC₉₀>8 μg/mL), but azole drugs were good, especially voriconazole and itraconazole (MIC₉₀ = 0.25 μg/mL).

Conclusion

The main causative agents of fungal infection were still the genus of Candida. Echinocandins were the first choice for clinical therapy of Candida infection, followed with 5-fluorocytosine and amphotericin B. Azole antifungal agents should be used with caution in Candida glabrata and Candida tropicalis infections.

Synthesis of TiO2-Cu2+/CuI Nanocomposites and Evaluation of Antifungal and Cytotoxic Activity

Fungal infections have become a significant public health concern due to their increasing recurrence and harmful effects on plants, animals, and humans. Opportunistic pathogens (among others from the genera Candida and Aspergillus) can be present in indoor air, becoming a risk for people with suppressed immune systems. Engineered nanomaterials are novel alternatives to traditional antifungal therapy. In this work, copper(I) iodide (CuI) and a copper-doped titanium dioxide-copper(I) iodide (TiO₂-Cu²⁺/CuI) composite nanomaterials (NMs)-were synthesized and tested as antifungal agents. The materials were synthesized using sol-gel (TiO₂-Cu²⁺) and co-precipitation (CuI) techniques. The resulting colloids were evaluated as antifungal agents against Candida parapsilosis and Aspergillus niger strains. The NMs were characterized by XRD, HRTEM, AFM, and DLS to evaluate their physicochemical properties. The NMs present a high size dispersion and different geometrical shapes of agglomerates. The antifungal capacity of the NMs by the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) was below 15 µg/mL against Candida parapsilosis and below 600 µg/mL against Aspergillus niger for both NMs. Holotomography microscopy showed that the NMs could penetrate cell membranes causing cell death through its rupture and reactive oxygen species (ROS) production. Cytotoxicity tests showed that NMs could be safe to use at low concentrations. The synthesized nanomaterials could be potential antifungal agents for biomedical or environmental applications.

Development and evaluation of RPA-NFO-LFT and RPA-Cas12a-LFT systems for the detection of Candida albicans

Recently, the growing number of medical interventions has led to the risk of invasive candidiasis. Among them, Candida albicans (C. albicans) infection has the highest incidence, which has led to great demand for developing early diagnosis methods. In this study, two lateral flow device based molecular assay systems, RPA-NFO-LFT and RPA-Cas12a-LFT, were established and optimized to achieve the detection of C. albicans. Firstly, efficient and specific primers for C. albicans detection were designed and screened, and the purification of amplification products was also explored. Then, many important conditions and issues for each system were investigated and discussed to improve the performances of the test strip devices in C. albicans detection. An evaluation study revealed that both systems showed favorable specificity and sensitivity in the detection of C. albicans samples with a lower detection limit of 10³ CFU ml^-1, while RPA-Cas12a-LFT is more accurate for visual interpretation and more stable toward samples that exhibit serum nucleic acid interference. Finally, the performances of RPA-NFO-LFT and RPA-Cas12a-LFT were compared with that of the conventional qPCR method. This work might provide a reference for the development of molecular assay devices in practical candidiasis diagnosis.

In vitro antifungal and antibiofilm activities of novel sulfonyl hydrazone derivatives against Candida spp

BACKGROUND

The aim of this study was to investigate the antifungal and antibiofilm activity of the new sulfonyl hydrazones compound derived from sulphonamides.

METHODS

In this study, new sulfonyl hydrazone series were synthesized via a green chemistry method. The structures of the synthesized compounds were characterized by elemental analyses and spectroscopic methods. The antifungal activities of the Anaf compounds against Candida strains under planktonic conditions were tested. The biofilm-forming ability of Candida strains was determined and the inhibitory effects of Anaf compounds on Candida biofilms compared with fluconazole were measured by MTT assay. Expression analysis of biofilm-related genes was investigated with qRT-PCR. The statistical analysis was performed using a one-way ANOVA test. CANDIDA: strains was determined and the inhibitory effects of Anaf compounds on Candida biofilms compared with fluconazole were measured by MTT assay. Expression analysis of biofilm-related genes was investigated with qRT-PCR. The statistical analysis was performed using a one-way ANOVA test.

RESULTS

A total of 16 (45.7%) out of 35 Candida isolates were determined as strong biofilm producers in this study. C. albicans was the most biofilm producer, followed by C. krusei and C. lusitaniae. The Anaf compounds had a broad spectrum of activity with MIC values ranging from 4 μg/ml to 64 μg/ml. Our data indicated that the Anaf compound had a significant effect on inhibiting biofilm formation in both fluconazole-susceptible and -resistant strains. The expression levels of hypha-specific genes als3, hwp1, ece1 and sap5 were downregulated by Anaf compounds.

CONCLUSIONS

Our study revealed that the Anaf compounds had antifungal activity and inhibited fungal biofilms, which may be related to the suppression of C. albicans adherence and hyphal formation. These results suggest that Anaf compounds may have therapeutic potential for the treatment and prevention of biofilm-associated Candida infections.

Establishment of a rapid diagnosis method for Candida glabrata based on the ITS2 gene using recombinase polymerase amplification combined with lateral flow strips

Candida glabrata is the second or third most common Candida-associated species isolated from hospital-acquired infections, surpassing even C. albicans in some hospitals. With the rapid progression of the disease course of C. glabrata infections, there is an urgent need for a rapid and sensitive on-site assay for clinical diagnosis. Isothermal amplification is a recently developed method for rapid nucleic acid detection that is being increasingly used for on-site detection, especially recombinase polymerase amplification (RPA). RPA combined with lateral flow strips (LFS) can rapidly amplify and visually detect the target gene within 20 min. The whole detection process can be controlled within 30–60 min by rapid sample pre-treatment. In this study, RPA-LFS was used to amplify the internal transcribed spacer region 2 gene of C. glabrata. The primer–probe design was optimized by introducing base mismatches (probe modification of one base) to obtain a highly specific and sensitive primer–probe combination for clinical sample detection. RPA-LFS was performed on 23 common clinical pathogens to determine the specificity of the assay system. The RPA-LFS system specifically detected C. glabrata without cross-reaction with other fungi or bacteria. Gradient dilutions of the template were tested to explore the lower limit of detection of this detection system and to determine the sensitivity of the assay. The sensitivity was 10 CFU/µL, without interference from genomic DNA of other species. The RPA-LFS and qPCR assays were performed on 227 clinical samples to evaluate the detection performance of the RPA-LFS system. Eighty-five samples were identified as C. glabrata, representing a detection rate of 37.5%. The results were consistent with qPCR and conventional culture methods. The collective findings indicate a reliable molecular diagnostic method for the detection of C. glabrata, and to meet the urgent need for rapid, specific, sensitive, and portable clinical field-testing.

Rapid Detection of Candida tropicalis in Clinical Samples From Different Sources Using RPA-LFS

Candida tropicalis is one of the few Candida species besides Candida albicans that is able to produce true hyphae. At present, the commonly used clinical methods for the identification of this organism are traditional fungal culture, CTB staining, and color development. Polymerase chain reaction (PCR) and real-time quantitative PCR (qPCR) are also used to identify this fungus. Since the course of C. tropicalis infection progresses rapidly, there is an urgent need for rapid, sensitive, real-time field assays to meet the needs of clinical diagnosis. Recombinase polymerase amplification (RPA) combined with lateral flow strip (LFS) can rapidly amplify and visualize target genes within 20 min, and by pre-processing samples from different sources, the entire process can be controlled within 30 min. In this study, RPA-LFS was used to amplify the internal transcribed spacer-2 (ITS2) gene of C. tropicalis, and primer-probe design was optimized by introducing base mismatches to obtain a specific and sensitive primer-probe combination for clinical sample detection. LFS assay for 37 common clinical pathogens was performed, sensitivity and specificity of the detection system was determined, reaction temperature and time were optimized, and 191 actual clinical samples collected from different sources were tested to evaluate the detection performance of the established RPA-LFS system to provide a reliable molecular diagnostic method for the detection of C. tropicalis, the results show that the RPA-LFS system can specifically detect C. tropicalis without cross-reacting with other fungi or bacterial, with a sensitivity of 9.94 CFU/µL, without interference from genomic DNA of other species, at an optimal reaction temperature of 39°C, and the whole reaction process can be controlled within 20 min, and to meet the clinical need for rapid, sensitive, real-time, and portable field testing.