Rapid simultaneous detection and identification of six species Candida using polymerase chain reaction and reverse line hybridization assay

Alginate‑carbon dot nanocomposite: A green approach towards designing turn-on aptasenor for Candida albicans fungus

Candida albicans fungus, an opportunistic microorganism that becomes a pathogen in its host, can often cause superficial and severe infections in human body. In this work, a turn-on fluorescent aptasenor based on Alginate‑carbon dot nanocomposite has been designed through a green approach. Carbon dots (CDs) with average size of 4 ± 1 nm were synthesized hydrothermally using Philodendron bipinnatifidum plant extract as precursor. Then, mixture of carbon dot and alginate was cross-linked by Ca2+ ions to make Alginate-CD nanocomposite with negligible effect on fluorescence intensity of CDs (λex = 360 nm, λem = 400 nm). The fluorescence quantum yield and lifetime were found as 4.1 % and 3.15 ns, respectively. The nanocomposite was characterize using different spectroscopic (Photoluminescence, UV-visible, XPS, FT-IR) and microscopic (TEM and SEM) analytical techniques. An aptamer was used to selectively target (1 → 3)-β-D-glucan on the surface of the Candida albicans cell wall. It was found that the fluorescence energy resonance transfer between nanocomposite and aptamer quenches the fluorescence intensity of nanocomposite, making it suitable for designing turn-on fluorescent probe. It was found that the fluorescence could be recovered in the presence of Candida albicans fungus (in <30 min), owing to higher affinity between aptamer and (1 → 3)-β-D-glucan on the surface of Candida albicans fungus, where there were two linear ranges: low concentration of 50-200 cells/mL and high concentration of 1000-6000 cells/mL (R2 ≥ 0.989 for both linear ranges), with limit of detection of 40 cells/mL. The selectivity of the designed probe was examined against a mixture of microbial agents (Staphylococcus aureus and Escherichia coli) and Curdlan polysaccharide (1→3)-b-D-Glucan (L). The designed biosensor showed an excellent ability to directly detect Candida albicans fungus via a simple and fast (<30 min) approach. The results of this experimental study show that Alginate-CD-aptamer nanocomposite is a bright prospect in clinical applications and a suitable alternative to traditional methods of Candida albicans diagnosis.

PCR: An Effective, Faster and Relevant Method for the Detection of Clinical Isolates of Candida albicans

Background:

Candida albicans is associated with infectious diseases with colonization, in both immunocompromised and immunocompetent patients. Antibiotic treatment can develop candidiasis.

Objective:

Evaluation of ITS 4 and ITS5 primer expression on clinical isolates of C. albicans.

Methods:

Fifty clinical isolates of C. albicans were collected from different sites viz. Catheter Tip (CT), High Vaginal Swab (HVS) and Urine (U).

Results:

Using the universal fungal primers ITS4 and ITS5, PCR produced a single monomorphic amplification at 520 bp indicating that the strains are of same genetic identity.

Conclusion:

This is an effective, faster and relevant method for the detection and characterization of clinically isolated strains of C. albicans.

Translation elongation factor 1-alpha gene as a marker for diagnosing of candidal onychomycosis

Background and Purpose:

Culture-based identification methods have been the gold standard for the diagnosis of candidal onychomycosis. Molecular technologies, such as polymerase chain reaction (PCR) assays, can provide an alternative for the rapid detection of Candida species. The present study was conducted to investigate a pan-Candida PCR assay based on the translation elongation factor 1-alpha (TEF-1α) gene for the detection of the most prevalent pathogenic Candida species.

Materials and Methods:

For the purpose of the study, an optimized pan-Candida PCR primer pair was designed, and the target was amplified and sequenced. The analytical and clinical diagnostic performance of the designed primers was tested using 17 reference strains, 137 nail scrapings suspected of onychomycosis, and 10 healthy nail specimens.

Results:

The use of the universal pan-Candida primers designed on TEF-1α gene resulted in the successful amplification of a 270-base pair fragment in all Candida species tested, except for C. glabrata, and reacted neither with other fungi nor with E. coli. The sequence difference count matrix showed poor insertion/deletion differences (0-2 nt) among Candida species. Among 137 nail specimens, 35% (n=48), 30.7% (n=42), and 40.1% (n=55) of the samples were found to be positive by direct microscopy, culture, and pan-Candida PCR, respectively.

Conclusion:

Based on the findings, the PCR-based detection targeting the DNA TEF-1α gene is a rapid and simple procedure for the diagnosis of candidal onychomycosis directly from nail sample.

Evaluation of PCR-reverse line blot hybridization assay for simultaneous identification of medically important saprophytic fungi

BACKGROUND

In immunocompromised patients suffering from invasive fungal infections, rapid identification of fungal species is important since the appropriate treatment is usually related to the responsible species. We describe here, an assay based on combination of PCR and reverse line blot hybridization (PCR/RLB) for differentiation causative agent of fungal infections.

MATERIALS AND METHODS

We performed PCR/RLB assay on 10 reference strains, which include Aspergillus species (A. fumigatus, A. flavus, A. niger, A. terreus, and A. clavatus), Mucor circnelloides, Rhizopus oryzae, Alternaria alternata, Cladosporium herbarum, and Fusarium solani. Besides, twenty-two clinical specimens from patients with proven fungal infections were analyzed for the identification of species. The obtained results were then compared with the results of culture and sequence analysis.

RESULTS

The fungal species-specific oligonucleotide probes were able to distinguish between all species represented in this study with the exception of cross-reactivity between A. niger and A. fumigatus species. Two specimens, which were represented as mixed fungi in culture, were identified properly by this method. Results of the RLB assay were concordant with the culture and ITS sequencing results.

CONCLUSION

Our result demonstrate that the RLB assay potentially is suitable for rapid and simultaneous identification of variety fungal pathogens directly from culture as well as from clinical specimens.

A Photonic Crystal Protein Hydrogel Sensor for Candida albicans

We report two-dimensional (2D) photonic crystal (PC) sensing materials that selectively detect Candida albicans (C. albicans). These sensors utilize Concanavalin A (Con A) protein hydrogels with a 2D PC embedded on the Con A protein hydrogel surface, that multivalently and selectively bind to mannan on the C. albicans cell surface to form crosslinks. The resulting crosslinks shrink the Con A protein hydrogel, reduce the 2D PC particle spacing, and blue-shift the light diffracted from the PC. The diffraction shifts can be visually monitored, measured with a spectrometer, or determined from the Debye diffraction ring diameter. Our unoptimized hydrogel sensor has a detection limit of around 32 CFU/mL for C. albicans. This sensor distinguishes between C. albicans and those microbes devoid of cell-surface mannan such as the gram-negative bacterium E. coli. This sensor provides a proof-of-concept for utilizing recognition between lectins and microbial cell surface carbohydrates to detect microorganisms in aqueous environments.

Identification of Candida Species Using MP65 Gene and Evaluation of the Candida albicans MP65 Gene Expression in BALB/C Mice

Background:

Systemic candidiasis is a major public health concern. In particular, in immunocompromised people, such as patients with neutropenia, patients with Acquired Immune Deficiency Syndrome (AIDS) and cancer who are undergoing antiballistic chemotherapy or bone marrow transplants, and people with diabetes. Since the clinical signs and symptoms are nonspecific, early diagnosis is often difficult. The 65-kDa mannoprotein (MP65) gene of Candida albicans is appropriate for detection and identification of systemic candidiasis. This gene encodes a putative b-glucanase mannoprotein of 65 kDa, which plays a major role in the host-fungus relationship, morphogenesis and pathogenicity.

Objectives:

The current study aimed to identify different species of Candida (C. albicans, C. glabrata and C. parapsilosis) using the Polymerase Chain Reaction (PCR) technique and also to evaluate C. albicans MP65 gene expression in BALB/C mice.

Materials and Methods:

All yeast isolates were identified on cornmeal agar supplemented with tween-80, germ tube formation in serum, and assimilation of carbon sources in the API 20 C AUX yeast identification system. Polymerase Chain Reaction was performed on all samples using species-specific primers for the MP65 65 kDa gene. After RNA extraction, cDNA synthesis was performed by the Maxime RT Pre Mix kit. Candida albicans MP65 gene expression was evaluated by quantitative Real-Time (q Real-Time) and Real-Time (RT) PCR techniques. The 2-ΔΔCT method was used to analyze relative changes in gene expression of MP65. For statistical analysis, nonparametric Wilcoxon test was applied using the SPSS version 16 software.

Results:

Using biochemical methods, one hundred, six and one isolates of clinical samples were determined as C. albicans, C. glabrata and C. parapsilosis, respectively. Species-specific primers for PCR experiments were applied to clinical specimens, and in all cases a single expected band for C. albicans, C. glabrata and C. parapsilosis was obtained (475, 361 and 124 base pairs, respectively). All species isolated by culture methods (100% positivity) were evaluated with PCR using species-specific primers to identify Candida species. Relative expression of Mp65 genes increased significantly after C. albicans injection into the mice (P < 0.05).

Conclusions:

The results of the current study showed that the PCR method is reproducible for rapid identification of Candida species with specific primers. Mp65 gene expression of C. albicans after injection into the mice was 2.3 folds higher than before injection, with this difference being significant. These results indicated that increase of Mp65 gene expression might be an early stage of infection; however definitive conclusions require further studies.

The Role of PCR in the Diagnosis of Candida Vulvovaginitis-a New Gold Standard?

PCR is recognized as a reliable technique for detection of all types of microorganisms. Being highly objective and reproducible also sensitive and specific, PCR is now widely used for sexually transmitted infection (STI) diagnosis. Potential, however, exists for detecting non-pathogens, and not identifying a pathogenic state decreases specificity or clinical significance. PCR Candida tests of vaginal specimens are now widely available and frequently used offering a modest to moderate increase in sensitivity and are likely to replace traditional culture and DNA homology testing. Nevertheless, there remain considerable gaps in our knowledge regarding the usefulness and applications of these expensive tests.

Phenotypic characterization and adhesive properties of vaginal Candida spp. strains provided by the CHU Farhat Hached (Sousse, Tunisia)

BACKGROUND

Vulvovaginal candidiasis is a common infection among women worldwide, being Candida albicans the most commonly isolated species. Therefore, controlling this opportunistic yeast is one of the key factors for reducing nosocomial infection.

AIMS

We investigated several virulence properties of 28 vaginal strains of Candida isolated from Tunisian women suffering from vulvovaginitis. We also analyzed the virulence properties of a clinical Candida krusei strain and five Candida reference strains.

METHODS

Candida strains were subjected to microscopic analysis and culture in Candida ID2 chromogenic medium. The adhesive properties of these strains were estimated by the microtiter plate - the safranin-staining - and the Congo red agar (CRA) methods, for determining yeast ability to form biofilms on biomaterials used in urinary catheter manufacturing. Their potency to produce hydrolytic enzymes was also studied.

RESULTS

Our results showed that nine out of the total studied strains produced phospholipase. In addition, very high protease activity was detected in 23 Candida strains. All Candida strains were beta-hemolytic and adhered to polystyrene microtiter plates in varying degrees. Two vaginal C. albicans strains were strongly adhesive to polystyrene and glass slides. Also, our results showed that vaginal Candida strains were more adhesive to the three tested materials than the reference strains.

CONCLUSIONS

This study shows the presence of a range of virulence and adhesion factors in clinical isolates of vaginal Candida. Consequently, control and treatment of vaginal candidiasis as a means to prevent biofilm formation on urinary catheters is of crucial importance.

Candida albicans or Candida dubliniensis?

Candida albicans is increasing as an opportunistic pathogen causing candidemia and candidiasis worldwide. In addition, other non-albicans Candida species are now also associated with pertinent infections. These include the closely related C. dubliniensis, which shares many phenotypic similarities with C. albicans. These similarities pose problems in the identification of isolates and have previously led to misidentification of these species. As a result, several identification techniques based on phenotypic and genotypic characteristics have been developed to differentiate between these Candida species. This review will focus on the similarities and differences between these two Candida species highlighting different identification methods and their advantages and disadvantages.