Evaluation of CAMP-Like Effect, Biofilm Formation, and Discrimination of Candida africana from Vaginal Candida albicans Species

Reported prevalence and comparison of diagnostic approaches for Candida africana: a systematic review with meta-analysis

This systematic review and meta-analysis evaluated reported prevalence and diagnostic methods for identifying Candida africana, an opportunistic yeast associated with vaginal and oral candidiasis. A comprehensive literature search yielded 53 studies meeting the inclusion criteria, 2 of which were case studies. The pooled prevalence of C. africana among 20,571 participants was 0.9% (95% CI: 0.7-1.3%), with significant heterogeneity observed (I2 = 79%, p < 0.01). Subgroup analyses revealed regional variations, with North America showing the highest prevalence (4.6%, 95% CI: 1.8-11.2%). The majority 84.52% of the C. africana have been isolated from vaginal samples, 8.37% from oral samples, 3.77% from urine, 2.09% from glans penis swabs, and 0.42% from rectal swabs, nasal swabs, and respiratory tract expectorations respectively. No C. africana has been isolated from nail samples. Hyphal wall protein 1 gene PCR was the most used diagnostic method for identifying C. africana. It has been used to identify 70% of the isolates. A comparison of methods revealed that the Vitek-2 system consistently failed to differentiate C. africana from Candida albicans, whereas MALDI-TOF misidentified several isolates compared with HWP1 PCR. Factors beyond diagnostic methodology may influence C. africana detection rates. We highlight the importance of adapting molecular methods for resource-limited settings or developing equally accurate but more accessible alternatives for the identification and differentiation of highly similar and cryptic Candida species such as C. africana.

Biochemical typing and evaluation of pathogenicity in vulvovaginal isolates of Candida albicans complex

Introduction

Candida albicans, C. dubliniensis, and C. africana form the Candida albicans complex.

Objective

To identify the phenotypic and pathogenic characteristics of isolates of the C. albicans complex preserved in a collection.

Materials and methods

Three hundred presumptive strains of the C. albicans complex were evaluated using CHROMagarTM Candida. Germ tube production was determined by three methods, chlamydospores formation was assessed and colonies were characterized in artisanal agars (Rosmarinus officinalis and Nicotiana tabacum). MALDI-TOF was used as the gold standard identification test. To detect pathogenicity factors, we evaluated the hemolytic activity of each isolate and cocultured with Staphylococcus aureus, coagulase enzyme production, and biofilm formation.

Results

Out of the 300 isolates, 43.7% produced germ tube in the heart-brain infusion broth and 47% of the isolates produced chlamydospores. In the artisan media, 6% of the isolates produced brown colonies on rosemary agar and 5% did so on tobacco agar. None of the strains hemolyzed the blood agar alone or cocultured with S. aureus. However, 50% of the isolates hemolyzed the potato dextrose agar supplemented with blood. All strains were coagulase producers, and biofilm production was variable. For germ tube production, the human serum method showed the same positivity as the milk broth method. All isolates were identified as C. albicans by MALDI-TOF.

Conclusions

The use of proteomics, molecular tests or a combination of methods is required for species identification.

Phenotypes characterization and ABC genotypes distribution of clinical Candida albicans isolates

BACKGROUND

Candidemia and vaginitis are the most common types of candidiasis mostly caused by Candida albicans species. C. albicans has several genotypes and the potential ability to form different phenotype colonies on specific media. This study aimed to evaluate the genotype distribution of blood and vaginal C. albicans isolates and phenotype characteristics on Spider and yeast peptone dextrose agar medium.

METHODS

A total of 40 clinical Candida albicans isolates comprising vagina (20) and blood (20) were used. ABC typing using CA-INT-R and CA-INT-L primers was performed to span the transposable group I intron of the 25S rDNA gene. For colony phenotypic characteristics, the Spider and YPDA media were used.

RESULTS

Among the blood and vaginal isolates, genotype A (12/60%) and genotype C (10/50%) were the most common types, respectively. The highest phenotype shape frequency of the colonies in blood and vaginal samples was the ring and the lowest was the hat/ring. The dominant color phenotype in blood and vaginal samples was gray. There was a significant relationship between genotype and phenotype forms in the blood sample on YPDA medium (p = 0.02). In the Spider medium, there were no significant differences between genotypes and phenotypes.

CONCLUSION

In this study, genotype A and genotype C were predominant in blood and vaginal samples, respectively. In both groups, YPD agar medium demonstrated the most variety of phenotypes that was related to genotypes A and C. The variety of phenotypes in both groups was the same in genotypes A and C on the Spider medium.

Interspecies Interactions within the Host: the Social Network of Group B Streptococcus

Group B Streptococcus (GBS) is a pervasive neonatal pathogen accounting for a combined half a million deaths and stillbirths annually. The most common source of fetal or neonatal GBS exposure is the maternal microbiota. GBS asymptomatically colonizes the gastrointestinal and vaginal mucosa of 1 in 5 individuals globally, although its precise role in these niches is not well understood. To prevent vertical transmission, broad-spectrum antibiotics are administered to GBS-positive mothers during labor in many countries. Although antibiotics have significantly reduced GBS early-onset neonatal disease, there are several unintended consequences, including an altered neonatal microbiota and increased risk for other microbial infections. Additionally, the incidence of late-onset GBS neonatal disease remains unaffected and has sparked an emerging hypothesis that GBS-microbe interactions in developing neonatal gut microbiota may be directly involved in this disease process. This review summarizes our current understanding of GBS interactions with other resident microbes at the mucosal surface from multiple angles, including clinical association studies, agriculture and aquaculture observations, and experimental animal model systems. We also include a comprehensive review of in vitro findings of GBS interactions with other bacterial and fungal microbes, both commensal and pathogenic, along with newly established animal models of GBS vaginal colonization and in utero or neonatal infection. Finally, we provide a perspective on emerging areas of research and current strategies to design microbe-targeting prebiotic or probiotic therapeutic intervention strategies to prevent GBS disease in vulnerable populations.

Prevalence of Closely Related Candida albicans Species among Patients with Vulvovaginal Candidiasis in Southern Poland Based on the hwp1 Gene Amplification

Candida albicans remains the most common species isolated from women with vulvovaginal candidiasis. However, closely related species such as Candida africana and Candida dubliniensis may also occur, although they are often misidentified. The aim of the study was to confirm the phenotypic identification of C. albicans and its closely related species isolated from women with genital tract infections by amplification of the hwp1 (hyphal wall protein 1) gene in a PCR assay. We report a detailed molecular identification of C. albicans and its closely related species among 326 patients in the Małopolska region, Poland. Initial phenotypic identifications were confirmed by amplification of the hwp1 gene. Based on molecular analysis, we revealed 307 strains (94.17%) as C. albicans and 17 as C. dubliniensis (5.22%). No strain of C. africana was detected. Two patients h ad co-infection with C. albicans and C. dubliniensis (0.61%). A PCR assay targeting the hwp1 gene was reliable for correctly identifying species among the C. albicans complex.

Distribution, antifungal susceptibility pattern and intra-Candida albicans species complex prevalence of Candida africana: A systematic review and meta-analysis

Candida africana is a pathogenic species within the Candida albicans species complex. Due to the limited knowledge concerning its prevalence and antifungal susceptibility profiles, a comprehensive study is overdue. Accordingly, we performed a search of the electronic databases for literature published in the English language between 1 January 2001 and 21 March 2020. Citations were screened, relevant articles were identified, and data were extracted to determine overall intra-C. albicans complex prevalence, geographical distribution, and antifungal susceptibility profiles for C. africana. From a total of 366 articles, 41 were eligible for inclusion in this study. Our results showed that C. africana has a worldwide distribution. The pooled intra-C. albicans complex prevalence of C. africana was 1.67% (95% CI 0.98–2.49). Prevalence data were available for 11 countries from 4 continents. Iran (3.02%, 95%CI 1.51–4.92) and Honduras (3.03%, 95% CI 0.83–10.39) had the highest values and Malaysia (0%) had the lowest prevalence. Vaginal specimens were the most common source of C. africana (92.81%; 155 out of 167 isolates with available data). However, this species has also been isolated from cases of balanitis, from patients with oral lesions, and from respiratory, urine, and cutaneous samples. Data concerning the susceptibility of C. africana to 16 antifungal drugs were available in the literature. Generally, the minimum inhibitory concentrations of antifungal drugs against this species were low.

In conclusion, C. africana demonstrates geographical variation in prevalence and high susceptibility to antifungal drugs. However, due to the relative scarcity of existing data concerning this species, further studies will be required to establish more firm conclusions.

Comparative Analysis of Virulence Factors of Homozygous and Heterozygous Strains of Candida albicans Vaginal Isolates

Although the epidemiology of pathogenic Candida species is changing due to invasive diseases, Candida albicans has become the common cause of human infections worldwide. Candida albicans is a diploid yeast with a mostly clonal mode of reproduction and without known complete sexual cycle. This species has two heterozygous and homozygous strains at hyphal wall protein 1 gene locus (hwp1). Little is known about virulence factors of these strains. The aim of this study was to evaluate the exoenzyme activity of heterozygous and homozygous C. albicans strains. A total of 60 stock Candida albicans species isolates, which consisted of 30 homozygous and 30 heterozygous strains, were used for exoenzyme activities. We used egg yolk agar, Sabouraud blood agar, and bovine serum albumin agar for evaluation of phospholipase, hemolysin, and proteinase activity, respectively. Homozygous strains of Candida albicans had more phospholipase and proteinase activity than heterozygous strains. However, there were no significant statistical differences between the two strains in the severity of exoenzymes production. Beta hemolysin activity was seen in 100% and 96.7% of the homozygous and heterozygous strains, respectively. The results of this study indicated that both of the strains exhibited exoenzyme activities in different ranges. There were no significant statistical differences in virulence factors between the homozygous and heterozygous strains.

Evaluation of biofilm formation in the homozygous and heterozygous strains of vaginal Candida albicans isolates

Background and Purpose

Candida albicans is one of the most opportunistic yeasts around the world. This species has two heterozygous and homozygous strains at hyphal wall protein 1 (hwp1) gene locus. A simple method for the discrimination of these two strains is the amplification of HWP1 gene. Regarding this, the aim of this study was to discriminate C. albicans heterozygous and homozygous strains via the amplification of hwp1 gene and evaluation of biofilm formation between the strains.

Materials and Methods

A total of 60 homozygous (n=30) and heterozygous (n=30) strains were discriminated among 126 C. albicans vaginal isolates by the amplification of HWP1 gene, using specific primers. The evaluation of biofilm formation was accomplished using the visual method.

Results

According to the results, the homozygous and heterozygous strains produced one and two DNA fragments, respectively. The frequency of homozygous strains among the C. albicans vaginal isolates was 76.2%. Biofilm formation activity in the heterozygous strains was more than that in the homozygous strains. However, statistical analysis showed no significant difference between the strains in terms of biofilm formation.

Conclusion

As the findings indicated, the frequency of the heterozygous strains in C. albicans was lower than that of the homozygous strains. Both of the strains could form biofilm in the different ranges of severity. High activity of biofilm formation in heterozygous strains may set the ground for its pathogenicity.