Vulvovaginal candidiasis is associated with the production of germ tubes by Candida albicans

Virulence Factors of Candida spp. and Host Immune Response Important in the Pathogenesis of Vulvovaginal Candidiasis

Vulvovaginal candidiasis (VVC) is one of the most common types of vaginal infections in women around the world and is often underestimated by both patients and doctors. Research on the pathogenesis of fungal vaginal infections over the last 20 years has resulted in a closer understanding of the virulence factors involved in Candida epithelial invasion and their mechanisms of action. Recently, attention was drawn to the enormous complexity of the interaction between yeast-like fungi and host cells, as well as the level of complexity of the host's response to infection and their impact on the course and treatment of VVC. Our work provides a broad description of already known and some new reports on Candida virulence factors (such as phenotypic switching or biofilm formation capacity) and their importance for tissue invasion in VVC. At the same time, we also focus on interactions with host cells and local innate immune mechanisms involved in the response to vaginal fungal invasion that are now considered equally important in this case. The presented review describes the most important aspects of the still unknown pathogenicity of Candida associated with vaginal infections.

Antifungal Activity of Linear and Disulfide-Cyclized Ultrashort Cationic Lipopeptides Alone and in Combination with Fluconazole against Vulvovaginal Candida spp

Vulvovaginal candidiasis (VVC) occurs in over 75% of women at least once during their lifetime and is an infection that significantly affects their health. Candida strains resistant to standard azole antifungal therapy and relapses of VVC are more and more common. Hypothetically, biofilm is one of the main reasons of relapses and failure of the therapy. Ultrashort cationic lipopeptides (USCLs) exhibit high antimicrobial activities. Our previous study on USCLs revealed that disulfide cyclization can result in selective antifungal compounds. Therefore, four USCL were selected and their antifungal activity were studied on 62 clinical strains isolated from VVC. The results confirmed previous premises that cyclic analogs have increased selectivity between fungal cells and keratinocytes and improved anticandidal activity compared to their linear analogs against both planktonic and biofilm cultures. On the other hand, linear lipopeptides in combination with fluconazole showed a synergistic effect. It was found that the minimum inhibitory concentrations of the tested compounds in combination with fluconazole were at least four times lower than when used separately. Our results indicate that combination therapy of VVC with USCLs and fluconazole at low non-toxic concentrations can be beneficial owing to the synergistic effect. However, further in vivo studies are needed to confirm this hypothesis.

Anticandidal Activity of Omiganan and Its Retro Analog Alone and in Combination with Fluconazole

Vulvovaginal candidiasis (VVC) is a vaginal infection that manifests itself as several symptoms which can lead to various life-threatening complications. The majority of VVC is caused by Candida albicans strains, and it is estimated that approximately 75% of women worldwide would suffer from this condition at least once during their lifetime. Surprisingly, the detailed pathomechanism of yeast-like fungi invasions in vagina is not yet fully understood. However, the ability to form biofilm on vaginal mucosa is considered as one of the critical factors associated with failure of the therapy and recurrences of the disease. Antimicrobial peptides (AMPs) are a promising class of compounds that are receiving a growing interest owing to their antibacterial, antifungal, and antibiofilm properties. Omiganan is a synthetic analog of Indolicidin that is characterized by wide spectrum of antimicrobial and antibiofilm activities. Recent reports suggest improved activity of analogs with a reversed sequence (retro-analog concept). Therefore, Omiganan and its retro analog were tested against planktonic forms and biofilm of 18 Candida strains isolated from VVC. Moreover, the synergy between the AMPs and fluconazole was studied as well. The AMPs appeared to be effective against C. albicans biofilm, and the reversion of the sequence generally led to an improved antimicrobial activity. Furthermore, confocal and scanning electron microscopic visualizations revealed the effectiveness of AMPs-fluconazole combinations also against fluconazole-resistant strains.

Impaired Th17 cell proliferation and decreased pro-inflammatory cytokine production in CXCR3/CXCR4 double-deficient mice of vulvovaginal candidiasis

Vulvovaginal candidiasis (VVC) is a common observed infection, affecting approximately 75% of women of reproductive age. Drug resistance represents a troublesome stumbling block associated with VVC therapy. Thus the aim of the present study was to provide information regarding the selection of potential drug targets for VVC. CXCR3-, CXCR4-, or CXCR/CXCR4 double-deficient mouse models of VVC were subsequently established, with changes to the load of Candida Albicans evaluated accordingly. The biological behaviors of the vaginal epithelial cells were characterized in response to the CXCR3-, CXCR4-, or CXCR3/CXCR4 double-knockout in vivo. Our initial observations revealed that in mice with VVC, CXCR3-, CXCR4-, or CXCR3 - CXCR4 double-knockout resulted in a decreased load of C. Albicans as well as reduced levels and proportion of Th17 cells. Proinflammatory cytokine production was found to be inhibited by CXCR3-, CXCR4-, or CXCR3/CXCR4 double-knockout whereby the mRNA and protein expressions CXCR3, CXCR4, IL-17, IL-6, and TNF-α exhibited decreased levels. CXCR3-, CXCR4-, or CXCR3/CXCR4 double-knockout appeared to function as positive proliferation factors, while playing a negative role in the processes of apoptosis and the cell cycle of vaginal epithelial cells. Taken together, the key findings of the study suggested that CXCR3/CXCR4 double-knockout could act to hinder the progression of VVC, highlighting its promise as a novel therapeutic target in the treatment of VVC. CXCR3 and CXCR4 genes may regulate Th17/IL-17 immune inflammatory pathways to participate in antifungal immunity.

Candida africana in recurrent vulvovaginal candidiasis (RVVC) patients: frequency and phenotypic and genotypic characteristics

PURPOSE

Up to 75 % of all women develop vulvovaginal candidiasis (VVC), with symptoms such as vulvar erythema, pruritus and abnormal vaginal discharge. Despite the global distribution of Candida africana, its role in recurrent vulvovaginal candidiasis (RVVC) is still unclear and requires further investigation. Here, we report on the frequency of C. africana among clinical isolates from patients with RVVC in Bushehr in southern Iran.

METHODOLOGY

Isolated Candida strains were identified by ITS-PCR-RFLP. Hyphal wall protein 1 (HWP1) was amplified to differentiate C. africana and the resulting sequences were subjected to phylogenetic analyses with a view to identifying similarities and differences in nucleotides.

RESULTS

Ten out of 119 strains originally identified as C. albicans turned out to be C. africana. Pairwise nucleotide alignment of HWP1 DNA sequences showed 100 % similarity between C. africana strains. Inter-species variation between Iranian C. africana HWP1 sequences and the only three available C. africana type sequences in GenBank revealed 99.7-100 % nucleotide similarity. Phylogenetic analysis of the HWP1 DNA sequences of 10 Iranian C. africana isolates, the 3 C. africana sequences available in GenBank and 2 representative Iranian C. albicans sequences revealed that all 11 Iranian C. africana strains formed a well-supported cluster separated from the remaining C. africana.

CONCLUSION

In our sample, C. africana was only isolated from 7.8 % of the patients with RVVC. While size polymorphisms in HPW1 genes allowed us to differentiate C. africana from C. albicans, no evidence of sequence variation within the Iranian C. africana isolates was observed.

Species distribution and susceptibility of Candida isolates from patient with vulvovaginal candidiasis in Southern China from 2003 to 2012

OBJECTIVE

To determine the Candida species involved and the antifungal susceptibility of Candida species isolated from patients with vulvovaginal candidiasis (VVC).

MATERIALS AND METHODS

Candida organisms were cultured from samples obtained from patients with VVC at Gynecology Department of Peking University Shenzhen Hospital from April 2003 to September 2012. Antifungal susceptibility testing was performed using a commercial agar diffusion test.

RESULTS

A total of 3181 yeasts isolates, mostly Candida, were obtained from 3141 patients with VVC. Two species of Candida were isolated from each of 40 patients (1.3%, 40/3141). C. albicans were the predominant Candida species (2705 strains, 85.0%) in VVC, followed by C. glabrata (337 strains, 10.6%), C. parapsilosis (49 strains, 1.5%), C. tropicalis (31 strains, 1.0%), Saccharomyces cerevisiae (23 strains, 0.7%), C. krusei (15 strains, 0.5%), Candida famata (11 strains, 0.4%), Rhodotorula sp. (6 strains, 0.2%), and C. lusitaniae (2 strains, 0.1%). Antifungal susceptibility was tested in a total of 1942 strains from patients with VVC. All of the C. albicans isolates obtained were susceptible to nystatin. The resistant rate of C. albicans to fluconazole, itraconazole, miconazole, clotrimazole was 1.1% (18/1612), 2.2% (36/1612), 4.2% (68/1612), and 0.9% (14/1612). The resistant rate of non-albicans to fluconazole, itraconazole, miconazole, and clotrimazole was 11.8% (39/329), 2.5% (8/329), 1.8% (6/329), and 4.3% (14/329).

CONCLUSIONS

C. albicans was the predominant Candida species isolated from this series of patients with VVC. Resistance of vaginal C. albicans isolates to antifungal agents was infrequent.

Antifungal Activity of Brazilian Propolis Microparticles against Yeasts Isolated from Vulvovaginal Candidiasis

Propolis, a resinous compound produced by Apis mellifera L. bees, is known to possess a variety of biological activities and is applied in the therapy of various infectious diseases. The aim of this study was to evaluate the in vitro antifungal activity of propolis ethanol extract (PE) and propolis microparticles (PMs) obtained from a sample of Brazilian propolis against clinical yeast isolates of importance in the vulvovaginal candidiasis (VVC). PE was used to prepare the microparticles. Yeast isolates (n = 89), obtained from vaginal exudates of patients with VVC, were exposed to the PE and the PMs. Moreover, the main antifungal drugs used in the treatment of VVC (Fluconazole, Voriconazole, Itraconazole, Ketoconazole, Miconazole and Amphotericin B) were also tested. Minimum inhibitory concentration (MIC) was determined according to the standard broth microdilution method. Some Candida albicans isolates showed resistance or dose-dependent susceptibility for the azolic drugs and Amphotericin B. Non-C. albicans isolates showed more resistance and dose-dependent susceptibility for the azolic drugs than C. albicans. However, all of them were sensitive or dose-dependent susceptible for Amphotericin B. All yeasts were inhibited by PE and PMs, with small variation, independent of the species of yeast. The overall results provided important information for the potential application of PMs in the therapy of VVC and the possible prevention of the occurrence of new symptomatic episodes.

Ultrastructural imaging of Candida albicans adhesion to rat genital epithelium through scanning and transmission electron microscopy

The adhesion of Candida albicans to the genital epithelium has not been fully investigated in vivo. The objective of this study was to evaluate the ultrastructural aspects of C. albicans adhesion in the lower genital system of female Wistar rats through scanning and transmission electron microscopy. The genital infection persisted until the end of the experiment, and all rats showed the same adhesion aspects. Various associated yeast/hyphae were observed in the lumen and adhered both at the vaginal and endocervical levels where the fungal filamentation process occurred. In the vaginal epithelium, closely adhered yeasts were observed as stretched strands bridging between yeasts and the epithelium surface. Different stages of the adhesion, where yeasts internalized into the epithelial cell inside a cytoplasmic vacuole, resembling endocytosis, and a wide fibrillar-floccular, glycocalyx-like layer on the yeasts were observed. On the endocervix, the adhesion occurred between the cilia. In the uterine body, only a yeast-like form was observed with superficial contact. This study reached the initial goal of demonstrating an experimental model for in vivo studies. Continuation of this line of research is important for studies of vulvovaginal candidiasis.

Antifungal activity of propolis extract against yeasts isolated from vaginal exudates

OBJECTIVE

The objective of this study was to evaluate the in vitro antifungal activity of propolis extract against yeasts Candida albicans and Candida non-albicans isolated from vaginal exudates, in comparison with nystatin.

DESIGN

Ninety-seven (97) vaginal yeasts strains were evaluated. These strains were obtained from different clinical conditions, isolated and stored at the Sector of Medical Mycology of the State University of Maringá (Paraná, Brazil). The assays of susceptibility to nystatin and propolis extracts (PE) were conducted through microdilution in broth (National Committee for Clinical Laboratory Standards-NCCLS, M-27A Document of 1997).

RESULTS

All the yeasts tested were inhibited by low concentrations of PE (maximum of 393.19 mug/mL of the total flavonoid content), including an isolate resistant to nystatin, regardless of the clinical conditions of the women and the species of yeast isolated.

CONCLUSIONS

The PE showed an outstanding performance against the tested vaginal yeast strains, and could be included among the novel therapeutic options for the treatment of vulvovaginal candidiasis.

Clinical characteristics of vulvovaginal candidiasis and antifungal susceptibilities of Candida species isolates among patients in southern China from 2003 to 2006

AIM

To determine the clinical characteristics of vulvovaginal candidiasis (VVC), the Candida species involved and the antifungal susceptibility of Candida species isolated from patients with VVC.

METHODS

Candida organisms were cultured from samples obtained from patients who presented with VVC to the Gynecology Department, Peking University Shenzhen Hospital. Antifungal susceptibility testing was performed using a commercial agar diffusion test.

RESULTS

Of the 1,070 cases of VVC reported in this study, 36.5% were uncomplicated VVC, and 63.5% were complicated VVC. Twenty-four patients were identified as having two species of Candida. Candid albicans alone was isolated from 89.5% of cases (n = 958). Candida glabrata was isolated from 85 cases (7.9%), Candida tropicalis from 10 (0.9%), Saccharomyces cerevisiae from eight (0.7%), Candida parapsilosis from six (0.6%), Candida famata from two (0.2%), and Candida krusei from one case (0.1%). All isolates of Candida albicans were susceptible to nystatin. The resistant rate of Candida albicans to azole agents was 0-4.9%.

CONCLUSION

Candida albicans was the predominant Candida species isolated from this series of patients with VVC. Resistance of vaginal Candida albicans isolates to antifungal agents was infrequent.

Effect of subinhibitory concentration of some established and experimental antifungal compounds on the germ tube formation in Candida albicans

The influence of subinhibitory concentrations of six established and 19 newly synthesized antifungal compounds on the dimorphic transition of three C. albicans strains was evaluated in the filamentation-inducing medium. Amphotericin B was found to produce almost complete inhibition in the germination at a concentration of 1/10 of the corresponding MIC and partial inhibition at a concentration as low as MIC/50. Flucytosine and four azole derivatives were proven ineffective. From the newly synthesized drugs, the incrustoporin derivative LNO6-22, two phenylguanidine derivatives (PG15, PG45), and four thiosalicylanilide derivatives, in particular, showed results comparable to those of amphotericin B, with a high inhibition of germ tube formation at concentrations of MIC/10. In general, concentrations of MIC/50 had no visible effect.

Low dose of Concanavalin-A enhances innate immune response and prevents liver injury in mice infected withCandida albicans

The mechanisms through which Candida albicans is recognized by immune cells and how it triggers host defence are not completely understood. In this study, we evaluated the effect of Concanavalin-A on the clearance of C. albicans by infected mice and their production of proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha). Subgroups of 5 animals were pretreated with Con-A (250 mug mL(-1) PBS) and after 96 h were infected intraperitoneally with 10(7) cells of C. albicans CR15 (an isolate from a HIV+ person); 30 min, 2, 6, 24 or 72 h after infection the mice were sacrificed. Phagocytosis of C. albicans by peritoneal macrophages increased 30 min after infection in mice pretreated with Con-A. The liver presented the greatest number of CFUs, and this number was reduced by pretreatment with Con-A. Control animals infected with C. albicans presented a significant increase in plasmatic alanine aminotransferase, which was not observed in mice treated with Con-A. Two hours after infection the production of TNF-alpha in the liver of mice pretreated with Con-A was significantly increased. These results suggest that a single dose of Con-A caused a beneficial modulating action of the inflammatory response during infection with C. albicans.

Candida and squamous (pre)neoplasia of immigrants and Dutch women as established in population-based cervical screening

The objective of this study was to establish the relationship between Candida vaginalis and (pre)neoplasia and the prevalence of Candida and (pre)neoplasia related to age and ethnicity. Data were collected from 445,671 asymptomatic women invited for mass screening between 1995 and 2002 and coded according to the Dutch cervical smear coding system (KOPAC) with six grades for (pre)neoplastic changes. Prevalence and relative risks (RRs) were established for Candida and squamous abnormalities in Dutch women and four groups of immigrants. The prevalence of Candida is significantly higher in the cohort of 30-year-old women and lower in the cohorts of 45-, 50-, 55-, and 60-year-old women. The RR of having Candida was higher for Surinamese women (1.24; CI 1.08-1.42). Furthermore, the RR of having mild dysplasia was higher for Surinamese women (1.47; CI 1.14-1.89) and for women born in other countries than in The Netherlands, Turkey, and Morocco (1.36; CI 1.13-1.62). No statistically significant relationship between (pre)neoplasia and Candida was observed. C. vaginalis is more frequent among Surinamese women. Presence of Candida is not associated with an increased risk for squamous abnormalities; therefore, women carrying Candida are not at an increased risk of developing cervical cancer.

Adherence of Candida albicans Is Inhibited by Yeast Mannan

The adherence of Candida albicans strain NIH A207 to plastic plates was inhibited by the addition of mannan, and plates coated with mannan also inhibited the adherence of C. albicans strains TIMM1768, TIMM2640, and JCM2076. Mannan coated the plastic plates under neutral and acidic conditions, but not under alkaline conditions. These results indicate that C. albicans cannot attach to mannan. Thus mannan-coated medical equipment might be useful to prevent C. albicans adherence.