Candida albicans can colonize on the mucous membrane of genitourinary tracts of healthy humans.
Candida virulence factors are: adherence, enzyme production, proteinase secretion, dimorphisms with antigenic variations, and cell surface composition (
12,
13). Changing from yeast to hypha is under the control of a complex set of environmental signals and has long been believed to be the main virulence factor of this pathogen (
14). Compared to other species such as
Candida krusei,
Cancida glabrata, and
Candida tropicalis,
Candida albicans has the most durable binding ability (
15). Phosphorylase and aspartyl protease enzymes are main agents needed for tissue invasion in the pathogenesis of the infection (
3,
16). The effects of estrogen on the vaginal mucosa are main factors for infection progression. Throughout the menstrual cycle, estrogen causes the thickened and cornified keratinized vaginal epithelium (
17). This is further confirmed by the fact that low estrogen producers (prepubescent girls and postmenopausal women) infrequently develop vaginitis. Vulvovaginal candidiasis show different frequency region to region and some studies have disclosed that the incidence of vulvovaginal candidiasis differs in various areas. It can be related to geographical conditions, social and cultural factors, hygiene customs, and diagnostic techniques (
18,
19). The prevalence of infection has been reported as 12.1% in Athens, 17.4% in Turkey, 12.2% in Brazil, 20.4% in India, 18.7% in Israel, and 6.5% in China (
3,
18-
22).
Candida albicans can be found in the cultures of vaginal discharge of 25% of pregnant women (16). Pregnant women have a two-fold increase in the frequency of vulvovaginal colonization by
Candida spp. compared to non-pregnant individuals. This association is influenced by elevated levels of circulating estrogens as well as accumulation of some substrates like glycogen in the vagina during pregnancy (
23,
24). This increased rate depends on the stage of pregnancy (the first, second, or third trimester of pregnancy), the level of glycogen, and the amount of bacterial microbiome, such as lactobacilli in the vaginal lumen that produce lactic acid and H
2O
2 and provides significant protection against fungal infections. Interestingly, none of the patients were pregnant in the present investigation. Masri et al. (
25) reported 17.2% VVC in pregnant women. They performed traditional tests such as Gram-staining, microscopic examination, and culture for species identification and reported
C. albicans as the most prevalent species (83.5%), followed by
C. glabrata (16%), whereas we used a precise molecular technique (PCR-FSP) for identification of
Candida species in the present investigation. To our knowledge, this is the first time that PCR-FSP is used to identify causative agents of vulvuvaginal candidiasis. Mucci et al. (
26) showed that the occurrence of VVC was 25% among pregnant women and
Candida albicans with a prevalence of 80.7% was the predominant
Candida species. Nnadi and Singh (
27) reported on 288 pregnant women, 175 were positive for VVC giving a prevalence rate of 60.8%. They also revealed that pregnant women with an age range of 26 - 30 years had the highest prevalence of infection (37.1%). Mohammadi et al. (
28) identified
Candida species isolated from VVC by the PCR-RFLP method in Kashan and reported
Candida albicans (87.2%) and
Candida glabrata (12%) as the most frequent species, in agreement of the present study. Nearly 5% - 8% (about 150 million worldwide) suffer from recurrent VVC (RVVC) (
29-
31). Medication of antibiotics is another major predisposing factor for expanding fungal vaginitis, supposedly through disturbance of the natural bacterial population existing at the mucosal interface (
32,
33). Reduced levels of acid-producing lactobacilli causes raised vaginal pH levels and increased fungal colonization of potential pathogens (
34). In accordance with this hypothesis, 35.6% of patients had used antibacterial agents in the present study. The major complaint of Candidal vulvovaginitis was itching in this survey and the usual clinical sign was vaginal discharge. In the same way, Ebrahimy et al. (
16) and Grigoriou et al. (
3) reported that itching was the most frequent complaint among patients with the
Candida infection with the rate of 98% and 85%, respectively. Invasion to the epithelial cells in the lower genitourinary tract by
Candida species can cause inflammation and itching due to the enzyme or toxin involved in the pathogenesis of
Candida species. Antifungal susceptibility testing (AFST) of
Candida species may provide good treatment outcome, assessment of antifungal efficiency, and monitoring of incidence of drug resistance. Unfortunately, we did not perform AFST on clinical isolates in the present study, however, suspected patients were treated empirically with clotrimazole, miconazole, and nystatin. Nystatin is used to treat
Candida infections in the mouth or stomach mucosa. It is not a choice for treatment of volvuvaginal candidiasis, however, it was as effective as miconazole and clotrimazole in the present survey. Achkar and Fries (
29) suggested that volvuvaginal candidiasis is often recognized without complementary tests and treated with unusual drugs, therefore the incidence of infection is unknown. Another limitation of the present study was to quit taking medication prior to the completion of treatment period, so we were not able to evaluate the drug effectiveness of antifungal agents on patients, precisely. It is highly recommended that incomplete treatment of infection be considered as exclusion criteria in same studies in the future. In the present investigation, the age range of 26 - 30 years had the highest occurrence of volvuvaginal candidiasis, which is in agreement with the findings of Hedayati et al. (
35), Mahmoudi Rad et al. (
36), and Asadi et al. (
37). There is a consequential association between infection and use of contraceptive pills. In this investigation, 40% of patients had also used contraceptive pills. Yusuf et al. (
38) revealed a meaningful association between use of contraceptives and the prevalence of vaginal
Candida infection. They disclosed among all contraceptives, use of oral contraceptive pills (OCP) was the most common cause of vaginitis compared to injectable one. We reported 54.6% of VVC, which is higher than reported by Dharmik et al. (
39), Dou et al. (
40), Mukasa et al. (
41), Masri et al. (
25), and Hedayati et al. (
35) who reported 18.4% in India, 51.4% in China, 45.3% in Uganda, 17.2% in Malaysia, and 17.2% in Mazandaran, Iran, respectively.
Candida albicans was the most prevalent species among patients, in accordance with previous studies from various countries (
21,
42-
44). Some studies have shown an increase of non-
albicans Candida species in volvuvaginal specimens (
45,
46), this may be related to the prolonged use of antifungal agents, incomplete therapeutic regimens, and self-prescribed antifungal therapy (
47). Furthermore, non-
albicans Candida species such as
Candida glabrata and
Candida krusei make a poor response to azole agents such as fluconazole, which can be a reason for increasing non-
albicans Candida species among patients with volvuvaginal candidiasis.