Vaginitis is a common clinical gynecological disease caused by vaginal bacteria, vaginal fungi, Trichomonas vaginalis and other pathogens [1]. Among that, vulvovaginal candidosis (VVC), accounting for 20–45% of all vaginitis, is the second most common vaginal inflammatory disease only after bacterial vaginosis, and is mainly Candida albicans vaginosis, accounting for 85–90%, resulted in premenstrual vulva or vaginal itching and other systems [2]. The matrix metalloproteinase-8 (MMP-8) and fibroblast mediated proinflammatory immune response may be major factors causing symptoms [3, 4].
Especially in recent years, with the abuse of broad-spectrum antibiotics, the use of immune inhibitors, and the application of all kinds of gynecological treatment instruments, the incidence of fungal vaginitis is gradually rising [5,6,7]. Vulvovaginal candidiasis (VVC) can cause pain, extreme discomfort, mental distress, anxiety, altered self-esteem, impaired work performance, and interference with sexual and emotional relationships [8, 9]. Clinical diagnosis of fungal vaginal disease is very difficult, because the sings and symptoms of fungal vaginal disease is not peculiar to the disease, and the pathogeny resulting in similar symptoms may be diverse, such as bacterial vaginal disease,vaginal trichomoniasis, etc. In addition, Candida albicans detected in vagina do not meanVVC, because candida can also live in the vagina to coexist with the host and does not cause symptoms. Thus, the diagnosis of VVC requires a combination of clinical manifestations and laboratory confirmation of the presence of candida. The detection of mycelium, blastospores and spores in vaginal discharge is the detection standard for the diagnosis of fungal vaginosis[10]. As a result, it is a challenge to correctly diagnose fungal vaginosis because of limitations in the sensitivity and specificity of microbes in the laboratory detection. In a prospective study of the clinical diagnostic accuracy of bacterial vaginosis, trichomoniasis, and VVC in 535 women with vulvovaginal disease, Lowe et al. found that the diagnostic sensitivity and specificity of classical diagnostic methods (history, vaginal examination, pH, and microscopic examination of local preparations) were 83.8% and 84.8%, respectively [11].
Clinical common vaginal fungal detection methods include 10% potassium hydroxide (KOH) microscopic examination,Gram stain,wet mount microscopy method and fungal culture method (golden standard) [12,13,14]. The potassium hydroxide method was used to detect fungi in corneal scrapes, but the sensitivity varied widely, e.g. 94.3%, 81.0%, and 62.3% [15,16,17]. Gram stain method may result from the loss of lactobacilli by the process of fixation or Gram staining and takes a long time.Wet mount microscopy method is simple and fast, but their accuracy and sensitivity are unknown. DNA hybridization technology can detect vaginal fungi with sensitivity and specificity up to 96.3% [18]. If whole genome sequencing method is used, higher detection rate can be achieved [19]. However, these methods are cumbersome and expensive, which are not practical for routine clinical detection. The golden standard, fungal culture method also takes three to five days to produce results, which is too long.
Zhao et al. detected Candida albicans in the vagina of 110 patients with suspected VVC using saline KOH(potassium hydroxide) suspension method, CFW (Calcofluor White), FB 85 (fluorescent brightener 85) method and fungal culture method respectively, and concluded that CFW had the highest sensitivity, specificity and accuracy [20]. Previously, CFW has been commonly used by many researchers to detect the presence of skin fungi, and this was the first time to use CFW to detect vaginal fungi [21].
Based on CFW [22], this study carried out vaginal discharge fungi detection for 198 gynecological outpatients, by liquid—based thin-layer fungi fluorescence morphology staining detection kit (liquid-based fungal method). which relies on the combination of fungal fluorescent staining solution in the kit and beta cell wall polysaccharides (such as chitin and cellulose, etc.) in the samples to mark the fluorescent material. Under the specific excitation light band (340–400 nm) of fluorescence microscope, fungal myceliume or spores can emit blue-green fluorescence, which is easier to identify than the traditional method, having simple operation and fewer steps. Again, it is faster to obtain results, having higher sensitivity and accuracy. In addition, the enrichment effect of the kit was further achieved by liquid—based thin-layer preparation method on the basis of CFW method to reduce the rate of missed detection. However, there are also shortcomings. For instance, the liquid—based thin-layer preparation fungi fluorescence staining detection kit(liquid-based fungal method) is only a qualitative detection of fungal infection, which can only identify fungal and non-fungal, but cannot identify the type of fungi.
