Vaginitis is a common complaint for females and is the most frequent reason for gynecology consultation in primary health care services. Vulvovaginal candidiasis (VVC), which accounts for 40–50% of all cases of infectious vulvovaginitis, has been known as a common problem worldwide. It is estimated that 75% of women experience at least one episode of VVC throughout her lifetime, and 5–8% of adult women have recurrent VVC (RVVC) which is defined as four or more culture-confirmed episodes in a 12-month period. A multitude data show that non-albicans Candida species (Candida spp.) are associated with RVVC, increasing worldwide. An increasing prevalence of fungal resistance is also reported in global and local antifungal surveillance studies. The increased RVVC incidence and drugs resistance cause an important public health issue and give great challenge to clinician's treatment strategy.
Knowledge of local epidemiological patterns such as clinical characteristics of cases, distribution of strains, and antifungal susceptibilities of Candida spp. is important and essential in guiding appropriate clinical decisions since the species distribution and resistance to Candida spp. differ among geographies. The selection of initial antifungal therapy is also reliant on robust epidemiological data. A few studies on the long-term monitoring of the species distribution and antifungal susceptibilities of vulvovaginitis Candida spp. have been reported by China. This study aimed to describe the trend of the species distribution and antifungal susceptibilities of vulvovaginitis Candida spp. in China from 2006 to 2013.
Candida strain collection
The study was conducted in Peking University First Hospital, a teaching facility of Peking University Health Science Center in Beijing, China. A total of 2204 isolates were collected from 2122 vulvovaginitis patients. We simply got these strains from the Repository Department of our hospital. All specimens were placed on CHROM-agar (Biocell Laboratory Ltd., Zhengzhou, China) to identify. Cultures were incubated for 24–48 h at 35°C in ambient air atmosphere before reading results.
This study was an antifungal, susceptibility, surveillance study, and no human rights issues were involved. We obtained these strains in an anonymized and de-identified form.
Susceptibility to clotrimazole (Rosco, Denmark), fluconazole (Rosco), miconazole (Rosco), itraconazole (Rosco), and nystatin (Rosco) was determined using an agar diffusion method (Neo-sensitabs, Rosco). The surface of improved Shadomy agar plate (Guangzhou Detgerm Microbiology Technology Co., Ltd.) was inoculated using a swab dipped in cell suspension which adjusted to a McFarland standard turbidity of 0.5. Disks (Rosco) of clotrimazole (10 μg), fluconazole (15 μg), miconazole (10 μg), itraconazole (8 μg), and nystatin (50 μg) were placed onto the surfaces of the inoculated plates. The plates were incubated in air at 35°C and read at 24 h. The zone diameters of all isolates were recorded accurately. Interpretation of all agents susceptibilities (susceptible [S], susceptible-dose dependent, and resistant [R]) was done according to the standard instructions. Quality control was performed using quality-control strains, ATCC 64548 and ATCC 64550.
Data processing and statistical analysis were performed with SPSS software (version 14.0, Inc., Chicago, IL, USA). Count data variables were expressed as frequencies and percentages. These enumeration data were performed with Chi-square test to compare the difference between groups. For all statistical analysis, statistical significance was accepted at P < 0.05 (two-sided).
Distribution of Candida
During the study period from 2006 to 2013, a total of 2204 Candida spp. isolated from 2122 patients with VVC were collected. The distribution of Candida species was as follows: Candida albicans (C. albicans), 80.5% (n = 1775); Candida glabrata (C. glabrata), 18.1% (n = 400); Candida krusei (C. krusei) 1.2% (n = 26); Candida tropicalis (C. tropicalis), 0.1% (n = 3) [Table 1]. Although C. albicans maintained the most common species associated with vulvovaginitis (80.5%), the percentage reduced from about 90% in 2006 to 77% in 2013 meanwhile the prevalence of C. glabrata increased from about 10% in 2003 to 20% in 2013. The proportion of C. krusei and C. tropicalis was very low (1.2%, 0.1%, respectively) in our survey. Of all the patients with positive Candida cultures, 76 (3.6%) cases isolated more than one culture (158 isolates) in different time. The prevalence of non-albicans Candida spp. among patients with multiple positive cultures was higher than among patients with a single positive culture; however, there was no statistical significance between two groups (P = 0.054, χ2 = 3.718). Moreover, the predominant non-albicans Candida spp. recovered was also C. glabrata, which account for 24.7%.
In vitro susceptibilities among Candida albicans
The susceptibility results for each species are presented in Tables 2 and 3. The results revealed that nystatin exhibited excellent activity against C. albicans and the whole resistance rates was only 0.2% [Table 2]. Notably, decreasing susceptibility to fluconazole, miconazole, and itraconazole was seen with C. albicans during 8-year period. Resistance to fluconazole increased from 2.4% in 2006 to 55.4% in 2012, but the rate dropped to 8.9% in 2013. With regards to miconazole and itraconazole, resistance rate increased from 2.4%, 7.1% in 2006 to 59.8%, 58.9% in 2013, respectively. There was only slightly fluctuant trend toward increased resistance to clotrimazole among C. albicans during the study period.
In vitro susceptibilities among non-albicans Candida species
The susceptibilities of the non-albicans species to five antifungal drugs are shown in Table 3. The results revealed that nystatin exhibited not only excellent antifungal activity against C. albicans but also one of the best choices for non-albicans species. Moreover, the resistance rates among C. glabrata, C. tropicalis, and C. krusei were 0.3%, 0, and 3.8%, respectively. However, resistant to different azole drugs was various among these species. The activity of all the four azole agents was low against C. glabrata (clotrimazole 16.6% S, fluconazole 9.2% S, itraconazole 35.2% S), and only miconazole was active against 56.5% of the isolates. Clotrimazole-resistance C. krusei strains were not found in this study. The activity of clotrimazole against to C. krusei was 96.2%, similar to nystatin. However, resistance to fluconazole (57.7%), miconazole (73.1%), and itraconazole (83.3%) was frequent among C. krusei isolates.
Antifungal susceptibility surveillance study was playing an increasingly important role in tracking the development of antifungal resistance and starting initial antifungal treatment. With the increasing use of antimicrobial agents, the distribution and susceptibilities of pathomycete may be changing from time to time. In our study, we found a descending prevalence of C. albicans (90–77%) and a rising prevalence of C. glabrata (10–20%) from 2006 to 2013, similar as described in other surveys. Factors such as antimicrobial agents, tumor chemotherapy agents, human organs transplantation, and human immunodeficiency diseases were deemed to contribute to the changing of species distribution. Regimens should be adjusted according to local surveillance results.
As we all know, treatment choice based on local susceptibility tests was indispensable and credible. In our study, we found that nystatin exhibited excellent activity against all Candida species (<4% R), which was in accordance with other reports. Besides the unique mechanism of changing cell membrane permeability, the excellent antifungal activity of nystatin was likely associated with relatively low-frequency use in clinical setting. In accordance with previous reports, increasing resistant to fluconazole was obviously among all species. Although the susceptibility of fluconazole was descending, it was still active against C. albicans (70% S) in our study. However, when implemented on C. glabrata and C. krusei, fluconazole had little effect to these species due to intrinsic resistance which prompted reconsideration of fluconazole as the first-line therapy to these species. With regard to clotrimazole, it maintained activity against C. albicans (>90% S) and C. krusei (>90% S) but shows less effect to C. glabrata (<20% S). The activity of miconazole and itraconazole against all species, especially for C. krusei was not sufficient. In a study by Fan et al., the resistant rate of C. albicans to azole agents was 0–4.9%. Richter et al. showed that resistance to fluconazole was observed infrequently (3.7%). Pfaller et al. reported that 90.2% of the Candida isolates tested were susceptible to fluconazole. The data shown in our study were relatively higher compared to other reports, requiring the attention of clinicians in this situation. However, the possibility of some system bias cannot be excluded due to the potential reasons of the different specimen, test method, and regional disparity.
There were several limitations in this study. First, some uncommon species may be absent using chromogenic culture media as a prequalification test limits the variety of species that can grow. Second, susceptibility tests were conducted using commercially available products, agar diffusion method (Neo-sensitabs, Rosco, Denmark) based in CLSI M44-A2 document. The high resistance rate in this study may be related to it. Third, expanding the scope of monitoring was necessary and more drug agents should be involved.
In conclusion, this study found that non-albicans Candida, especially C. glabrata, which was associated with RVVC was increasing. The drugs in vitro susceptibility were different among different vulvovaginal Candida species and it had changed over time. Nystatin was the optimal choice for the treatment of VVC at present. Regimens should be adjusted according to local surveillance results.
Financial support and sponsorship
This study was supported by a grant from the National Natural Science Foundation of China (No. 81571394).
Conflicts of interest
There are no conflicts of interest.
The authors are thankful to all the clinicians and microbiologists for referring vulvovaginal yeast isolates to the mycology reference laboratory. Excellent technical support received from Min Zhao is acknowledged.
1. Mendling W, Brasch J. German Society for Gynecology and Obstetrics; Working Group for Infections and Infectimmunology in Gynecology and Obstetrics; German Society of Dermatology, the Board of German Dermatologists; German Speaking Mycological Society. Guideline vulvovaginal candidosis (2010) of the German Society for Gynecology and Obstetrics, the Working Group for Infections and Infectimmunology in Gynecology and Obstetrics, the German Society of Dermatology, the Board of German Dermatologists and the German Speaking Mycological Society Mycoses. 2012;55(Suppl 3):1–13 doi: 10.1111/j.1439-0507201202185.x
2. Sobel JD. Recurrent vulvovaginal candidiasis Am J Obstet Gynecol. 2016;214:15–21 doi: 10.1016/j.ajog.2015.06.067
3. Liu XP, Fan SR, Peng YT, Zhang HP. Species distribution and susceptibility of Candida isolates from patient with vulvovaginal candidiasis in Southern China from 2003 to 2012 J Mycol Med. 2014;24:106–11 doi: 10.1016/j.mycmed.2014.01.060
4. Pfaller MA, Diekema DJ, Gibbs DL, Newell VA, Ellis D, Tullio V, et al Results from the ARTEMIS DISK Global Antifungal Surveillance Study, 1997 to 2007: A 10.5-year analysis of susceptibilities of Candida species to fluconazole and voriconazole as determined by CLSI standardized disk diffusion J Clin Microbiol. 2010;48:1366–77 doi: 10.1128/JCM.02117-09
5. Wang H, Xiao M, Chen SC, Kong F, Sun ZY, Liao K, et al In vitro susceptibilities of yeast species to fluconazole and voriconazole as determined by the 2010 National China Hospital Invasive Fungal Surveillance Net (CHIF-NET) study J Clin Microbiol. 2012;50:3952–9 doi: 10.1128/JCM.01130-12
6. Gamarra S, Morano S, Dudiuk C, Mancilla E, Nardin ME, de Los Angeles Méndez E, et al Epidemiology and antifungal susceptibilities of yeasts causing vulvovaginitis in a teaching hospital Mycopathologia. 2014;178:251–8 doi: 10.1007/s11046-014-9780-2
7. Tadec L, Talarmin JP, Gastinne T, Bretonnière C, Miegeville M, Le Pape P, et al Epidemiology, risk factor, species distribution, antifungal resistance and outcome of Candidemia at asingle French hospital: A 7-year study Mycoses. 2016;59:296–303 doi: 10.1111/myc.12470
8. Foxman B, Muraglia R, Dietz JP, Sobel JD, Wagner J. Prevalence of recurrent vulvovaginal candidiasis in 5 European countries and the United States: Results from an internet panel survey J Low Genit Tract Dis. 2013;17:340–5 doi: 10.1097/LGT.0b013e318273e8cf
9. Mashburn J. Vaginal infections update J Midwifery Womens Health. 2012;57:629–34 doi: 10.1111/j.1542-2011.2012.00246.x
10. Fischer G. Chronic vulvovaginal candidiasis: What we know and what we have yet to learn Australas J Dermatol. 2012;53:247–54 doi: 10.1111/j.1440-0960.2011.00860.x
11. Richter SS, Galask RP, Messer SA, Hollis RJ, Diekema DJ, Pfaller MA. Antifungal susceptibilities of Candida species causing vulvovaginitis and epidemiology of recurrent cases J Clin Microbiol. 2005;43:2155–62 doi: 10.1128/JCM.43.5.2155–2162.2005
12. Fan SR, Liu XP. In vitro miconazole susceptibility and clinical outcome in vulvovaginal candidiasis Int J Gynaecol Obstet. 2007;97:207–8 doi: 101016/j.ijgo.2007.03.017
13. Fan SR, Liu XP, Li JW. Clinical characteristics of vulvovaginal candidiasis and antifungal susceptibilities of Candida species isolates among patients in Southern China from 2003 to 2006 J Obstet Gynaecol Res. 2008;34:561–6 doi: 10.1111/j.1447-0756.2008.00817.x
14. Pfaller MA, Andes DR, Diekema DJ, Horn DL, Reboli AC, Rotstein C, et al Epidemiology and outcomes of invasive candidiasis due to non-albicans species of Candida in 2,496 patients: Data from the Prospective Antifungal Therapy (PATH) registry 2004-2008 PLoS One. 2014;9:e101510 doi: 10.1371/journal.pone.0101510
15. Choukri F, Benderdouche M, Sednaoui P. In vitro susceptibility profile of 200 recent clinical isolates of Candida spp. to topical antifungal treatments of vulvovaginal candidiasis, the imidazoles and nystatin agents J Mycol Med. 2014;24:303–7 doi: 10.1016/j.mycmed.2014.05.001
16. Fan S, Liu X, Wu C, Xu L, Li J. Vaginal nystatin versus oral fluconazole for the treatment for recurrent vulvovaginal candidiasis Mycopathologia. 2014;179:95–101 doi: 10.1007/s11046-014-9827-4
17. Pfaller MA, Diekema DJ, Gibbs DL, Newell VA, Bijie H, Dzierzanowska D, et al Results from the ARTEMIS DISK Global Antifungal Surveillance Study, 1997 to 2007: 10.5-year analysis of susceptibilities of noncandidal yeast species to fluconazole and voriconazole determined by CLSI standardized disk diffusion testing J Clin Microbiol. 2009;47:117–23 doi: 10.1128/JCM.01747-08
18. Li F, Wu L, Cao B, Zhang Y, Li X, Liu Y. Surveillance of the prevalence, antibiotic susceptibility, and genotypic characterization of invasive candidiasis in a teaching hospital in China between 2006 to 2011 BMC Infect Dis. 2013;13:353 doi: 10.1186/1471-2334-13-353
19. Pfaller MA, Jones RN, Castanheira M. Regional data analysis of Candida non-albicans strains collected in United States medical sites over a 6-year period, 2006-2011 Mycoses. 2014;57:602–11 doi: 10.1111/myc.12206
20. Hamad M, Kazandji N, Awadallah S, Allam H. Prevalence and epidemiological characteristics of vaginal candidiasis in the UAE Mycoses. 2014;57:184–90 doi: 10.1111/myc.12141
Edited by: Li-Min Chen