Candida causes recurrent vulvovaginal candidiasis by forming morphologically disparate biofilms on the human vaginal epithelium

Yihong Pan; Yao Sun; Lanqian Chen; Yali Cheng; Panpan Jin; Weidan Zhang; Lingzhi Zheng; Junyan Liu; Tieli Zhou; Zhenbo Xu; Cheng Li; Xenia Kostoulias; Cathy J Watson; David McGiffin; Anton Y Peleg; Yue Qu

doi:10.1016/j.bioflm.2023.100162

Candida causes recurrent vulvovaginal candidiasis by forming morphologically disparate biofilms on the human vaginal epithelium

Biofilm. 2023 Oct 22:6:100162. doi: 10.1016/j.bioflm.2023.100162. eCollection 2023 Dec 15.

Authors

Yihong Pan^{1

2}, Yao Sun^{1

3}, Lanqian Chen⁴, Yali Cheng², Panpan Jin², Weidan Zhang², Lingzhi Zheng², Junyan Liu^{5

6}, Tieli Zhou³, Zhenbo Xu^{5

6

7}, Cheng Li⁷, Xenia Kostoulias^{8

9}, Cathy J Watson¹⁰, David McGiffin¹¹, Anton Y Peleg^{8

9}, Yue Qu^{1

8

9}

Affiliations

¹ Wenzhou Medical University-Monash BDI Alliance in Clinical and Experimental Biomedicine, The First Affiliated Hospital of Wenzhou Medical University, Zhejiang, 325000, China.
² Department of Obstetrics and Gynaecology, Taizhou Hospital of Wenzhou Medical University, Zhejiang, 318050, China.
³ Department of Laboratory Medicine, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, 325000, China.
⁴ Department of Pathology, Taizhou Hospital of Wenzhou Medical University, Zhejiang, 318050, China.
⁵ School of Food Science and Engineering, Guangdong Province Key Laboratory for Green Processing of Natural Products and Product Safety, Engineering Research Center of Starch and Vegetable Protein Processing, Ministry of Education, South China University of Technology, Guangzhou, 510640, China.
⁶ Department of Civil and Environmental Engineering, University of Maryland, College Park, MD, 20742, United States.
⁷ Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, 02139, United States.
⁸ Department of Infectious Diseases, The Alfred Hospital and Monash University, Melbourne, 3004, Australia.
⁹ Department of Microbiology, Infection Program, Biomedical Discovery Institute, Monash University, Clayton, 3800, Australia.
¹⁰ School of Population and Global Health, University of Melbourne, Carlton, 3053, Australia.
¹¹ Department of Cardiothoracic Surgery, The Alfred and Monash University, Melbourne, Victoria, 3004, Australia.

Abstract

Background: Recurrent vulvovaginal candidiasis (RVVC) is a recalcitrant medical condition that affects many women of reproductive age. The importance of biofilm formation by Candida in RVVC has been recently questioned. This study aimed to elucidate the fundamental growth modes of Candida in the vagina of patients with RVVC or sporadic vulvovaginal candidiasis (VVC) and to assess their roles in the persistence of RVVC.

Methods: Vaginal tissues were sampled from twelve patients clinically and microbiologically diagnosed as RVVC or VVC at a post-antifungal-treatment and asymptomatic period. High-resolution scanning electron microscopy, fluorescence in situ hybridization in combination with Candida-specific 18S rRNA probes and viable fungal burden were used to qualitatively and quantitatively evaluate Candida growth in the human vagina. The presence of Candida biofilm extracellular polymeric substances was examined using confocal laser scanning microscopy and biopsy sections pre-stained with Concanavalin A. Histopathological analysis was carried out on infected vaginal tissues stained with hematoxylin and eosin. Lastly, the susceptibility of epithelium-associated Candida biofilms to fluconazole at the peak serum concentration was evaluated.

Results: Candida species grew on the vaginal epithelium of RVVC patients as morphologically disparate biofilms including monolayers, microcolonies, and macro-colonies, in addition to sporadic adherent cells. Candida biofilm growth on the vaginal epithelium was associated with mild lymphocytic infiltration of the vaginal mucosa. These epithelium-based Candida biofilms presented an important characteristic contributing to the persistence of RVVC that is the high tolerance to fluconazole.

Conclusions: In summary, our study provides direct evidence to support the presence of Candida biofilms in RVVC and an important role of biofilm formation in disease persistence.

Keywords: And persistence; Antifungal resistance; Biopsy; Candida biofilms; Histopathology; Patients; Recurrent vulvovaginal candidiasis (RVVC).