Abstract
Probiotics can potentially prevent and treat diseases. We examined the inhibitory activity of bacteriocin-like inhibitory substances (BLISs) from potentially probiotic lactobacilli and streptococci on Candida albicans and non-Candida albicans clinical isolates from women with vulvovaginitis. Using agar well diffusion assays, BLISs inhibited both Candida albicans and non-Candida albicans isolates. The BLIS from L. pentosus isolates had the highest anti-Candida activity (33/45; 73.3%), followed by BLISs from isolates of L. paracasei subsp. paracasei (31/45; 68.9%), L. rhamnosus I (30/45; 66.7%), L. delbrueckii subsp. lactis I (30/45; 66.7%), and S. uberis II (30/45; 66.7%). Upon characterization according to the retained activity under variable physical and chemical conditions, the BLISs showed stability against heat, pH, and surfactants, but were protease-sensitive, which suggests a proteinaceous nature of the active substances. Using crystal violet assays, the BLISs reduced the Candida biofilm biomass significantly as compared to a control group that lacked BLISs. In vivo testing of the antagonistic activity was performed using the Galleria mellonella (G. mellonella) larvae model. BLISs significantly improved survival in G. mellonella larvae treated with Candida isolates on the first, second, and seventh days, as compared to larvae inoculated with Candida only (p < 0.01). The results show that BLISs can be used as biotherapeutic agents in vulvovaginal candidiasis.
Highlights
Vulvovaginal candidiasis (VVC) is a common condition that is typically mitigated by over-the-counter topical or systemic antifungal drugs
The inhibitory activity against all Candida isolates ranged from 51.1% (23/45 isolates) for the bacteriocin-like inhibitory substances (BLISs) from Streptococcus uberis I to 73.3% (33/45 isolates) for the BLIS from L. pentosus
BLISs from other potential probiotic isolates did not show a significant difference in antagonistic activity against NCAC isolates versus CA isolates (Table 1)
Summary
Vulvovaginal candidiasis (VVC) is a common condition that is typically mitigated by over-the-counter topical or systemic antifungal drugs. Pathogenic Candida species have developed resistance to many antifungal agents [2]. In addition to resistance issues, many currently available antifungal drugs have narrow spectra and cause side effects [4]. Lactobacilli are dominant in the vagina of the vast majority of healthy premenopausal women [5]. As part of the microbiota, lactobacilli can prevent vulvovaginal infections [6]. The antifungal activities are not always explained by hydrogen peroxide, a typical antimicrobial factor in lactobacilli [7]. Lactic acid bacteria such as Enterococci and Streptococci can produce antimicrobial peptides such as bacteriocins [9]. Streptococcus uberis, the main causative agent of bovine mastitis, produces a lantibiotic bacteriocin (nisin U) [10]. Lactobacillus plantarum and Lactobacillus curvatus are able to synthesize bacteriocins [11]
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