Lactobacillus crispatus L1: high cell density cultivation and exopolysaccharide structure characterization to highlight potentially beneficial effects against vaginal pathogens

Abstract

BackgroundVaginal lactic acid bacteria defend the host against pathogens through a combination of competitive exclusion, competition for nutrients, production of antimicrobial substances and through the activation of the immune system. A new human isolate named Lactobacillus crispatus L1 was characterized in this work, and a preliminary evaluation of its probiotic potential is described together with a process to obtain a high productivity of viable biomass.ResultsIn a simulated digestion process 1.8⋅1010 cells∙ml−1 survived the gastric environment with 80% viability, without being affected by small intestine juices. Experiments on six different C sources were performed to analyze growth and organic acids production and, glucose, provided the best performances. A microfiltration strategy was exploited to improve the cellular yield in 2 L-fermentation processes, reaching 27 g · l−1 of dry biomass. Moreover, L. crispatus L1 demonstrated a greater stability to high concentrations of lactic acid, compared to other lactobacilli. The specific L. crispatus L1 exopolysaccharide was purified from the fermentation broth and characterized by NMR showing structural features and similarity to exopolysaccharides produced by pathogenic strains. Live L. crispatus L1 cells strongly reduced adhesion of a yeast pathogenic strain, Candida albicans in particular, in adherence assays. Interestingly a higher expression of the human defensin HBD-2 was also observed in vaginal cells treated with the purified exopolysaccharide, indicating a possible correlation with C. albicans growth inhibition.ConclusionsThe paper describes the evaluation of L. crispatus L1 as potential vaginal probiotic and the fermentation processes to obtain high concentrations of viable cells.

Antifungal defense of probiotic Lactobacillus rhamnosus GG is mediated by blocking adhesion and nutrient depletion

“…Impairment of C . albicans adhesion in response to lactobacilli has previously been reported [22, 23], and Oliveira et al [46] showed an impact of L . rhamnosus ATCC7469 on several virulence attributes such as proteinase and haemolytic activity, germ tube and biofilm formation.…”

“…Previous studies addressing the mechanisms behind probiotic action on C . albicans explored the ability of probiotic bacteria to inhibit fungal growth [18–21], to prevent adhesion [22, 23] or to influence anti-fungal immune responses [23, 24], respectively. Despite the numerous studies on probiotics, the mechanisms behind the beneficial effects of probiotics on human health and well-being are still unclear.…”

Modulation of immunity and gut microbiota after dietary administration of alginate encapsulated Shewanella putrefaciens Pdp11 to gilthead seabream (Sparus aurata L.)

“…In addition, specimens of Senegalese sole farmed under high stocking density and receiving a diet supplemented with SpPdp11 showed a higher resistance to disease in comparison with fish fed the diet without the probiotic [67], and this higher resistance was related to important changes in the intestinal microbiota, such as the presence of L. fermentum only in fish fed the diet supplemented with the probiotic [43]. Strains of L. crispatus have been associated with the ability to exert competitive exclusion and antimicrobial against vaginal human pathogens [69e71], being proposed as potential vaginal probiotic [72]. On the other hand, some trains of L. gasseri and L. johnsonii have also shown probiotic characteristics such as immunomodulatory [73] and anti-infective [74e76].…”

Advances in Microbiology, Infectious Diseases and Public Health

“…HBD-2 was induced in the distal tubules in the loops of Henle and collecting ducts in pyelonephritic kidneys (Lehmann et al 2002). Higher levels of neutrophil α-defensins are detectable in the vagina during infections with Neisseria gonorrhoeae, Trichomonas vaginalis or Chlamydia trachomatis (Donnarumma et al 2014b). α and β-defensins are expressed in the male reproductive tracts of humans, distributed in epididymus and seminiferous tubules, in the germ cells, Leyding cells and Sertoli cells (Yamaguchi et al 2002) HBD-2 in the genitourinary epithelia protect from infections caused by Candida (Wiechuła et al 2007).…”