Background: Vulvovaginal candidiasis (VVC), the second leading cause of genital infection in women of reproductive age, is caused by yeasts of the genus Candida. Treatment is usually empirical and performed with azoles, which have shown increasing ineffectiveness due to resistance from these species. This therapeutic challenge has led to the search for new treatment strategies. Lactobacillus spp. produce several components with microbicidal effects, such as lactic acid. These species are the main components of a healthy vaginal microbiota and have been used as probiotics. The aim of this work was to investigate the in vitro inhibitory effects of Lactobacillus casei Shirota on both the Candida spp. that cause VVC and on C. auris. Methods: The microbicidal effects of L. casei Shirota on the main VVC-causing species, C. albicans, C. tropicalis, C. norvegensis and C. parapsilosis, in addition to C. auris were investigated by counting the Colony-forming Units (CFUs) after cocultivation. The antifungal activity of lactic acid against these Candida strains was assessed using the microtiter broth dilution method to determine the minimum inhibitory concentrations (MICs). The effects of L. casei Shirota on hyphal and early biofilm formation was measured by optical microscopy. Results: L. casei Shirota showed inhibitory action against all tested Candida spp., ranging from 66.9 to 95.6% inhibition depending on the species. This inhibition is possibly related to the production of lactic acid, since lactic acid has shown microbicidal action against these same Candida spp. at a concentration of 5 mg/mL, which corresponds to half of the normal physiological concentration. In addition, L. casei Shirota was able to reduce the formation of C. albicans hyphae and early biofilms, showing strong anti-Candida effects. Conclusions: These results suggest that L. casei Shirota has antifungal activity against the Candida species that cause VVC. L. casei also has microbicidal action against C. auris.

Antimicrobial resistance is known to be one of the greatest global threats to human health, and is one of the main causes of death worldwide. In this scenario, polymyxins are last-resort antibiotics to treat infections caused by multidrug-resistant bacteria. Currently, the reference test to evaluate the susceptibility of isolates to polymyxins is the broth microdilution method; however, this technique has numerous complications and challenges for use in laboratory routines. Several phenotypic methods have been reported as being promising for implementation in routine diagnostics, including the BMD commercial test, rapid polymyxin NP test, polymyxin elution test, culture medium with polymyxins, and the Polymyxin Drop Test, which require materials for use in routines and must be easy to perform. Furthermore, Sensititre^®, molecular tests, MALDI-TOF MS, and Raman spectroscopy present reliable results, but the equipment is not found in most microbiology laboratories. In this context, this review discusses the main laboratory methodologies that allow the detection of resistance to polymyxins, elucidating the challenges and perspectives.

Lactobacillus spp. and other beneficial bacteria are predominant in the vaginal microbiota and represent an opportunity to correct dysbiosis if administered intravaginally. Since no commercial formulations are available, developing magistral formulations is an option, provided that they ensure viability and therapeutic efficacy. To evaluate their stability and culturability, four magistral formulations containing 10⁹ microorganisms were tested: vaginal capsules, vaginal ointment, gelatinous ovules, and waxy ovules. Certified strains of L. crispatus, L. johnsonii, L. gasseri, Limosilactobacillus reuteri, and Lacticaseibacillus rhamnosus, as well as a combination of the five, were used. The formulations were tested for pharmaco-technical stability using average weight and disintegration tests, as well as evaluation organoleptic. In addition, microbial recovery was evaluated by counting Colony-Forming Units (CFUs). All forms, except the gelatinous ovules, allowed microbial recovery at concentrations from 10⁷ to 10⁹ CFUs, ensuring stability for 60 days. The recovery varied depending on the strains and dosage forms employed, with the most favorable outcomes for vaginal capsules. This highlights the need for standardized strains and excipients in magistral formulations. Further studies are needed to evaluate the viability of other strains of different excipients, vehicles, or different storage; however, capsules have demonstrated efficacy and are an excellent candidate for vaginal use formulations of Lactobacillus spp.