Antifungal clinical trials and guidelines: what we know and do not know

Probiotics and their postbiotics for the control of opportunistic fungal pathogens: A review

During past twenty years the opportunistic fungal infections have been emerging, causing morbidity and mortality. The fungi belonging to Aspergillus, Mucor, Rhizopus, Candida, Fusarium, Penicillium, Dermatophytes and others cause severe opportunistic fungal infections. Among these Aspergillus and Candida spp cause majority of the diseases. The continuum of fungal infections will prolong to progress in the surroundings of the growing inhabitants of immunocompromised individuals. Presently many chemical-based drugs were used as prophylactic and therapeutic agents. Prolonged usage of antibiotics may lead to some severe effect on the human health. Also, one of the major threats is that the fungal pathogens are becoming the drug resistant. There are many physical, chemical, and mechanical methods to prevent the contamination or to control the disease. Owing to the limitations that are observed in such methods, biological methods are gaining more interest because of the use of natural products which have comparatively less side effects and environment friendly. In recent years, research on the possible use of natural products such as probiotics for clinical use is gaining importance. Probiotics, one of the well studied biological products, are safe upon consumption and are explored to treat various fungal infections. The antifungal potency of major groups of probiotic cultures such as Lactobacillus spp, Leuconostoc spp, Saccharomyces etc. and their metabolic byproducts which act as postbiotics like organic acids, short chain fatty acids, bacteriocin like metabolites, Hydrogen peroxide, cyclic dipeptides etc. to inhibit these opportunistic fungal pathogens have been discussed here.

Reason and reality-identifying barriers to patient enrolment for clinical trials in invasive candidiasis

OBJECTIVES

Enrolment of subjects to clinical trials investigating novel drugs for infectious diseases is an ongoing challenge. In this study, we evaluate factors associated with non-enrolment in treatment trials for invasive candidiasis.

METHODS

We conducted a retrospective review of pre-screening logs of patients that were assessed for enrolment in the three clinical trials ACTIVE (NCT00413218), APX001-201 (NCT03604705) and ReSTORE (NCT03667690), investigating novel drugs for invasive candidiasis between September 2007 and August 2021 to identify reasons for study ineligibility.

RESULTS

Two hundred and fifty-six patients with invasive candidiasis were identified for potential study participation with n = 154 for the ACTIVE trial, n = 89 for APX001-201 and n = 13 for ReSTORE. Half of the potential participants were unable or unwilling to consent. We further identified comorbid conditions such as hepatic or renal impairment [21 hepatic and renal cases (13.6%) in ACTIVE; 12 hepatic (13.5%) and 28 renal cases (31.5%) in APX], prior antifungal treatment [11 cases (7.1%) in ACTIVE; 16 (18.0%) in APX; 7 (38.5%) in ReSTORE] and the last positive culture obtained ≥96 h prior to dosing [1 case (0.6%) in ACTIVE; 7 (7.9%) in APX; 5 (38.5%) in ReSTORE] as relevant reasons for non-enrolment. We also identified criteria repetitively used in the analysed studies that did not contribute substantially to ineligibility rates. Ultimately, 254/256 patients (99.2%) were ineligible for enrolment in the respective trial.

CONCLUSIONS

This study identified barriers to enrolment in clinical trials assessing novel antifungal agents in invasive candidiasis. Identification of eligibility criteria associated with non-enrolment allows modification of future trial designs and may ultimately result in higher recruitment rates.

Essential Oils in Respiratory Mycosis: A Review

Respiratory mycosis is a major health concern, due to the expanding population of immunosuppressed and immunocompromised patients and the increasing resistance to conventional antifungals and their undesired side-effects, thus justifying the development of new therapeutic strategies. Plant metabolites, namely essential oils, represent promising preventive/therapeutic strategies due to their widely reported antifungal potential. However, regarding fungal infections of the respiratory tract, information is disperse and no updated compilation on current knowledge is available. Therefore, the present review aims to gather and systematize relevant information on the antifungal effects of several essential oils and volatile compounds against the main type of respiratory mycosis that impact health care systems. Particular attention is paid to Aspergillus fumigatus, the main pathogen involved in aspergillosis, Candida auris, currently emerging as a major pathogen in certain parts of the world, and Cryptococcus neoformans, one of the main pathogens involved in pulmonary cryptococcosis. Furthermore, the main mechanisms of action underlying essential oils’ antifungal effects and current limitations in clinical translation are presented. Overall, essential oils rich in phenolic compounds seem to be very effective but clinical translation requires more comprehensive in vivo studies and human trials to assess the efficacy and tolerability of these compounds in respiratory mycosis.

Diagnosis and Treatment of Invasive Candidiasis

Candida species, belonging to commensal microbial communities in humans, cause opportunistic infections in individuals with impaired immunity. Pathogens encountered in more than 90% cases of invasive candidiasis include C. albicans, C. glabrata, C. krusei, C. tropicalis, and C. parapsilosis. The most frequently diagnosed invasive infection is candidemia. About 50% of candidemia cases result in deep-seated infection due to hematogenous spread. The sensitivity of blood cultures in autopsy-proven invasive candidiasis ranges from 21% to 71%. Non-cultural methods (beta-D-glucan, T2Candida assays), especially beta-D-glucan in combination with procalcitonin, appear promising in the exclusion of invasive candidiasis with high sensitivity (98%) and negative predictive value (95%). There is currently a clear deficiency in approved sensitive and precise diagnostic techniques. Omics technologies seem promising, though require further development and study. Therapeutic options for invasive candidiasis are generally limited to four classes of systemic antifungals (polyenes, antimetabolite 5-fluorocytosine, azoles, echinocandins) with the two latter being highly effective and well-tolerated and hence the most widely used. Principles and methods of treatment are discussed in this review. The emergence of pan-drug-resistant C. auris strains indicates an insufficient choice of available medications. Further surveillance, alongside the development of diagnostic and therapeutic methods, is essential.

Probiotic properties of Lactobacillus casei - MYSRD 108 and Lactobacillus plantarum-MYSRD 71 with potential antimicrobial activity against Salmonella paratyphi

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This study reports the anti-salmonella activity by cell free supernatant of potential probiotics strains.

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Lactobacillus casei MYSRD 108 and Lactobacillus plantarum MYSRD 71 strains exhibited strong survival and antagonistic activities for probiotic application in the gastrointestinal tract against S. paratyphi biofilm.

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The CFS were characterized by various constraints and represented antagonistic activity against Salmonella due to the presence of organic acids that lowered the pH.

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The strains may be used to produce antimicrobial compounds which can be a substitute for chemical preservatives in food industry.

A total of 130 isolates were screened, twelve isolates were characterized for probiotic attributes and two isolates with best probiotic features were evaluated in the study. Isolates MYSRD108 and MYSRD71 survived gastric conditions and were susceptible to tested antibiotics. Isolates showed more vital cell surface traits such as autoaggregation of 89.2 and 88.5% and cell surface hydrophobicity of 61 and 64%. PCR amplification followed by 16sRNA sequencing results confirmed that the isolates as Lactobacillus casei (MYSRD 108) and Lactobacillus plantarum (MYSRD 71). During this study, the Cells and their Cell Free Supernatant (CFS) were examined for antimicrobial activity. Both the isolates inhibited different bacterial pathogens in which the growth of S. paratyphi was significantly reduced. Further, their CFS also showed inhibitory effects against S. paratyphi with agar well diffusion and Minimum Inhibitory Concentration using Broth micro dilution method. The antimicrobial compounds in the CFS was characterized to different constraints such as pH neutralization, heat treatment, Hydrogen peroxide test and storage stability at -20> °C and represented that the antagonistic acitivity against Salmonella is due to the presence of organic acids in the supernatants that lowered the pH. These strains were further examined for the inhibition of S. paratyphi biofilm. The results indicated that CFS reduced S. paratyphi biofilm by more than 75% and the number of Salmonella biofilm was effectively reduced using 15% concentration of CFS. These strains may be used to produce antimicrobial compounds which can be a substitute for chemical preservatives in food industry.

What is the elephant in the room when considering new therapies for fungal diseases?

The global scenario of antimicrobial resistance is alarming, and the development of new drugs has not appeared to make substantial progress. The constraints on drug discovery are due to difficulties in finding new targets for therapy, the high cost of development, and the mismatch between the time of drug introduction in a clinic and microorganism adaptation to a drug. Policies to address neglected diseases miss the broad spectrum of mycosis. Society is not aware of the actual threat represented by fungi to human health, food security, and biodiversity. The evidence discussed here is critical for warning governments to establish effective surveillance policies for fungi.HIGHLIGHTSFungal diseases are ignored even among neglected disease classifications.There are few options to treat mycoses, which is an increasing concern regarding fungal resistance to drugs, as evidenced by the spread of Candida auris.Fungal diseases represent a real threat to human health and food security.Investment in research to investigate the potential of repurposing drugs already in use could obtain results in the short term.

Empirical antifungal treatment for diagnosed and undiagnosed invasive fungal disease in patients with hematologic malignancies

BACKGROUND

Empirical antifungal therapy is effective in some patients with risk factors for invasive fungal disease (IFD) who do not qualify for the EORTC/MSG criteria for IFD, but who fail to respond to anti-bacterial and anti-viral therapy.

OBJECTIVE

This retrospective single-center study investigated the epidemiology of IFD and empirical antifungal therapy in patients with hematological malignancies.

METHODS

This study recruited 893 patients with hematologic malignancies who had failed to respond to anti-bacterial and anti-viral treatment and received antifungal therapy, but not for antifungal prophylaxis. Antifungal therapy regimens included amphotericin B, voriconazole, itraconazole and caspofungin. A total of 689 patients were diagnosed with proven, probable, or possible IFD, while 159 patients did not meet the EORTC/MSG criteria for IFD diagnosis but recovered with antifungal treatment, and 45 were excluded from having IFD. Effective treatment was defined as the disappearance or resolution of clinical symptoms of IFD.

RESULTS

Patients diagnosed with IFD underwent chemotherapy at a higher proportion, and had significantly higher neutrophil counts compared to those who did not qualify for the EORTC/MSG criteria for IFD but responded to antifungals. The mortality due to all causes within 3 months was significantly higher for patients diagnosed with proven IFD, compared with those who did not qualify for the EORTC/MSG criteria for IFD. There was no discontinuation reported due to adverse events of caspofungin.

CONCLUSION

Empirical antifungal treatment could help save the lives of some patients with severe infections who are strongly suspected of having IFD.

Probiotic lactobacilli inhibit early stages of Candida albicans biofilm development by reducing their growth, cell adhesion, and filamentation

We evaluated the inhibitory effects of the probiotic Lactobacillus species on different phases of Candida albicans biofilm development. Quantification of biofilm growth and ultrastructural analyses were performed on C. albicans biofilms treated with Lactobacillus rhamnosus, Lactobacillus casei, and Lactobacillus acidophilus planktonic cell suspensions as well as their supernatants. Planktonic lactobacilli induced a significant reduction (p < 0.05) in the number of biofilm cells (25.5-61.8 %) depending on the probiotic strain and the biofilm phase. L. rhamnosus supernatants had no significant effect on the mature biofilm (p > 0.05), but significantly reduced the early stages of Candida biofilm formation (p < 0.01). Microscopic analyses revealed that L. rhamnosus suspensions reduced Candida hyphal differentiation, leading to a predominance of budding growth. All lactobacilli negatively impacted C. albicans yeast-to-hyphae differentiation and biofilm formation. The inhibitory effects of the probiotic Lactobacillus on C. albicans entailed both cell-cell interactions and secretion of exometabolites that may impact on pathogenic attributes associated with C. albicans colonization on host surfaces and yeast filamentation. This study clarifies, for the first time, the mechanics of how Lactobacillus species may antagonize C. albicans host colonization. Our data elucidate the inhibitory mechanisms that define the probiotic candicidal activity of lactobacilli, thus supporting their utility as an adjunctive therapeutic mode against mucosal candidal infections.