Drug susceptibility profile of Candida glabrata clinical isolates from Iran and genetic resistant mechanisms to caspofungin

Candida glabrata (Nakaseomyces glabrata): A systematic review of clinical and microbiological data from 2011 to 2021 to inform the World Health Organization Fungal Priority Pathogens List

Recognising the growing global burden of fungal infections, the World Health Organization (WHO) established an advisory group consisting of experts in fungal diseases to develop a Fungal Priority Pathogen List. Pathogens were ranked based on their research and development needs and perceived public health importance using a series of global surveys and pathogen characteristics derived from systematic reviews. This systematic review evaluates the features and global impact of invasive disease caused by Candida glabrata (Nakaseomyces glabrata). PubMed and Web of Science were searched for studies reporting on mortality, morbidity (hospitalization and disability), drug resistance (including isolates from sterile and non-sterile sites, since these reflect the same organisms causing invasive infections), preventability, yearly incidence, diagnostics, treatability, and distribution/emergence in the last 10 years. Candida glabrata (N. glabrata) causes difficult-to-treat invasive infections, particularly in patients with underlying conditions such as immunodeficiency, diabetes, or those who have received broad-spectrum antibiotics or chemotherapy. Beyond standard infection prevention and control measures, no specific preventative measures have been described. We found that infection is associated with high mortality rates and that there is a lack of data on complications and sequelae. Resistance to azoles is common and well described in echinocandins-in both cases, the resistance rates are increasing. Candida glabrata remains mostly susceptible to amphotericin and flucytosine. However, the incidence of the disease is increasing, both at the population level and as a proportion of all invasive yeast infections, and the increases appear related to the use of antifungal agents.

Molecular Mechanisms Associated with Antifungal Resistance in Pathogenic Candida Species

Candidiasis is a highly pervasive infection posing major health risks, especially for immunocompromised populations. Pathogenic Candida species have evolved intrinsic and acquired resistance to a variety of antifungal medications. The primary goal of this literature review is to summarize the molecular mechanisms associated with antifungal resistance in Candida species. Resistance can be conferred via gain-of-function mutations in target pathway genes or their transcriptional regulators. Therefore, an overview of the known gene mutations is presented for the following antifungals: azoles (fluconazole, voriconazole, posaconazole and itraconazole), echinocandins (caspofungin, anidulafungin and micafungin), polyenes (amphotericin B and nystatin) and 5-fluorocytosine (5-FC). The following mutation hot spots were identified: (1) ergosterol biosynthesis pathway mutations (ERG11 and UPC2), resulting in azole resistance; (2) overexpression of the efflux pumps, promoting azole resistance (transcription factor genes: tac1 and mrr1; transporter genes: CDR1, CDR2, MDR1, PDR16 and SNQ2); (3) cell wall biosynthesis mutations (FKS1, FKS2 and PDR1), conferring resistance to echinocandins; (4) mutations of nucleic acid synthesis/repair genes (FCY1, FCY2 and FUR1), resulting in 5-FC resistance; and (5) biofilm production, promoting general antifungal resistance. This review also provides a summary of standardized inhibitory breakpoints obtained from international guidelines for prominent Candida species. Notably, N. glabrata, P. kudriavzevii and C. auris demonstrate fluconazole resistance.

Assessment of Risk Factors and Clinical Outcomes in Hospitalized COVID-19 Patients with Candida spp. Co-infections: Species Distribution and Antifungal Susceptibility Patterns of Isolates

INTRODUCTION

Fungal co-infections are considered an important complication in hospitalized patients with SARS-CoV-2 that can be attributed to disease aggravation, increased mortality, and poor outcomes. This study was conducted to determine the species distribution and antifungal susceptibility patterns of Candida isolates from hospitalized COVID-19 patients in Shiraz, Iran, in addition to associated risk factors and outcomes of co-infections with Candida species.

MATERIALS AND METHODS

In this single-center study, a total of 106 hospitalized COVID-19 patients were evaluated for clinical characteristics and outcomes. Species identification was performed by ITS1-5.8S-ITS2 gene sequencing. Antifungal susceptibility testing to fluconazole, itraconazole, voriconazole, posaconazole, caspofungin, amphotericin B, and nystatin was determined according to the M27-A3/S4 CLSI protocol.

RESULTS

Candida species were recovered from 48% (51/106) of hospitalized COVID-19 patients. Statistical analysis showed that patients who had heart failure, bacterial co-infection, and were receiving empirical antifungal therapy had a higher risk of developing Candida co-infection. In total, 71 Candida isolates were recovered, of which C. albicans (69%) was the most prevalent isolate. The majority of the Candida isolates were susceptible to all classes of tested antifungal drugs.

DISCUSSION

Our results elucidate a high rate of Candida co-infections among hospitalized COVID-19 patients. Comorbidities such as heart failure, HTN, COPD, bacterial infections as well as therapeutic interventions including catheterization, mechanical ventilation, and ICU admission increased the risk of Candida spp. isolation from the bloodstream, respiratory tract and urine samples, which led to a higher in-hospital mortality rate. Additionally, obtained data clarified that empirical antifungal therapy was not as successful as anticipated.

Antifungal Resistance in Clinical Isolates of Candida glabrata in Ibero-America

In different regions worldwide, there exists an intra-and inter-regional variability in the rates of resistance to antifungal agents in Candida glabrata, highlighting the importance of understanding the epidemiology and antifungal susceptibility profiles of C. glabrata in each region. However, in some regions, such as Ibero-America, limited data are available in this context. Therefore, in the present study, a systematic review was conducted to determine the antifungal resistance in C. glabrata in Ibero-America over the last five years. A literature search for articles published between January 2015 and December 2020 was conducted without language restrictions, using the PubMed, Embase, Cochrane Library, and LILACS databases. The search terms that were used were "Candida glabrata" AND "antifungal resistance" AND "Country", and 22 publications were retrieved from different countries. The use of azoles (fluconazole, itraconazole, voriconazole, posaconazole, isavuconazole, ketoconazole, and miconazole) varied between 4.0% and 100%, and that of echinocandins (micafungin, caspofungin, and anidulafungin) between 1.1% and 10.0%. The limited information on this subject in the region of Ibero-America emphasizes the need to identify the pathogens at the species level and perform antifungal susceptibility tests that may lead to the appropriate use of these drugs and the optimal doses in order to avoid the development of antifungal resistance or multi-resistance.

Effectiveness of Phytoactive Molecules on Transcriptional Expression, Biofilm Matrix, and Cell Wall Components of Candida glabrata and Its Clinical Isolates

Toxicity challenges by antifungal arsenals and emergence of multidrug resistance scenario has posed a serious threat to global community. To cope up with this alarming situation, phytoactive molecules are richest, safest, and most effective source of broad spectrum antimicrobial compounds. In the present investigation, six phytoactive molecules [cinnamaldehyde (CIN), epigallocatechin, vanillin, eugenol (EUG), furanone, and epigallocatechin gallate] were studied against Candida glabrata and its clinical isolates. Among these, CIN and EUG which are active components of cinnamon and clove essential oils, respectively, exhibited maximum inhibition against planktonic growth of C. glabrata at a concentration of 64 and 128 μg mL-1, respectively. These two molecules effectively inhibited and eradicated approximately 80% biofilm of C. glabrata and its clinical isolates from biomaterials. CIN and EUG increased reactive oxygen species generation, cell lysis, and ergosterol content in plasma membrane and reduced virulence attributes (phospholipase and proteinase) as well as catalase activity of C. glabrata cells. Reduction of mitochondrial membrane potential with increased release of cytochrome c from mitochondria to cytosol indicated initiation of early apoptosis in CIN- and EUG-treated C. glabrata cells. Transcriptional analysis showed that multidrug transporter (CDR1) and ergosterol biosynthesis genes were downregulated in the presence of CIN, while getting upregulated in EUG-treated cells. Interestingly, genes such as 1,3-β-glucan synthase (FKS1), GPI-anchored protein (KRE1), and sterol importer (AUS1) were downregulated upon treatment of CIN/EUG. These results provided molecular-level insights about the antifungal mechanism of CIN and EUG against C. glabrata including its resistant clinical isolate. The current data established that CIN and EUG can be potentially formulated in new antifungal strategies.