Molecular Characterization of Candida auris Isolates at a Major Tertiary Care Center in Lebanon

Adhesive and biofilm-forming Candida glabrata Lebanese hospital isolates harbour mutations in subtelomeric silencers and adhesins

BACKGROUND

The prevalence of Candida glabrata healthcare-associated infections is on the rise worldwide and in Lebanon, Candida glabrata infections are difficult to treat as a result of their resistance to azole antifungals and their ability to form biofilms.

OBJECTIVES

The first objective of this study was to quantify biofilm biomass in the most virulent C. glabrata isolates detected in a Lebanese hospital. In addition, other pathogenicity attributes were evaluated. The second objective was to identify the mechanisms of azole resistance in those isolates.

METHODS

A mouse model of disseminated systemic infection was developed to evaluate the degree of virulence of 41 azole-resistant C. glabrata collected from a Lebanese hospital. The most virulent isolates were further evaluated alongside an isolate having attenuated virulence and a reference strain for comparative purposes. A DNA-sequencing approach was adopted to detect single nucleotide polymorphisms (SNPs) leading to amino acid changes in proteins involved in azole resistance and biofilm formation. This genomic approach was supported by several phenotypic assays.

RESULTS

All chosen virulent isolates exhibited increased adhesion and biofilm biomass compared to the isolate having attenuated virulence. The amino acid substitutions D679E and I739N detected in the subtelomeric silencer Sir3 are potentially involved- in increased adhesion. In all isolates, amino acid substitutions were detected in the ATP-binding cassette transporters Cdr1 and Pdh1 and their transcriptional regulator Pdr1.

CONCLUSIONS

In summary, increased adhesion led to stable biofilm formation since mutated Sir3 could de-repress adhesins, while decreased azole susceptibility could result from mutations in Cdr1, Pdh1 and Pdr1.

Candida glabrata hospital isolate from Lebanon reveals micafungin resistance associated with increased chitin and resistance to a cell-surface-disrupting agent

OBJECTIVES

This study aimed to identify the resistance mechanisms to micafungin and fluconazole in a clinical isolate of Candida glabrata.

METHODS

The isolate was whole-genome sequenced to identify amino acid changes in key proteins involved in antifungal resistance, and the isolate was further characterised by pathogenicity-related phenotypic assays that supported the sequencing results.

RESULTS

Amino acid substitutions were detected in 8 of 17 protein candidates. Many of these substitutions were novel, including in CHS3, CHS3B, and KRE5, which are involved in the development of micafungin resistance. Regarding fluconazole resistance, overexpression of efflux pumps was observed. Our isolate did not exhibit an increased virulence potential compared with the control strain; however, a significant increase in chitin content and potential to resist the cell surface disruptant sodium dodecyl sulphate was observed.

CONCLUSIONS

This clinical Candida glabrata isolate experienced a change in cell wall architecture, which correlates with the development of micafungin resistance.

Phenotypic and Genotypic Characterization of Candida parapsilosis complex isolates from a Lebanese Hospital

The opportunistic fungal pathogen Candida parapsilosis is a major causative agent of candidiasis leading to death in immunocompromised individuals. Azoles are the first line of defense in treatment by inhibiting ERG11 , involved in the synthesis of ergosterol, the main sterol fungal sterol. Resistance to azoles is on the increase worldwide including in Lebanon. The purpose of this study is to characterize nine hospital isolates labeled as C. parapsilosis : four resistant and five sensitive to fluconazole. Phenotypic characterization was achieved through a battery of tests that target pathogenicity attributes such as virulence, biofilm formation, stress resistance, and ergosterol content. Genotypic analysis was done through whole genome sequencing to mutations in key virulence and resistance genes. Phylogenetic comparison was performed to determine strain relatedness and clonality. Genomic data and phylogenetic analysis revealed that three of the nine C. parapsilosis isolates were misidentified; two as C. orthopsilosis and C. metapsilosis belonging to the C. parapsilosis complex, while the third was C. albicans. Moreover, several known and novel mutations in key drug resistance and virulence genes were identified such as ERG11 , ERG3 , ERG6 , CDR1 , and FAS2 . Phylogenetic analysis revealed a high degree of relatedness and clonality within our C. parapsilosis isolates. Our results showed that resistant isolates had no increased ergosterol content, no statistically significant difference in virulence, but exhibited an increase in biofilm content compared to the sensitive isolates. In conclusion, our study, the first of its kind in Lebanon, suggests several mechanisms of antifungal drug resistance in C. parapsilosis hospital isolates.

Genomic characterization of ST38 NDM-5-producing Escherichia coli isolates from an outbreak in the Czech Republic

A 2-year national genomic screening in the Czech Republic identified a notable prevalence of the New Delhi metallo-β-lactamase 5 (NDM-5)-producing Escherichia coli sequence type 38 (ST38) in the city of Brno. Forty-two ST38 E. coli isolates harbored the blaNDM-5 gene on the chromosome. Virulence factors confirmed the persistence of these isolates through biofilm formation. Single Nucleotide Polymorphisms (SNPs)-based phylogeny and CRISPR assay typing showed minimal genomic variations, implying a clonally driven outbreak. Results suggest that this high-risk clone may impose a nationwide problem.

Nosocomial infection of C. auris in COVID-19 Intensive Care Unit in Türkiye and Phylogenetic Analysis of Isolates

BACKGROUND

The difficulties in the identification of C. auris and the delays in the implementation of infection control precautions contribute to outbreaks. This study analyzed 10 patients with COVID-19 and C. auris candidemia, their characteristic and clinical features and phylogenetic features, and the antifungal susceptibilities of the isolates.

METHOD

C. auris were detected in the COVID-19 ICU of a university hospital between January and August 2021. Identification to species level was performed using MALDI-TOF MS. Antifungal susceptibilities were determined by the Sensititre YeastOne YO10 panel. The isolates were whole genome sequenced to assess genetic relatedness and a phylogenetic tree was drawn including various C. auris clades.

RESULTS

The mean growth time in blood cultures was 38.8 h. C. auris candidemia developed on the average 27th day of ICU admission. All were susceptible to anidulafungin and micafungin, while they were resistant to fluconazole and amphotericin B. Only three isolates were found to be resistant to caspofungin. All patients died. With the WGS method, all isolates were found in a close resemblance to each other in terms of total nucleotide similarity (with a minimum of 96% pairwise alignment). Our isolates showed the closest similarity to South Asian clade (Clade I).

CONCLUSIONS

This study is the first to evaluate the phylogenetic characteristics of C. auris using WGS and to determine antifungal susceptibilities in Türkiye on COVID-19 patients. The mortality rate was very high in patients who have both COVID-19 and C. auris candidemia.

Antifungal Use and Resistance in a Lower-Middle-Income Country: The Case of Lebanon

Antimicrobial resistance is a serious threat, particularly in low- and middle-income countries (LMICs). Antifungal resistance is often underestimated in both healthcare and non-clinical settings. In LMICs, it is believed that the inappropriate use of antifungals, limited surveillance systems, and low diagnostic capacities are significant drivers of resistance. Like other LMICs, Lebanon lacks antifungal use and resistance surveillance programs, and the impact of antifungal resistance in the country remains unclear, especially during the unfolding economic crisis that has severely affected medical care and access to safe food and water. Interestingly, the widespread use of antifungals in medicine and agriculture has raised concerns about the development of antifungal resistance in Lebanon. In this light, we aimed to survey available antifungal drugs in the country and evaluate susceptibility patterns of prevalent fungal species to guide empiric treatments and develop antifungal stewardship programs in Lebanon. We noted that the economic crisis resulted in significant increases in antifungal drug prices. Additionally, a comprehensive literature search across PubMed, ScienceDirect, and Google Scholar databases identified 15 studies on fungal infections and antifungal resistance conducted from 1998 to 2023 in Lebanon. While data on antifungal resistance are limited, 87% of available studies in Lebanon focused on candidiasis, while the remaining 13% were on aspergillosis. Overall, we observed a marked antimicrobial resistance among Candida and Aspergillus species. Additionally, incidences of Candida auris infections have increased in Lebanese hospitals during the COVID-19 pandemic, with a uniform resistance to fluconazole and amphotericin-B. Taken together, a One Health approach, reliable diagnostics, and prudent antifungal use are required to control the spread of resistant fungal pathogens in healthcare and agricultural settings.

The Impact of COVID-19 on the Epidemiology and Outcomes of Candidemia: A Retrospective Study from a Tertiary Care Center in Lebanon

Invasive fungal infections, notably candidemia, have been associated with COVID-19. The epidemiology of candidemia has significantly changed during the COVID-19 pandemic. We aim to identify the microbiological profile, resistance rates, and outcomes of COVID-19-associated candidemia (CAC) compared to patients with candidemia not associated with COVID-19. We retrospectively collected data on patients with candidemia admitted to the American University of Beirut Medical Center between 2004 and 2022. We compared the epidemiology of candidemia during and prior to the COVID-19 pandemic. Additionally, we compared the outcomes of critically ill patients with CAC to those with candidemia without COVID-19 from March 2020 till March 2022. Among 245 candidemia episodes, 156 occurred prior to the pandemic and 89 during the pandemic. Of the latter, 39 (43.8%) were CAC, most of which (82%) were reported from intensive care units (ICU). Non-albicans Candida (NAC) spp. were predominant throughout the study period (67.7%). Candida auris infection was the most common cause of NAC spp. in CAC. C. glabrata had decreased susceptibility rates to fluconazole and caspofungin during the pandemic period (46.1% and 38.4%, respectively). The mortality rate in the overall ICU population during the pandemic was 76.6%, much higher than the previously reported candidemia mortality rate observed in studies involving ICU patients. There was no significant difference in 30-day mortality between CAC and non-CAC (75.0% vs. 78.1%; p = 0.76). Performing ophthalmic examination (p = 0.002), CVC removal during the 48 h following the candidemia (p = 0.008) and speciation (p = 0.028) were significantly associated with a lower case-fatality rate. The epidemiology of candidemia has been significantly affected by the COVID-19 pandemic at our center. Rigorous infection control measures and proper antifungal stewardship are essential to combat highly resistant species such as C. auris.

Similarities and Differences among Species Closely Related to Candida albicans: C. tropicalis, C. dubliniensis, and C. auris

Although Candida species are widespread commensals of the microflora of healthy individuals, they are also among the most important human fungal pathogens that under certain conditions can cause diseases (candidiases) of varying severity ranging from mild superficial infections of the mucous membranes to life-threatening systemic infections. So far, the vast majority of research aimed at understanding the molecular basis of pathogenesis has been focused on the most common species—Candida albicans. Meanwhile, other closely related species belonging to the CTG clade, namely, Candida tropicalis and Candida dubliniensis, are becoming more important in clinical practice, as well as a relatively newly identified species, Candida auris. Despite the close relationship of these microorganisms, it seems that in the course of evolution, they have developed distinct biochemical, metabolic, and physiological adaptations, which they use to fit to commensal niches and achieve full virulence. Therefore, in this review, we describe the current knowledge on C. tropicalis, C. dubliniensis, and C. auris virulence factors, the formation of a mixed species biofilm and mutual communication, the environmental stress response and related changes in fungal cell metabolism, and the effect of pathogens on host defense response and susceptibility to antifungal agents used, highlighting differences with respect to C. albicans. Special attention is paid to common diagnostic problems resulting from similarities between these species and the emergence of drug resistance mechanisms. Understanding the different strategies to achieve virulence, used by important opportunistic pathogens of the genus Candida, is essential for proper diagnosis and treatment.

COVID-19 and C. auris: A Case-Control Study from a Tertiary Care Center in Lebanon

Many healthcare centers around the world have reported the surge of Candida auris (C. auris) outbreaks during the COVID-19 pandemic, especially among intensive care unit (ICU) patients. This is a retrospective study conducted at the American University of Beirut Medical Center (AUBMC) between 1 October 2020 and 15 June 2021, to identify risk factors for acquiring C. auris in patients with severe COVID-19 infection and to evaluate the impact of C. auris on mortality in patients admitted to the ICU during that period. Twenty-four non-COVID-19 (COV−) patients were admitted to ICUs at AUBMC during that period and acquired C. auris (C. auris+/COV−). Thirty-two patients admitted with severe COVID-19 (COV+) acquired C. auris (C. auris+/COV+), and 130 patients had severe COVID-19 without C. auris (C. auris−/COV+). Bivariable analysis between the groups of (C. auris+/COV+) and (C. auris−/COV+) showed that higher quick sequential organ failure assessment (qSOFA) score (p < 0.001), prolonged length of stay (LOS) (p = 0.02), and the presence of a urinary catheter (p = 0.015) or of a central venous catheter (CVC) (p = 0.01) were associated with positive culture for C. auris in patients with severe COVID-19. The multivariable analysis showed that prolonged LOS (p = 0.008) and a high qSOFA score (p < 0.001) were the only risk factors independently associated with positive culture for C. auris. Increased LOS (p = 0.02), high “Candida score” (p = 0.01), and septic shock (p < 0.001) were associated with increased mortality within 30 days of positive culture for C. auris. Antifungal therapy for at least 7 days (p = 0.03) appeared to decrease mortality within 30 days of positive culture for C. auris. Only septic shock was associated with increased mortality in patients with C. auris (p = 0.006) in the multivariable analysis. C. auris is an emerging pathogen that constitutes a threat to the healthcare sector.