Mixed yeast infections in Taiwan

Pichia kudriavzevii (Candida krusei): A systematic review to inform the World Health Organisation priority list of fungal pathogens

In response to the growing global threat of fungal infections, in 2020 the World Health Organisation (WHO) established an Expert Group to identify priority fungi and develop the first WHO fungal priority pathogen list (FPPL). The aim of this systematic review was to evaluate the features and global impact of invasive infections caused by Pichia kudriavzevii (formerly known as Candida krusei). PubMed and Web of Science were used to identify studies published between 1 January 2011 and 18 February 2021 reporting on the criteria of mortality, morbidity (defined as hospitalisation and length of stay), drug resistance, preventability, yearly incidence, and distribution/emergence. Overall, 33 studies were evaluated. Mortality rates of up to 67% in adults were reported. Despite the intrinsic resistance of P. kudriavzevii to fluconazole with decreased susceptibility to amphotericin B, resistance (or non-wild-type rate) to other azoles and echinocandins was low, ranging between 0 and 5%. Risk factors for developing P. kudriavzevii infections included low birth weight, prior use of antibiotics/antifungals, and an underlying diagnosis of gastrointestinal disease or cancer. The incidence of infections caused by P. kudriavzevii is generally low (∼5% of all Candida-like blood isolates) and stable over the 10-year timeframe, although additional surveillance data are needed. Strategies targeting the identified risk factors for developing P. kudriavzevii infections should be developed and tested for effectiveness and feasibility of implementation. Studies presenting data on epidemiology and susceptibility of P. kudriavzevii were scarce, especially in low- and middle-income countries (LMICs). Thus, global surveillance systems are required to monitor the incidence, susceptibility, and morbidity of P. kudriavzevii invasive infections to inform diagnosis and treatment. Timely species-level identification and susceptibility testing should be conducted to reduce the high mortality and limit the spread of P. kudriavzevii in healthcare facilities.

Multiplex size marker (YEAST PLEX) for rapid and accurate identification of pathogenic yeasts

Background

Multiple yeast species can cause human disease, involving superficial to deep‐seated infections. Treatment of these infections depends on the accurate identification of causative agents; however, reliable methods are not available in many laboratories, especially not in resource‐limited settings. Here, a new multiplex assay for rapid and low‐cost identification of pathogenic yeasts is described.

Methods

A two‐step multiplex assay named YEAST PLEX that comprises of four tubes and identifies 17 clinically important common to rare yeasts was designed and evaluated. The set also provides PCR amplicon of unidentified species for direct sequencing. The specificity of YEAST PLEX was tested using 28 reference strains belonging to 17 species and 101 DNA samples of clinically important non‐target bacteria, parasites, and fungi as well as human genomic DNA. The method was further analyzed using 203 previously identified and 89 unknown clinical yeast isolates. Moreover, the method was tested for its ability to identify mixed yeast colonies by using 18 mixed suspensions of two or three species.

Results

YEAST PLEX was able to identify all the target species without any non‐specific PCR products. When compared to PCR‐sequencing/MALDI‐TOF, the results of YEAST PLEX were in 100% agreement. Regarding the 89 unknown clinical isolates, random isolates were selected and subjected to PCR‐sequencing. The results of sequencing were in agreement with those of YEAST PLEX. Furthermore, this method was able to correctly identify all yeasts in mixed suspensions.

Conclusion

YEAST PLEX is an accurate, low‐cost, and rapid method for identification of yeasts, with applicability, especially in developing countries.

High prevalence of asymptomatic nosocomial candiduria due to Candida glabrata among hospitalized patients with heart failure: a matter of some concern?

Background and Purpose:

Heart failure is a leading cause of hospitalization, and asymptomatic candiduria is common in hospitalized patients with low morbidity. However, in most patients, it is resolved spontaneously on the removal of the catheter. Despite the publication of guidelines, there are still controversies over the diagnosis and management of candiduria. However, in hospitalized patients with heart failure, the decision to treat candiduria is especially important since the nosocomial infections are associated with an increase in morbidity, mortality, length of hospital stay, and healthcare costs. Some species of Candida, such as Candida glabrata, are increasingly resistant to the first-line and second-line antifungal medications. The present study aimed to investigate the incidence of asymptomatic Candida urinary tract infection due to C. glabrata and antifungal susceptibility of Candida isolates in hospitalized patients with heart failure.

Materials and Methods:

In total, 305 hospitalized patients with heart failure were studied to identify asymptomatic nosocomial candiduria during 2016-17 in one private hospital in the north of Iran. The Sabouraud’s dextrose agar culture plates with a colony count of >10⁴ colony-forming unit/ml of urine sample were considered as Candida urinary tract infection. Candida species were identified based on the morphology of CHROMagar Candida (manufactured by CHROMagar, France) and PCR-RFLP method with MspI restriction enzyme. Antifungal susceptibility testing of the isolates was performed using five mediations, including itraconazole, voriconazole, fluconazole, amphotericin B, and caspofungin by broth microdilution method according to CLSI M27-S4.

Results:

In this study, the rate of asymptomatic Candida urinary tract infection was 18.8%, which was more common in people above 51 years old and females (70%). In addition to the urinary and intravascular catheter, the occurrence of candiduria in hospitalized patients had significant relationships with a history of surgical intervention, diastolic heart failure, and use of systemic antibiotics (P>0.05). Among Candida spp., non-albicans Candida species was the most common infectious agent (59.7%). Moreover, C. glabrata (n=27, 40.3%) (alone or with other species) and Candida albicans (n=27, 40.3%) were the most common agents isolated in Candida urinary tract infection. Based on the results of the in vitro susceptibility test, the C. glabrata isolates were 15%, 59%, 70%, 74%, and 85% susceptible to caspofungin, amphotericin B, itraconazole, voriconazole, and fluconazole, respectively.

Conclusion:

According to the findings, there was a high prevalence of asymptomatic Candida urinary tract infection in hospitalized patients with heart failure. Besides, it was suggested that there was a shift towards non-albicans Candida, especially C. glabrata, in these patients. Therefore, asymptomatic candiduria in hospitalized patients with heart failure should be considered significant. Furthermore, the identification of Candida species along with antifungal susceptibility is essential and helps the clinicians to select the appropriate antifungal agent for better management of such cases.

MixInYeast: A Multicenter Study on Mixed Yeast Infections

Invasive candidiasis remains one of the most prevalent systemic mycoses, and several studies have documented the presence of mixed yeast (MY) infections. Here, we describe the epidemiology, clinical, and microbiological characteristics of MY infections causing invasive candidiasis in a multicenter prospective study. Thirty-four centers from 14 countries participated. Samples were collected in each center between April to September 2018, and they were sent to a reference center to confirm identification by sequencing methods and to perform antifungal susceptibility testing, according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST). A total of 6895 yeast cultures were identified and MY occurred in 150 cases (2.2%). Europe accounted for the highest number of centers, with an overall MY rate of 4.2% (118 out of 2840 yeast cultures). Of 122 MY cases, the most frequent combinations were Candida albicans/C. glabrata (42, 34.4%), C. albicans/C. parapsilosis (17, 14%), and C. glabrata/C. tropicalis (8, 6.5%). All Candida isolates were susceptible to amphotericin B, 6.4% were fluconazole-resistant, and two isolates (1.6%) were echinocandin-resistant. Accurate identification of the species involved in MY infections is essential to guide treatment decisions.

Implications of mixed viral infections on plant disease ecology and evolution

Mixed viral infections occur more commonly than would be expected by chance in nature. Virus-virus interactions may affect viral traits and leave a genetic signature in the population, and thus influence the prevalence and emergence of viral diseases. Understanding about how the interactions between viruses within a host shape the evolutionary dynamics of the viral populations is needed for viral disease prevention and management. Here, we first synthesize concepts implied in the occurrence of virus-virus interactions. Second, we consider the role of the within-host interactions of virus-virus and virus-other pathogenic microbes, on the composition and structure of viral populations. Third, we contemplate whether mixed viral infections can create opportunities for the generation and maintenance of viral genetic diversity. Fourth, we attempt to summarize the evolutionary response of viral populations to mixed infections to understand how they shape the spatio-temporal dynamics of viral populations at the individual plant and field scales. Finally, we anticipate the future research under the reconciliation of molecular epidemiology and evolutionary ecology, drawing attention to the need of adding more complexity to future research in order to gain a better understanding about the mechanisms operating in nature.

Candida glabrata's Genome Plasticity Confers a Unique Pattern of Expressed Cell Wall Proteins

Candida glabrata is the second most common cause of candidemia, and its ability to adhere to different host cell types, to microorganisms, and to medical devices are important virulence factors. Here, we consider three characteristics that confer extraordinary advantages to C. glabrata within the host. (1) C. glabrata has a large number of genes encoding for adhesins most of which are localized at subtelomeric regions. The number and sequence of these genes varies substantially depending on the strain, indicating that C. glabrata can tolerate high genomic plasticity; (2) The largest family of CWPs (cell wall proteins) is the EPA (epithelial adhesin) family of adhesins. Epa1 is the major adhesin and mediates adherence to epithelial, endothelial and immune cells. Several layers of regulation like subtelomeric silencing, cis-acting regulatory regions, activators, nutritional signaling, and stress conditions tightly regulate the expression of many adhesin-encoding genes in C. glabrata, while many others are not expressed. Importantly, there is a connection between acquired resistance to xenobiotics and increased adherence; (3) Other subfamilies of adhesins mediate adherence to Candida albicans, allowing C. glabrata to efficiently invade the oral epithelium and form robust biofilms. It is noteworthy that every C. glabrata strain analyzed presents a unique pattern of CWPs at the cell surface.