Azole-resistant Candida Glabrata Research Articles

Asymptomatic Candida glabrata urinary tract infection in an immunocompetent young female: A case report.

Fungal urinary tract infections (UTIs) are becoming increasingly common in hospitalized patients and Candida species are the most prevalent organisms. However, recurrent candiduria in young healthy outpatients is rare thus require further examination to find the etiologic factors. We described a case of recurrent asymptomatic c caused by azole-resistant C. glabrata in a healthy young female who only had previous use of antibiotics without other risk factors. However, after removal of the predisposing factor and the use of sensitive antifungal agents, the patient's urine cultures remained positive. This phenomenon indicated to us that the patient might have an immune-related genetic deficiency. We found a novel caspase-associated recruitment domain-containing protein 9 (CARD9) gene mutation (c.808-11G > T) which might be the cause of recurrent asymptomatic candiduria in this immune-competent young female without any underlying diseases. We report a case of recurrent asymptomatic candiduria caused by azole-resistant Candida glabrata in a young healthy female with a novel CARD9 mutation. A functional study of this mutation should be performed in the future to determine its effect on asymptomatic fungal UTIs.

Investigation of culturable human gut mycobiota from the segamat community in Johor, Malaysia.

Although several studies have already been carried out in investigating the general profile of the gut mycobiome across several countries, there has yet to be an officially established baseline of a healthy human gut mycobiome, to the best of our knowledge. Microbial composition within the gastrointestinal tract differ across individuals worldwide, and most human gut fungi studies concentrate specifically on individuals from developed countries or diseased cohorts. The present study is the first culture-dependent community study assessing the prevalence and diversity of gut fungi among different ethnic groups from South East Asia. Samples were obtained from a multi-ethnic semi-rural community from Segamat in southern Malaysia. Faecal samples were screened for culturable fungi and questionnaire data analysis was performed. Culturable fungi were present in 45% of the participants' stool samples. Ethnicity had an impact on fungal prevalence and density in stool samples. The prevalence of resistance to fluconazole, itraconazole, voriconazole and 5-fluorocytosine, from the Segamat community, were 14%, 14%, 11% and 7% respectively. It was found that Jakun individuals had lower levels of antifungal resistance irrespective of the drug tested, and male participants had more fluconazole resistant yeast in their stool samples. Two novel point mutations were identified in the ERG11 gene from one azole resistant Candida glabrata, suggesting a possible cause of the occurrence of antifungal resistant isolates in the participant's faecal sample.

Emergence of Azole Resistant Candida Glabrata as an Important Cause of Hospital Acquired Infection: Its Risk Factors and Impact

Candida spp. colonizes the human host and coexists with members of the human microbiome. Candida glabrata are aggressive pathogens, have many virulence factors that lead to serious recurrent candidiasis. Their ability to form a complex biofilm, inability to form hyphae, and inability to secrete hydrolase lead to antifungal resistance. Candidemia is the fourth most common bloodstream infection [1]. Candidemia remains a major source of mortality and morbidity. Mortality among patients with invasive candidiasis is as high as 40%, even when patients receive antifungal therapy [2]. More than 90% of invasive diseases are caused by the 5 most common Candida spp. C. albicans, C. glabrata, C. tropicalis, C. parapsilosis, and C. krusei [3]. The distribution of Candida species has been changing over the last decade, with a decrease in the proportion of C. albicans and an increase in C. glabrata and C. parapsilosis. More than 50% of bloodstream infections are caused by non-albicans Candida [2,4]. The largest proportional increase in the USA is in C. glabrata, which accounts for one third or more of all candidemia isolates [5-7]. C.glabrata are associated with high mortality. Candida glabrata develop acquired resistance following exposure to antifungal agents [8]. 50% of C. glabrata are resistant to fluconazole [9,10]. Furthermore, 9% of C. glabrata that are resistant to fluconazole are also resistant to the echinocandins [8,11].

Missense mutation in CgPDR1 regulator associated with azole-resistant Candida glabrata recovered from Thai oral candidiasis patients.

Non-albicans Candida (NAC) species are increasingly identified as pathogens causing oral candidiasis. Incidence rates for azole resistance among NAC species have been continuously reported. This study aimed to evaluate the azole susceptibility profiles and to characterise the azole resistance mechanisms of oral clinical NAC isolates. In vitro susceptibility patterns of 85 NAC species isolates were determined by the broth microdilution method. Azole resistance-related genes (ERG3, ERG11 and PDR1) of Candida glabrata isolates were sequenced to determine the presence of nucleotide substitutions. Expression levels of various resistance-related genes were also evaluated by RT-qPCR in azole-susceptible, susceptible dose-dependent (SDD) and resistant Candida isolates. Two C. glabrata isolates (2.4% of all NAC isolates) were resistant to all three azoles tested (fluconazole, itraconazole and ketoconazole). All clinical isolates of Candida tropicalis and Candida kefyr were susceptible to azoles. Silent mutations were found in the CgERG11 and CgERG3 genes of clinical C. glabrata isolates. Interestingly, two missense mutations in CgPDR1 (N768D and E818K) were identified only in resistant C. glabrata isolates. The presence of a CgPDR1 missense mutation in resistant isolates is associated with overexpression of its own product as well as multidrug transporters including ABC and MFS transporters. A gain-of-function (GOF) mutation in CgPDR1 is associated with upregulation of various drug transporters, which appears to serve as a primary mechanism for azole resistance in the detected C. glabrata isolates. Therefore, analysis of GOF mutations in the PDR1 regulator provides a better understanding of the development of antifungal resistance.

Contribution of CgPDR1-Regulated Genes in Enhanced Virulence of Azole-Resistant Candida glabrata

In Candida glabrata, the transcription factor CgPdr1 is involved in resistance to azole antifungals via upregulation of ATP binding cassette (ABC)-transporter genes including at least CgCDR1, CgCDR2 and CgSNQ2. A high diversity of GOF (gain-of-function) mutations in CgPDR1 exists for the upregulation of ABC-transporters. These mutations enhance C. glabrata virulence in animal models, thus indicating that CgPDR1 might regulate the expression of yet unidentified virulence factors. We hypothesized that CgPdr1-dependent virulence factor(s) should be commonly regulated by all GOF mutations in CgPDR1. As deduced from transcript profiling with microarrays, a high number of genes (up to 385) were differentially regulated by a selected number (7) of GOF mutations expressed in the same genetic background. Surprisingly, the transcriptional profiles resulting from expression of GOF mutations showed minimal overlap in co-regulated genes. Only two genes, CgCDR1 and PUP1 (for PDR1 upregulated and encoding a mitochondrial protein), were commonly upregulated by all tested GOFs. While both genes mediated azole resistance, although to different extents, their deletions in an azole-resistant isolate led to a reduction of virulence and decreased tissue burden as compared to clinical parents. As expected from their role in C. glabrata virulence, the two genes were expressed as well in vitro and in vivo. The individual overexpression of these two genes in a CgPDR1-independent manner could partially restore phenotypes obtained in clinical isolates. These data therefore demonstrate that at least these two CgPDR1-dependent and -upregulated genes contribute to the enhanced virulence of C. glabrata that acquired azole resistance.

High burden of antimicrobial resistance in Asia

Antimicrobial resistance is associated with high mortality rates and high medical costs. Marked variations in the resistance profiles of bacterial and fungal pathogens as well as the quality of public hygiene have had a considerable impact on the effectiveness of antimicrobial agents in Asian countries. In Asia, one of the epicentres of antimicrobial drug resistance, there is an alarming number of antibiotic-resistant species, including penicillin- and erythromycin-resistant Streptococcus pneumoniae, ampicillin-resistant Haemophilus influenzae, multidrug-resistant (MDR) Acinetobacter baumannii, extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae (particularly mediated by CTX-M-9, CTX-M-14 and CTX-M-15), New Delhi metallo-β-lactamase 1 (NDM-1)-producing Enterobacteriaceae, MDR Salmonella enterica serotypes Choleraesuis and Typhi, carbapenem-resistant A. baumannii (OXA-58 and OXA-23 carbapenemases) and azole-resistant Candida glabrata. A few clones of MDR A. baumannii and hospital-acquired meticillin-resistant Staphylococcus aureus (MRSA) have been widely disseminated in hospital settings in Asia, and K. pneumoniae carbapenemase (KPC)-producing K. pneumoniae strains have been widely distributed in China. In addition, the emergence of extensively drug-resistant Mycobacterium tuberculosis (XDR-TB) has illustrated the need for regular monitoring of resistance profiles of clinical isolates as well as the deliberative use of fluoroquinolones. Continuous surveillance of resistance data from clinical isolates as well as implementation of strict infection control policies in healthcare settings are required to mitigate the progression of antimicrobial resistance.

Mutations in the CgPDR1 and CgERG11 genes in azole-resistant Candida glabrata clinical isolates from Slovakia

Candida glabrata is an important human pathogen that is naturally less susceptible to antimycotics compared with Candida albicans. Ten unmatched C. glabrata clinical isolates were selected from a collection of isolates exhibiting decreased susceptibilities to azole antifungals. Overexpression of the CgPDR1 gene, encoding the main multidrug resistance transcription factor, and its target genes CgCDR1 and CgCDR2, coding for drug efflux transporters, was observed in six fluconazole-resistant isolates. Sequence analysis of the polymerase chain reaction (PCR)-amplified DNA fragments of each isolate's CgPDR1 gene was used to identify two novel L347F and H576Y mutations in CgPdr1p. These proved to be responsible for fluconazole resistance in transformants of the C. glabrata pdr1Δ mutant strain. Five isolates harbouring the H576Y mutation also contained the mutation E502V in CgErg11p 14C-lanosterol-demethylase. Heterologous expression of the CgERG11 mutant allele did not provide evidence for its involvement in azole resistance. In four fluconazole-sensitive isolates that were itraconazole-resistant, slightly enhanced CgCDR2 expression was observed. No upregulation of the CgERG11 gene was observed in any of the ten isolates. The results demonstrate that decreased susceptibilities of C. glabrata clinical isolates to azole antifungals mainly results from gain-of-function mutations in the gene encoding the CgPdr1p transcription factor.

Rhodotorula glutinis fungemia in a liver–kidney transplant patient

A 54-year-old man underwent simultaneous liver-kidney transplantation. During his prolonged hospitalization, he developed catheter-related fungemia with Rhodotorula glutinis and azole-resistant Candida glabrata. Management of the Rhodotorula fungemia was complicated by his renal insufficiency, hepatic insufficiency, and the concurrent fungemia with multi-azole resistant C. glabrata. He was treated with combination therapy with voriconazole and micafungin with subsequent clearance of the fungemia. Rhodotorula species are emerging as human pathogens with the increasing number of immunosuppressed patients in the last few decades. This is the first report of a R. glutinis fungemia in a solid organ transplant recipient.

Epidemiology of candidemia in Swiss tertiary care hospitals: secular trends, 1991-2000.

Candida species are among the most common bloodstream pathogens in the United States, where the emergence of azole-resistant Candida glabrata and Candida krusei are major concerns. Recent comprehensive longitudinal data from Europe are lacking. We conducted a nationwide survey of candidemia during 1991-2000 in 17 university and university-affiliated hospitals representing 79% of all tertiary care hospital beds in Switzerland. The number of transplantations and bloodstream infections increased significantly (P<.001). A total of 1137 episodes of candidemia were observed: Candida species ranked seventh among etiologic agents (2.9% of all bloodstream isolates). The incidence of candidemia was stable over a 10-year period. C. albicans remained the predominant Candida species recovered (66%), followed by C. glabrata (15%). Candida tropicalis emerged (9%), the incidence of Candida parapsilosis decreased (1%), and recovery of C. krusei remained rare (2%). Fluconazole consumption increased significantly (P<.001). Despite increasing high-risk activities, the incidence of candidemia remained unchanged, and no shift to resistant species occurred.

Enhanced oxidative killing of azole-resistant Candida glabrata strains with ERG11 deletion.

The susceptibility of genetically defined Candida glabrata strains to killing by H2O2 and neutrophils was assessed. Fluconazole-susceptible L5L and L5D strains demonstrated survival rates higher than those of two fluconazole-resistant strains lacking the ERG11 gene coding for 14 alpha-demethylase. Fluconazole resistance can occur by mechanisms which increase fungal susceptibility to oxidative killing by H2O2 and neutrophils.