PURPOSE: The incidence of Candida bloodstream infections (BSI) has increased over the past two decades. The rank order of occurrence and the susceptibility to antifungals of the various Candida species causing BSI are important factors driving the establishment of empirical treatment protocols; however, very limited multi-institutional data are available on Candida bloodstream isolates in Korea. MATERIALS AND METHODS: We investigated the susceptibility to azole antifungals and species distribution of 143 Candida bloodstream isolates recovered from eight university hospitals over a six-month period. Minimal inhibitory concentrations (MICs) of fluconazole, itraconazole, and voriconazole for each isolate were determined by the broth microdilution method of the Clinical and Laboratory Standards Institute (CLSI). RESULTS: The Candida species recovered most frequently from the blood cultures was C. albicans (49%), followed by C. parapsilosis (22%), C. tropicalis (14%), and C. glabrata (11%). The MIC ranges for the Candida isolates were 0.125 to 64microgram/mL for fluconazole, 0.03 to 2microgram/mL for itraconazole, and 0.03 to 1microgram/mL for voriconazole. Overall, resistance to fluconazole was found in only 2% of the Candida isolates (3/143), while the dose-dependent susceptibility was found in 6% (8/143). The resistance and dose-dependent susceptibility of itraconazole were found in 4% (6/143) and 14% (20/143) of the isolates, respectively. All bloodstream isolates were susceptible to voriconazole (MIC, < or = 1microgram/mL). CONCLUSION: Our findings show that C. albicans is the most common cause of Candida-related BSI, followed by C. parapsilosis, and that the rates of resistance to azole antifungals are still low among bloodstream isolates in Korea.
Antifungal Agents/*pharmacology ; Azoles/*pharmacology ; Bacteremia/*microbiology ; Candida/classification/*drug effects/isolation & purification ; Candidiasis/*microbiology ; Drug Resistance, Fungal ; Fluconazole/pharmacology ; Hospitals, University ; Humans ; Itraconazole/pharmacology ; Microbial Sensitivity Tests ; Population Surveillance ; Pyrimidines/pharmacology ; Triazoles/pharmacology

BACKGROUND: Fluorescent dye Rhodamine 6G (R6G) is a substrate of multidrug resistance pumps and its accumulation is reduced in some azole-resistant Candida isolates with the upregulation of multidrug efflux transporter genes. Despite reports on species-specific differences in azole susceptibility in various Candida species, only a few studies have been reported on the R6G accumulation among clinical isolates of Candida species. In this study, we compared R6G accumulation between six different Candida species. METHODS: The intracellular accumulation of R6G and minimal inhibitory concentrations (MICs) of three triazole agents were investigated in 48 strains of six Candida species (14 C. albicans, 9 C. tropicalis, 8 C. glabrata, 8 C. krusei, 7 C. parapsilosis, and 2 C. haemulonii). R6G accumulation was measured by using flow cytometry and the geometric mean of the fluorescence intensity (GMF) was used to compare the accumulation between the Candida isolates. RESULTS: The GMF values for the C. tropicalis, C. albicans, C. krusei, C. parapsilosis, and C. glabrata isolates were 167.3+/-18.5, 126.9+/-6.6, 88.5+/-18.5, 50.8+/-7.0, and 38.1+/-3.9, respectively. C. glabrata had a significantly lower mean GMF than all the other Candida species (P<0.05). While some Candida strains with trailing growth phenomenon and increased fluconazole MIC did not have a reduced GMF, three Candida strains with increased MICs to all three triazole agents had a reduced GMF. CONCLUSIONS: This study found species-specific differences in R6G accumulation in Candida. In addition, the intracellular R6G accumulation can be used to investigate the drug efflux mechanism in azole-resistant Candida strains.
Antifungal Agents/pharmacology ; Azoles/pharmacology ; Candida/chemistry/isolation & purification/*metabolism ; Candidiasis/drug therapy ; Drug Resistance, Fungal ; Flow Cytometry/*methods ; Fluconazole/pharmacology ; Fluorescent Dyes/*analysis ; Humans ; Microbial Sensitivity Tests ; Rhodamines/*analysis ; Species Specificity

Identification and validation of a new target is one of the most important steps for new antituberculosis (TB) drug discovery. Researches have shown that Mycobacterium tuberculosis (Mtb) encodes 20 CYP450 enzymes which play important roles in the synthesis and metabolism of lipid, cholesterol utilization, and the electron transport of respiratory chain in Mtb. With the critical roles within the organism as well as the protein structures of six Mtb CYP450 enzymes being clarified, some of them have been highlighted as potential anti-tuberculosis targets. In this paper, the phylogenetic analysis, the structural features, and the enzymatic functions of Mtb CYPs, as well as the mechanism of interactions with selective inhibitors such as azole antifungal agents for the CYPs have been reviewed and summarized. The druggability of the CYPs has also been analyzed for their further utility as targets in high throughput screening and rational design of more selective inhibitors.
Antitubercular Agents ; chemistry ; pharmacology ; Azoles ; chemistry ; pharmacology ; Cytochrome P-450 Enzyme Inhibitors ; chemistry ; pharmacology ; Cytochrome P-450 Enzyme System ; genetics ; metabolism ; Drug Delivery Systems ; methods ; Drug Discovery ; Humans ; Mycobacterium tuberculosis ; drug effects ; enzymology ; genetics ; Phylogeny ; Tuberculosis ; drug therapy ; microbiology

Antifungal drug resistance is a significant clinical problem, and antifungal agents that can evade resistance are urgently needed. In infective niches, resistant organisms often co-existed with sensitive ones, or a subpopulation of antibiotic-susceptible organisms may evolve into resistant ones during antibiotic treatment and eventually dominate the whole population. In this study, we established a co-culture assay in which an azole-resistant Candida albicans strain was mixed with a susceptible strain labeled with green fluorescent protein to mimic in vivo conditions and screen for antifungal drugs. Fluconazole was used as a positive control to verify the validity of this co-culture assay. Five natural molecules exhibited antifungal activity against both susceptible and resistant C. albicans. Two of these compounds, retigeric acid B (RAB) and riccardin D (RD), preferentially inhibited C. albicans strains in which the efflux pump MDR1 was activated. This selectivity was attributed to greater intracellular accumulation of the drugs in the resistant strains. Changes in sterol and lipid compositions were observed in the resistant strains compared to the susceptible strain, and might increase cell permeability to RAB and RD. In addition, RAB and RD interfered with the sterol pathway, further aggregating the decrease in ergosterol in the sterol synthesis pathway in the MDR1-activated strains. Our findings here provide an alternative for combating resistant pathogenic fungi.
ATP-Binding Cassette Transporters ; genetics ; metabolism ; Antifungal Agents ; chemistry ; metabolism ; pharmacology ; Azoles ; pharmacology ; Biosynthetic Pathways ; drug effects ; genetics ; Candida albicans ; chemistry ; drug effects ; metabolism ; Cell Membrane ; chemistry ; metabolism ; Coculture Techniques ; Drug Resistance, Fungal ; drug effects ; Ergosterol ; metabolism ; Fungal Proteins ; genetics ; metabolism ; Lipids ; chemistry ; Molecular Structure ; Permeability ; Phenyl Ethers ; chemistry ; metabolism ; pharmacology ; Sterols ; chemistry ; metabolism ; Stilbenes ; chemistry ; metabolism ; pharmacology ; Triterpenes ; chemistry ; metabolism ; pharmacology

Gene mutation of Candida albicans is one of the main causes for azole drug resistance. Different types of variation play different roles in promoting the process of drug resistance. ERG series of gene mutations primarily affect the ergosterol synthesis pathway. When the regulatory factors TAC1 for CDR1 gene and Mrr1 for MDR1 gene generate mutations, the expression level of drug efflux pump protein in Candida albicans may be changed. In addition, gene copy number variation is also gaining attention. Therefore, the research of mutation resistance-associated genes has a positive meaning to explore the mechanism of drug resistance in Candida albicans.
ATP-Binding Cassette, Sub-Family B, Member 1 ; genetics ; Antifungal Agents ; pharmacology ; Azoles ; pharmacology ; Candida albicans ; drug effects ; genetics ; Cytochrome P-450 Enzyme System ; genetics ; DNA Copy Number Variations ; Drug Resistance, Fungal ; Fungal Proteins ; genetics ; Membrane Transport Proteins ; genetics ; Mutation ; genetics