• We are sorry, but NCBI web applications do not support your browser and may not function properly. More information
Logo of jcmPermissionsJournals.ASM.orgJournalJCM ArticleJournal InfoAuthorsReviewers
J Clin Microbiol. Aug 2007; 45(8): 2385–2391.
Published online Jun 20, 2007. doi:  10.1128/JCM.00381-07
PMCID: PMC1951250

Changes in Karyotype and Azole Susceptibility of Sequential Bloodstream Isolates from Patients with Candida glabrata Candidemia[down-pointing small open triangle]

Abstract

We examined the changes in genotypes and azole susceptibilities among sequential bloodstream isolates of Candida glabrata during the course of fungemia and the relationship of these changes to antifungal therapy. Forty-one isolates were obtained from 15 patients (9 patients who received antifungal therapy and 6 patients who did not) over periods of up to 36 days. The isolates were analyzed using pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) and tested for antifungal susceptibility to fluconazole, itraconazole, and voriconazole. PFGE typing consisted of electrophoretic karyotyping and restriction endonuclease analysis of genomic DNA by use of NotI (REAG-N). The 41 isolates yielded 23 different karyotypes and 11 different REAG-N patterns but only 3 MLST types. The sequential strains from each patient had identical or similar REAG-N patterns. However, they had two or three different karyotypes in 6 (40%) of 15 patients. The isolates from these six patients exhibited the same or similar azole susceptibilities, and five patients did not receive antifungal therapy. Development of acquired azole resistance in sequential isolates was detected for only one patient. For this patient, an isolate of the same genotype obtained after azole therapy showed three- or fourfold increases in the MICs of all three azole antifungals and exhibited increased expression of the CgCDR1 efflux pump. This study shows that karyotypic changes can develop rapidly among sequential bloodstream strains of C. glabrata from the same patient without antifungal therapy. In addition, we confirmed that C. glabrata could acquire azole resistance during the course of fungemia in association with azole therapy.

Candida glabrata has recently emerged as one of the most common causes of Candida bloodstream infections (BSIs) worldwide (18, 19). This species is innately less susceptible to azoles than most other Candida species and mutates readily in vitro or in vivo and acquires secondary azole resistance rapidly following short-term exposure to triazole-derived agents (4, 5, 21-23). While acquired azole resistance is reported to be uncommon in most Candida species recovered from blood cultures, the development of azole resistance was recently documented in sequential BSI isolates of C. glabrata (15, 23). The reason for the rapid development of secondary antifungal resistance in C. glabrata is unknown, but its haploid nature is thought to be a contributing factor (10). Generally, the induction of stable azole resistance in Candida albicans isolates occurs gradually, which presumably reflects its diploid genome (8).

An assessment of the genotype patterns and antifungal susceptibilities of sequential Candida isolates from the same patient has been used to investigate whether the development of antifungal resistance was due to the acquisition of a new isolate or a change in an existing isolate (2, 4, 5, 21-23). Although sequential clinical isolates of C. glabrata from the same patient usually yield the same genotype (2, 12), C. glabrata may undergo rapid genotypic change during human infection due to its haploid nature, unlike diploid Candida species. To date, however, research is lacking on genotypic variation and its relationship to antifungal therapy among clonal isolates of C. glabrata obtained sequentially from blood cultures from the same patient.

This study assessed the genotype change and acquisition of antifungal resistance in clonal isolates of C. glabrata from the same patient during the course of fungemia and their relationship with antifungal therapy. Forty-one sequential BSI isolates of C. glabrata obtained from 15 patients (6 patients who received antifungal therapy and 9 patients who did not receive antifungal therapy) who were admitted to the same hospital over a 7-year period were analyzed. Genotyping was performed using multilocus sequence typing (MLST), electrophoretic karyotyping (EK), and restriction endonuclease analysis of genomic DNA using NotI (REAG-N) followed by pulsed-field gel electrophoresis (PFGE). In addition, we compared the expressions of CgCDR1 and CgCDR2 among the sequential BSI isolates of C. glabrata.

MATERIALS AND METHODS

Microorganisms.

Forty-one blood isolates were obtained from 15 patients, each of whom had one or more blood cultures positive for C. glabrata on two or more separate days. The patients were admitted to the Chonnam University Hospital between 1997 and 2003. The charts of the 15 patients with C. glabrata fungemia were reviewed retrospectively. Patient data (age, sex, and admission diagnoses), the number of positive blood cultures, the presence of central venous catheter (CVC)-related candidemia, the dates and dosages of antifungal drug administration, and outcomes of the fungemia were recorded (24). Candida glabrata was identified through assimilation tests by using the API 20C and ATB 32C systems (BioMérieux, Marcy l'Etoile, France) and by assessing the isolates on CHROMagar Candida medium (Gemini BioProducts, Woodland, CA).

PFGE analysis.

PFGE was performed using a procedure previously described (24, 25) for EK and REAG-N. For EK, isolates that differed by one or more bands were considered to have different karyotypes (24, 25). For REAG-N, strains with banding patterns with identical sizes and numbers of bands were assigned to the same type, strains with banding patterns that differed by three or fewer bands were considered closely related and described as subtypes (a or b) of a given clonal type, and strains with banding patterns that differed by four or more bands were considered different and assigned to separate types (25, 28). When serial isolates from the same patient show a minor genotypic change (subtype) in the REAG-N pattern, it represents the occurrence of microevolution (25). All isolates were analyzed at least twice (mean, three times; range, two to five times) by repeating the procedure.

MLST.

Multilocus enzyme sequence typing was performed using a previously described procedure (9). Candida DNA was extracted by using a QIAGEN DNA tissue kit (QIAGEN, Crawley, United Kingdom) according to the manufacturer's instructions. The six genes selected for MLST were FKS, LEU2, NMT1, TRP1, UGP1, and URA3. All loci were sequenced in both the forward and reverse directions with primers the same as those used for the PCRs. Sequencing reactions were performed in a 20-μl volume with 3 pmol of oligonucleotide primer, 25 ng of template, 4 μl of BigDye Terminator cycle sequencing ready reaction mix (PE Applied Biosystems, Foster City, CA), and 2 μl of 5× sequencing buffer (80 mM Tris-Cl [pH 9.0], 2 mM MgCl2). The reaction products were analyzed with an ABI Prism 377 DNA sequencer (PE Applied Biosystems). The allele profiles of the strains were defined using the six MLST loci. Each unique allele profile was designated as a sequence type (ST), which was determined by comparing the database at the MLST website (www.mlst.net).

Real-time RT-PCR.

Total RNA extraction and real-time reverse transcription-PCR (RT-PCR) were performed using the modified method of Sanguinetti et al. (23). The expression of CgCDR1 and CgCDR2 was quantified using real-time RT-PCR with ROTOR Gene 3000 (Corbett Research, Sydney, Australia). Each set of primer pairs and fluorescent probes was used as previously reported (23). For the target genes and the URA3 reference gene, a primer pair and a TaqMan probe, which hybridize to the region between the primer-specific sequences, were synthesized and labeled by Operon Biotechnologies (Huntsville, AL). Real-time PCR was performed with a Quantitect PCR probe kit (QIAGEN, Hilden, Germany) with a 25-μl volume of PCR mixture containing 2× Quantitect buffer, 0.25 μM each primer pair, 0.1 μM each probe, and 8 μl of cDNA. After 15 min of denaturation at 95°C, 45 cycles were performed. Cycling conditions were 95°C for 15 s and 59°C for 60 s. The concentration of each gene was calculated with reference to the respective standard curve by use of Corbett Research software and normalized as the ratio of the target (CgCDR1 and CgCDR2) and housekeeping (CgURA3) gene concentrations from separate reactions. Each reaction was performed in triplicate. For all isolates, the relative gene expression was reported as the change (n-fold) determined from the mean normalized expression relative to the mean normalized expression of C. glabrata ATCC 90030.

Antifungal susceptibility testing.

Fungal susceptibilities to amphotericin B, fluconazole, itraconazole, and voriconazole were tested using the standard methods of the Clinical and Laboratory Standards Institute (CLSI; formerly NCCLS) as given in document M27-A2 (17). Two reference strains, Candida parapsilosis ATCC 22019 and Candida krusei ATCC 6258, were tested as quality control isolates in each antifungal susceptibility test.

RESULTS

Clinical characteristics of the patients.

The patients included six (patients 1 to 6) who did not receive antifungal therapy and nine (patients 7 to 15) given antifungal therapy (Table (Table1).1). Seven patients (patients 7 to 11, 14, and 15) had sequential isolates even after the initiation of antifungal therapy. The most common underlying conditions in the patients were gastrointestinal diseases (seven patients). Three patients (patients 9, 10, and 13) were diagnosed with CVC-related fungemia. Previous fluconazole use was noted for two patients (patients 5 and 11). Only one patient had neutropenia (patient 5). The fungemia resolved completely in two of the six patients who did not receive antifungal therapy and in six of the nine patients who received antifungal therapy.

TABLE 1.
Clinical summary for 15 patients with C. glabrata fungemia in this study

Comparison of genotypes among isolates from different patients.

Table Table22 presents the sequences of the isolates, antifungal susceptibilities, genotyping results, and CgCDR1 and CgCDR2 gene expression for the isolates from each of the 15 patients. When analyzed using the PFGE methods, the 41 isolates from the 15 patients yielded 23 different karyotypes and 11 different REAG-N patterns. MLST identified only three distinct types. Isolates from nine patients, five patients, and one patient belonged to ST7, to ST3, and to a new ST type, respectively. The allele profiles for the six loci (FKS, LEU2, NMT1, TRP1, UGP1, and URA3) were 578736 for ST3, 344334 for ST7, and 365239 for the new ST type. Isolates from two patients (patients 9 and 10) shared identical EK, MLST, and REAG-N types (Fig. (Fig.1).1). These two patients had been admitted to the same surgical intensive care unit; their hospital stays overlapped, and both patients were diagnosed with CVC-related fungemia.

FIG. 1.
Representative genotyping patterns of C. glabrata obtained by EK and REAG-N. Sequential BSI isolates of C. glabrata were obtained from five patients who did not receive antifungal therapy (patients 1 to 5) and from four patients who received antifungal ...
TABLE 2.
Antifungal susceptibilities, genotypes, and expression characteristics of CgCDR1 and CgCDR2 genes for sequential C. glabrata isolates from each of 15 patients

Comparison of genotypes among sequential isolates from the same patient.

The sequential strains from each patient had identical karyotypes in nine (60%) patients, while they had two or three different karyotypes in six (40%) patients (patients 1 to 4, 6, and 14). For the last six patients, the isolates from the same patient differed from each other by only one or two chromosome bands in the molecular size range of >1,600 kb in EK, although they were the same in the low-molecular-weight chromosome bands (<1,600 kb). By REAG-N typing, the sequential isolates from each patient had identical patterns for six patients, while they exhibited minor genetic differences (one or two bands) for nine (60%) patients, suggesting that microevolution had occurred (Table (Table22 and Fig. Fig.1).1). Overall, the sequential isolates from 11 of 15 patients (73%) exhibited karyotypic changes or microevolution. The isolation intervals among these isolates for each patient ranged from 1 to 24 days. Five of the six patients whose isolates had two or more different karyotypes and four of the nine patients whose isolates showed microevolution had no association with previous antifungal therapy. For all patients, the sequential isolates from the same patient had the same MLST type.

Development of azole resistance in sequential isolates.

With the exception of those from one patient, the sequential strains from each patient had the same or similar antifungal susceptibilities. The exception was patient 7, who had three positive blood cultures for C. glabrata; the second and third positive cultures were made 2 and 36 days, respectively, after the first. The patient received antifungal therapy after the second positive blood culture was obtained. The MICs of the first two isolates for fluconazole, itraconazole, and voriconazole were 16, 1, and 0.25 μg/ml, respectively. In contrast, the third isolate (isolate 7-3), obtained 36 days after the first positive culture, showed two- or threefold increases in the MICs of all three azole antifungals (fluconazole, 128 μg/ml; itraconazole, 4 μg/ml; and voriconazole, 2 μg/ml). By this time, the patient had received a cumulative dose of 1.1 g of fluconazole and 0.4 g of itraconazole. The three isolates from this patient retained the same MLST, karyotype, and REAG-N patterns. However, the resistant isolate showed an increase in the ethidium bromide staining intensity of the karyotypic bands compared to that for the susceptible isolate, which was the consistent finding in repeated trials (Fig. (Fig.11).

Expression of CgCDR1 and CgCDR2 in sequential isolates.

Levels of CgCDR1 and CgCDR2 expression relative to that of C. glabrata ATCC 90030 (fluconazole MIC, 8 μg/ml) for all isolates are shown in Table Table2.2. The fluconazole MICs of the isolates from 14 patients (all except patient 7) were clustered between 8 and 32 μg. No significant differences were observed for the levels of expression of CgCDR1 and CgCDR2 between fluconazole-susceptible isolates (MIC, ≤8 μg/ml) and dose-dependently susceptible isolates (MIC, 16 to 32 μg/ml) (Table (Table2).2). In contrast, the strain with acquired azole resistance from patient 7 (isolate 7-3) revealed a high abundance of CgCDR1 (145 times that of C. glabrata ATCC 90030) compared to the other BSI isolates (up to 19.9-fold). The level of CgCDR2 (3.5 times that of C. glabrata ATCC 90030) for this isolate was not significantly higher than those for the other isolates (up to 6.8-fold). Compared to the first BSI isolate (isolate 7-1) from patient 7, the resistant isolate exhibited 13.2- and 3.5-fold upregulation of CgCDR1 and CgCDR2, respectively. In contrast, for the other 14 patients, the sequential same-patient isolates differed somewhat in the levels of upregulation (0.3- to 3.6-fold for CgCDR1 and 0.3- to 4.2-fold for CgCDR2, relative to that of the corresponding first blood isolate from each patient).

DISCUSSION

EK using PFGE can discriminate heterogeneous strains within the same Candida species, including C. albicans, C. parapsilosis, and C. glabrata, by use of chromosome number or size (2, 12, 14, 24, 25). Previously, we reported that same-patient sequential BSI isolates of C. albicans had a stable karyotype (25). In addition, the serial BSI isolates of C. parapsilosis from one episode of CVC-related fungemia showed the same stable karyotype (24). Sequential C. glabrata same-patient isolates are usually reported to yield the same karyotype (2, 12), and karyotyping has been used to study linking changes in the antifungal resistance of C. glabrata isolates to treatment in some studies (4, 21). Unlike other Candida species, however, we found that the sequential BSI isolates of C. glabrata from blood cultures from the same patient had two or three different karyotypes in 6 (40%) of 15 patients. Since the sequential BSI Candida isolates from the same patient are usually reported to yield the same clonal isolates (24, 25), our data strongly suggest that for epidemiological purposes, karyotypic differences should not always be interpreted as a new strain of C. glabrata.

In a previous study of C. albicans, different karyotypes of C. albicans isolates could occur only with a difference in REAG patterns, which represents the occurrence of a new strain (25). In contrast, in this study of C. glabrata, we found that same-patient sequential isolates of C. glabrata which had different karyotypes had the same or similar REAG patterns. This difference might have been due to the critical genetic characteristics distinguishing between C. albicans and C. glabrata: C. glabrata has a haploid genome, in contrast to the diploid genome of C. albicans. C. glabrata is more closely related to Saccharomyces cerevisiae than to other Candida species, and many studies have shown increased chromosomal recombination or rearrangements in the yeast S. cerevisiae (13).

Klempp-Selb et al. (14) reported that seven isolates from a patient with C. glabrata fungemia had five different karyotype patterns, although the differences were only minor. They suggested that these karyotypic differences were due to chromosome rearrangement within a single strain. Note that the changes observed in the EK patterns of isolates from a single patient in our study were usually restricted to one or two chromosome bands at molecular sizes of >1,600 kb. Therefore, one additional consideration is that the variation in the high-molecular-weight portion of the gel might indicate in vitro chromosomal instability, including artifactual breakage of large chromosomes.

In our study, the 41 BSI isolates from the 15 patients yielded 23 different karyotypes and 11 different REAG-N patterns but only 3 different MLST patterns, indicating that MLST is of limited value for differentiating the clinical isolates of C. glabrata compared to the two PFGE methods. One PFGE type was shared by isolates obtained from two patients with CVC-related fungemia who had been hospitalized in the same intensive care unit on overlapping dates, suggesting the intrahospital spread of this C. glabrata isolate. In addition, the sequential isolates of nine patients (60%) showed minor genetic differences (one or two bands) by REAG-N, suggesting that microevolution had occurred. In C. albicans, microevolution frequently occurred at colonization sites but occurred only rarely among consecutive blood isolates from the same patient (25). Our study shows that microevolution occurred frequently among sequential BSI isolates of C. glabrata.

Cormican et al. (7) described both microevolution and karyotype variation in serial clinical isolates of C. glabrata. They frequently noted pattern variation of a single band among isolates from a single patient on consecutive days and on occasion from isolates from the same body site on the same day. In this study, the BSI isolates from 11 patients exhibited karyotypic changes or microevolution, and 6 of these patients did not receive antifungal therapy. Our data show that prior antifungal exposure is not necessary for the development of karyotypic changes or microevolution in BSI isolates of C. glabrata. In 11 cases of candidemia in which the sequential isolates showed karyotypic changes or microevolution, the isolation intervals among the isolates in each patient ranged from 1 to 24 days, which indicates that these genotype changes can occur rapidly.

Our study shows that for one of seven candidemic patients who had sequential isolates after fluconazole therapy, the strain developed increased MICs to all triazole agents. Although the three sequential strains from this patient had the same genotype, the last strain with acquired azole resistance showed increased ethidium bromide staining of the karyotype bands, which suggests that the resistant isolate underwent mutations involving chromosome duplication (16). The resistant strain produced a 13.2-fold increase in CgCDR1 transcripts, while CgCDR2 was upregulated only 3.5-fold, compared to the first BSI isolate from the same patient. Sanguinetti et al. (23) documented the development of azole resistance in four pairs of sequential isolates obtained from separate patients with C. glabrata BSIs. They noticed that CgCDR1 upregulation was always clearly manifested in fluconazole-resistant isolates, while CgCDR2 was expressed at moderate levels, which supports the idea that CgCDR1 is more closely associated with azole resistance than CgCDR2 (22). Our patient had received cumulative doses of 1.5 g of triazole antifungals, which is a dose much smaller than those (6.0 to 12.2 g) reported by Sanguinetti et al. (23). Bennett et al. (4) reported that exposure of C. glabrata to subtherapeutic concentrations of fluconazole may result in resistance. Recently, another case of invasive candidiasis and candidemia due to a C. glabrata isolate that developed resistance to all triazole antifungals after a course of fluconazole treatment was reported (15). Our study, together with others (15, 23), confirms that C. glabrata can acquire azole resistance during BSI in association with azole therapy.

Although the specific reasons for the recent emergence of C. glabrata as a major cause of BSI are unknown, fluconazole use is most likely involved in the emergence of C. glabrata infections (11). However, of 15 patients with C. glabrata fungemia analyzed in this study, only 2 patients had a history of fluconazole use. The most common underlying conditions in our patients were gastrointestinal diseases. Since systemic C. glabrata infections frequently arise from the host's endogenous microflora, mainly that in the orointestinal and genitourinary tracts (5), this suggests the possible entrance of C. glabrata stains into the bloodstream from disruption of the gastrointestinal mucosal surfaces in our patients.

The molecular mechanism for the genotypic change in serial C. glabrata isolates is completely unknown. Although serial strains of C. albicans from patients usually have stable karyotypes (3, 25), chromosome translocations can contribute to karyotypic variability in vitro (26). Several studies have demonstrated that karyotypic variation in C. albicans is associated with high-frequency phenotypic switching, which occurs primarily in the chromosome harboring ribosomal DNA cistrons (20, 26). In our study on serial isolates of C. glabrata, one or two chromosomal bands larger than 1,600 bp are particularly variable, suggesting that this variation is due to a variable number of ribosomal DNA repeats (1). Brockert et al. (6) reported that the majority of C. glabrata strains switch spontaneously at high frequency between core phenotypes and the irregular wrinkle phenotype, and switching occurs at sites of infection. It has been suggested that the switching of C. glabrata represents a supervirulence factor regulating several genes, the combined expression of which facilitates pathogenesis (27). Our study showed that in addition to karyotype changes, microevolution occurs frequently in C. glabrata during the course of fungemia. However, the relevance of this genotypic change is unknown, and future investigation is needed to determine the mechanisms and phenotypic consequences of the genotypic changes in C. glabrata both in vivo and in vitro.

Acknowledgments

This work was supported by a CNU specialization grant funded by Chonnam National University and by a grant from the National Institute of Health, Ministry of Health and Welfare, Republic of Korea.

Footnotes

[down-pointing small open triangle]Published ahead of print on 20 June 2007.

REFERENCES

1. Asakura, K., S. Iwaguchi, M. Homma, T. Sukai, K. Higashide, and K. Tanaka. 1991. Electrophoretic karyotypes of clinically isolated yeasts of Candida albicans and C. glabrata. J. Gen. Microbiol. 137:2531-2539. [PubMed]
2. Barchiesi, F., L. Falconi Di Francesco, D. Arzeni, F. Caselli, D. Gallo, and G. Scalise. 1999. Electrophoretic karyotyping and triazole susceptibility of Candida glabrata clinical isolates. Eur. J. Clin. Microbiol. Infect. Dis. 18:184-187. [PubMed]
3. Barton, R. C., A. van Belkum, and S. Scherer. 1995. Stability of karyotype in serial isolates of Candida albicans from neutropenic patients. J. Clin. Microbiol. 33:794-796. [PMC free article] [PubMed]
4. Bennett, J. E., K. Izumikawa, and K. A. Marr. 2004. Mechanism of increased fluconazole resistance in Candida glabrata during prophylaxis. Antimicrob. Agents Chemother. 48:1773-1777. [PMC free article] [PubMed]
5. Borst, A., M. T. Raimer, D. W. Warnock, C. J. Morrison, and B. A. Arthington-Skaggs. 2005. Rapid acquisition of stable azole resistance by Candida glabrata isolates obtained before the clinical introduction of fluconazole. Antimicrob. Agents Chemother. 49:783-787. [PMC free article] [PubMed]
6. Brockert, P. J., S. A. Lachke, T. Srikantha, C. Pujol, R. Galask, and D. R. Soll. 2003. Phenotypic switching and mating type switching of Candida glabrata at sites of colonization. Infect. Immun. 71:7109-7118. [PMC free article] [PubMed]
7. Cormican, M. G., R. J. Hollis, and M. A. Pfaller. 1996. DNA macrorestriction profiles and antifungal susceptibility of Candida (Torulopsis) glabrata. Diagn. Microbiol. Infect. Dis. 25:83-87. [PubMed]
8. Cowen, L. E., D. Sanglard, D. Calabrese, C. Sirjusingh, J. B. Anderson, and L. M. Kohn. 2000. Evolution of drug resistance in experimental populations of Candida albicans. J. Bacteriol. 182:1515-1522. [PMC free article] [PubMed]
9. Dodgson, A. R., C. Pujol, D. W. Denning, D. R. Soll, and A. J. Fox. 2003. Multilocus sequence typing of Candida glabrata reveals geographically enriched clades. J. Clin. Microbiol. 41:5709-5717. [PMC free article] [PubMed]
10. Fidel, P. L., Jr., J. A. Vazquez, and J. D. Sobel. 1999. Candida glabrata: review of epidemiology, pathogenesis, and clinical disease with comparison to C. albicans. Clin. Microbiol. Rev. 12:80-96. [PMC free article] [PubMed]
11. Hajjeh, R. A., A. N. Sofair, L. H. Harrison, G. M. Lyon, B. A. Arthington-Skaggs, S. A. Mirza, M. Phelan, J. Morgan, W. Lee-Yang, M. A. Ciblak, L. E. Benjamin, L. T. Sanza, S. Huie, S. F. Yeo, M. E. Brandt, and D. W. Warnock. 2004. Incidence of bloodstream infections due to Candida species and in vitro susceptibilities of isolates collected from 1998 to 2000 in a population-based active surveillance program. J. Clin. Microbiol. 42:1519-1527. [PMC free article] [PubMed]
12. Kaufmann, C. S., and W. G. Merz. 1989. Electrophoretic karyotypes of Torulopsis glabrata. J. Clin. Microbiol. 27:2165-2168. [PMC free article] [PubMed]
13. Klein, H. L. 2001. Spontaneous chromosome loss in Saccharomyces cerevisiae is suppressed by DNA damage checkpoint functions. Genetics 159:1501-1509. [PMC free article] [PubMed]
14. Klempp-Selb, B., D. Rimek, and R. Kappe. 2000. Karyotyping of Candida albicans and Candida glabrata from patients with Candida sepsis. Mycoses 43:159-163. [PubMed]
15. Magill, S. S., C. Shields, C. L. Sears, M. Choti, and W. G. Merz. 2006. Triazole cross-resistance among Candida spp.: case report, occurrence among bloodstream isolates, and implications for antifungal therapy. J. Clin. Microbiol. 44:529-535. [PMC free article] [PubMed]
16. Marichal, P., H. Vanden Bossche, F. C. Odds, G. Nobels, D. W. Warnock, V. Timmerman, C. Van Broeckhoven, S. Fay, and P. Mose-Larsen. 1997. Molecular biological characterization of an azole-resistant Candida glabrata isolate. Antimicrob. Agents Chemother. 41:2229-2237. [PMC free article] [PubMed]
17. National Committee for Clinical Laboratory Standards/CLSI. 2002. Reference method for broth dilution antifungal susceptibility testing of yeasts. Approved standard M27-A2, 2nd ed. National Committee for Clinical Laboratory Standards, Wayne, PA.
18. Pfaller, M. A., and D. J. Diekema. 2004. Rare and emerging opportunistic fungal pathogens: concern for resistance beyond Candida albicans and Aspergillus fumigatus. J. Clin. Microbiol. 42:4419-4431. [PMC free article] [PubMed]
19. Pfaller, M. A., S. A. Messer, L. Boyken, S. Tendolkar, R. J. Hollis, and D. J. Diekema. 2004. Geographic variation in the susceptibilities of invasive isolates of Candida glabrata to seven systemically active antifungal agents: a global assessment from the ARTEMIS Antifungal Surveillance Program conducted in 2001 and 2002. J. Clin. Microbiol. 42:3142-3146. [PMC free article] [PubMed]
20. Ramsey, H., B. Morrow, and D. R. Soll. 1994. An increase in switching frequency correlates with an increase in recombination of the ribosomal chromosomes of Candida albicans strain 3153A. Microbiology 140:1525-1531. [PubMed]
21. Redding, S. W., W. R. Kirkpatrick, S. Saville, B. J. Coco, W. White, A. Fothergill, M. Rinaldi, T. Eng, T. F. Patterson, and J. Lopez-Ribot. 2003. Multiple patterns of resistance to fluconazole in Candida glabrata isolates from a patient with oropharyngeal candidiasis receiving head and neck radiation. J. Clin. Microbiol. 41:619-622. [PMC free article] [PubMed]
22. Sanglard, D., F. Ischer, D. Calabrese, P. A. Majcherczyk, and J. Bille. 1999. The ATP binding cassette transporter gene CgCDR1 from Candida glabrata is involved in the resistance of clinical isolates to azole antifungal agents. Antimicrob. Agents Chemother. 43:2753-2765. [PMC free article] [PubMed]
23. Sanguinetti, M., B. Posteraro, B. Fiori, S. Ranno, R. Torelli, and G. Fadda. 2005. Mechanisms of azole resistance in clinical isolates of Candida glabrata collected during a hospital survey of antifungal resistance. Antimicrob. Agents Chemother. 49:668-679. [PMC free article] [PubMed]
24. Shin, J. H., D. H. Shin, J. W. Song, S. J. Kee, S. P. Suh, and D. W. Ryang. 2001. Electrophoretic karyotype analysis of sequential Candida parapsilosis isolates from patients with persistent or recurrent fungemia. J. Clin. Microbiol. 39:1258-1263. [PMC free article] [PubMed]
25. Shin, J. H., M. R. Park, J. W. Song, D. H. Shin, S. I. Jung, D. Cho, S. J. Kee, M. G. Shin, S. P. Suh, and D. W. Ryang. 2004. Microevolution of Candida albicans strains during catheter-related candidemia. J. Clin. Microbiol. 42:4025-4031. [PMC free article] [PubMed]
26. Soll, D. R. 2000. The ins and outs of DNA fingerprinting the infectious fungi. Clin. Microbiol. Rev. 13:332-370. [PMC free article] [PubMed]
27. Srikantha, T., R. Zhao, K. Daniels, J. Radke, and D. R. Soll. 2005. Phenotypic switching in Candida glabrata accompanied by changes in expression of genes with deduced functions in copper detoxification and stress. Eukaryot. Cell 4:1434-1445. [PMC free article] [PubMed]
28. Tenover, F. C., R. D. Arbeit, R. V. Goering, P. A. Mickelsen, B. E. Murray, D. H. Persing, and B. Swaminathan. 1995. Interpreting chromosomal DNA restriction patterns produced by pulsed-field gel electrophoresis: criteria for bacterial strain typing. J. Clin. Microbiol. 33:2233-2239. [PMC free article] [PubMed]

Articles from Journal of Clinical Microbiology are provided here courtesy of American Society for Microbiology (ASM)
PubReader format: click here to try

Formats:

Related citations in PubMed

See reviews...See all...

Cited by other articles in PMC

See all...

Links

Recent Activity

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more...