Comparison of restriction enzyme analysis and pulsed-field gradient gel electrophoresis as typing systems for Candida albicans

Genetic relationships between Candida albicans strains isolated from dental plaque, trachea, and bronchoalveolar lavage fluid from mechanically ventilated intensive care unit patients

Candida albicans often resides in the oral cavity of healthy humans as a harmless commensal organism. This opportunistic fungus can cause significant disease in critically ill patients, such as those undergoing mechanical ventilation in the intensive care unit (ICU) having compromised local airway defense mechanisms. The goal of this study was to determine the intra- and inter-patient genetic relationship between strains of C. albicans recovered from dental plaque, tracheal secretions, and the lower airway by bronchoalveolar lavage of patients undergoing mechanical ventilation. Three pulsed-field gel electrophoresis (PFGE) typing methods were used to determine the genetic relatedness of the C. albicans strains, including electrophoretic karyotyping (EK) and restriction endonuclease analysis of the genome using SfiI (REAG-S) and BssHII (REAG-B). The C. albicans isolates from dental plaque and tracheo-bronchial sites from the same patient were genetically indistinguishable and retained over time, whereas strains from different patients usually separated into different genotypes. Among the three methods, REAG-B proved to be the most discriminatory method to differentiate isolates. The finding of genetically similar strains from the oral and tracheo-bronchial sites from the same patient supports the notion that the oral cavity may serve as an important source for C. albicans spread to the trachea and lung of mechanically ventilated patients.

High-throughput identification and quantification of Candida species using high resolution derivative melt analysis of panfungal amplicons

Fungal infections pose unique challenges to molecular diagnostics; fungal molecular diagnostics consequently lags behind bacterial and viral counterparts. Nevertheless, fungal infections are often life-threatening, and early detection and identification of species is crucial to successful intervention. A high throughput PCR-based method is needed that is independent of culture, is sensitive to the level of one fungal cell per milliliter of blood or other tissue types, and is capable of detecting species and resistance mutations. We introduce the use of high resolution melt analysis, in combination with more sensitive, inclusive, and appropriately positioned panfungal primers, to address these needs. PCR-based amplification of the variable internal transcribed regions of the rDNA genes generates an amplicon whose sequence melts with a shape that is characteristic and therefore diagnostic of the species. Simple analysis of the differences between test and reference melt curves generates a single number that calls the species. Early indications suggest that high resolution melt analysis can distinguish all eight major species of Candida of clinical significance without interference from excess human DNA. Candida species, including mixed and novel species, can be identified directly in vaginal samples. This tool can potentially detect, count, and identify fungi in hundreds of samples per day without further manipulation, costs, or delays, offering a major step forward in fungal molecular diagnostics.

Application of molecular techniques to the study of hospital infection

Nosocomial infections are an important source of morbidity and mortality in hospital settings, afflicting an estimated 2 million patients in United States each year. This number represents up to 5% of hospitalized patients and results in an estimated 88,000 deaths and 4.5 billion dollars in excess health care costs. Increasingly, hospital-acquired infections with multidrug-resistant pathogens represent a major problem in patients. Understanding pathogen relatedness is essential for determining the epidemiology of nosocomial infections and aiding in the design of rational pathogen control methods. The role of pathogen typing is to determine whether epidemiologically related isolates are also genetically related. To determine molecular relatedness of isolates for epidemiologic investigation, new technologies based on DNA, or molecular analysis, are methods of choice. These DNA-based molecular methodologies include pulsed-field gel electrophoresis (PFGE), PCR-based typing methods, and multilocus sequence analysis. Establishing clonality of pathogens can aid in the identification of the source (environmental or personnel) of organisms, distinguish infectious from noninfectious strains, and distinguish relapse from reinfection. The integration of molecular typing with conventional hospital epidemiologic surveillance has been proven to be cost-effective due to the associated reduction in the number of nosocomial infections. Cost-effectiveness is maximized through the collaboration of the laboratory, through epidemiologic typing, and the infection control department during epidemiologic investigations.

Parity among interpretation methods of MLEE patterns and disparity among clustering methods in epidemiological typing of Candida albicans

The typing of C. albicans by MLEE (multilocus enzyme electrophoresis) is dependent on the interpretation of enzyme electrophoretic patterns, and the study of the epidemiological relationships of these yeasts can be conducted by cluster analysis. Therefore, the aims of the present study were to first determine the discriminatory power of genetic interpretation (deduction of the allelic composition of diploid organisms) and numerical interpretation (mere determination of the presence and absence of bands) of MLEE patterns, and then to determine the concordance (Pearson product-moment correlation coefficient) and similarity (Jaccard similarity coefficient) of the groups of strains generated by three cluster analysis models, and the discriminatory power of such models as well [model A: genetic interpretation, genetic distance matrix of Nei (d(ij)) and UPGMA dendrogram; model B: genetic interpretation, Dice similarity matrix (S(D1)) and UPGMA dendrogram; model C: numerical interpretation, Dice similarity matrix (S(D2)) and UPGMA dendrogram]. MLEE was found to be a powerful and reliable tool for the typing of C. albicans due to its high discriminatory power (>0.9). Discriminatory power indicated that numerical interpretation is a method capable of discriminating a greater number of strains (47 versus 43 subtypes), but also pointed to model B as a method capable of providing a greater number of groups, suggesting its use for the typing of C. albicans by MLEE and cluster analysis. Very good agreement was only observed between the elements of the matrices S(D1) and S(D2), but a large majority of the groups generated in the three UPGMA dendrograms showed similarity S(J) between 4.8% and 75%, suggesting disparities in the conclusions obtained by the cluster assays.

Invasive Candidiasis in Immunocompromised Hospitalized Patients

The frequency of infections by Candida species is increasing worldwide, with candidemia representing the fourth most common bloodstream infection in the U.S. The risk of infection is especially high in the immunocompromised, hospitalized patient. The treatment of and prophylaxis for Candida infection have led to the emergence of resistant species and the acquisition of resistance in previously susceptible species. Current therapeutic options include amphotericin B and its lipid compounds, fluconazole, itraconazole, voriconazole, and caspofungin. Research is focusing on better diagnostics and the evaluation of strategies such as prophylaxis in high-risk hosts and pre-emptive therapy.

'Genotypic shuffling' of sequential clones of Candida albicans in HIV-infected individuals with and without symptomatic oral candidiasis

Although HIV-infected individuals harbour multiple strains of oral Candida albicans, little is known of their micro-evolution over time. Therefore, a prospective study was conducted with 16 HIV-infected ethnic Chinese individuals with and without symptoms of oropharyngeal candidiasis to evaluate the genotype distribution of oral C. albicans isolates during HIV disease progression. Oral-rinse samples were obtained from all individuals and up to five C. albicans colonies were selected for each visit, over a 12 month period of multiple visits. After identification of isolates using standard mycological criteria, the genetic similarities of yeast isolates within and between sequential clones of C. albicans were assessed by DNA fingerprinting through random amplification of polymorphic DNA (RAPD). The results of RAPD gel profiles and the lineage of each isolate were further analysed using commercially available software. RAPD studies revealed the prevalence of up to 14 different genotypes per individual during the study period, with multiple genotypes isolated simultaneously from a single oral rinse. Computer analysis of RAPD profiles revealed that yeasts isolated over sequential visits from symptomatic individuals demonstrated a striking level of relatedness compared with isolates from asymptomatic individuals. Genetically identical C. albicans strains also formed 'loosely' connected subclusters that overlapped multiple visits, implying genetic 'shuffling' in these isolates during disease progression. These data point to varying evolutionary genetic trends in C. albicans associated with symptomatic oral candidiasis and asymptomatic carriage in HIV disease.

Effect of fluoride on cariogenic oral microorganisms (an in vitro study)

The effect of sodium fluoride and sodium monofluorophosphate at concentrations of 1, 5, 10, 50, 100 and 1000 mg/l in phosphate buffer (pH 6.5) as well as in UHT milk were studied on cultures and suspensions of Streptococcus mutans, Lactobacillus acidophilus and Candida albicans. Using serial tenfold dilutions up to 10(-7) of 24-48 hour cultures, a subsequent 0, 60 and 120 min incubation caused no decrease in the number of CFUs. Growth kinetic studies in the Bioscreen biophotometer (Labsystem, Finland) revealed that sodium fluoride in different concentrations (from 0.875 mg/l up to 500 mg/l) influenced the growth dynamics of S. mutans and C. albicans: the exponential phase flattened out at the highest fluoride concentrations (500 mg/l) present in the growth media. The lag phase of C. albicans became longer. The results of these experiments indicate that sodium fluoride administered at higher concentrations than the usual caries preventive dosage made the generation time of cariogenic oral bacteria and fungi longer, slowing down their multiplication.

Evaluation of internal transcribed spacer region of ribosomal DNA sequence analysis for molecular characterization of Candida albicans and Candida dubliniensis isolates from HIV-infected patients

Molecular typing systems have been needed to study Candida colonization in HIV-infected patients, particularly for investigating virulence and fluconazole resistance. Three methods--electrophoretic karyotyping (EK), detection of restriction fragment length polymorphisms (RFLP) and randomly amplified polymorphic DNA analysis (RAPD)--have been most frequently used. In this study, comparative sequence analysis of the internal transcribed spacer (ITS) region of rDNA was evaluated for delineation of Candida isolates from 14 HIV-infected patients. EK, ITS sequence analysis, RFLP and RAPD resulted in 11, 10, 9 and 8 DNA genotypes, respectively, from 39 Candida albicans isolates. The 10 genotypes observed using ITS sequence analysis were defined by six variation sites in the sequence. Molecular typing of sequential oral isolates showed the persistence of the same genotype of C. albicans in nine patients, and genotype variation in one patient. EK and RAPD showed that another patient was co-infected by two distinct genotypes and ITS analysis identified one of the two genotypes as Candida dubliniensis. Comparative ITS sequence analysis is a quick and reproducible method that provides clear and objective results, and it also identifies C. dubliniensis. The discriminatory power of this new typing approach could be improved by concomitant analysis of other DNA polymorphic sequences.

Mucosal candidiasis

This article examines the ecology and epidemiology of gastrointestinal candidiasis, esophageal candidiasis, chronic mucocutaneous candidiasis, urinary tract candidiasis, and vulvovaginal candidiasis. Such issues as pathogenesis and host defenses, clinical manifestations, diagnosis, and treatment are discussed.

Identification of four distinct genotypes of Candida dubliniensis and detection of microevolution in vitro and in vivo

The present study investigates further the population structure of Candida dubliniensis and its ability to exhibit microevolution. Using 98 isolates (including 80 oral isolates) from 94 patients in 15 countries, we confirmed the existence of two distinct populations within the species C. dubliniensis, designated Cd25 group I and Cd25 group II, respectively, on the basis of DNA fingerprints generated with the C. dubliniensis-specific probe Cd25. The majority of Cd25 group I isolates (48 of 71, 67.6%) were from human immunodeficiency virus (HIV)-infected individuals, whereas the majority of Cd25 group II isolates (19 of 27, 70.4%) were from HIV-negative individuals (P < or = 0.001). Nucleotide sequence analysis of the internal transcribed spacer (ITS) regions of the rRNA genes from 19 representative isolates revealed the presence of four separate genotypes. All of the Cd25 group I isolates tested belonged to genotype 1, while the Cd25 group II population was comprised of three distinct genotypes (genotypes 2 to 4), which corresponded to distinct clades within the Cd25 group II population. These findings were confirmed using genotype-specific PCR primers with 70 isolates. We also showed that C. dubliniensis can exhibit microevolution in vivo and in vitro as occurs in other yeast species. DNA fingerprinting using the C. dubliniensis probes Cd25, Cd24, and Cd1 and karyotype analysis of multiple oral isolates recovered from the same specimen from each of eight separate patients revealed microevolution in six of eight of the clonal populations. Similarly, sequential clonal isolates from various anatomical sites in two separate patients exhibited microevolution. Microevolution was also shown to occur when two clinical isolates susceptible to fluconazole were exposed to the drug in vitro. The epidemiological significance of the four C. dubliniensis genotypes and the ability of C. dubliniensis to undergo microevolution has yet to be established.

Subtyping and antifungal susceptibilities of Candida spp. in the intensive care unit of a Greek general hospital

This study identified the Candida spp., susceptibility to antifungal agents and the prevailing Candida albicans subtypes responsible for infections or colonization of 42 patients in the ICU over a 6-month period. Most isolates were C. albicans (66.1%) and Candida tropicalis (28.3%) all of which were susceptible in vitro to antifungal agents. Subtypes of the C. albicans isolates were identified by pulsed field gel electrophoresis Sfi I chromosomal digests. Two major C. albicans subtypes were identified, whereas subtype heterogeneity was found among strains of Candida glabrata and C. tropicalis. Sfi I PFGE restriction patterns were able to discriminate between sub-populations of C. albicans isolates, clustering them into distinct, epidemiologically congruous groups.

Epidemiological typing of Candida albicans from bloodstream infections by restriction enzyme analysis

Candida albicans blood culture isolates (n = 142) from 130 patients treated in 7 acute care hospitals in Southern Finland between 1986 and 1995 were typed by restriction enzyme analysis (REA) with EcoRI and MspI. REA revealed 118 distinct DNA types: 13 were detected in > 1 patient and 105 DNA types were unique. Patients with identical DNA types were not temporally or geographically clustered. Among 11 patients with more than 1 C. albicans isolate during 1 episode of fungemia the DNA type remained the same, except in 1 patient. These results indicate that REA is a powerful tool for the epidemiological typing of C. albicans infections.

The ins and outs of DNA fingerprinting the infectious fungi

DNA fingerprinting methods have evolved as major tools in fungal epidemiology. However, no single method has emerged as the method of choice, and some methods perform better than others at different levels of resolution. In this review, requirements for an effective DNA fingerprinting method are proposed and procedures are described for testing the efficacy of a method. In light of the proposed requirements, the most common methods now being used to DNA fingerprint the infectious fungi are described and assessed. These methods include restriction fragment length polymorphisms (RFLP), RFLP with hybridization probes, randomly amplified polymorphic DNA and other PCR-based methods, electrophoretic karyotyping, and sequencing-based methods. Procedures for computing similarity coefficients, generating phylogenetic trees, and testing the stability of clusters are then described. To facilitate the analysis of DNA fingerprinting data, computer-assisted methods are described. Finally, the problems inherent in the collection of test and control isolates are considered, and DNA fingerprinting studies of strain maintenance during persistent or recurrent infections, microevolution in infecting strains, and the origin of nosocomial infections are assessed in light of the preceding discussion of the ins and outs of DNA fingerprinting. The intent of this review is to generate an awareness of the need to verify the efficacy of each DNA fingerprinting method for the level of genetic relatedness necessary to answer the epidemiological question posed, to use quantitative methods to analyze DNA fingerprint data, to use computer-assisted DNA fingerprint analysis systems to analyze data, and to file data in a form that can be used in the future for retrospective and comparative studies.

The ins and outs of DNA fingerprinting the infectious fungi

DNA fingerprinting methods have evolved as major tools in fungal epidemiology. However, no single method has emerged as the method of choice, and some methods perform better than others at different levels of resolution. In this review, requirements for an effective DNA fingerprinting method are proposed and procedures are described for testing the efficacy of a method. In light of the proposed requirements, the most common methods now being used to DNA fingerprint the infectious fungi are described and assessed. These methods include restriction fragment length polymorphisms (RFLP), RFLP with hybridization probes, randomly amplified polymorphic DNA and other PCR-based methods, electrophoretic karyotyping, and sequencing-based methods. Procedures for computing similarity coefficients, generating phylogenetic trees, and testing the stability of clusters are then described. To facilitate the analysis of DNA fingerprinting data, computer-assisted methods are described. Finally, the problems inherent in the collection of test and control isolates are considered, and DNA fingerprinting studies of strain maintenance during persistent or recurrent infections, microevolution in infecting strains, and the origin of nosocomial infections are assessed in light of the preceding discussion of the ins and outs of DNA fingerprinting. The intent of this review is to generate an awareness of the need to verify the efficacy of each DNA fingerprinting method for the level of genetic relatedness necessary to answer the epidemiological question posed, to use quantitative methods to analyze DNA fingerprint data, to use computer-assisted DNA fingerprint analysis systems to analyze data, and to file data in a form that can be used in the future for retrospective and comparative studies.

Epidemiology of oropharyngeal Candida colonization and infection in patients receiving radiation for head and neck cancer

Oral mucosal colonization and infection with Candida are common in patients receiving radiation therapy for head and neck cancer. Infection is marked by oral pain and/or burning and can lead to significant patient morbidity. The purpose of this study was to identify Candida strain diversity in this population by using a chromogenic medium, subculturing, molecular typing, and antifungal susceptibility testing of clinical isolates. These results were then correlated with clinical outcome in patients treated with fluconazole for infection. Specimens from 30 patients receiving radiation therapy for head and neck cancer were cultured weekly for Candida. Patients exhibiting clinical infection were treated with oral fluconazole. All isolates were plated on CHROMagar Candida and RPMI medium, subcultured, and submitted for antifungal susceptibility testing and molecular typing. Infections occurred in 27% of the patients and were predominantly due to Candida albicans (78%). Candida carriage occurred in 73% of patients and at 51% of patient visits. Yeasts other than C. albicans predominated in carriage, as they were isolated from 59% of patients and at 52% of patient visits. All infections responded clinically, and all isolates were susceptible to fluconazole. Molecular typing showed that most patients had similar strains throughout their radiation treatment. One patient, however, did show the acquisition of a new strain. With this high rate of infection (27%), prophylaxis to prevent infection should be evaluated for these patients.

Evaluation of DNA-based typing procedures for strain categorization of Candida spp

DNA-based procedures have replaced earlier epidemiologic methodologies that relied on nonreproducible and insensitive measurements of phenotypic characteristics to identify a specific strain as the source of infection. The reliability (interlaboratory percent agreement for strain delineation) and sensitivity (recognition of subtle strain-to-strain variation) of similar DNA-based typing systems by different laboratories were evaluated. Ten isolates (five epidemiologic-related and five unrelated strains each) of Candida albicans, C. lusitaniae, C. parapsilosis, C. tropicalis, and Candida (Torulopsis) glabrata were characterized in a blinded fashion by three laboratories. All 50 isolates were subtyped in each laboratory by electrophoretic karyotyping (EK) analysis using contour-clamped homogenous electric field (CHEF) electrophoresis protocols. In addition, two laboratories also performed restriction endonuclease analysis of genomic DNA (REAG) using the restriction endonucleases SfiI and BssHII followed by CHEF electrophoresis separation of resulting fragments. DNA strain identification of the 50 isolates by the three different laboratories using similar CHEF methodologies demonstrated the following species-dependent, interlaboratory reproducibility: C. tropicalis (82%), C. parapsilosis (83%), C. albicans (90%), C. lusitaniae (93%), and C. glabrata (100%). In addition, agreement was higher by the CHEF method (83 to 100%), when compared with the strain types identified by the REAG (60 to 100%) method. Five to seven strains of each Candida species evaluated were detected by the different methodologies used for this study. This study indicates that these procedures are relatively discriminatory and reliable tools to study strain-to-strain variations in epidemiologic evaluations of these yeasts.

Candida glabrata: review of epidemiology, pathogenesis, and clinical disease with comparison to C. albicans

Until recently, Candida glabrata was considered a relatively nonpathogenic commensal fungal organism of human mucosal tissues. However, with the increased use of immunosuppressive agents, mucosal and systemic infections caused by C. glabrata have increased significantly, especially in the human immunodeficiency virus-infected population. A major obstacle in C. glabrata infections is their innate resistance to azole antimycotic therapy, which is very effective in treating infections caused by other Candida species. Candida glabrata, formerly known as Torulopsis glabrata, contrasts with other Candida species in its nondimorphic blastoconidial morphology and haploid genome. C. glabrata currently ranks second or third as the causative agent of superficial (oral, esophageal, vaginal, or urinary) or systemic candidal infections, which are often nosocomial. Currently, however, there are few recognized virulence factors of C. glabrata and little is known about the host defense mechanisms that protect against infection. Two established animal models (systemic and vaginal) have been established to study treatment, pathogenesis, and immunity. Treatment of C. glabrata infections can include azoles but often requires amphotericin B or flucytosine. This review summarizes all known clinical and experimental information about C. glabrata infections with comparisons to C. albicans as a means of contrasting the two species commonly observed and emphasizing the many recognized differences.

Typing of Candida albicans and Candida parapsilosis: species-related limitations of electrophoretic karyotyping and restriction endonuclease analysis of genomic DNA

Species-related discrimination limits of electrophoretic karyotyping (EK) and restriction endonuclease analysis of genomic DNA (REAG), using pulse-field gel electrophoresis, in typing Candida albicans (CA) and Candida parapsilosis (CP) were compared. Eleven CA and 12 CP isolates from individual neonates and three CA and three CP control isolates were used. For CA, EK and REAG with sfiI displayed seven and six banding-patterns, respectively. One karyotype and two SfiI banding-patterns were observed among the control-isolates. Combining EK/REAG (SfiI) demonstrated nine composites and three distinct control-composites. For CP, EK displayed nine karyotypes, REAG (SfiI) demonstrated four banding-patterns, and REAG (BssHII) yielded six banding-patterns. EK and REAG/SfiI failed to distinguish any CP-controls whereas REAG/BssHII distinguished 2/3 CP-controls. Combining EK/REAG (SfiI) showed 10 composites indistinguishable from CP-controls whereas EK/REAG (BssHII) demonstrated 11 composites and three distinct control-composites. These results illustrate that singly, EK and REAG have significant limitation in typing Candida species though EK is more precise. Combining both methods yields better results but the appropriate restriction endonuclease may vary by strains or species. These findings underscore the importance of combining multiple typing methods, testing several control isolates, and correlating the results with careful epidemiological assessment.

Identification and expression of multidrug transporters responsible for fluconazole resistance in Candida dubliniensis

Candida dubliniensis is a recently described Candida species associated with oral candidosis in human immunodeficiency virus (HIV)-infected and AIDS patients, from whom fluconazole-resistant clinical isolates have been previously recovered. Furthermore, derivatives exhibiting a stable fluconazole-resistant phenotype have been readily generated in vitro from fluconazole-susceptible isolates following exposure to the drug. In this study, fluconazole-resistant isolates accumulated up to 80% less [3H] fluconazole than susceptible isolates and also exhibited reduced susceptibility to the metabolic inhibitors 4-nitroquinoline-N-oxide and methotrexate. These findings suggested that C. dubliniensis may encode multidrug transporters similar to those encoded by the C. albicans MDR1, CDR1, and CDR2 genes (CaMDR1, CaCDR1, and CaCDR2, respectively). A C. dubliniensis homolog of CaMDR1, termed CdMDR1, was cloned; its nucleotide sequence was found to be 92% identical to the corresponding CaMDR1 sequence, while the predicted CdMDR1 protein was found to be 96% identical to the corresponding CaMDR1 protein. By PCR, C. dubliniensis was also found to encode homologs of CDR1 and CDR2, termed CdCDR1 and CdCDR2, respectively. Expression of CdMDR1 in a fluconazole-susceptible delta pdr5 null mutant of Saccharomyces cerevisiae conferred a fluconazole-resistant phenotype and resulted in a 75% decrease in accumulation of [3H]fluconazole. Northern analysis of fluconazole-susceptible and -resistant isolates of C. dubliniensis revealed that fluconazole resistance was associated with increased expression of CdMDR1 mRNA. In contrast, most studies showed that overexpression of CaCDR1 was associated with fluconazole resistance in C. albicans. Increased levels of the CdMdr1p protein were also detected in fluconazole-resistant isolates. Similar results were obtained with fluconazole-resistant derivatives of C. dubliniensis generated in vitro, some of which also exhibited increased levels of CdCDR1 mRNA and CdCdr1p protein. These results demonstrate that C. dubliniensis encodes multidrug transporters which mediate fluconazole resistance in clinical isolates and which can be rapidly mobilized, at least in vitro, on exposure to fluconazole.

Candida dubliniensis: phylogeny and putative virulence factors

Candida dubliniensis is a recently identified species which is implicated in oral candidosis in HIV-infected and AIDS patients. The species shares many phenotypic characteristics with, and is phylogenetically closely related to, Candida albicans. In this study the phylogenetic relationship between these two species was investigated and a comparison of putative virulence factors was performed. Four isolates of C. dubliniensis from different clinical sources were chosen for comparison with two reference C. albicans strains. First, the distinct phylogenetic position of C. dubliniensis was further established by the comparison of the sequence of its small rRNA subunit with representative Candida species. The C. dubliniensis isolates formed true unconstricted hyphae under most induction conditions tested but failed to produce true hyphae when induced using N-acetylglucosamine. Oral C. dubliniensis isolates were more adherent to human buccal epithelial cells than the reference C. albicans isolates when grown in glucose and equally adherent when grown in galactose. The C. dubliniensis isolates were sensitive to fluconazole, itraconazole, ketoconazole and amphotericin B. Homologues of seven tested C. albicans secretory aspartyl proteinase (SAP) genes were detected in C. dubliniensis by Southern analysis. In vivo virulence assays using a systemic mouse model suggest that C. dubliniensis is marginally less virulent than C. albicans. These data further confirm the distinct phenotypic and genotypic nature of C. dubliniensis and suggest that this species may be particularly adapted to colonization of the oral cavity.

Nosocomial Candida glabrata colonization: an epidemiologic study

Candida glabrata has emerged as an important nosocomial pathogen, yet little is known about its epidemiology. We prospectively followed 98 patients admitted to a medical intensive care unit and the bone marrow transplant unit of a university hospital. Samples from environmental surfaces and the hands of hospital personnel were also cultured. Patients with newly acquired C. glabrata strains were compared to controls who were culture negative for C. glabrata. C. glabrata was recovered from multiple sites from 24 patients and three environmental surfaces. Sixteen patients (17%) acquired C. glabrata after admission to the study units. Significant risk factors for the nosocomial acquisition of C. glabrata were prolonged duration of hospitalization in the unit and prior antimicrobial use. Strain delineation by restriction enzyme analysis revealed 28 different strains of C. glabrata; three strain types were common to nine patients. The environmental isolates were of the same strain type and common to five patients (four patients with newly acquired strains). These results suggest the possibility of exogenous nosocomial acquisition of C. glabrata, including the possible acquisition from the hospital environment. Transmission may be by indirect contact since identical strains of C. glabrata were recovered from patients who were geographically and temporally associated.

Evaluation of the discriminatory power of pulsed-field gel electrophoresis and PCR fingerprinting for epidemiologic typing of Candida species

OBJECTIVE: To evaluate the discriminatory power of genotyping methods (PCR fingerprinting and pulsed-field gel electrophoresis) validated for Candida albicans in other Candida species. METHODS: Molecular typing methods are increasingly being applied for studies where the interpretation of data essentially relies on the typing results rather than epidemiologic data. In this situation, the discriminatory power (ability to identify differences among epidemiologically unrelated strains) of the typing method is important in allowing one to draw valid conclusions. By applying PCR fingerprinting, electrophoretic karyotyping, and restriction fragment endonuclease analysis using standard restriction enzymes and primers proven to be useful in previous studies, we evaluated whether the use of multiple genotyping methods is sufficient to delineate known unrelated strains among seven Candida species. RESULTS: All three methods identified individual genotypes for each of the seven Candida species studied. However, optimal strain delineation required the combined use of all three typing methods and was observed only within the small number of C. albicans and C. tropicalis isolates tested in this study. CONCLUSION: Typing assays that are able to delineate a certain Candida species may not be used blindly for other species of that genus. Regarding the limited number of strains tested, further validation of the discriminative power of genotyping methods (including in C. tropicalis) should be done.

Rapid differentiation of closely related Candida species and strains by pyrolysis-mass spectrometry and Fourier transform-infrared spectroscopy

Two rapid spectroscopic approaches for whole-organism fingerprinting of pyrolysis-mass spectrometry (PyMS) and Fourier transform-infrared spectroscopy (FT-IR) were used to analyze a group of 29 clinical and reference Candida isolates. These strains had been identified by conventional means as belonging to one of the three species Candida albicans, C. dubliniensis (previously reported as atypical C. albicans), and C. stellatoidea (which is also closely related to C. albicans). To observe the relationships of the 29 isolates as judged by PyMS and FT-IR, the spectral data were clustered by discriminant analysis. On visual inspection of the cluster analyses from both methods, three distinct clusters, which were discrete for each of the Candida species, could be seen. Moreover, these phenetic classifications were found to be very similar to those obtained by genotypic studies which examined the HinfI restriction enzyme digestion patterns of genomic DNA and by use of the 27A C. albicans-specific probe. Both spectroscopic techniques are rapid (typically, 2 min for PyMS and 10 s for FT-IR) and were shown to be capable of successfully discriminating between closely related isolates of C. albicans, C. dubliniensis, and C. stellatoidea. We believe that these whole-organism fingerprinting methods could provide opportunities for automation in clinical microbial laboratories, improving turnaround times and the use of resources.

Genetic characterization of a phospholipase C gene from Candida albicans: presence of homologous sequences in Candida species other than Candida albicans

Phospholipase C (PLC) enzymes are essential in regulating several important cellular functions in eukaryotes, including yeasts. In this study, PCR was used to identify a gene encoding PLC activity in Candida albicans, using oligonucleotide primers complementary to sequences encoding highly conserved amino acid regions within the X domains of previously characterized eukaryotic phospholipase C genes. The nucleotide sequence of the C. albicans gene, CAPLC1 (2997 bp), was determined from a recombinant clone containing C. albicans 132A genomic DNA; it encoded a polypeptide of 1099 amino acids with a predicted molecular mass of 124.6 kDa. The deduced amino acid sequence of this polypeptide (CAPLC1) exhibited many of the features common to previously characterized PLCs, including specific X and Y catalytic domains. The CAPLC1 protein also exhibited several unique features, including a novel stretch of 18-19 amino acid residues within the X domain and an unusually long N-terminus which did not contain a recognizable EF-hand Ca(2+)-binding domain. An overall amino acid homology of more than 27% with PLCs previously characterized from Saccharomyces cerevisiae and Schizosaccharomyces pombe suggested that the CAPLC1 protein is a delta-form of phosphoinositide-specific PLC (PI-PLC). PLC activity was detected in cell-free extracts of both yeast and hyphal forms of C. albicans 132A following 7 h and 24 h growth using the PLC-specific substrate p-nitrophenylphosphorylcholine (p-NPPC). In addition, CAPLC1 mRNA was detected by reverse transcriptase PCR in both yeast and hyphal forms of C. albicans 132A at the same time intervals. Expression of CAPLC1 activity was also detected in extracts of Escherichia coli DH5 alpha harbouring plasmids which contained portions of the CAPLC1 gene lacking sequences encoding part of the N-terminus. Southern hybridization and PCR analyses revealed that all C. albicans and Candida dubliniensis isolates examined possessed sequences homologous to CAPLC1. Sequences related to CAPLC1 were detected in some but not all isolates of Candida tropicalis, Candida glabrata and Candida parapsilosis tested, but not in the isolates of Candida krusei, Candida kefyr, Candida guillermondii and Candida lusitaniae examined. This paper reports the first description of the cloning and sequencing of a PLC gene from a pathogenic yeast species.

Variation in morphotype, karyotype and DNA type of fluconazole resistant Candida albicans from an AIDS patient

Azole-resistant oropharyngeal and oesophageal candidiasis is a recent phenomenon observed in patients with AIDS usually previously treated with fluconazole. Some variation has been observed in antifungal susceptibility testing among separate colonies of Candida albicans from the same patient. This raises the question of whether there are multiple clones present or simply phenotypic variation in expression of azole resistance. To address this question we took 18 isolates grown from multiple swabs taken before and after experimental azole therapy from a single HIV-positive individual with fluconazole-resistant oral candidiasis and compared morphotype, karyotype, PCR-based DNA typing and azole susceptibility. Ten of the isolates were from a single 2-day period. Amongst these 10 there were seven morphotypes, five karyotypes and four polymerase chain reaction (PCR) types. Three further morphotypes, one karyotype and two PCR types were found amongst the eight isolates obtained during the subsequent 4 months. Limited variation in susceptibility to two azoles--fluconazole and D0870--was also seen. This work emphasizes both the large genotype and phenotypic variability of C. albicans isolates in the mouth of AIDS patients with fluconazole resistance, and the difficulties in interpretation of present typing methods.

An electrophoretic molecular karyotype of a clinical isolate of Aspergillus fumigatus and localization of the MDR-like genes AfuMDR1 and AfuMDR2

The molecular karyotype of a clinical isolate of Aspergillus fumigatus (10AF/86/10) was determined by contour-clamped homogeneous electric field gel electrophoresis. Five chromosomal bands were resolved by this method. The resolved chromosomes ranged in size from 1.7 to 4.8 Mb, and together constituted a total genomic size of at least 15.8 Mb. Southern analysis of the separated chromosomes located the position of two MDR-like genes, AfuMDR1 and AfuMDR2, on chromosomes III and IV, respectively. The methods described herein may enable the application of molecular karyotyping of A. fumigatus in epidemiologic surveillance studies.

Parity among the randomly amplified polymorphic DNA method, multilocus enzyme electrophoresis, and Southern blot hybridization with the moderately repetitive DNA probe Ca3 for fingerprinting Candida albicans

Randomly amplified polymorphic DNA (RAPD) analysis, multilocus enzyme electrophoresis (MLEE), and Southern blot hybridization with moderately repetitive DNA probes have emerged as effective fingerprinting methods for the infectious fungus Candida albicans. The three methods have been compared for their capacities to identify identical or highly related isolates, to cluster weakly related isolates, to discriminate between unrelated isolates, and to assess microevolution within a strain. By computing similarity coefficients between 29 isolates from three cities within the continental United States, strong concordance of the results is demonstrated for RAPD analysis, MLEE, and Southern blot hybridization with the moderately repetitive probe Ca3, and weaker concordance of the results is demonstrated for these three fingerprinting methods and Southern blot hybridization with the moderately repetitive probe CARE2. All methods were also demonstrated to be able to resolve microevolution within a strain, with the Ca3 probe exhibiting the greatest resolving power. The strong correlations demonstrated between polymorphic markers assessed by the four independent fingerprinting methods and the nonrandom association between loci demonstrated by RAPD analysis and MLEE provide evidence for strong linkage disequilibrium and a clonal population structure for C. albicans. In addition, a synapomorphic allele, Pep-3A, was found to be present in all members of one of the three clusters discriminated by RAPD analysis, MLEE, and Ca3 fingerprinting, supporting the concordance of the clustering capacities of the three methods, the robustness of the clusters, and the clonal nature of the clusters.

Identification of Candida species by randomly amplified polymorphic DNA fingerprinting of colony lysates

We have characterized a method that produces simple yet diagnostic fingerprints that are unique to isolates of Candida species. DNA from individual colonies can be amplified from crude single-colony lysates. Randomly amplified polymorphic DNA (RAPD) fingerprints generated from a single primer correctly identified the species of most (>98%) of the isolates identified with CHROMagar Candida plates as non-Candida albicans Candida species. RAPD fingerprints were much more informative than the plates, since they distinguished between all tested species and required less time. Most (91%) of these identifications agreed with those assigned by API 20C tests. In almost every incident of species identity mismatch, electrophoretic karyotyping showed that the RAPD fingerprint was correct. This underscores the improved objectivity and reliability of this method over those of conventional diagnostic tools. The identities of approximately 30% of C. albicans isolates identified in clinical laboratories by positive germ tube tests are not verified by either testing on CHROMagar Candida plates or RAPD fingerprinting. Data suggest that clinical isolates conventionally identified as C. albicans in clinical settings are heterogeneous, consisting of both misidentified and atypical yeasts. RAPD fingerprints obtained from primary culture plate colonies allows for rapid, highly accurate determinations of Candida species, hence permitting earlier selection of appropriate antifungal agents in the clinical setting.

Comparative analysis of genetic variability among Candida albicans isolates from different geographic locales by three genotypic methods

The objective of the present study was to conduct a comparative genotypic analysis of Candida albicans isolates from the United States, Europe, and Southeast Asia to determine whether differences between isolates might be associated with geographic locations. The genotypes of 86 unrelated isolates of C. albicans (from the United States and Europe) and 26 isolates from Singapore were examined by three DNA typing methods. Computer-assisted methods were used to analyze the gel patterns for all isolates. A dendrogram based on the overall similarity of the patterns obtained by restriction endonuclease analysis (REA) with EcoRI clustered the U.S. and European isolates into two major groups (groups A and B). The Singaporean isolates demonstrated unique REA profiles, with nine isolates having both or neither of the REA-characteristic 3.7- and 4.2-kb bands present in groups A and B. By REA profiles, the Singaporean isolates were related to each other with similarity values (S(AB)s) of > 0.80, but only one isolate mixed with the U.S. and European isolates at this S(AB) (an arbitrary threshold for genetic similarity). Randomly amplified polymorphic DNA (RAPD) analysis generated DNA profiles that clustered the C. albicans isolates into approximately the same number of distinct typing groups as REA. However, isolates identical to each other by REA were generally different from each other by RAPD analysis. In a composite dendrogram prepared from the results obtained by RAPD analysis, the isolates from the United States and Europe clustered in major groups with S(AB)s of > 0.85, while Singaporean isolates connected to these clusters at S(AB)s of > or = 0.75. Pulsed-field gel electrophoresis was less discriminatory, discerning about one-third as many distinct subtypes as REA or RAPD analysis; the Singaporean isolates were distributed randomly with the U.S. and European isolates. These results suggest that a high degree of genetic diversity exists between C. albicans isolates from Southeast Asia and those from the United States and Europe.

Antifungal drug susceptibilities of oral Candida dubliniensis isolates from human immunodeficiency virus (HIV)-infected and non-HIV-infected subjects and generation of stable fluconazole-resistant derivatives in vitro

Candida dubliniensis is a recently described species of Candida associated with oral candidiasis in human immunodeficiency virus (HIV)-infected individuals. Nineteen oral isolates of C. dubliniensis recovered from 10 HIV-positive and 4 HIV-negative individuals and one vaginal isolate from an additional HIV-negative subject were assessed for fluconazole susceptibility by broth microdilution (BMD), hyphal elongation assessment, and Etest. The susceptibilities of these 20 isolates to itraconazole and amphotericin B and of 10 isolates to ketoconazole were also determined by BMD only. Sixteen of the C. dubliniensis isolates were susceptible to fluconazole (MIC range, 0.125 to 1.0 microgram ml-1), and four (recovered from two AIDS patients) were fluconazole resistant (MIC range, 8 to 32 micrograms ml-1). Fluconazole susceptibility data obtained by hyphal elongation assessment correlated well with results obtained by BMD, but the corresponding Etest MIC results were one to four times higher. All of the isolates tested were found to be sensitive to itraconazole, ketoconazole, and amphotericin B. Sequential exposure of two fluconazole-sensitive (MIC, 0.5 microgram ml-1) C. dubliniensis isolates to increasing concentrations of fluconazole in agar medium resulted in the recovery of derivatives which expressed a stable fluconazole-resistant phenotype (BMD-determined MIC range, 16 to 64 micrograms ml-1), even after a minimum of 10 consecutive subcultures on drug-free medium and following prolonged storage at -70 degrees C. The clonal relationship between the parental isolates and their respective fluconazole-resistant derivatives was confirmed by genomic DNA fingerprinting and karyotype analysis. The results of this study demonstrate that C. dubliniensis is inherently susceptible to commonly used antifungal drugs, that fluconazole resistance does occur in clinical isolates, and that stable fluconazole resistance can be readily induced in vitro following exposure to the drug.

Application of RAPD and restriction enzyme analysis to the study of oral carriage of Candida albicans

The genetic similarity of nineteen isolates of Candida albicans from four patients were compared by restriction fragment length polymorphism (RFLP) using EcoRI or HinfI, which both detected five types, and by random amplification of polymorphic DNA (RAPD), which detected three types. Phenotypically unusual isolates also produced distinct patterns with both typing systems demonstrating the carriage of two groups of C. albicans as well as the presence of more than one type in some subjects. Methods of DNA preparation were compared for the production of reproducible patterns; including using the supernatant fluid of boiled intact or spheroplasted cells for RAPD, and DNA precipitated from chloroform extracted cell lysate for RFLP and RAPD. Consistent patterns were produced from the DNA precipitate by RAPD and after an additional precipitation by RFLP, thus removing the necessity for lengthy extraction procedures or the use of toxic chemicals for purification.

Elevated aspartic proteinase secretion and experimental pathogenicity of Candida albicans isolates from oral cavities of subjects infected with human immunodeficiency virus

Isolates of Candida albicans from the oral cavities of subjects at different stages of human immunodeficiency virus (HIV) infection or uninfected controls were examined for (i) production of aspartic proteinase(s), a putative virulence-associated factor(s); (ii) the presence in the fungal genome of two major genes (SAP1 and SAP2) of the aspartic proteinase family; and (iii) experimental pathogenicity in a murine model of systemic infection. It was found that the fungal isolates from symptomatic patients secreted, on average, up to eightfold more proteinase than the isolates from uninfected or HIV-infected but asymptomatic subjects. This differential property was stably expressed by the strains even after years of maintenance in stock cultures. Moreover, representative high-proteinase isolates were significantly more pathogenic for mice than low-proteinase isolates of C. albicans. The characters high proteinase and increased virulence were not associated with a single molecular type or category identifiable through DNA fingerprinting or pulsed-field electrophoretic karyotype, and both SAP1 and SAP2 genes were present in both categories of isolates, on the same respective chromosomes. In conclusion, our data suggest that during HIV infection more-virulent strains or biotypes of C. albicans which are identifiable by direct analysis of virulence determinants are selected. It also appears that the biotype switch to increased aspartic proteinase and virulence properties occurs before the HIV-infected subject enters the symptomatic stage and overt AIDS.

Evaluation of an optimized system for random amplified polymorphic DNA (RAPD)-analysis for genotypic mapping of Candida albicans strains

A simple, rapid, and cost-effective protocol has been developed for a PCR-based molecular typing method for Candida albicans, which includes the use of a commercially available medium (Chelex 100 Resin) for DNA extraction and a single set of two arbitrarily chosen oligonucleotide (10 nt length) primers for random amplified DNA(RAPD)-analysis. The optimized parameters for the amplification components and conditions for the selected primer combination have been determined to avoid artifactual variation (absence/presence of bands) in RAPD banding patterns in repeated assays. The optimized RAPD-assay consistently generated DNA-patterns of 33 genetically unrelated C. albicans isolates that contained ten polymorphic markers in the non-artifactual banding patterns. The intralaboratory reproducibility of RAPD patterns was efficient and consistent provided the optimized amplification conditions were rigidly controlled. Interlaboratory reproducibility was tempered by slight variations in time of cyclers of different thermocyclers. In comparison, the RAPD assay was almost equal to restriction enzyme analysis (REA) (Eco RI digested chromosomal DNA) in discrimination, and the RAPD assay was able to group isolates of C. albicans that were untypable by REA. The protocol outlined for an optimized RAPD-assay of C. albicans has the potential to be widely useful epidemiological screening tool that can be easily applied in the clinical laboratory.

Contribution of molecular typing methods and antifungal susceptibility testing to the study of a candidemia cluster in a burn care unit

We investigated a cluster of cases of Candida septicemia diagnosed in four burn patients. Twenty clinical isolates of Candida albicans and two of Candida parapsilosis, plus eight isolates of C. albicans recovered from nurses' clothes, were analyzed by antifungal susceptibility testing and three genotyping methods (restriction fragment length polymorphism analysis with EcoRI and HinfI, arbitrarily primed PCR, and karyotyping). The high MICs of the azoles for all of the C. albicans isolates tested suggest either a natural resistance of the endogenous flora or the transmission of isolates with acquired resistance. The genotyping methods demonstrated the involvement of four different strains, cross-infections with one C. albicans strain and one C. parapsilosis strain, and identity between some of the strains from the patients and nurses. The origins of the strains remain unclear. Our results show that the use of a combination of at least two different methods such as those used in the present study is recommended for C. albicans typing.

Random amplified polymorphic DNA for strain delineation within Candida tropicalis

Candida tropicalis DNA was used as a template in a polymerase chain reaction (PCR) utilizing a 10-mer primer to generate random amplified polymorphic DNA (RAPD). RAPD patterns associated with 25 primers were obtained for six epidemiologically-unrelated isolates, then a subset of six primers were selected to screen a panel of 18 isolates of C. tropicalis and six isolates of Candida paratropicalis, a species that resembles C. tropicalis but has a sucrose-negative phenotype. The panel, which included nine epidemiologically-related isolates from an outbreak of sternal wound infections, was typed without knowledge of each isolate's origin. The RAPD profiles of the epidemiologically-related isolates were identical to very similar; in contrast, the profiles of most unrelated isolates showed more dissimilarity. While RAPD profiles of C. albicans and Candida parapsilosis differed substantially from those of C. tropicalis, the profiles obtained for C. paratropicalis were consistent with it being a variant of C. tropicalis.

Molecular typing of Candida albicans in oral candidiasis: karyotype epidemiology with human immunodeficiency virus-seropositive patients in comparison with that with healthy carriers

Candida albicans organisms isolated from the oral cavities of healthy carriers (26 individuals) and compromised hosts (40 human immunodeficiency virus [HIV]-seropositive patients, all showing symptomatic oral candidiasis) were compared by resolving chromosome-sized DNA molecules into electrophoretic karyotypes. Seven- to 10-band electrophoretic patterns were obtained, with significant and reproducible differences in the distributions of the DNA bands. Seven distinct classes were identified and were designated type a (8 bands), type b (8 bands), type c (7 bands), type d (9 bands), type x (10 bands), type y (10 bands), and type z (9 bands). Four of these (types a to d) were the most representative within all of the isolated strains (95.5%), and the other three (types x to z) were observed only once in three HIV-seropositive individuals (4.5%). Only types b and c were isolated from healthy carriers, with the percentage of their isolation being 61.5 and 38.5%, respectively, while all the described karyotypes were isolated from HIV-seropositive patients, with type b being the most frequent (45%); this was followed by types c (25%), a (15%), and d (7.5%). The prevalence of type b and c karyotypes in HIV-infected individuals, as well as in healthy carriers, suggests that commensal strains in the oral cavities of healthy individuals may become the prevalent agents of subsequent oral candidiasis in compromised hosts. However, replacement of the original, commensal strain, if there is one, cannot be excluded in a compromised host, although strain replacement may be more reasonably hypothesized for types a and d, since only these types were isolated at a relative high percentage from the oral lesions of HIV-infected individuals.

Comparative study of the GenePath group 4 reagent system and other CHEF systems for karyotype analysis of Candida spp

The commercial GenePath Group 4 Reagent Candida kit (BioRad), designed to simplify the electrophoretic karyotyping of Candida spp. was evaluated against several other established contour-clamped homogeneous electric field (CHEF) systems for Candida. This comparison allowed assessment of both the GenePath system and the other CHEF systems regarding the sources of technical variability of the assays and variation in karyotypic analysis. The GenePath system appeared to be a simple, rapid and reliable tool for karyotyping of Candida spp. with a discriminatory power comparable with established CHEF systems. The evaluation showed that the variability of the CHEF systems for subtyping of Candida is largely a function of technical variabilities in the assay system (reagents, sample preparation, running conditions, and test performance), and of analytical variabilities due to imprecision or observers bias. Lack of standardization of these factors may contribute to variability among investigators and have an impact on the ultimate conclusions of an epidemiological study using CHEF methods.

Validity of contour-clamped homogeneous electric field electrophoresis as a typing system for Candida albicans

Instigated by an increase in serious human Candida infections and aided by advances in technology, there has been renewed interest in the study of the epidemiology of fungal infections. Among the newer techniques available, contour-clamped homogeneous electric field (CHEF) electrophoresis has shown great promise as a tool for typing strains of Candida albicans. However, few studies have addressed the reproducibility of the preparatory and electrophoretic methods. Through a series of analyses on clinical isolates of C. albicans, we were able to demonstrate that (a) sample preparation induced no appreciable artifacts in CHEF banding patterns; (b) the electrophoretic patterns were reproducible over time; (c) changes in colony morphology were not associated with changes in the electrophoretic pattern, and (d) the method was more sensitive than restriction enzyme analysis (REA) for demonstrating strain differences. CHEF electrophoresis is a sensitive and reproducible tool for the study of Candida epidemiology. Further use and study of this methodology is warranted.

Candida colonization and subsequent infections in critically ill surgical patients

OBJECTIVE

The authors determined the role of Candida colonization in the development of subsequent infection in critically ill patients.

DESIGN

A 6-month prospective cohort study was given to patients admitted to the surgical and neonatal intensive care units in a 1600-bed university medical center.

METHODS

Patients having predetermined criteria for significant Candida colonization revealed by routine microbiologic surveillance cultures at different body sites were eligible for the study. Risk factors for Candida infection were recorded. A Candida colonization index was determined daily as the ratio of the number of distinct body sites (dbs) colonized with identical strains over the total number of dbs tested; a mean of 5.3 dbs per patient was obtained. All isolates (n = 322) sequentially recovered were characterized by genotyping using contour-clamped homogeneous electrical field gel electrophoresis that allowed strain delineation among Candida species.

RESULTS

Twenty-nine patients met the criteria for inclusion; all were at high risk for Candida infection; 11 patients (38%) developed severe infections (8 candidemia); the remaining 18 patients were heavily colonized, but never required intravenous antifungal therapy. Among the potential risk factors for candida infection, three discriminated the colonized from the infected patients--i.e., length of previous antibiotic therapy (p < 0.02), severity of illness assessed by APACHE II score (p < 0.01), and the intensity of Candida spp colonization (p < 0.01). By logistic regression analysis, the latter two who were the independent factors that predicted subsequent candidal infection. Candida colonization always preceded infection with genotypically identical Candida spp strain. The proposed colonization indexes reached threshold values a mean of 6 days before Candida infection and demonstrated high positive predictive values (66 to 100%).

CONCLUSIONS

The intensity of Candida colonization assessed by systematic screening helps predicting subsequent infections with identical strains in critically ill patients. Accurately identifying high-risk patients with Candida colonization offers opportunity for intervention strategies.