Stability of allelic frequencies and distributions of Candida albicans microsatellite loci from U.S. population-based surveillance isolates

Dual effects of vaginal Candida albicans on human papillomavirus infection: A large-scale multicenter study in Chinese women

OBJECTIVES

Vaginal infections caused by Candida albicans and human papillomavirus (HPV) are common, yet their interactions remain complex and poorly understood.

METHODS

We conducted a nationwide, multicenter cohort study in China involving 6,689 women aged 18 to 50 years to examine the association between C. albicans infection and HPV acquisition and persistence. C. albicans infection was defined by positive results on both wet-mount microscopy and culture. HPV genotypes (21 types) and other sexually transmitted infections (STIs, eight types) were detected using polymerase chain reaction. Cervical lesions were assessed via the ThinPrep cytologic test (TCT).

RESULTS

In cross-sectional analyses, C. albicans infection was associated with a lower likelihood of concurrent HPV detection (odds ratio (OR), 0.92, 95 % confidence interval (CI), 0.88-0.96), affecting both high-risk and low-risk genotypes. However, longitudinal follow-up analyses revealed that baseline C. albicans infections was linked to an increased risk of persistent HPV infection among women already infected (hazard ratio (HR), 1.77, 95 % CI, 1.03-3.06). The presence of C. albicans was not significantly associated with other STIs or abnormal cervical cytology. These findings suggest a dual effect of C. albicans on HPV: protection against initial viral acquisition but promotion of viral persistence in those already infected.

CONCLUSIONS

Our findings reveal an unexpected dual role of C. albicans in HPV infection: initial protective effects, followed by enhanced viral persistence during co-infection. These results highlight the complexity of host-microbe interactions in the vaginal environment and underscore the need to consider fungal colonization in the natural history of HPV. The contrasting effects of C. albicans on HPV acquisition and persistence provide novel insights into the complex dynamics of polymicrobial interactions in the female reproductive tract.

SIGNIFICANCE

Statement: This study demonstrates for the first time that C. albicans exhibits opposing effects on HPV infection at different stages, suggesting stage-specific host-microbe interactions that may influence viral pathogenesis. These findings have important implications for understanding the role of fungal colonization in viral infections and may inform strategies for HPV management.

Unveiling the hidden link: fungi and HPV in cervical lesions

Background

Cervical cancer, primarily driven by high-risk human papillomavirus (HR-HPV) infection, ranks as the second most common cancer globally. Understanding combined infections' role, including Cervical fungi, is crucial in cervical carcinogenesis. This study aims to explore the potential correlation between HR-HPV, cervical fungi, and cervical cancer, while adjusting for various factors.

Methods

The study population comprised patients undergoing colposcopy and conization due to abnormal cervical screening results. Clinical data including age, gravidity, HPV (human papillomavirus) genotypes, cervical pathology, and p16/Ki67 expression were extracted. Cervical TCT (ThinPrep Pap Test) and HPV testing are utilized for screening cervical lesions, with fungal presence suggested by TCT results. 5,528 participants were included in this study. Statistical analyses investigated associations between HPV/fungi co-infection and cervical lesions, employing multinomial logistic regression and interaction analysis.

Results

Co-infection with fungi and HPV may decrease the risk of cervical lesions compared to HPV infection alone. In the co-infection group, compared with HPV infection alone, the risk of low-grade squamous intraepithelial lesions (LSIL) was reduced by 27% (OR = 0.73, 95% CI: 0.59-0.90), the risk of high-grade squamous intraepithelial lesions (HSIL) was reduced by 35% (OR = 0.65, 95% CI: 0.51-0.82), and the risk of cervical cancer was reduced by 43% (OR = 0.57, 95% CI: 0.35-0.92). The interaction analysis revealed a negative interaction between fungal and HPV infections in the development of cervical cancer (RERI = -6.25, AP = -0.79, SI = 0.52), HSIL (RERI = -19.15, AP = -0.37, SI = 0.72) and LSIL (RERI = -1.87, AP = -0.33, SI = 0.71), suggesting a sub-additive effect, where the combined effect of the two infections was less than the sum of their individual effects. This indicates that fungal infection may attenuate the promoting effect of HPV on cervical lesions. In exploring the potential mechanism, we found that the co-infection group had significantly lower p16 positivity (54.6%) compared to the HPV-only group (60.2%) (p = 0.004), while there was no statistically significant difference in Ki67 positivity.

Conclusion

This study unveils the intricate relationship between cervical fungi and HPV in cervical lesions. Co-infection with fungi and HPV against cervical lesions compared to HPV infection alone, indicating a novel clinical interaction. Lower p16 positivity in co-infection hints at a protective mechanism, urging further exploration.

Prevalence of Candida albicans in High-Risk Human Papillomavirus-Positive Women: A Study in Diyarbakır Province, Turkey

The human papillomavirus (HPV) is a significant public health concern due to its association with the development of cervical cancer. Although inflammation caused by Candida spp. has been shown to facilitate oncogenesis, the interactions between HPV and Candida spp. remain unclear. This study aimed to determine the prevalence and genotype distribution of HR-HPV infection HR-HPV-positiveCandida albicans in HR-HPV-positive individuals in Diyarbakır province in Turkey. Cervical samples were taken from 350 participants aged 20-69 years who applied to Diyarbakır Gazi Yaşargil Training and Research Hospital, Gynecology and Obstetrics Clinic. For detection of HPV presence and HR-HPV genotyping, PCR/direct cycle sequencing was used. E6/E7 mRNA expression of HPV-16, -18, -31, -33, and -45 was determined by type-specific real-time NASBA assay (NucliSENS EasyQ(®)HPV v1.1). The presence of Candida albicans in cervical specimens of HR-HPV-positive women was investigated by RAPD-PCR and culture methods. Results. Of the 350 women who participated in the study, 24% were HPV positive and 10.5% were found to be HR-HPV positive. HR-HPV positivity was most frequently detected in the age range of 40-49 years. Among HR-HPV-positive women, C. albicans was found in 59.4%. Conclusion. The most frequent HR-HPV genotype was HPV16, followed by HPV31. Of women who tested positive for HR-HPV, C. albicans was discovered in 59.4%. C. albicans infection may occur when the immune system is weakened or the balance of the vaginal flora is disturbed, increasing tissue damage in the vaginal area and the risk of carcinogenesis of HR-HPV. Therefore, knowing the presence of Candida infection in HR-HPV-positive women is essential to plan the treatment and prevent the risk of secondary disease.

DNA microsatellite genotyping of potentially pathogenic Candida albicans and C. dubliniensis isolated from the oral cavity and dental prostheses

This study investigated the incidence, genetic diversity, antifungal sensitivity, and virulence of Candida albicans and C. dubliniensis isolated from subjects using dental prostheses and subjects clinically indicated for the first prosthetic rehabilitation. Subjects were divided into four groups and samples were collected twice: at first rehabilitation by removable partial (A) and total (C) dental prostheses, and replacement of the removable partial (B) and total (D) prostheses. Yeasts were genotyped using DNA microsatellite markers. Microbiological methods were used to screen for azole antifungal resistance and exoenzyme production. In the initial sampling, oral colonization by Candida was observed in 31 (53.4%) subjects in groups A (33.3%), B (68.2%), and D (65%); 20 (47.6%) subjects displayed colonization of prostheses: groups B (50%) and D (45%). The second sampling (±30 days) revealed Candida in 2 (3.4%: oral cavity) and 4 (6.9%: prosthetic) subjects from group B. C. albicans and C. dubliniensis displayed both polyclonal and monoclonal patterns of infection. Azole-resistant C. albicans and SAPs⁺ strains were prevalent. Related strains were found in one or several oral sites (mucosa and prosthesis), as well as intra- and inter-subject, -gender, -group, and -time of sampling. However, the patterns of clonality can be altered under dental care.

Molecular fingerprints to identify Candida species

A wide range of molecular techniques have been developed for genotyping Candida species. Among them, multilocus sequence typing (MLST) and microsatellite length polymorphisms (MLP) analysis have recently emerged. MLST relies on DNA sequences of internal regions of various independent housekeeping genes, while MLP identifies microsatellite instability. Both methods generate unambiguous and highly reproducible data. Here, we review the results achieved by using these two techniques and also provide a brief overview of a new method based on high-resolution DNA melting (HRM). This method identifies sequence differences by subtle deviations in sample melting profiles in the presence of saturating fluorescent DNA binding dyes.

Endemic genotypes of Candida albicans causing fungemia are frequent in the hospital

Genotyping of Candida albicans strains causing candidemia can uncover the presence of endemic genotypes in the hospital. Using a highly reproducible and discriminatory microsatellite marker panel, we studied the genetic diversity of 217 C. albicans isolates from the blood cultures of 202 patients with candidemia (from January 2007 to December 2011). Each isolate represented 1 candidemia episode. Multiple episodes were defined as the isolation of C. albicans in further blood cultures taken ≥7 days after the last isolation in blood culture. Of the 202 patients, 188 had 1 episode, 13 had 2 episodes, and 1 had 3 episodes. Identical genotypes showed the same alleles for all 6 markers. The genotypes causing both episodes were identical in most patients with 2 episodes (11/13; 84.6%). In contrast, 2 different genotypes were found in the patient with 3 episodes, one causing the first and second episodes and the other causing the third episode (isolated 6 months later). We found marked genetic diversity in 174 different genotypes: 155 were unique, and 19 were endemic and formed 19 clusters (2 to 6 patients per cluster). Up to 25% of the patients were infected by endemic genotypes that infected 2 or more different patients. Some of these endemic genotypes were found in the same unit of the hospital, mainly neonatology, whereas others infected patients in different wards.

Microsatellite-based genotyping of Candida albicans isolated from patients with superficial candidiasis

This study aimed to examine the genotype distribution of Candida albicans and the major genotypes involved in superficial candidiasis. The genotypes of C. albicans isolated from the infection sites of patients with superficial candidiasis (referred to as infection isolates) were analyzed by fragment analysis using 4 microsatellite markers (HIS3, CDC3, CAI and CAIII). Genotypes of the infection isolates were compared with those of C. albicans isolated from oral mucosa of non-candidiasis patients (referred to as oral isolates). Isolates of C. albicans showed 4 major genotypes for HIS3/CAI (" a " for 148 : 148 / 23 : 23," b " for 148 : 160 / 33 : 41," c " for 148 : 164 / 32 : 41 and " d " for 152 : 152 / 18 : 27). The genotypes " a "," b " and " d " were commonly found in oral (4.7, 8.8 and 7.6%, respectively) and infection (6.6, 9.2 and 15.4%, respectively) isolates. No isolates of genotype " c " were isolated from infection sites. The genotype " a " was found in the isolates from patients with genitalia candidiasis. Genotyping of multiple isolates from an individual patient showed that C. albicans from infection sites was genetically homogenous as compared with that of oral isolates, even in the same patient with candidiasis.

Candidemia surveillance in Brazil: evidence for a geographical boundary defining an area exhibiting an abatement of infections by Candida albicans group 2 strains

Prospective population surveillance has been conducted for candidemia in Brazil (A. L. Colombo, M. Nucci, B. J. Park, et al., J. Clin. Microbiol. 44:2816-2823, 2006). In the present study, a total of 63 isolates from 61 patients, representing 11 medical centers from nine geographic regions, were characterized by multilocus sequence typing (MLST). A total of 48 unique profiles or diploid sequence types (DSTs) were observed, with nine new sequence types (STs) and 32 new DSTs. There were no apparent correlations between center/region and DST patterns. Subtypes were compared to those in a known characterized reference set, including a large database of strains obtained worldwide. Significantly, only one C. albicans group 2 isolate was found in our collection, although isolates from this particular group are commonly found worldwide. These data, combined with information from other previously reported studies, establish a statistically significant diminishment of group 2 strains in Central and South America, including Mexico and portions of the Southwestern United States.

Molecular phylogenetics and epidemiology of Candida albicans

Candida albicans, a diploid yeast commensal and opportunist pathogen, has evolved unusual mechanisms for maintenance of genetic diversity in the absence of a complete sexual cycle. These include chromosomal polymorphisms, mitotic recombination events, and gains and losses of heterozygosity, superimposed on a fundamentally clonal mode of reproduction. Molecular typing of C. albicans strains shows geographical evolutionary associations but these have become partially blurred, probably as a result of extensive human travel. Individual patients usually carry a single C. albicans strain type, but this may undergo microvariation leading to detection of mixtures of closely related types. Associations have been found between clade 1, the most common multilocus sequence typing cluster of related C. albicans strains, and resistance to flucytosine and terbinafine. There are also clade-related associations with lengths of tandem repeats in some cell-surface proteins, but not with virulence or type of infection.

Comparison of microsatellite length polymorphism and multilocus sequence typing for DNA-Based typing of Candida albicans

For genotyping Candida albicans isolates, two PCR-based methods have recently emerged: multilocus sequence typing (MLST), based on the sequence of selected genes, and microsatellite length polymorphism (MLP), based on the length of PCR products containing variable numbers of short DNA repeats. To compare the two methods in their abilities to differentiate and group C. albicans isolates, we selected 50 independent isolates collected at the National Reference Center for Mycoses and Antifungals. MLST typing was performed using sequencing of seven loci as described at (http://test1.mlst.net). The MLP method consisted of a single multiplex PCR testing three different loci. Dendrograms were constructed by the unweighted pair group cluster method with Euclidean metric for both methods. The correlation between the distance matrices was performed with a Mantel test tested with 1,000 random permutations. The sensitivity and specificity of the MLP typing system were determined after allocating MLST groups for the greater number of isolates of each distinct MLP group. The discriminatory power index was >0.99, and the distances between the isolates were highly correlated with both systems. The Mantel coefficient and the Pearson product-moment correlation coefficient were 35,699 and 0.32, respectively (P < or = 1.2 x 10(-6)). Using MLP, the average specificity and sensitivity of clustering compared to MLST were 83% and 73%, respectively, when the singletons were excluded. The two methods are similarly discriminatory and can be interchangeable depending on the objectives. MLP is less expensive and faster than MLST. However, MLST is currently more accurate and additional standardization is needed for MLP.

Species identification and strain differentiation of clinical Candida isolates using the DiversiLab system of automated repetitive sequence-based PCR

The DiversiLab system, which uses repetitive sequence-based PCR (rep-PCR) to genotype micro-organisms, was evaluated as a molecular typing tool for members of the genus Candida. Initially, 41 clinical Candida spp. (7 Candida krusei, 10 Candida parapsilosis, 7 Candida albicans, 10 Candida tropicalis and 7 Candida glabrata), previously identified at the species level by morphological and biochemical analysis, were analysed with the DiversiLab system. Species identification was confirmed by DNA sequence analysis of the contiguous internal transcribed spacer (ITS) region (ITS1–5.8S–ITS2). On the basis of an 80 % similarity threshold, rep-PCR consistently clustered like species and this set of isolates, along with five ATCC reference strains, was used to create a DNA fingerprint library with the DiversiLab software. Subsequently, an additional set of 115 clinical Candida isolates, identified biochemically as C. albicans (n=94), C. glabrata (n=8), C. parapsilosis (n=5), C. tropicalis (n=3), C. krusei (n=3) and Candida lusitaniae (n=2), isolated at a regional reference laboratory, were typed using DiversiLab. One hundred and six of these isolates clustered with members of the Candida library at >80 % similarity and thus could be assigned species identification, and initial calculations showed that identification via rep-PCR fingerprinting was 95 % concordant (101/106) with the biochemical/morphological identification. However, ITS region sequencing of the five discrepant samples, as well as the nine isolates that were <80 % similar to the database samples, showed that nine were misidentified with traditional biochemical/morphological methods. For the misidentified isolates, the sequence-based identification was in agreement with the DiversiLab clustering, yielding an actual correlation of >99 %. As traditional techniques can take several days to provide information about Candida at the genus/species level, genotyping with the DiversiLab system holds promise for more-rapid speciation of members of this genus. This system may also be useful for epidemiological studies such as source tracking that require Candida subspecies discrimination.

Microevolution in genomic short sequence repeats of Candida albicans in non-neutropenic patients

The genome of the yeast Candida albicans harbours many genomic short sequence repeats (SSRs). These are stable upon transition of colonization to infection in immune-compromised patients. We show here that in non-neutropenic patients this transition may coincide with variation in several of the SSRs. This may have implications for stage-specific expression of C. albicans pathogenicity factors.

Evidence for a pseudo-outbreak of Candida guilliermondii fungemia in a university hospital in Brazil

Fungal infections due to Candida species represent an important cause of nosocomial bloodstream infections. We report a large pseudo-outbreak of Candida guilliermondii fungemia that occurred in a university hospital in Brazil. C. guilliermondii was identified in 64 (43%) of the 149 blood samples drawn between June 2003 and July 2004. The samples were from patients in different wards of the hospital but concentrated in pediatric units. None of the patients had clinical signs of fungemia, and observational analysis revealed errors in the collection of blood samples. During the investigation of the pseudo-outbreak, C. guilliermondii was isolated from environmental surfaces and from the skin and nails of members of the nursing team. Through a subtyping analysis it was found that some of the nonpatient isolates were highly related to the patient isolates, and all the patient isolates were highly related. This is consistent with the hypothesis that the pseudo-outbreak was from a limited number of common sources. The adoption of intervention measures was effective in resolving the outbreak, supporting the hypothesis that the outbreak was due to poor techniques of drawing blood samples for culture.

Uniform distribution of three Candida albicans microsatellite markers in two French ICU populations supports a lack of nosocomial cross-contamination

BACKGROUND

The nosocomial acquisition of Candida albicans is a growing concern in intensive care units (ICUs) and understanding the route of contamination is relevant for infection control guidelines.

METHODS

To analyze whether there is a specific ecology for any given hospital, we genotyped C. albicans isolates of the ICU of Versailles hospital (Hospital A) and compared the results with those previously obtained in another ICU in Henri Mondor hospital (Hospital B) using three polymorphic microsatellite markers (PMM).

RESULTS

Among 36 patients with at least one positive culture for C. albicans, 26 had a specific multilocus genotype, two shared a common multilocus genotype, and 8 had the most common multilocus genotype found in the general population. The time interval between periods of hospitalization between patients with common genotypes differed by 13 to 78 days, thus supporting a lack of direct contamination. To confirm this hypothesis, the multilocus genotypic distributions of the three PMM were compared between the two hospitals. No statistically significant difference was observed. Multiple correspondences analysis did not indicate the association of a multilocus genotypic distribution with any given hospital.

CONCLUSION

The present epidemiological study supports the conclusions that each patient harbours his/her own isolate, and that nosocomial transmission is not common in any given ICU. This study also supports the usefulness and practicability of PMM for studying the epidemiology of C. albicans.

Multilocus sequence typing for analyses of clonality of Candida albicans strains in Taiwan

Multilocus sequence typing (MLST) was used to characterize the genetic profiles of 51 Candida albicans isolates collected from 12 hospitals in Taiwan. Among the 51 isolates, 16 were epidemiologically unrelated, 28 were isolates from 11 critically ill, human immunodeficiency virus (HIV)-negative patients, and 7 were long-term serial isolates from 3 HIV-positive patients. Internal regions of seven housekeeping genes were sequenced. A total of 83 polymorphic nucleotide sites were identified. Ten to 20 different genotypes were observed at the different loci, resulting, when combined, in 45 unique genotype combinations or diploid sequence types (DSTs). Thirty (36.1%) of the 83 individual changes were synonymous and 53 (63.9%) were nonsynonymous. Due to the diploid nature of C. albicans, MLST was more discriminatory than the pulsed-field gel electrophoresis-BssHII-restricted fragment method in discriminating epidemiologically related strains. MLST is able to trace the microevolution over time of C. albicans isolates in the same patient. All but one of the DSTs of our Taiwanese strain collections were novel to the internet C. albicans DST database (http://test1.mlst.net/). The DSTs of C. albicans in Taiwan were analyzed together with those of the reference strains and of the strains from the United Kingdom and United States by unweighted-pair group method using average linkages and minimum spanning tree. Our result showed that the DNA type of each isolate was patient specific and associated with ABC type and decade of isolation but not associated with mating type, anatomical source of isolation, hospital origin, or fluconazole resistance patterns.

Population structure and properties of Candida albicans, as determined by multilocus sequence typing

We submitted a panel of 416 isolates of Candida albicans from separate sources to multilocus sequence typing (MLST). The data generated determined a population structure in which four major clades of closely related isolates were delineated, together with eight minor clades comprising five or more isolates. By Fisher's exact test, a statistically significant association was found between particular clades and the anatomical source, geographical source, ABC genotype, decade of isolation, and homozygosity versus heterozygosity at the mating type-like locus (MTL) of the isolates in the clade. However, these associations may have been influenced by confounding variables, since in a univariate analysis of variance, only the clade associations with ABC type and anatomical source emerged as statistically significant, providing the first indication of possible differences between C. albicans strain type clades and their propensity to infect or colonize different anatomical locations. There were no significant differences between clades with respect to distributions of isolates resistant to fluconazole, itraconazole, or flucytosine. However, the majority of flucytosine-resistant isolates belonged to clade 1, and these isolates, but not flucytosine-resistant isolates in other clades, bore a unique mutation in the FUR1 gene that probably accounts for their resistance. A significantly higher proportion of isolates resistant to fluconazole, itraconazole, and flucytosine were homozygous at the MTL, suggesting that antifungal pressure may trigger a common mechanism that leads both to resistance and to MTL homozygosity. The utility of MLST for determining clade assignments of clinical isolates will form the basis for strain selection for future research into C. albicans virulence.

New microsatellite multiplex PCR for Candida albicans strain typing reveals microevolutionary changes

Five new microsatellite loci were described and characterized for use as molecular markers for the identification and genetic differentiation of Candida albicans strains. Following the typing of 72 unrelated clinical isolates, the analysis revealed that they were all polymorphic, presenting from 5 to 30 alleles and 8 to 46 different genotypes. The discriminatory power obtained by combining the information generated by three microsatellites used in a multiplex PCR amplification strategy was 0.99, the highest ever reported. The multiplex PCR was later used to test a total of 114 C. albicans strains, including multiple isolates from the same patient collected from different body locations and along episodes of vulvovaginal infections. Three different scenarios for strain relatedness were identified: (i) different isolates that were revealed to be the same strain, (ii) isolates that were the same strain but that apparently underwent a process of microevolution, and (iii) isolates that corresponded to different strains. Analysis of the microevolutionary changes between isolates from recurrent infections indicated that the genotype alterations observed could be the result of events that lead to the loss of heterozygosity (LOH). In one case of recurrent infection, LOH was observed at the CAI locus, and this could have been related to exposure to fluconazole, since such strains were exposed to this antifungal during treatment. The analysis of microsatellites by a multiplex PCR strategy was found to be a highly efficient tool for the rapid and accurate differentiation of C. albicans strains and adequate for the identification of fine microevolutionary events that could be related to strain microevolution in response to environmental stress conditions.

Microsatellite marker analysis as a typing system for Candida glabrata

Candida glabrata is one of the most important causes of nosocomial fungal infection. We investigated, using a multiplex PCR, three polymorphic microsatellite markers, RPM2, MTI, and ERG3, in order to obtain a rapid genotyping method for C. glabrata. One set of primers was designed for each locus, and one primer of each set was dye labeled to read PCR signals using an automatic sequencer. Eight reference strains including other Candida species and 138 independent C. glabrata clinical isolates were tested. The clinical isolates were collected from different anatomical sites of adult patients either hospitalized in different wards of two different hospitals or not hospitalized. Since C. glabrata is haploid, one single PCR product for each PCR set was obtained and assigned to an allele. The numbers of different alleles were 5, 7, and 15 for the RPM2, MTI, and ERG3 loci, respectively. The number of allelic associations was 21, leading to a discriminatory power of 0.84. The markers were stable after 25 subcultures, and the amplifications were specific for C. glabrata. A factorial correspondence analysis did not indicate any correlation between the 21 multilocus genotypes and the clinical data (source, sex, ward, anatomical sites). Microsatellite marker analysis is a rapid and reliable technique to investigate clinical issues concerning C. glabrata. However, its discriminatory power should be improved by testing other polymorphic microsatellite loci.

Use of microsatellite markers and gene dosage to quantify gene copy numbers in Candida albicans

With microsatellite marker typing, the number of alleles must be known for calculation of allelic frequencies in the diploid Candida albicans for a given locus. We describe a gene dosage with a double real-time PCR. Such a dosage should also be useful in exploring the loss of heterozygosity in C. albicans.