Evaluation of Candida ID, a new chromogenic medium for fungal isolation and preliminary identification of some yeast species

Recurrent candida prosthetic endocarditis over fifteen years managed with medical therapy and four valvular surgeries: a case report and review of literature

Background

Candida prosthetic endocarditis (CPE) is an uncommon disease involving less than 1 % of infective endocarditis patients and associated with high recurrence rate. Immunosuppresion, intravenous drug abuse, cardiac surgery and indwelling foreign bodies are the major risk factors for CPE. There are very few reported cases of CPE where more than one surgery was performed and there has generally been limited follow up on these cases.

Case presentation

We report a case of a 35 year old woman who had mitral valve annuloplasty complicated by recurrent episodes of CPE leading to multiple mitral valve replacements (MVR). She underwent MVR surgeries a total of four times over an eighteen year period and had good functionality during most of this time while being on antifungal suppressive treatment. This is a unique case in terms of numbers of surgeries performed, the length of the follow up and the involvement of three different Candida species.

Conclusion

Current guidelines for the treatment of candida endocarditis recommend surgical treatment followed by long term antifungal therapy although the cure rate by all treatments is low. However we feel that based on this one case it is reasonable to consider multiple redo valve replacement surgeries in conjunction with antifungal treatment for selected patients stable enough to tolerate the surgery.

An evaluation of risk factors in pregnant women with Candida vaginitis and the diagnostic value of simultaneous vaginal and rectal sampling

In this study, we investigated the epidemiological characteristics of VVC among pregnant women. We conducted a prospective survey among 372 pregnant women to investigate the prevalence, clinical forms, etiological agents, and predisposing factors of VVC. In addition, we determined the relationship between vaginal and rectal flora by simultaneously obtaining one high vaginal swab and one rectal swab from each patient using sterile cotton-tipped swabs. Furthermore, we compared the recovery and identification performances of chromID Candida agar to Sabouraud dextrose agar with gentamicin and chloramphenicol. Clinically and mycologically confirmed cases of VVC were detected in 139 (37.4%) and vaginal colonization described in 42 (11.3%) of 372 pregnant women. Rectal cultures were also positive in 98 of the 139 (70.5%) VVC cases. Candida albicans and C. glabrata were identified in vaginal samples in 58.0 versus 19.0% and from rectal samples in 49.0 versus 13.5%, respectively. Increases in gestational week and gravidae were identified to be statistically significant in patients with acute VVC (AVVC) and symptomatic recurrent VVC (RVVC), and asymptomatic RVVC (P = 0.04 and P = 0.03, respectively). In the laboratory diagnosis of VVC, specifically tailored chromogenic media are reliable tools for both the recovery and rapid identification of common Candida spp., particularly C. albicans, as well as for the detection of polyfungal populations in vaginal samples (P > 0.05). In addition, rectal colonization is a common finding in cases of AVVC and symptomatic-RVVC cases and corresponds well with the presence of the same yeast species in the vagina.

Yeast identification--past, present, and future methods

The focus of this review is the evolution of biochemical phenotypic yeast identification methods with emphasis on conventional approaches, rapid screening tests, chromogenic agars, comprehensive commercial methods, and the eventual migration to genotypic methods. As systemic yeast infections can be devastating and resistance is common in certain species, accurate identification to the species level is paramount for successful therapy and appropriate patient care.

Evaluation of Albicans ID2 and Biggy agar for the isolation and direct identification of vaginal yeast isolates

In this study, 250 vaginal samples from patients with vulvovaginal candidosis were inoculated onto two chromogenic media, Albicans ID2 and Biggy agar, as well as onto Sabouraud chloramphenicol agar, yielding a total of 63 yeast (25.2 %) on all three media. These strains were identified as Candida glabrata in 20 (31.8 %) samples, Candida albicans in 15 samples (23.8 %), Candida tropicalis in 10 samples (15.9 %), Candida krusei in five samples (7.9 %), Candida kefyr in five samples (7.9 %), Candida dubliniensis in four samples (6.3 %), Candida parapsilosis in two samples (3.2 %) and Candida guilliermondii in two samples (3.2 %). Mixed fungal cultures and bacterial growth or filamentous fungi were not detected on any of the selected media. The sensitivity and specificity of the Albicans ID2 and Biggy agar with regard to the identification of C. albicans were 80.0 and 64.6 %, and 86.7 and 56.3 %, respectively. This study showed these two chromogenic media to be as effective as Sabouraud chloramphenicol agar with respect to fungal detection. However, neither Albicans ID2 nor Biggy agar was sufficient for reliable differentiation of yeasts to the species level.

Diagnostic biologique des candidoses systémiques : difficultés et perspectives

The diagnosis of systemic Candidiasis is difficult to establish and biologic diagnosis raises problems. Blood culture which is the gold standard for the diagnosis of systemic Candidiasis lacks sensitivity and usually takes several days to become positive. Early diagnostic approach is imperative to avoid delays in the initiation for treatment. Therefore, nonculture methods like test for Candida antigen detection, metabolite detection or Candida DNA detection by PCR are being developed for the laboratory diagnosis. Candida derived metabolites and antigens detection lacks sensitivity. A new strategy consisting of the combined detection of mannanemia and an antibody response was developed. The combined detection has a high specificity and sensitivity in the diagnosis of invasive candidiasis. The results of tests for the detection of yeast DNA by PCR obtained recently are promising in terms of sensitivity, specificity and identification of species of Candida.

Prospective evaluation of the new chromogenic medium CandiSelect 4 for differentiation and presumptive identification of the major pathogenic Candida species

The rapid identification of pathogenic yeasts is a crucial step in ensuring that effective antifungal treatment is started as early as possible. CandiSelect 4 (CS4; Bio-Rad) is a new chromogenic medium for the isolation of fungi, the direct identification of Candida albicans and the presumptive identification of the major pathogenic Candida species. The performance of CS4 was compared with that of another chromogenic medium, CHROMagar Candida (CA; Becton Dickinson). For primary cultures, 502 of the 1549 (32 %) samples were culture-positive. A total of 542 yeasts were isolated including 465 monomicrobial and 37 mixed cultures: 392 C. albicans, 60 Candida glabrata, 25 Candida tropicalis, 12 Candida krusei and 53 other Candida species. The percentage of C. albicans isolates that could be identified directly after 24, 48 and 72 h culture was 31.6, 82.9 and 92.1 %, respectively, for CS4, and 32.9, 82.9 and 91.1 % for CA. The presumptive identification of C. glabrata, C. tropicalis and C. krusei was evaluated after 48 h incubation. The percentage of strains with morphologically typical colonies was 80, 68 and 84.6 %, respectively, for CS4 compared with 75, 76 and 76.9 % for CA. For pure subcultures, from 24 h, all isolates of C. albicans (n=21) were directly identifiable on the two chromogenic media CA and CS4. At 48 h, the proportion of typical strains observed on the two chromogenic media was identical for C. glabrata (85 %) and C. krusei (100 %). A slight difference in favour of CS4 was observed for C. tropicalis (100 vs 95 %). CS4 also allowed the growth of several other fungi. CS4 can be recommended as a primary isolation medium for the identification of C. albicans, and for the rapid and effective differentiation of the major pathogenic Candida species.

Evaluation of the new chromogenic medium Candida ID 2 for isolation and identification of Candida albicans and other medically important Candida species

The usefulness of Candida ID 2 (CAID2) reformulated medium (bioMérieux, France) has been compared with that of the former Candida ID (CAID; bioMérieux), Albicans ID 2 (ALB2; bioMérieux), and CHROMagar Candida (CAC; Chromagar, France) chromogenic media for the isolation and presumptive identification of clinically relevant yeasts. Three hundred forty-five stock strains from culture collections, and 103 fresh isolates from different clinical specimens were evaluated. CAID2 permitted differentiation based on colony color between Candida albicans (cobalt blue; sensitivity, 91.7%; specificity, 97.2%) and Candida dubliniensis (turquoise blue; sensitivity, 97.9%; specificity, 96.6%). Candida tropicalis gave distinguishable pink-bluish colonies in 97.4% of the strains in CAID2 (sensitivity, 97.4%; specificity, 100%); the same proportion was reached in CAC, where colonies were blue-gray (sensitivity, 97.4%; specificity, 98.7%). CAC and CAID2 showed 100% sensitivity values for the identification of Candida krusei. However, with CAID2, experience is required to differentiate the downy aspect of the white colonies of C. krusei from other white-colony-forming species. The new CAID2 medium is a good candidate to replace CAID and ALB2, and it compares well to CAC for culture and presumptive identification of clinically relevant Candida species. CAID2 showed better results than CAC in some aspects, such as quicker growth and color development of colonies from clinical specimens, detection of mixed cultures, and presumptive differentiation between C. albicans and C. dubliniensis.

Evaluation of 5 new media containing extracts of seeds applied to Candida dubliniensis screening

Candida dubliniensis is a recently described pathogenic species that shares many phenotypic features with Candida albicans and so may be misidentified in microbiologic laboratories. The aim of this study is to find a useful and cost-effective method suitable for screening C. dubliniensis before proceeding to further identification. We examined the colony morphology and chlamydospore production of 26 C. dubliniensis isolates and 100 C. albicans isolates on the following 5 proposed media: sesame seed agar (SSA), rapeseed agar, canary grass seed agar, millet seed agar, and linseed agar (LA). The best results were obtained with SSA and LA because all 26 C. dubliniensis isolates showed rough colonies with peripheral hyphal fringes and abundant chlamydospores after 24 to 48 h of incubation at 25 degrees C. All C. albicans isolates (100%) showed smooth colonies without hyphal fringes or chlamydospores. These 2 media consist of new and simple tools for presumptive differentiation of C. dubliniensis from C. albicans.

Candida colonization of the vagina in elderly residents of a long-term-care hospital

The present study was conducted in order to determine the prevalence of vaginal colonization by Candida spp in elderly residents of a long-term-care hospital and to examine the determinants of vaginal candidiasis. Vaginal swabs for Gram stain and culture were obtained from 106 bedridden residents of a long-term-care hospital (study group; mean age, 83+/-7 years) and a control group of 50 similarly aged women admitted to an acute-care hospital for non-genital problems (mean age, 81+/-8 years). The characteristics of patients who tested positive for Candida spp were compared with those who tested negative. Candida spp were isolated from 34 (32%) patients in the study group and from four (8%) control patients (p=0.001). In the study group, Candida glabrata was by far the most common species isolated (51.2%). The warm and moist environment in the perineal area created by diaper use in incontinent individuals, together with decubitus ulcers and immobilization, which are common in elderly patients receiving long-term care, might be responsible for the high occurrence of vaginal colonization with Candida in these women.

Comparison of three differential media for the presumptive identification of yeasts

This study evaluated three differential media, CHROMagar Candida, BiGGY agar and Albicans ID2 agar, for the presumptive identification of yeast species. In total, 215 yeast isolates were included in the study. The sensitivity and specificity of CHROMagar Candida, BiGGY agar and Albicans ID2 agar for the detection of Candida albicans were 100% and 100%, 91% and 92.7%, and 99.2% and 92.7%, respectively. CHROMagar Candida was a reliable tool for the presumptive identification of C. albicans, Candida tropicalis, Candida krusei and Candida glabrata. Albicans ID2 agar was useful for the detection of C. albicans.

Routine use of a commercial test, GLABRATA RTT, for rapid identification of Candida glabrata in six laboratories

When evaluated in six clinical laboratories from six countries with 1,174 fresh isolates, including 715 Candida glabrata and 459 non-C. glabrata strains, GLABRATA RTT (Fumouze Diagnostics, Levallois Perret, France) yielded an overall sensitivity and an overall specificity of 95.8 and 98.9%, respectively. The results were consistent from one laboratory to another. The five false-positive results corresponded to C. parapsilosis (n = 2), C. tropicalis, C. guilliermondii, and C. lusitaniae. GLABRATA RTT allows a rapid, cost-effective, and reliable presumptive identification of C. glabrata.

Routine use of a one minute trehalase and maltase test for the identification of Candida glabrata in four laboratories

AIMS

To evaluate the rapid identification of Candida glabrata using a one minute trehalase and maltase test in four clinical laboratories.

METHOD

The test was evaluated with 944 freshly isolated yeasts comprising 572 C glabrata and 372 non-C glabrata strains. These strains were isolated on one of three differential media-Candida ID, CHROMagar Candida, or Albicans ID2 medium-and all strains were fully identified using standard methods.

RESULTS

The trehalase and maltase test allowed the overall identification of 550 of 572 C glabrata strains (sensitivity, 96.2%) and only 11 of 372 isolates of other yeast species yielded a false positive result (specificity, 96.8 %). Sensitivity and specificity were consistent from one laboratory to another. Using Candida ID medium, the rapid trehalase and maltase test showed a sensitivity of 95% and specificity of 96.2%. Using CHROMagar Candida, sensitivity and specificity were 95.6% and 98.1%, respectively. Using Albicans ID2 medium (tested by two laboratories), the sensitivity was 100% and 98.5% and specificity was 98.1% and 98.2%. In 60% of cases, the test could be performed directly from the primary isolation medium, thus reducing the time for identification.

CONCLUSION

The rapid trehalase and maltase test was highly reliable for the presumptive identification of C glabrata on primary isolation using three different chromogenic media. Direct recognition of C albicans by means of their characteristic colour on chromogenic media coupled with one minute trehalase maltase testing performed only on suspect colonies of C glabrata allowed for rapid presumptive identification of the two yeast species most commonly encountered in clinical samples.

Rapid identification of Candida glabrata with a new commercial test, GLABRATA RTT

The GLABRATA RTT test (Fumouze Diagnostics, Levallois Perret, France) is based on the ability of Candida glabrata to hydrolyze trehalose but not maltose. It requires an inoculum of only four to six colonies, and the results are available within 20 min. We tested GLABRATA RTT with 330 stock isolates grown in subcultures on four different primary fungal isolation media and obtained a sensitivity of 94 to 98% (depending on the medium used) and a specificity of 97.3 to 98.6%. The false-positive results corresponded to C. tropicalis, C. famata, and C. lusitaniae. GLABRATA RTT thus offers rapid and reliable identification of C. glabrata.

Rapid identification of Candida species by using nuclear magnetic resonance spectroscopy and a statistical classification strategy

Nuclear magnetic resonance (NMR) spectra were acquired from suspensions of clinically important yeast species of the genus Candida to characterize the relationship between metabolite profiles and species identification. Major metabolites were identified by using two-dimensional correlation NMR spectroscopy. One-dimensional proton NMR spectra were analyzed by using a staged statistical classification strategy. Analysis of NMR spectra from 442 isolates of Candida albicans, C. glabrata, C. krusei, C. parapsilosis, and C. tropicalis resulted in rapid, accurate identification when compared with conventional and DNA-based identification. Spectral regions used for the classification of the five yeast species revealed species-specific differences in relative amounts of lipids, trehalose, polyols, and other metabolites. Isolates of C. parapsilosis and C. glabrata with unusual PCR fingerprinting patterns also generated atypical NMR spectra, suggesting the possibility of intraspecies discontinuity. We conclude that NMR spectroscopy combined with a statistical classification strategy is a rapid, nondestructive, and potentially valuable method for identification and chemotaxonomic characterization that may be broadly applicable to fungi and other microorganisms.

Identification of Candida glabrata by a 30-second trehalase test

Rapid (30-s) trehalase tests done with material from colonies of 482 yeasts suspended in a drop of trehalose solution on a commercially supplied glucose test strip were positive for 225 (99.1%) of 227 Candida glabrata isolates grown on either of two differential media, Candida ID medium or CandiSelect medium. The test was positive for only 3 (1.2%) and 12 (4.7%) of 255 isolates of other medically important yeast species grown on the same two media, respectively. A rapid maltase test done with a subset of 255 yeast isolates was negative for all but 1 of 64 trehalase-positive C. glabrata isolates, raising the specificity of the rapid testing for C. glabrata to 98.4 to 100%, depending on the isolation medium used. Rapid trehalase and maltase tests done independently in two laboratories with 217 yeast isolates showed sensitivities of 96.0 to 98.0% and specificities of 98.2 to 99.4% for identification of C. glabrata from colonies grown on Candida ID medium. The specificity was much lower because of frequent false-positive trehalose test results when the source of colonies was Sabouraud agar formulated with 4% glucose. We conclude that direct recognition of C. albicans as blue colonies on Candida ID isolation medium coupled with the performance of the 30-s trehalase and maltase tests for C. glabrata among the white colonies on this medium will allow the rapid presumptive identification of the two yeast species most commonly encountered in clinical samples.

Prospective evaluation of the new chromogenic medium Candida ID, in comparison with Candiselect, for isolation of molds and isolation and presumptive identification of yeast species

We conducted a prospective evaluation of Candida ID chromogenic medium (bioMérieux, Marcy l'Etoile, France) with 786 clinical specimens in comparison with Candiselect medium (Bio-Rad, Marnes la Coquette, France). Candida ID chromogenic medium identified 97.7% of Candida albicans strains; enabled presumptive identification of C. tropicalis, C. lusitaniae, C. guillermondii, and C. kefyr and better detection of yeast combinations (11.4% more often); and was more sensitive for the isolation of filamentous fungi (17.7% more often). However, Candida ID chromogenic medium appeared to be less selective vis-à-vis bacteria, with bacterial colonies sometimes pigmented blue.

Performance of candida ID, a new chromogenic medium for presumptive identification of Candida species, in comparison to CHROMagar Candida

Candida ID agar allows identification of Candida albicans and differentiation of other Candida species. In comparison with CHROMagar Candida, we evaluated the performance of this medium directly from 596 clinical specimens. In particular, detection of C. albicans after 24 h of incubation was easier on Candida ID (sensitivity, 96.8%) than on CHROMagar (sensitivity, 49.6%).