Annals of Clinical Microbiology, The official Journal of the Korean Society of Clinical Microbiology
Myeong Hee Kim
Department of Laboratory Medicine, Kyung Hee University College of Medicine and Kyung Hee University Hospital at Gangdong, Seoul, Korea
Corresponding to Myeong Hee Kim, E-mail: meikim96@hanmail.net
Ann Clin Microbiol 2024;27(4):257-265. https://doi.org/10.5145/ACM.2024.27.4.5
Received on 7 October 2024, Revised on 12 November 2024, Accepted on 14 November 2024, Published on 20 December 2024.
Copyright © Korean Society of Clinical Microbiology.
This is an Open Access article which is freely available under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND) (https://creativecommons.org/licenses/by-nc-nd/4.0/).
Cryptococcosis is a major invasive fungal infection affecting both immunocompromised and immunocompetent hosts worldwide and is mainly caused by Cryptococcus neoformans and Cryptococcus gattii. C. neoformans accounts for 90% of all infections and primarily causes central nervous system infections. Although C. gattii is primarily found in tropical and subtropical regions, infections have recently been reported in temperate areas such as Korea. Genetic studies in Korea indicated that most C. neoformans strains are of the VNIST5 type and show genetic homogeneity. In contrast, genetic studies on C. gattii are limited. Cryptococcosis is diagnosed using microscopy, serological tests, culture, and molecular tests. Although it can be detected in the cerebrospinal fluid or body fluids using the India ink method, confirmation through culture is essential for a definitive diagnosis. Cryptococcal antigen testing is economical, highly sensitive, and specific; therefore, it is widely used for the diagnosis of cryptococcosis. Molecular methods have recently been introduced; however, their applications remain limited. The recommended treatment for cryptococcal infections includes amphotericin B alone or in combination with flucytosine or fluconazole. Secondary resistance to flucytosine and fluconazole is common. The Clinical and Laboratory Standards Institute and European Committee on Antimicrobial Susceptibility Testing recommend the broth microdilution method. Several commercial methods for antifungal susceptibility testing have been developed and are currently in use; however, more data are required to establish breakpoints.
Cryptococcosis, Cryptococcus neoformans, Cryptococcus gattii, Laboratory diagnosis
There are more than 30 identified species of Cryptococcus, with Cryptococcus neoformans and Cryptococcus gattii being the major pathogens causing cryptococcosis [1,2]. These two pathogens exhibit different characteristics in terms of geographical distribution, epidemiology, and clinical symptoms. Infections caused by C. neoformans primarily affect immunocompromised hosts by targeting the central nervous system and causing meningoencephalitis. In contrast, C. gattii infects immunocompetent hosts and predominantly affects the respiratory system [3–5].
C. neoformans is widely distributed globally, accounting for 90% of cryptococcal infections, and is commonly found in natural environments, particularly in bird droppings and soil [6]. In contrast, C. gattii has been associated with eucalyptus trees in tropical and subtropical climates until the late 1990s. However, it has recently been found in temperate regions, such as North America [7,8], and infections have rarely been reported in Asia, including Korea [9–13].
In Korea, the incidence of cryptococcal infections has been increasing among immunocompromised patients, including those undergoing treatment for malignant diseases, organ transplant recipients, and those with acquired immune deficiency syndrome (AIDS). In this review, we aimed to comprehensively examine recent epidemiological and diagnostic methods for cryptococcal infections.
Cryptococcosis is associated with high morbidity and mortality. Human immunodeficiency virus (HIV) and AIDS are major risk factors in sub-Saharan Africa. However, there are an increasing number of cryptococcosis reports among non-HIV-associated immunocompromised risk groups and immunocompetent individuals [14]. For example, C. neoformans infections have been reported in immunocompetent patients in Korea [15–17].
The major causative agents of cryptococcosis are C. neoformans and C. gattii, which are classified into five serotypes based on the antigenicity of their capsules: serotype A, C. neoformans; serotype D, C. deneoformans; serotype AD, a hybrid of C. neoformans/C. deneoformans; and serotypes B and C, C. gattii. Subsequent genetic studies using molecular tests have revealed variations within C. neoformans and C. gattii, leading to the reclassification of C. neoformans into C. neoformans and C. deneoformans, and C. gattii into f ive different species: C. gattii, C. bacillisporus, C. decagattii, C. deuterogattii, and C. tetragattii [18]. These two species are divided into the following eight molecular types based on genetic differences: serotype A— VNI and VNII; serotype AD—VNIII; serotype D—VNIV; serotypes B and C— VGI, VGII, VGIII, and VGIV [19,20]. Globally, C. neoformans VNI is the most common genotype, followed by C. neoformans VNII, C. deneoformans VNIV, C. bacillisporus VGIII, C. gattii VGI, C. neoformans/deneoformans hybrid VNIII, and C. gattii VGII. Among HIV-infected individuals, C. neoformans VNI is the most common genotype, followed by C. gattii VGII. In Korea, C. neoformans VNI is the most frequently isolated genotype, and other molecular types identified are VNIV, VGI, VGII, and VGIII [12,13]. The International Society of Human and Animal Mycoses working group proposed a multilocus sequence typing (MLST) method to obtain global genotype data, highlighting its high discriminatory power and interlaboratory reproducibility. The proposed international standard genetic loci are CAP59, GPD1, LAC1, PLB1, SOD1, URA5, and IGS1 [19]. In Asia, including Korea, Japan, and China, studies using MLST have indicated that C. neoformans VNI-ST5, which has low genetic diversity, is the most common [10,12,21–25] (Table 1). Among the few genotyping studies in Korea, some have reported that among the 46 clinical specimens collected between 2008 and 2012, 95.7% were C. neoformans VNI-ST5, with the remainder being the VNI-ST31 genotype [13]. In another study involving 140 clinical specimens collected from 1993 to 2014, C. neoformans VNI-ST5 was predominant, and ST31 and ST127 were also identified; the three isolates of C. gattii were identified as ST57, ST7, and ST113 [12]. Research indicates that C. neoformans is genetically homogeneous and that genotypes appearing in the environment are closely related to those found in clinical specimens [12]. C. gattii infections are rare in Korea; therefore, information on the molecular characteristics of C. gattii strains is limited.
Table 1. Distribution of molecular types of Cryptococcus neoformans and Cryptococcus gattii isolates from Korea, Japan, and China by multilocus sequence typing
| Country | Source | Molecular type | Reference | |||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| VNI | VNII | VNIV | VGI | VGII | VGIII | |||||||||||||||||
| ST4 | ST5 | ST31 | ST32 | ST38 | ST53 | ST63 | ST191 | ST359 | ST360 | ST43 | ST127 | ST57 | ST159 | ST7 | ST21 | ST44 | ST126 | ST173 | ST113 | |||
| Korea | Clinical | 32 | 4 | 1 | 1 | 1 | 1 | [12] | ||||||||||||||
| Environmental | 7 | 3 | ||||||||||||||||||||
| Korea | Clinical | 2 | [21] | |||||||||||||||||||
| Japan | Clinical | 31 | 1 | 3 | [22] | |||||||||||||||||
| Environmental | 4 | 4 | ||||||||||||||||||||
| China | Clinical | 34 | 3 | 1 | 2 | 1 | 1 | 1 | [10] | |||||||||||||
| China | Clinical | 22 | 1 | 1 | [23] | |||||||||||||||||
| China | Environmental | 5 | 54 | 1 | 10 | 8 | 3 | [24] | ||||||||||||||
| China | Clinical | 2 | 1 | 2 | 1 | 1 | [25] | |||||||||||||||
Abbreviation: ST, sequence type.
Cryptococcal infection can be diagnosed by microscopic observation of encapsulated yeast-like fungi in tissues or body fluids, such as cerebrospinal fluid (CSF), and confirmed by culture. Antigen (Ag) testing is also sensitive and specific, aiding in diagnosis.
C. neoformans can be detected in CSF or body fluids using the India ink method. The capsule of C. neoformans is composed of polysaccharides, such as glucuronoxylomannan and galactoxylomannan, which are best observed using India ink staining. The ink particles do not penetrate the capsule and form a halo around the cells [26]. However, its sensitivity is less than 90% and in cases of low fungal burden, such as during early infection (≤ 1000 CFU/mL), sensitivity decreases further, necessitating confirmation by culture [27]. Additionally, a positive microscopic finding should only be considered a treatment failure or relapse if it is accompanied by clinical deterioration or a positive culture result in patients undergoing treatment [14].
It is recommended to culture a large volume (5-10 mL) of CSF with a culture positivity rate of 90%-95% [27]. In addition to CSF, C. neoformans can also be cultured from blood, sputum, pleural fluid, urine, and prostate fluid. The positivity rate in blood cultures is approximately 10%-30%, and it is beneficial to perform a tissue biopsy alongside CSF and blood cultures, owing to the low sputum positivity rate in pulmonary cryptococcosis (10%-20%) [27]. C. neoformans forms colonies within approximately three days of culture and appears as cream-beige-colored mucoid colonies on Sabouraud dextrose agar (SDA) due to the encapsulation of yeast cells. Birdseed agar containing caffeic acid, produces brown and black colonies. Microscopically, they appear as round yeasts on SDA and as budding yeasts with thick dark walls on cornmeal-tween 80 agar.
Detecting cryptococcal Ag is a highly reliable method for diagnosing cryptococcosis [28,29]. Cryptococcal Ag can be detected in the serum, plasma, or CSF using latex agglutination, with sensitivity and specificity both exceeding 90% despite some manufacturer variability, although the sensitivity is somewhat lower for C. gattii detection [30–32]. Serum Ag tests revealed 66% and less than 10%-30% positivity in systemic and pulmonary cryptococcosis cases, respectively [27]. Due to their similar antigenicity to Trichosporon beigelii, false positives can occur in the serum and CSF of patients with disseminated trichosporonosis [28]. Rare false positives have also been reported in patients with gram-negative bacterial sepsis or cancer [28,33]. Moreover, false negatives may occur when the fungal burden is very low, there is a prozone-like phenomenon, or the capsule is not well-developed [34].
Molecular diagnostic methods have not been widely developed, owing to the availability, high sensitivity, and low cost of cryptococcal Ag testing. The FilmArray meningitis/encephalitis panel (Biomerieux) is a multiplex polymerase chain reaction assay used to detect C. neoformans and C. gattii in CSF for the diagnosis of cryptococcal meningitis. Meta-analysis suggested that this test has high diagnostic accuracy, with a sensitivity and specificity of 90% and 97%, respectively. The false positive and negative rates were found to be 11.4% and 2.2%, respectively [35]. However, the Filmarray M/E panel is limited because it cannot differentiate between C. neoformans and C. gattii. Next-generation sequencing can detect low fungal burdens before clinical symptoms appear [36]. However, these molecular methods are not widely used because of their high costs and limited availability.
Resistance to antifungal agents among Cryptococcus spp. is relatively common and often associated with prior drug exposure [37]. Secondary resistance frequently arises when flucytosine or fluconazole is used as a monotherapy, owing to the use of amphotericin B either alone or in combination with flucytosine or f luconazole, which is recommended for the treatment of cryptococcal meningitis or other invasive infections [14].
Triazoles and amphotericin B target fungal cells either by directly attacking or altering the synthesis of the enzyme Erg 11 or by depleting ergosterol, respectively [37–40]. Flucytosine resistance can occur through genetic mutations that prevent drug uptake or disrupt the target nucleic acid synthesis pathways. Additionally, cell capsule formation may alter the cell walls and induce resistance. Fluconazole resistance arises from modification of efflux pumps [37,39]. Cryptococcus spp. are inherently resistant to echinocandins because of cellular changes that enable rapid or transient adaptation, leading to resistance to these agents [41].
Breakpoints (BPs) and epidemiological cut-off values (ECVs) play important roles in predicting clinical outcomes. The development of BPs requires pharmacokinetic and pharmacodynamic data from animal models, whereas ECVs require clinical and microbiological outcome data obtained from clinical trials. ECVs are a new interpretive endpoint that classify strains as wild-type and non-wild-type without categorizing them as susceptible or resistant, which is not the same as susceptibility or resistance. ECVs can be developed according to the guidelines of the Clinical and Laboratory Standards Institute (CLSI) M57 document [42]. There is no established clinical minimum inhibitory concentration (MIC) BP for fluconazole against Cryptococcus spp. and there are insufficient data to suggest that high MICs are correlated with poor outcomes [14]. Accurate species identification is necessary to interpret the ECVs proposed by the CLSI. The cutoff values for C. neoformans VNI, C. gattii VGI, and C. deuterogattii VGII are 8 µg/mL, 16 µg/mL, 32 µg/mL, respectively [42]. An increase in MIC by more than two-fold during treatment suggests the development of resistance, necessitating more thorough clinical monitoring [14]. The European Committee on Antimicrobial Susceptibility Testing (EUCAST) has not proposed an ECV for fluconazole; however, it provides ECVs for C. neoformans with amphotericin B (1 mg/L), posaconazole (0.5 mg/L), and voriconazole (0.5 mg/L). Additionally, EUCAST provided ECVs for C. gattii with amphotericin B (0.5 mg/L) and posaconazole (1 mg/L) [43].
The CLSI and EUCAST recommend the broth microdilution (BMD) method [43,44]. Several commercial methods have been developed based on this reference method and are currently in use, including VITEK 2 (bioMérieux), Sensititre YeastOne panel/plate (Thermo Fisher Scientific), and the E-test (bioMérieux). These methods are convenient, effective, and widely used [45]. However, it is necessary to accumulate suitable clinical data to establish the BPs for these commercial methods.
Cryptococcus spp., which are known to cause infections in immunocompromised individuals, have recently been reported to infect immunocompetent hosts. Additionally, infections by C. gattii have been reported in temperate regions, indicating a shift in the epidemiology of Cryptococcus spp. infections. A recent study in Korea confirmed the epidemiological homogeneity between clinical isolates and environmental strains. However, research on genotypes in Korea remains limited. Antifungal susceptibility testing uses various commercial methods based on the BMD method; however, BPs have not yet been established. Thus, the collection of clinical data is considered necessary for appropriate diagnosis and treatment.
It is not a human population study; therefore, approval by the Institutional Review Board or the obtainment of informed consent is not required.
No potential conflicts of interest relevant to this article were reported.
None.
None.
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2. Maziarz EK, Perfect JR. Cryptococcosis. Infect Dis Clin North Am 2016;30:179-206. 
3. Speed B, Dunt D. Clinical and host differences between infections with the two varieties of Cryptococcus neoformans. Clin Infect Dis 1995;21:28-34.
4. Galanis E, MacDougall L, Kidd S, Morshed M; British Columbia Cryptococcus gattii Working Group. Epidemiology of Cryptococcus gattii, British, Columbia, Canada, 1999-2007. Emerg Infect Dis 2010;16:251-7.
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9. Chen J, Varma A, Diaz MR, Litvintseva AP, Wollenberg KK, Kwon-Chung KJ. Cryptococcus neoformans strains and infection in apparently immunocompetent patients, China. Emerg Infect Dis 2008;14:755-62.
10. Wu SY, Lei Y, Kang M, Xiao YL, Chen ZX. Molecular characterisation of clinical Cryptococcus neoformans and Cryptococcus gattii isolates from Sichuan province, China. Mycoses 2015;58:280-7.
11. Kaocharoen S, Ngamskulrungroj P, Firacative C, Trilles L, Piyabongkarn D, Banlunara W, et al. Molecular epidemiology reveals genetic diversity amongst isolates of the Cryptococcus neoformans/C. gattii species complex in Thailand. PLoS Negl Trop Dis 2013;7:e2297.
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16. Choo MJ, Shin SO, Yang SK, Jin HR. Cryptococcal infection combined with cholesteatoma. Korean J Otolaryngol-Head Neck Surg 1999;42:639-42.
17. Hyun JJ, Choi JH, Park S, Jeong HW, Jung SJ, Kee SY, et al. A case report on cryptococcal lymphadenitis in an immunocompetent adult patient. Infect Chemother 2005;37:350-4.
18. Takashima M and Sugita T. Taxonomy of pathogenic yeasts Candida, Cryptococcus, Malassezia, and Trichosporon. Med Mycol J 2022;63:119-32.
19. Meyer W, Aanensen DM, Boekhout T, Cogliati M, Diaz MR, Esposto MC, et al. Consensus multi-locus sequence typing scheme for Cryptococcus neoformans and Cryptococcus gattii. Med Mycol 2009;47:561-70.
20. Khayhan K, Hagen F, Pan W, Simwami S, Fisher MC, Wahyuningsih R, et al. Geographically structured populations of Cryptococcus neoformans variety grubii in Asia correlate with HIV status and show a clonal population structure. PLoS One 2013;8:e72222.
21. Choi YH, Ngamskulrungroj P, Varma A, Sionov E, Hwang SM, Carriconde F, et al. Prevalence of the VNIc genotype of Cryptococcus neoformans in non-HIV-associated cryptococcosis in the Republic of Korea. FEMS Yeast Res 2010;10:769-78.
22. Mihara T, Izumikawa K, Kakeya H, Ngamskulrungroj P, Umeyama T, Takazono T, et al. Multilocus sequence typing of Cryptococcus neoformans in non-HIV associated cryptococcosis in Nagasaki, Japan. Med Mycol 2013;51:252-60.
23. Dou HT, Xu YC, Wang HZ, Li TS. Molecular epidemiology of Cryptococcus neoformans and Cryptococcus gattii in China between 2007 and 2013 using multilocus sequence typing and the DiversiLab system. Eur J Clin Microbiol Infect Dis 2015;34:753-62.
24. Dou H, Wang H, Xie S, Chen X, Xu Z, Xu Y. Molecular characterization of Cryptococcus neoformans isolated from the environment in Beijing, China. Med Mycol 2017;55:737-47.
25. Zang X, Ke W, Wang L, Wu H, Huang Y, Deng H, et al. Molecular epidemiology and microbiological characteristics of Cryptococcus gattii VGII isolates from China. PLoS Negl Trop Dis 2022;16:e0010078.
26. Zaragoza O, Rodrigues ML, De Jesus M, Frases S, Dadachova E, Casadevall A. The capsule of the fungal pathogen Cryptococcus neoformans. Adv Appl Microbiol 2009;68:133-216.
27. Shin JH. Laboratory diagnosis of opportunistic fungal infections. Ann Clin Microbiol 1998;1:37-43.
28. de Repentigny L. Serodiagnosis of candidiasis, aspergillosis, and cryptococcosis. Clin Infect Dis 1992;14(suppl 1):S11-22.
29. Williams DA, Kiiza T, Kwizera R, Kiggundu R, Velamakanni S, Meya DB, et al. Evaluation of fingerstick cryptococcal antigen lateral flow assay in HIV-infected persons: a diagnostic accuracy study. Clin Infect Dis 2015;61:464-7.
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1. Gushiken AC, Saharia KK, Baddley JW. Cryptococcosis. Infect Dis Clin North Am 2021;35:493-514.
2. Maziarz EK and Perfect JR. Cryptococcosis. Infect Dis Clin North Am 2016;30:179–206.
3. Speed B and Dunt D. Clinical and host differences between infections with the two varieties of Cryptococcus neoformans. Clin Infect Dis 1995;21:28–34.
4. Galanis E, MacDougall L, Kidd S, Morshed M; British Columbia Cryptococcus gattii Working Group. Epidemiology of Cryptococcus gattii, British, Columbia, Canada, 1999-2007. Emerg Infect Dis 2010;16:251–7.
5. Mitchell DH, Sorrell TC, Allworth AM, Heath CH, McGregor AR, Papanaoum K, et al. Cryptococcal disease of the CNS in immunocompetent hosts: influence of cryptococcal variety on clinical manifestations and outcome. Clin Infect Dis 1995;20:611–6.
6. May RC, Stone NRH, Wiesner DL, Bicanic T, Nielsen K. Cryptococcus: from environmental saprophyte to global pathogen. Nat Rev Microbiol 2016;14:106–17.
7. Datta K, Bartlett KH, Marr KA. Cryptococcus gattii: emergence in western North America: exploitation of a novel ecological niche. Interdiscip Perspect Infect Dis 2009;2009:176532.
8. Kidd SE, Hagen F, Tscharke RL, Huynh M, Bartlett KH, Fyfe M, et al. A rare genotype of Cryptococcus gattii caused the cryptococcosis outbreak on Vancouver Island (British Columbia, Canada). Proc Natl Acad Sci USA 2004;101:17258-63.
9. Chen J, Varma A, Diaz MR, Litvintseva AP, Wollenberg KK, Kwon-Chung KJ. Cryptococcus neoformans strains and infection in apparently immunocompetent patients, China. Emerg Infect Dis 2008;14:755-62.
10. Wu SY, Lei Y, Kang M, Xiao YL, Chen ZX. Molecular characterisation of clinical Cryptococcus neoformans and Cryptococcus gattii isolates from Sichuan province, China. Mycoses 2015;58:280-7.
11. Kaocharoen S, Ngamskulrungroj P, Firacative C, Trilles L, Piyabongkarn D, Banlunara W, et al. Molecular epidemiology reveals genetic diversity amongst isolates of the Cryptococcus neoformans/C. gattii species complex in Thailand. PLoS Negl Trop Dis 2013;7:e2297.
12. Park SH, Choi SC, Lee KW, Kim MN, Hwang SM. Genotypes of clinical and environmental isolates of Cryptococcus neoformans and Cryptococcus gattii in Korea. Mycobiology 2015;43:360-5.
13. Hwang SM. Molecular typing of clinical Cryptococcus gattii isolates in Korea. J Bacteriol Virol 2012;42:152-5.
14. Chang CC, Harrison TS, Bicanic TA, Chayakulkeeree M, Sorrell TC, Warris A, et al. Global guideline for the diagnosis and management of cryptococcosis: an initiative of the ECMM and ISHAM in cooperation with the ASM. Lancet Infect Dis 2024;24:e495-512.
15. Park SW, Choi JY, Kim AY, Chang DS. A case of cryptococcal abscess involving deep neck space in an immunocompetent patient. Korean J Otorhinolaryngol-Head Neck Surg 2011;54:638-41.
16. Choo MJ, Shin SO, Yang SK, Jin HR. Cryptococcal infection combined with cholesteatoma. Korean J Otolaryngol-Head Neck Surg 1999;42:639-42.
17. Hyun JJ, Choi JH, Park S, Jeong HW, Jung SJ, Kee SY, et al. A case report on cryptococcal lymphadenitis in an immunocompetent adult patient. Infect Chemother 2005;37:350-4.
18. Takashima M and Sugita T. Taxonomy of pathogenic yeasts Candida, Cryptococcus, Malassezia, and Trichosporon. Med Mycol J 2022;63:119-32.
19. Meyer W, Aanensen DM, Boekhout T, Cogliati M, Diaz MR, Esposto MC, et al. Consensus multi-locus sequence typing scheme for Cryptococcus neoformans and Cryptococcus gattii. Med Mycol 2009;47:561-70.
20. Khayhan K, Hagen F, Pan W, Simwami S, Fisher MC, Wahyuningsih R, et al. Geographically structured populations of Cryptococcus neoformans variety grubii in Asia correlate with HIV status and show a clonal population structure. PLoS One 2013;8:e72222.
21. Choi YH, Ngamskulrungroj P, Varma A, Sionov E, Hwang SM, Carriconde F, et al. Prevalence of the VNIc genotype of Cryptococcus neoformans in non-HIV-associated cryptococcosis in the Republic of Korea. FEMS Yeast Res 2010;10:769-78.
22. Mihara T, Izumikawa K, Kakeya H, Ngamskulrungroj P, Umeyama T, Takazono T, et al. Multilocus sequence typing of Cryptococcus neoformans in non-HIV associated cryptococcosis in Nagasaki, Japan. Med Mycol 2013;51:252-60.
23. Dou HT, Xu YC, Wang HZ, Li TS. Molecular epidemiology of Cryptococcus neoformans and Cryptococcus gattii in China between 2007 and 2013 using multilocus sequence typing and the DiversiLab system. Eur J Clin Microbiol Infect Dis 2015;34:753-62.
24. Dou H, Wang H, Xie S, Chen X, Xu Z, Xu Y. Molecular characterization of Cryptococcus neoformans isolated from the environment in Beijing, China. Med Mycol 2017;55:737-47.
25. Zang X, Ke W, Wang L, Wu H, Huang Y, Deng H, et al. Molecular epidemiology and microbiological characteristics of Cryptococcus gattii VGII isolates from China. PLoS Negl Trop Dis 2022;16:e0010078.
26. Zaragoza O, Rodrigues ML, De Jesus M, Frases S, Dadachova E, Casadevall A. The capsule of the fungal pathogen Cryptococcus neoformans. Adv Appl Microbiol 2009;68:133-216.
27. Shin JH. Laboratory diagnosis of opportunistic fungal infections. Ann Clin Microbiol 1998; 1:37-43.
28. de Repentigny L. Serodiagnosis of candidiasis, aspergillosis, and cryptococcosis. Clin Infect Dis 1992;14(suppl 1):S11-22.
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