Long-term surveillance and treatment of subclinical cryptococcosis and nasal colonization by Cryptococcus neoformans and C. gattii species complex in captive koalas (Phascolarctes cinereus)

The CARD9 Gene in Koalas (Phascolarctos cinereus): Does It Play a Role in the Cryptococcus-Koala Interaction?

Cryptococcus is a genus of fungal pathogens that can infect and cause disease in a range of host species and is particularly prominent in koalas (Phascolarctos cinerus). Like other host species, koalas display a range of outcomes upon exposure to environmental Cryptococcus, from external nasal colonization to asymptomatic invasive infection and, in rare cases, severe clinical disease resulting in death. Host factors contributing to these varied outcomes are poorly understood. Due to their close relationship with eucalypt trees (a key environmental niche for Cryptococcus gattii) and suspected continual exposure to the pathogen, koalas provide a unique opportunity to examine host susceptibility in natural infections. Caspase recruitment domain-containing protein 9 (CARD9) is a key intracellular signaling protein in the fungal innate immune response. Humans with mutations in CARD9 succumb to several different severe and chronic fungal infections. This study is the first to sequence and explore CARD9 variation in multiple koalas using Sanger sequencing. Four CARD9 exons were successfully sequenced in 22 koalas from a New South Wales, Australia population. We found minimal variation between koalas across all four exons, an observation that was also made when CARD9 sequences were compared between koalas and six other species, including humans and mice. Ten single-nucleotide polymorphisms (SNP) were identified in this study and explored in the context of cryptococcal exposure outcomes. While we did not find any significant association with variation in cryptococcal outcomes, we found a high degree of conservation between species at several SNP loci that requires further investigation. The findings from this study lay the groundwork for further investigations of CARD9 and Cryptococcus both in koalas and other species, and highlight several considerations for future studies.

Cryptococcus neoformans rapidly invades the murine brain by sequential breaching of airway and endothelial tissues barriers, followed by engulfment by microglia

Cryptococcus neoformans causes lethal meningitis and accounts for approximately 10%-15% of AIDS-associated deaths worldwide. There are major gaps in our understanding of how this fungus invades the mammalian brain. To investigate the dynamics of C. neoformans tissue invasion, we mapped fungal localization and host cell interactions in infected brain, lung, and upper airways using mouse models of systemic and airway infection. To enable this, we developed an in situ imaging pipeline capable of measuring large volumes of tissue while preserving anatomical and cellular information by combining thick tissue sections, tissue clarification, and confocal imaging. We confirm high fungal burden in mouse upper airway after nasal inoculation. Yeast in turbinates were frequently titan cells, with faster kinetics than reported in mouse lungs. Importantly, we observed one instance of fungal cells enmeshed in lamina propria of the upper airways, suggesting penetration of airway mucosa as a possible route of tissue invasion and dissemination to the bloodstream. We extend previous literature positing bloodstream dissemination of C. neoformans, by finding viable fungi in the bloodstream of mice a few days after intranasal infection. As early as 24 h post systemic infection, the majority of C. neoformans cells traversed the blood-brain barrier, and were engulfed or in close proximity to microglia. Our work presents a new method for investigating microbial invasion, establishes that C. neoformans can breach multiple tissue barriers within the first days of infection, and demonstrates microglia as the first cells responding to C. neoformans invasion of the brain.IMPORTANCECryptococcal meningitis causes 10%-15% of AIDS-associated deaths globally. Still, brain-specific immunity to cryptococci is a conundrum. By employing innovative imaging, this study reveals what occurs during the first days of infection in brain and in airways. We found that titan cells predominate in upper airways and that cryptococci breach the upper airway mucosa, which implies that, at least in mice, the upper airways are a site for fungal dissemination. This would signify that mucosal immunity of the upper airway needs to be better understood. Importantly, we also show that microglia, the brain-resident macrophages, are the first responders to infection, and microglia clusters are formed surrounding cryptococci. This study opens the field to detailed molecular investigations on airway immune response, how fungus traverses the blood-brain barrier, how microglia respond to infection, and ultimately how microglia monitor the blood-brain barrier to preserve brain function.

Molecular epidemiological investigation of Cryptococcus spp. carried by captive koalas (Phascolarctos cinereus) in Japan

Cryptococcus neoformans and Cryptococcus gattii cause cryptococcosis, a systemic mycosis that infects a wide range of species. Recent molecular biological investigations have allowed for the genotyping of these species, providing more detailed information on their pathogenicity and infection routes. Koalas (Phascolarctos cinereus) are frequently colonized by Cryptococcus spp., but molecular epidemiological studies have yet to be conducted in Japan. Here, we conducted multi-locus sequence typing (MLST) analysis on Cryptococcus spp. colonization isolates obtained from all koalas kept in seven parks across Japan. Out of 46 koalas examined, 10 (22%) were positive for C. gattii and 3 (6.5%) were positive for C. neoformans. All C. gattii isolates belonged to molecular type VGI and were either sequence type (ST) 51 or a novel ST, and all C. neoformans isolates belonged to molecular type VNI and ST23. Despite the frequent movement of koalas between parks, the STs were relatively park-specific, suggesting that the floor of the rearing barns is a source of infection and may act as a reservoir. MLST analysis confirmed that C. gattii was transported, established, and spread by koalas in areas where C. gattii was not originally present. MLST analysis is considered useful in assessing the pathogenicity and tracing the transmission routes of Cryptococcus spp. carried by koalas.IMPORTANCEThis is the first study to conduct a multi-locus sequence typing analysis on Cryptococcus spp. carried by captive koalas in Japan. Cryptococcosis remains a globally high-fatality fungal infection in humans, and captive koalas are known to carry a high percentage of Cryptococcus spp. Through this research, the molecular types and transmission routes of Cryptococcus spp. carried by koalas have been elucidated, revealing the potential role of enclosure flooring as a reservoir. It has been confirmed that Cryptococcus gattii, which is not endemic in Japan, has become established through koalas and is spreading to new individuals in Japan. This study is believed to provide valuable insights into koala conservation and contribute to the One Health approach for Cryptococcosis, a zoonotic infection.

Cryptococcus neoformans rapidly invades the murine brain by sequential breaching of airway and endothelial tissues barriers, followed by engulfment by microglia

The fungus Cryptococcus neoformans causes lethal meningitis in humans with weakened immune systems and is estimated to account for 10-15% of AIDS-associated deaths worldwide. There are major gaps in our understanding of how this environmental fungus evades the immune system and invades the mammalian brain before the onset of overt symptoms. To investigate the dynamics of C. neoformans tissue invasion, we mapped early fungal localisation and host cell interactions at early times in infected brain, lung, and upper airways using mouse models of systemic and airway infection. To enable this, we developed an in situ imaging pipeline capable of measuring large volumes of tissue while preserving anatomical and cellular information by combining thick tissue sections, tissue clarification, and confocal imaging. Made possible by these techniques, we confirm high fungal burden in mouse upper airway turbinates after nasal inoculation. Surprisingly, most yeasts in turbinates were titan cells, indicating this microenvironment enables titan cell formation with faster kinetics than reported in mouse lungs. Importantly, we observed one instance of fungal cells enmeshed in lamina propria of upper airways, suggesting penetration of airway mucosa as a possible route of tissue invasion and dissemination to the bloodstream. We extend previous literature positing bloodstream dissemination of C. neoformans, via imaging C. neoformans within blood vessels of mouse lungs and finding viable fungi in the bloodstream of mice a few days after intranasal infection, suggesting that bloodstream access can occur via lung alveoli. In a model of systemic cryptococcosis, we show that as early as 24 h post infection, majority of C. neoformans cells traversed the blood-brain barrier, and are engulfed or in close proximity to microglia. Our work establishes that C. neoformans can breach multiple tissue barriers within the first days of infection. This work presents a new method for investigating cryptococcal invasion mechanisms and demonstrates microglia as the primary cells responding to C. neoformans invasion.

Shared and unique antibody and B cell profiles in HIV-positive and HIV-negative individuals with cryptococcal meningoencephalitis

Host non-T cell markers to aid in the diagnosis of cryptococcal meningoencephalitis (CM) have not been identified. In this case-control study, we characterized antibody and B cell profiles in HIV-negative and HIV-positive Vietnamese individuals of the Kinh ethnicity recently diagnosed with CM and controls. The study included 60 HIV-negative with no known immunocompromising condition and 60 HIV-positive individuals, with 30 CM cases and 30 controls in each group. Participants were matched by age, sex, HIV serostatus, and CD4 count in the HIV-positive group. Plasma immunoglobulin (Ig) levels, including IgG1, IgG2, IgM, and IgA, Cryptococcus spp. glucuronoxylomannan (GXM)- and laminarin (branched ${\rm{\beta }}$-[1-3]-glucan)-binding IgG, IgM, IgA levels, and peripheral blood B cell subsets were measured. Logistic regression, principal component, and mediation analyses were conducted to assess associations between antibody, B cell levels, and CM. The results showed that GXM-IgG levels were higher and IgG1 and IgG2 were lower in CM cases than controls, regardless of HIV status. In HIV-negative individuals, IgG2 mediated an inverse association between CD19+CD27+CD43+CD5- (B-1b-like) cells and CM. In HIV-positive individuals, lower levels of IgA, laminarin-IgA, and CD19+CD27+IgM+IgD- (IgM+ memory B) cells were each associated with CM. The shared and distinct antibody and B cell profiles identified in HIV-negative and HIV-positive CM cases may inform the identification of non-T-cell markers of CM risk or unsuspected disease, particularly in HIV-negative individuals.

Antifungal antibodies present in intravenous immunoglobulin derived from China

Fungal infections usually occur in immunocompromised patients. Intravenous immunoglobulin (IVIG) has been used as therapeutic interventions for many infectious diseases, but seldom applied in mycosis due to unknown antifungal specificity. This study aims to determine the presence of antifungal antibodies in IVIG. Binding reactivity of IVIG with crude and recombinant antigens of Candida albicans, Aspergillus fumigatus, Cryptococcus neoformans and Talaromyces marneffei were observed in a dose-dependent manner, similar with mixed normal human sera. The antifungal specificity was further confirmed by competitive enzyme-linked immunosorbent assays (ELISA) inhibited by rabbit specific antifungal polyclonal antibodies (PAbs) and homogenous crude antigens with inhibitions of 65.5-87.2% and 73.1-94.2%, respectively. Moreover, IVIG also reacted with fungal glycoproteins (Csa2, Cpl1 and Mp1p) in a dose-dependent way, which was inhibited by specific rabbit PAbs and homogenous antigens with different inhibitions and pulled down 72.8-83.8% of specific antibodies if preabsorption IVIG with Dynabeads® coupled with homogenous glycoproteins. These results furthermore verified the antifungal specificity of IVIG. Among four brands of IVIG, there was different antifungal IgG against C. albicans (P < 0.05) and C. neoformans (P < 0.05), while no difference for A. fumigatus (P = 0.086) and T. marneffei (P = 0.057). IVIG contained a significantly higher level of specific IgG for C. albicans than other three fungi (P <0.001). In conclusion, we proved antifungal IgG against C. albicans, A. fumigatus, C. neoformans and T. marneffei present in IVIG, which might be expected to provide a possible immunoregulation choice for mycosis and an evaluation to humoral immunity against fungi.

Important Mycoses of Wildlife: Emphasis on Etiology, Epidemiology, Diagnosis, and Pathology—A Review: PART 1

Simple Summary

The number of wild animals is steadily declining globally, so the early diagnosis and proper treatment of emerging diseases are vital. Fungal diseases are commonly encountered in practice and have a high zoonotic potential. This article describes aspergillosis, candidiasis, histoplasmosis, cryptococcosis, and penicilliosis, and is only the first part of a detailed review. The laboratory methods (fungal isolation, gross pathology, histopathology, histochemistry, cytology, immunohistochemistry, radiography, CT, PCR, or ELISA) used in the diagnosis and the clinical details that provide a complete view of the mycoses are presented.

Abstract

In the past few years, there has been a spurred tripling in the figures of fungal diseases leading to one of the most alarming rates of extinction ever reported in wild species. Some of these fungal diseases are capable of virulent infections and are now considered emerging diseases due to the extremely high number of cases diagnosed with fungal infections in the last few decades. Most of these mycotic diseases in wildlife are zoonotic, and with the emergence and re-emergence of viral and bacterial zoonotic diseases originating from wildlife, which are causing devastating effects on the human population, it is important to pay attention to these wildlife-borne mycotic diseases with zoonotic capabilities. Several diagnostic techniques such as fungal isolation, gross pathology, histopathology, histochemistry, cytology, immunohistochemistry, radiography, CT, and molecular methods such as PCR or ELISA have been invaluable in the diagnosis of wildlife mycoses. The most important data used in the diagnosis of these wildlife mycoses with a zoonotic potential have been re-emphasized. This will have implications for forestalling future epidemics of these potential zoonotic mycotic diseases originating from wildlife. In conclusion, this review will highlight the etiology, epidemiology, diagnosis, pathogenesis, pathogenicity, pathology, and hematological/serum biochemical findings of five important mycoses found in wild animals.

A Possible Link between the Environment and Cryptococcus gattii Nasal Colonisation in Koalas (Phascolarctos cinereus) in the Liverpool Plains, New South Wales

Cryptococcosis caused by yeasts of the Cryptococcus gattii species complex is an increasingly important mycological disease in humans and other mammals. In Australia, cases of C. gattii-related cryptococcosis are more prevalent in the koala (Phascolarctos cinereus) compared to humans and other animals, likely due to the close association that both C. gattii and koalas have with Eucalyptus species. This provides a cogent opportunity to investigate the epidemiology of spontaneous C. gattii infections in a free-living mammalian host, thereby offering insights into similar infections in humans. This study aimed to establish a link between nasal colonisation by C. gattii in free-ranging koalas and the tree hollows of Eucalyptus species, the key environmental source of the pathogen. We (i) detected and genotyped C. gattii from nine out of 169 free-ranging koalas and representative tree hollows within their home range in the Liverpool Plains, New South Wales, and (ii) examined potential environmental predictors of nasal colonisation in koalas and the presence of C. gattii in tree hollows. Phylogenetic analyses based on multi-locus sequence typing (MLST) revealed that the koalas were most likely colonised by the most abundant C. gattii genotypes found in the Eucalyptus species, or closely related genotypes. Importantly, the likelihood of the presence of C. gattii in tree hollows was correlated with increasing hollow size.

Koala cathelicidin PhciCath5 has antimicrobial activity, including against Chlamydia pecorum

Devastating fires in Australia over 2019-20 decimated native fauna and flora, including koalas. The resulting population bottleneck, combined with significant loss of habitat, increases the vulnerability of remaining koala populations to threats which include disease. Chlamydia is one disease which causes significant morbidity and mortality in koalas. The predominant pathogenic species, Chlamydia pecorum, causes severe ocular, urogenital and reproductive tract disease. In marsupials, including the koala, gene expansions of an antimicrobial peptide family known as cathelicidins have enabled protection of immunologically naïve pouch young during early development. We propose that koala cathelicidins are active against Chlamydia and other bacteria and fungi. Here we describe ten koala cathelicidins, five of which contained full length coding sequences that were widely expressed in tissues throughout the body. Focusing on these five, we investigate their antimicrobial activity against two koala C. pecorum isolates from distinct serovars; MarsBar and IPTaLE, as well as other bacteria and fungi. One cathelicidin, PhciCath5, inactivated C. pecorum IPTaLE and MarsBar elementary bodies and significantly reduced the number of inclusions compared to the control (p<0.0001). Despite evidence of cathelicidin expression within tissues known to be infected by Chlamydia, natural PhciCath5 concentrations may be inadequate in vivo to prevent or control C. pecorum infections in koalas. PhciCath5 also displayed antimicrobial activity against fungi and Gram negative and positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). Electrostatic interactions likely drive PhciCath5 adherence to the pathogen cell membrane, followed by membrane permeabilisation leading to cell death. Activity against E. coli was reduced in the presence of 10% serum and 20% whole blood. Future modification of the PhciCath5 peptide to enhance activity, including in the presence of serum/blood, may provide a novel solution to Chlamydia infection in koalas and other species.

Pathological Properties of Cryptococcus pseudolongus on the Mycelia and Fruit Body of Lentinula edodes

Recently, Cryptococcus pseudolongus has been reported as a new pathogen of shiitake (Lentinula edodes). However, its pathological properties are not much known. To further understand its impact on the mushroom, we investigated the pathogen's interactions with the mycelium of shiitake, histopathological properties, host range, and sensitivity to diverse antifungal agents. The strain C. pseudolongus DUCC 4014 inhibited the mycelial growth of L. edodes strain (cultivar Sanjo 701ho) and caused browning in the mycelia confronted with the yeast on PDA. Spray inoculation of the yeast caused an abnormal browning symptom on the cap and/or gills of three shiitake cultivars grown on sawdust media in vinyl bags. Scanning electron microscopic images of the abnormally browned parts of shiitake fruit body illustrated that mushroom tissues were loosed and dispersed in the middle and edge of the cap and the arrangement of basidiospores borne on basidia in the gills was disturbed compared to those of normal shiitake fruit body. Spray inoculation also led to developing abnormal browning on the harvested fruit body, indicating C. pseudolongus could be a problem during mushroom storage. But the yeast was not able to induce abnormal browning on mushrooms of Pleurotus ferulae, Pleurotus fostreatus, and Agaricus bisporus. But it induced browning only on button mushroom (A. bisporus) when they were inoculated after wounding. Tests with 16 kinds of fungicides revealed that the cell growth of C. pseudolongus could be inhibited by benzalkonium chloride at MIC 7 μg/ml and benomyl at MIC 3 μg/ml.

Cryptococcus in Wildlife and Free-Living Mammals

Cryptococcosis is typically a sporadic disease that affects a broad range of animal species globally. Disease is a consequence of infection with members of the Cryptococcus neoformans or Cryptococcus gattii species complexes. Although cryptococcosis in many domestic animals has been relatively well-characterized, free-living wildlife animal species are often neglected in the literature outside of occasional case reports. This review summarizes the clinical presentation, pathological findings and potential underlying causes of cryptococcosis in various other animals, including terrestrial wildlife species and marine mammals. The evaluation of the available literature supports the hypothesis that anatomy (particularly of the respiratory tract), behavior and environmental exposures of animals play vital roles in the outcome of host–pathogen–environment interactions resulting in different clinical scenarios. Key examples range from koalas, which exhibit primarily C. gattii species complex disease presumably due to their behavior and environmental exposure to eucalypts, to cetaceans, which show predominantly pulmonary lesions due to their unique respiratory anatomy. Understanding the factors at play in each clinical scenario is a powerful investigative tool, as wildlife species may act as disease sentinels.

Isolation of Cryptococcus neoformans var. grubii (serotype A) and C. magnus from the nasal lining of free-ranging quokkas (Setonix brachyurus)

Cryptococcus species are environmental yeasts, with a worldwide distribution and remarkable environmental adaptation. Although many species do not cause disease, C. neoformans and C. gattii are causative agents of cryptococcosis, a life threatening infection and a significant public health problem worldwide. Infection especially affects immunocompromised animals and humans. In wildlife, cryptococcosis appears to be more prevalent in captive populations. The objective of this study was to assess whether apparently healthy quokkas (Setonix brachyurus) harbor Cryptococcus spp. Using cultural and molecular methods, we studied yeasts isolated from nasal swabs collected from 130 free-ranging quokkas on Rottnest Island (RI, n = 97) and the mainland (n = 33) of Western Australia. Unspeciated Cryptococcus spp. (from four quokkas), C. neoformans var. grubii (serotype A) (two quokkas) and C. magnus (one quokka) were isolated from the nasal lining of apparently healthy quokkas from RI. Cryptococcus neoformans var. grubii was isolated from animals captured in a human-populated area on RI. There was no significant effect of the presence of Cryptococcus on the results of haematology, blood chemistry, peripheral blood cell morphology or clinical examination. To the best of our knowledge, this is the first documented isolation of C. neoformans var. grubii (serotype A) and C. magnus in a free-ranging macropod in Western Australia. The public health implications of this finding should be further explored.

Prevalence of cryptococcal antigenemia and nasal colonization in a free-ranging koala population

Cryptococcosis, caused by environmental fungi in the Cryptococcus neoformans and Cryptococcus gattii species complexes, affects a variety of hosts, including koalas (Phascolarctos cinereus). Cryptococcal antigenemia and nasal colonization are well characterized in captive koalas, but free-ranging populations have not been studied systematically. Free-ranging koalas (181) from the Liverpool Plains region of New South Wales, Australia, were tested for cryptococcal antigenemia (lateral flow immunoassay) and nasal colonization (bird seed agar culture). Results were related to environmental and individual koala characteristics. Eucalypt trees (14) were also randomly tested for the presence of Cryptococcus spp. by bird seed agar culture. In sum, 5.5% (10/181) and 6.6% (12/181) of koalas were positive for antigenemia and nasal colonization, respectively, on at least one occasion. And 64.3% (9/14) of eucalypts were culture-positive for Cryptococcus spp. URA5 restriction fragment length polymorphism analysis identified most isolates as C. gattii VGI, while C. neoformans VNI was only found in one koala and one tree. Colonized koalas were significantly more likely to test positive for antigenemia. No associations between antigenemia or colonization, and external environmental characteristics (the relative abundance of Eucalyptus camaldulensis and season), or individual koala characteristics (body condition, sex, and age), could be established, suggesting that antigenemia and colonization are random outcomes of host-pathogen-environment interactions. The relationship between positive antigenemia status and a relatively high abundance of E. camaldulensis requires further investigation. This study characterizes cryptococcosis in a free-ranging koala population, expands the ecological niche of the C. gattii/C. neoformans species complexes and highlights free-ranging koalas as important sentinels for this disease.

Intranasal Inoculation of Cryptococcus neoformans in Mice Produces Nasal Infection with Rapid Brain Dissemination

Cryptococcus neoformans is an important fungal pathogen, causing life-threatening pneumonia and meningoencephalitis. Brain dissemination of C. neoformans is thought to be a consequence of an active infection in the lung which then extravasates to other sites. Brain invasion results from dissemination via either transport by free yeast cells in the bloodstream or Trojan horse transport within mononuclear phagocytes. We assessed brain dissemination in three mouse models of infection: intravenous, intratracheal, and intranasal models. All three modes of infection resulted in dissemination of C. neoformans to the brain in less than 3 h. Further, C. neoformans was detected in the entirety of the upper respiratory tract and the ear canals of mice. In recent years, intranasal infection has become a popular mechanism to induce pulmonary infection because it avoids surgery, but our findings show that instillation of C. neoformans produces cryptococcal nasal infection. These findings imply that immunological studies using intranasal infection should assume that the initial sites of infection of infection are brain, lung, and upper respiratory tract, including the nasal airways.IMPORTANCECryptococcus neoformans causes an estimated 181, 000 deaths each year, mostly associated with untreated HIV/AIDS. C. neoformans has a ubiquitous worldwide distribution. Humans become infected from exposure to environmental sources, after which the fungus lays dormant within the human body. Upon AIDS-induced immunosuppression or therapy-induced immunosuppression (required for organ transplant recipients or those suffering from autoimmune disorders), cryptococcal disease reactivates and causes life-threatening meningitis and pneumonia. This study showed that upon contact with the host, C. neoformans can quickly (a few hours) reach the host brain and also colonizes the nose of infected animals. Therefore, this work paves the way to better knowledge of how C. neoformans travels through the host body. Understanding how C. neoformans infects, disseminates, and survives within the host is critically required so that we can prevent infections and the disease caused by this deadly fungus.

Jet-Setting Koalas Spread Cryptococcus gattii VGII in Australia

Cryptococcus gattii molecular type VGII is one of the etiologic agents of cryptococcosis, a systemic mycosis affecting a wide range of host species. Koalas (Phascolarctos cinereus) exhibit a comparatively high prevalence of cryptococcosis (clinical and subclinical) and nasal colonization, particularly in captivity. In Australia, disease associated with C. gattii VGII is typically confined to Western Australia and the Northern Territory (with sporadic cases reported in eastern Australia), occupying an enigmatic ecologic niche. A cluster of cryptococcosis in captive koalas in eastern Australia (five confirmed cases, a further two suspected), caused predominantly by C. gattii VGII, was investigated by surveying for subclinical disease, culturing koala nasal swabs and environmental samples, and genotyping cryptococcal isolates. URA5 restriction fragment length polymorphism analysis, multilocus sequence typing (MLST), and whole-genome sequencing (WGS) provided supportive evidence that the transfer of koalas from Western Australia and subsequently between several facilities in Queensland spread VGII into uncontaminated environments and environments in which C. gattii VGI was endemic. MLST identified VGII isolates as predominantly sequence type 7, while WGS further confirmed a limited genomic diversity and revealed a basal relationship with isolates from Western Australia. We hypothesize that this represents a founder effect following the introduction of a koala from Western Australia. Our findings suggest a possible competitive advantage for C. gattii VGII over VGI in the context of this captive koala environment. The ability of koalas to seed C. gattii VGII into new environments has implications for the management of captive populations and movements of koalas between zoos.IMPORTANCE Cryptococcus gattii molecular type VGII is one of the causes of cryptococcosis, a severe fungal disease that is acquired from the environment and affects many host species (including humans and koalas). In Australia, disease caused by C. gattii VGII is largely confined to western and central northern parts of the country, with sporadic cases reported in eastern Australia. We investigated an unusual case cluster of cryptococcosis, caused predominantly by C. gattii VGII, in a group of captive koalas in eastern Australia. This research identified that the movements of koalas between wildlife parks, including an initial transfer of a koala from Western Australia, introduced and subsequently spread C. gattii VGII in this captive environment. The spread of this pathogen by koalas could also impact other species, and these findings are significant in the implications they have for the management of koala transfers and captive environments.

Cryptococcosis in the koala (Phascolarctos cinereus): pathogenesis and treatment in the context of two atypical cases

Disseminated cryptococcosis caused by Cryptococcus gattii (molecular type VGI) was diagnosed in an adult free-ranging female koala (Phascolarctos cinereus). Subclinical cryptococcosis was later diagnosed in this koala's joey. In the adult koala, a pathological fracture of the tibia was associated with the bone lysis of marked focal cryptococcal osteomyelitis. Limb-sparing orthopedic intervention, in the setting of disseminated cryptococcosis, was judged to have a poor prognosis, and the adult koala was euthanized. The joey was removed and hand-reared. Serological testing revealed persistent and increasing cryptococcal capsular antigenemia in the absence of clinical signs of disease and it was subsequently treated with oral fluconazole for approximately 16 months, rehabilitated and released into the wild. It was sighted 3 months post-release in a good state of health and again at 18 months post-release but was not recaptured on either occasion. This is the first published report of cryptococcal appendicular osteomyelitis in a koala. It is also the first report of concurrent disease in a dependent juvenile and the successful treatment of subclinical cryptococcosis to full resolution of the cryptococcal antigenemia in a free-ranging koala. This paper provides a discussion of cryptococcal osteomyelitis in animals, host-pathogen-environment interactions and treatment and monitoring protocols for cryptococcosis in koalas. Published reports describing the treatment of cryptococcosis in koalas are also collated and summarised.

Cryptococcal pathogenic mechanisms: a dangerous trip from the environment to the brain

Cryptococcus neoformans is an opportunistic pathogenic yeast that causes serious infections, most commonly of the central nervous system (CNS). C. neoformans is mainly found in the environment and acquired by inhalation. It could be metaphorically imagined that cryptococcal disease is a "journey" for the microorganism that starts in the environment, where this yeast loads its suitcase with virulence traits. C. neoformans first encounters the infected mammalian host in the lungs, a site in which it must choose the right elements from its "virulence suitcase" to survive the pulmonary immune response. However, the lung is often only the first stop in this journey, and in some individuals the fungal trip continues to the brain. To enter the brain, C. neoformans must "open" the main barrier that protects this organ, the blood brain barrier (BBB). Once in the brain, C. neoformans expresses a distinct set of protective attributes that confers a strong neurotropism and the ability to cause brain colonisation. In summary, C. neoformans is a unique fungal pathogen as shown in its ability to survive in the face of multiple stress factors and to express virulence factors that contribute to the development of disease.

Review of some pharmacokinetic and pharmacodynamic properties of anti-infective medicines administered to the koala (Phascolarctos cinereus)

Although koalas are iconic Australian animals, no pharmacokinetic studies of any first-line medicines used to treat diseased or injured koalas had been published prior to 2010. Traditionally, medicine dosages suggested for this species underwent linear extrapolation from those recommended for domesticated species. The koala, a specialist folivore whose natural diet consists of almost exclusively Eucalyptus spp. foliage has anatomical and physiological adaptations for detoxifying their diet which also affect medicine pharmacokinetic profiles. This review addresses aspects of medicine absorption, clearance, and other indices (such as medicine binding to plasma proteins) of enrofloxacin/marbofloxacin and chloramphenicol used for the systemic treatment of chlamydiosis, and fluconazole ± amphotericin, and posaconazole for the treatment of cryptococcosis. Based on observations from published studies, this review includes suggestions to improve therapeutic outcomes when administering medicines to diseased koalas.

ATYPICAL PRESENTATION OF CRYPTOCOCCUS NEOFORMANS IN A KOALA (PHASCOLARCTOS CINEREUS): A MAGNETIC RESONANCE IMAGING AND COMPUTED TOMOGRAPHY STUDY

Cryptococcosis is a worldwide and potentially fatal mycosis documented in wild and captive koalas ( Phascolarctos cinereus ) caused by Cryptococcus neoformans . Though mainly a subclinical disease, when the nasal cavity is affected, epistaxis, mucopurulent nasal discharge, dyspnea, and facial distortion may occur. This report describes a case of cryptococcosis in a koala where unilateral exophthalmos was the only evident clinical sign and magnetic resonance imaging and computed tomography findings are described. Both advanced imaging techniques should be considered as standard and complementary techniques for nasal cavity evaluation in koalas.

Cathelicidins in the Tasmanian devil (Sarcophilus harrisii)

Tasmanian devil joeys, like other marsupials, are born at a very early stage of development, prior to the development of their adaptive immune system, yet survive in a pathogen-laden pouch and burrow. Antimicrobial peptides, called cathelicidins, which provide innate immune protection during early life, are expressed in the pouch lining, skin and milk of devil dams. These peptides are active against pathogens identified in the pouch microbiome. Of the six characterised cathelicidins, Saha-CATH5 and 6 have broad-spectrum antibacterial activity and are capable of killing problematic human pathogens including methicillin-resistant S. aureus and vancomycin-resistant E. faecalis, while Saha-CATH3 is active against fungi. Saha-CATH5 and 6 were toxic to human A549 cells at 500 μg/mL, which is over seven times the concentration required to kill pathogens. The remaining devil cathelicidins were not active against tested bacterial or fungal strains, but are widely expressed throughout the body, such as in immune tissues, in digestive, respiratory and reproductive tracts, and in the milk and pouch, which indicates that they are likely also important components of the devil immune system. Our results suggest cathelicidins play a role in protecting naive young during pouch life by passive immune transfer in the milk and may modulate pouch microbe populations to reduce potential pathogens.

Some pharmacokinetic indices of oral fluconazole administration to koalas (Phascolarctos cinereus) infected with cryptococcosis

Three asymptomatic koalas serologically positive for cryptococcosis and two symptomatic koalas were treated with 10 mg/kg fluconazole orally, twice daily for at least 2 weeks. The median plasma Cmax and AUC0-8 h for asymptomatic animals were 0.9 μg/mL and 4.9 μg/mL·h, respectively; and for symptomatic animals 3.2 μg/mL and 17.3 μg/mL·h, respectively. An additional symptomatic koala was treated with fluconazole (10 mg/kg twice daily) and a subcutaneous amphotericin B infusion twice weekly. After 2 weeks the fluconazole Cmax was 3.7 μg/mL and the AUC0-8 h was 25.8 μg/mL*h. An additional three koalas were treated with fluconazole 15 mg/kg twice daily for at least 2 weeks, with the same subcutaneous amphotericin protocol co-administered to two of these koalas (Cmax : 5.0 μg/mL; mean AUC0-8 h : 18.1 μg/mL*h). For all koalas, the fluconazole plasma Cmax failed to reach the MIC90 (16 μg/mL) to inhibit C. gattii. Fluconazole administered orally at either 10 or 15 mg/kg twice daily in conjunction with amphotericin is unlikely to attain therapeutic plasma concentrations. Suggestions to improve treatment of systemic cryptococcosis include testing pathogen susceptibility to fluconazole, monitoring plasma fluconazole concentrations, and administration of 20-25 mg/kg fluconazole orally, twice daily, with an amphotericin subcutaneous infusion twice weekly.

Cryptococcus gattii genotype VGIIb infection in Japan

This report describes a case of Cryptococcus gattii VGIIb infection of the pulmonary and central nervous systems in an immunocompetent Japanese man with a travel history, and it hypothesizes the place where he was infected with C. gattii using the genotype information.

Cryptococcus gattii infections

Understanding of the taxonomy and phylogeny of Cryptococcus gattii has been advanced by modern molecular techniques. C. gattii probably diverged from Cryptococcus neoformans between 16 million and 160 million years ago, depending on the dating methods applied, and maintains diversity by recombining in nature. South America is the likely source of the virulent C. gattii VGII molecular types that have emerged in North America. C. gattii shares major virulence determinants with C. neoformans, although genomic and transcriptomic studies revealed that despite similar genomes, the VGIIa and VGIIb subtypes employ very different transcriptional circuits and manifest differences in virulence phenotypes. Preliminary evidence suggests that C. gattii VGII causes severe lung disease and death without dissemination, whereas C. neoformans disseminates readily to the central nervous system (CNS) and causes death from meningoencephalitis. Overall, currently available data indicate that the C. gattii VGI, VGII, and VGIII molecular types more commonly affect nonimmunocompromised hosts, in contrast to VGIV. New, rapid, cheap diagnostic tests and imaging modalities are assisting early diagnosis and enabling better outcomes of cerebral cryptococcosis. Complications of CNS infection include increased intracranial pressure, severe neurological sequelae, and development of immune reconstitution syndrome, although the mortality rate is low. C. gattii VGII isolates may exhibit higher fluconazole MICs than other genotypes. Optimal therapeutic regimens are yet to be determined; in most cases, initial therapy with amphotericin B and 5-flucytosine is recommended.

Cryptococcus neoformans induces antimicrobial responses and behaves as a facultative intracellular pathogen in the non mammalian model Galleria mellonella

Cryptococcus neoformans is an encapsulated opportunistic fungal pathogen that is found in multiple niches in the environment and that can cause fatal meningoencephalitis in susceptible patients, mainly HIV+ individuals. Cryptococcus also infects environmental hosts such as nematodes, insects and plants. In particular, C. neoformans can kill the lepidopteran Galleria mellonella, which offers a useful tool to study microbial virulence and drug efficacy. Galleria mellonella immunity relies on innate responses based on melanization, accumulation of antimicrobial peptides, and cellular responses as phagocytosis or multicellular encapsulation. In this work we have investigated the immune response of G. mellonella during cryptococcal infection. We found that G. mellonella infected with C. neoformans had a high lytic activity in their hemolymph. This response was temperature- and capsule-dependent. During interaction with phagocytic cells, C. neoformans behaved as an intracellular pathogen since it could replicate within hemocytes. Non-lytic events were also observed. In contrast to Candida species, C. neoformans did not induce melanization of G. mellonella after infection. Finally, passage of C. neoformans through G. mellonella resulted in changes in capsule structure as it has been also reported during infection in mammals. Our results highlight that G. mellonella is an optimal model to investigate innate immune responses against C. neoformans.

Cryptococcus lacticolor sp. nov. and Rhodotorula oligophaga sp. nov., novel yeasts isolated from the nasal smear microbiota of Queensland koalas kept in Japanese zoological parks

A total of 515 yeast strains were isolated from the nasal smears of Queensland koalas and their breeding environments in Japanese zoological parks between 2005 and 2012. The most frequent species in the basidiomycetous yeast biota isolated from koala nasal passages was Cryptococcus neoformans, followed by Rhodotorula minuta. R. minuta was the most frequent species in the breeding environments, while C. neoformans was rare. Seven strains representing two novel yeast species were identified. Analyses of the 26S rDNA (LSU) D1/D2 domain and nuclear ribosomal DNA internal transcribed spacer region sequences indicated that these strains represent new species with close phylogenetic relationships to Cryptococcus and Rhodotorula. A sexual state was not found for either of these two novel yeasts. Key phenotypic characters confirmed that these strains could be placed in Cryptococcus and Rhodotorula. The names Cryptococcus lacticolor sp. nov. (type strain TIMM 10013(T) = JCM 15449(T) = CBS 10915(T) = DSM 21093(T), DDBJ/EMBL/Genbank Accession No.; AB375774 (ITS) and AB375775 (26S rDNA D1/D2 region), MycoBank ID; MB 802688, Fungal Barcoding Database ID; 3174), and Rhodotorula oligophaga sp. nov. (type strain TIMM 10017(T) = JCM 18398(T) = CBS 12623(T) = DSM 25814(T), DDBJ/EMBL/Genbank Accession No.; AB702967 (ITS) and AB702967 (26S rDNA D1/D2 region), MycoBank ID; MB 802689, Fungal Barcoding Database ID; 3175) are proposed for these new species.

Global Molecular Epidemiology of Cryptococcus neoformans and Cryptococcus gattii: An Atlas of the Molecular Types

Cryptococcosis is a fungal disease affecting more than one million people per year worldwide. The main etiological agents of cryptococcosis are the two sibling species Cryptococcus neoformans and Cryptococcus gattii that present numerous differences in geographical distribution, ecological niches, epidemiology, pathobiology, clinical presentation and molecular characters. Genotyping of the two Cryptococcus species at subspecies level supplies relevant information to understand how this fungus has spread worldwide, the nature of its population structure, and how it evolved to be a deadly pathogen. At present, nine major molecular types have been recognized: VNI, VNII, VNB, VNIII, and VNIV among C. neoformans isolates, and VGI, VGII, VGIII, and VGIV among C. gattii isolates. In this paper all the information available in the literature concerning the isolation of the two Cryptococcus species has been collected and analyzed on the basis of their geographical origin, source of isolation, level of identification, species, and molecular type. A detailed analysis of the geographical distribution of the major molecular types in each continent has been described and represented on thematic maps. This study represents a useful tool to start new epidemiological surveys on the basis of the present knowledge.