Cryptococcus neoformans in the koala (Phascolarctos cinereus): colonization by C n. var. gattii and investigation of environmental sources

Geographical distribution of the Cryptococcus gattii species complex: a systematic review

The taxonomy of the Cryptococcus gattii species complex continues to evolve, and has been divided into five pathogenic species. The objective of this systematic review was to summarise the geographical distribution of the C gattii species complex and the species within the C gattii species complex. We searched PubMed for articles related to human, animal, ecological, or laboratory-based studies of C gattii species complex isolates with traceable geographical origin published from January, 1970, until September, 2021. Having extracted their geographical origin, we used ArcMap to construct maps according to the highest degree of resolution allowed by their reported taxonomy, to reflect the most likely area of transmission on the basis of published reports of human isolates. 604 such articles were included in the study. This review indicated that although C gattii species complex isolates have been reported globally, understanding their heterogeneous geographical distribution by species can have implications for researchers and clinicians in formulating research questions and considering diagnostic quandaries.

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.

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.

The aetiology and clinical characteristics of cryptococcal infections in Far North Queensland, tropical Australia

Cryptococcal infections are an important cause of morbidity and mortality in tropical Australia. This retrospective audit was conducted to characterise the aetiology, temporospatial epidemiology, and clinical course of 49 cryptococcal infections in Far North Queensland between 1 January 1999 and 31 December 2019. Cryptococcus gattii was identified in 15/32 (47%) in whom it was possible to speciate the organism. Among these 15 patients, 13 (87%) had a rural residential address, 10 (67%) were Indigenous Australians and 11 (73%) presented during the May-November dry season. When compared to the 17 patients with Cryptococcus neoformans infection, patients with C. gattii were less likely to be immunocompromised (0/15 versus 8/17 (47%), p = 0.003). Neurosurgery was necessary in 5/15 C. gattii cases and 3/17 (18%) C. neoformans cases (p = 0.42). Outcomes were generally good with 42/49 (86%) cases—and 14/15 (93%) with C. gattii infection—surviving to hospital discharge. These positive outcomes are likely to be explained by the development of standardised treatment guidelines during the study period, low rates of comorbidity in the patients with C. gattii infection and access to liposomal amphotericin and neurosurgical support in the well-resourced Australian healthcare system.

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.

An analysis of the population of Cryptococcus neoformans strains isolated from animals in Poland, in the years 2015-2019

Fungi belonging to the Cryptococcus neoformans/C. gattii species complex (CNGSC) are pathogens causing severe infections in humans and animals, that for humans may result in a mortality rate ranging up to 70%. The CNGSC is divided into eight major molecular types, that may differ in their virulence and susceptibility. In order to fully understand the epidemiology of cryptococcosis, it is important to study the world distribution and population structure of these pathogens. The present study is the first presenting a population of strains isolated in Poland and one of the few using a multi-species animal group as a source of the specimen. The pathogen was present in 2.375% of the tested animals. The URA5-RFLP and MALDI-TOF MS analyses have revealed that the population consisted exclusively of C. neoformans strains, with a predominance of major molecular type VNIV (C. neoformans var. neoformans). The MALDI-TOF MS was used to perform the CNGSC strains identification on both the species and sub-species level. Despite the fact that the animals providing the specimens were not treated with 5-fluorocytosine, around 10% of the tested population presented MIC values exceeding 64 mg/L, indicating the existence of the 5-fluorocytosine-resistant strains in the environment.

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.

Comparing immunochromatography with latex antigen agglutination testing for the diagnosis of cryptococcosis in cats, dogs and koalas

Although the point-of-care cryptococcal antigen lateral flow assay (LFA) has revolutionized the diagnosis of cryptococcosis in human patients, to date there has been no large-scale examination of this test in animals. We therefore assessed the LFA in cats, dogs and koalas suspected of having cryptococcosis. In sum, 528 serum specimens (129 from cats, 108 from dogs, 291 from koalas) were tested using the LFA and one of two commercially available latex cryptococcal antigen agglutination test (LCAT) kits. The LCAT is a proven and well-accepted method in veterinary patients and therefore taken as the "gold standard" against which the LFA was compared. The LFA achieved a sensitivity of 92%, 100%, and 98% in cats, dogs, and koalas, respectively, with corresponding negative predictive values of 94%, 100%, and 98%. The specificity of the LFA was 81%, 84%, and 62% for cats, dogs, and koalas, respectively, with corresponding positive predictive values of 76%, 48%, and 69%. These findings suggest the most appropriate role for the LFA is as a screening test to rule out a diagnosis of cryptococcosis in cats, dogs, and koalas. Point-of-care accessibility makes it equally suited for use in the field and as a cage-side test in veterinary hospitals. The suboptimal specificity of the LFA makes it less suited to definitive confirmation of cryptococcosis in animals; therefore, all LFA-positive test results should be confirmed by LCAT testing. The discrepancy between these observations and the high specificity of the LFA in humans may reflect differences in the host-pathogen interactions amongst the species.

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.

Identification of the environmental source of infection for a domestic ferret with cryptococcosis

Cryptococcosis, caused by the Cryptococcus gattii and C. neoformans species complexes, is an environmentally acquired mycosis affecting a broad range of host species. Among 9 communally housed ferrets, a 5-y-old castrated male ferret domiciled in an outdoor enclosure in Sydney, Australia was diagnosed with sinonasal cryptococcosis. Clinical signs resolved during 18 mo of itraconazole therapy, but the ferret was eventually euthanized because of splenic hemangiosarcoma. At postmortem, microscopic foci of persistent cryptococcosis were detected. The diagnosis raised concerns that the owners and other ferrets were exposed to a common environmental source of infection, thus prompting an investigation. Soil samples, swabs of a hollow eucalypt log (used for behavioral enrichment), and nasal swabs from 8 asymptomatic ferrets were collected. Nasal exudate (obtained at diagnosis) and tissues (collected at postmortem) were available from the clinical case. Bird seed agar culture resulted in a heavy growth of Cryptococcus spp. from one environmental site (the log), one nasal swab, and nasal exudate and tissues from the clinical case. All other samples were culture-negative. Sub-cultured isolates from the log were a mixture of C. gattii molecular type VGI and C. neoformans molecular type VNI. Ferret isolates were a similar mixture of C. gattii VGI (all disease isolates) and C. neoformans VNI (nasal-colonizing isolate). Multilocus sequence typing further revealed the ferret isolates as identical to environmental isolates collected from the log, confirming the log as the source of clinical disease and nasal colonization. The log was removed to prevent further exposure to a high environmental load of Cryptococcus spp.

The mycobiome of Australian tree hollows in relation to the Cryptococcus gattii and C. neoformans species complexes

Cryptococcosis is a fungal infection caused by members of the Cryptococcus gattii and C. neoformans species complexes. The C. gattii species complex has a strong environmental association with eucalypt hollows (particularly Eucalyptus camaldulensis), which may present a source of infection. It remains unclear whether a specific mycobiome is required to support its environmental survival and growth. Conventional detection of environmental Cryptococcus spp. involves culture on differential media, such as Guizotia abyssinica seed agar. Next-generation sequencing (NGS)-based culture-independent identification aids in contextualising these species in the environmental mycobiome. Samples from 23 Australian tree hollows were subjected to both culture- and amplicon-based metagenomic analysis to characterize the mycobiome and assess relationships between Cryptococcus spp. and other fungal taxa. The most abundant genera detected were Coniochaeta, Aspergillus, and Penicillium, all being commonly isolated from decaying wood. There was no correlation between the presence of Cryptococcus spp. in a tree hollow and the presence of any other fungal genus. Some differences in the abundance of numerous taxa were noted in a differential heat tree comparing samples with or without Cryptococcus-NGS reads. The study expanded the known environmental niche of the C. gattii and C. neoformans species complexes in Australia with detections from a further five tree species. Discrepancies between the detection of Cryptococcus spp. using culture or NGS suggest that neither is superior per se and that, rather, these methodologies are complementary. The inherent biases of amplicon-based metagenomics require cautious interpretation of data through consideration of its biological relevance.

Disseminated Sporotrichosis in a Bilby (Macrotis lagotis)

A male bilby (Macrotis lagotis) was presented to the Murdoch University Veterinary Anatomical Pathology Service following humane destruction due to severe lethargy. The bilby was emaciated with a focal ulcerated skin lesion on the dorsal tail base. Multifocal to coalescing foci of pyogranulomatous and often necrotizing inflammation was present within multiple organs, including the tail wound, adrenal glands, kidneys, lungs, brain, testes, lymph nodes, heart, liver, spleen and salivary glands. Admixed were abundant intrahistiocytic and extracellular pleomorphic yeast (round, oval and cigar-shaped) up to 6 μm diameter, often with a thin clear halo and occasional narrow-based budding. The diagnosis of disseminated sporotrichosis was confirmed via culture and sequencing of the internal transcribed spacer region of the causative agent, Sporothrix schenckii sensu lato. The route of entry of infection was considered most likely to have been via cutaneous inoculation of the tail base wound. To the authors' knowledge, this report describes the first known case of sporotrichosis in a native Australian animal.

Multi-locus sequence typing as a tool to investigate environmental sources of infection for cryptococcosis in captive birds

A systematic investigation into environmental sources of infection was conducted at an Australian zoological park after cryptococcosis, caused by Cryptococcus gattii VGI, was diagnosed in a red-tailed black cockatoo (Calyptorhynchus banksii) residing in a large aviary with a diverse range of other avian species. A single tree with an extensive hollow was identified as the likely source of infection based on heavy culture of C. gattii VGI, multi-locus sequence typing and phylogenetic analysis of environmental and disease-related isolates. This led to the careful removal of the tree to reduce the risk of future cases of cryptococcosis in this aviary.

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.

Searching for clues for eighteen years: Deciphering the ecological determinants of Cryptococcus gattii on Vancouver Island, British Columbia

Cryptococcus gattii emerged on Vancouver Island in 1999 for unknown reasons, causing human and animal fatalities and illness. The apparent emergence of this fungus in another temperate area, this time in the Pacific Northwest, suggests the fungus may have expanded its ecological niche. Yet studies that directly examine the potential roles of climatic and land use changes on C. gattii are still lacking. We aim to summarize the existing global literature on the ecology of C. gattii, with particular focus on the gap in knowledge surrounding the potential effects of climatic and land use changes. We systematically reviewed English peer-reviewed literature on the ecological determinants of C. gattii. We included studies published from January 1970 through June 2016 and identified 56 relevant studies for our review. We identified environmental isolations of C. gattii from 18 countries, spanning 72 separate regions across six continents. Fifty-three tree species were associated with C. gattii, spanning 10 climate classifications and 36 terrestrial ecoregions. No studies directly tested the potential effects of climatic changes (including climatic oscillations and global climate change) on C. gattii, while only one study directly assessed those of land use change. To improve model predictions of current and future distributions of C. gattii, more focus is needed on the potential effects of climatic and land use changes to help decrease the public health risk. The apparent emergence of C. gattii in British Columbia is also an opportunity to explore the factors behind emerging infectious diseases in Canada and elsewhere.

A new method for studying cryptococcosis in a murine model using 99mTc-Cryptococcus gattii

Cryptococcus gattii is one of the etiologic agents of cryptococcosis, a systemic mycosis that occurs in healthy and immunosuppressed humans and animals worldwide. Primary pulmonary infection caused by C. gattii is usually followed by fungal dissemination to the central nervous system, resulting in high mortality rates. In this context, animal models of cryptococcosis are useful in the study of fungal pathogenesis and host response against the pathogen, and for testing novel therapeutic options. The most frequently applied method to study fungal dissemination from the lungs to other organs is by culturing tissues, which is not accurate for the detection and quantification of fungal load at early stages of the infection. To overcome this problem, the purpose of this study was to develop a new method for the quantification of Cryptococcus dissemination. One C. gattii strain was efficiently radiolabeled with technetium-99m (99mTc), without affecting viability of the cells. Further, the 99mTc-C. gattii (111 MBq) strain was used to infect mice by intratracheal and intravenous route for biodistribution studies. 99mTc-C. gattii was successfully used in detection of the yeast in the brain of mice 6 hours postinoculation, while the detection using colony forming units was possible only 24 hours postinfection. Our results provided an alternative method that could be applied in further investigations regarding the efficacy of antifungals, fungal virulence, and host-pathogen interactions.

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.

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.

The spectrum of fungi that infects humans

Few among the millions of fungal species fulfill four basic conditions necessary to infect humans: high temperature tolerance, ability to invade the human host, lysis and absorption of human tissue, and resistance to the human immune system. In previously healthy individuals, invasive fungal disease is rare because animals' sophisticated immune systems evolved in constant response to fungal challenges. In contrast, fungal diseases occur frequently in immunocompromised patients. Paradoxically, successes of modern medicine have put increasing numbers of patients at risk for invasive fungal infections. Uncontrolled HIV infection additionally makes millions vulnerable to lethal fungal diseases. A concerted scientific and social effort is needed to meet these challenges.

Computed tomographic anatomy of the nasal cavity, paranasal sinuses and tympanic cavity of the koala

OBJECTIVE

To use cross-sectional imaging (helical computed tomography (CT)) combined with conventional anatomical dissection to define the normal anatomy of the nasal cavity and bony cavitations of the koala skull.

METHODS

Helical CT scans of the heads of nine adult animals were obtained using a multislice scanner acquiring thin slices reconstructed in the transverse, sagittal and dorsal planes. Subsequent anatomical dissection permitted confirmation of correct identification and further delineation of bony and air-filled structures visible in axial and multiplanar reformatted CT images.

RESULTS

The nasal cavity was relatively simple, with little scrolling of nasal conchae, but bony cavitations were complex and extensive. A rostral maxillary recess and ventral conchal, caudal maxillary, frontal and sphenoidal paranasal sinuses were identified and characterised. Extensive temporal bone cavitation was shown to be related to a large epitympanic recess.

CONCLUSIONS

The detailed anatomical data provided are applicable to future functional and comparative anatomical studies, as well as providing a preliminary atlas for clinical investigation of conditions such as cryptococcal rhinosinusitis, a condition more common in the koala than in many other species.

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.

Molecular epidemiology of Italian clinical Cryptococcus neoformans var. grubii isolates

Cryptococcus neoformans variety grubii is the major etiological agent of cryptococcal meningitis in both immunocompromised and immunocompetent patients. The current PCR-based molecular methods are not sufficient to discriminate among the different populations of this yeast. Therefore, the aim of the present study was to investigate the genotypes of the Italian clinical C. neoformans var. grubii isolates by multilocus sequence typing (MLST). A total of 53 isolates, each representative of a single case, were studied. Genotyping was performed using the ISHAM Cryptococcus MLST consensus scheme and the results were compared to the publically available global C. neoformans var. grubii MLST dataset. A total of 16 genotypes were identified; 14 were new genotypes, one was identical to sequence type (ST) ST81, which had been previously reported from Thailand, and one to ST23 already identified in Uganda, the USA and Korea. Sequence type ST61 was the most numerous, including 16 isolates. Network phylogenetic analysis showed that the Italian isolates could be divided into at least three clusters with similarities with those recovered in Africa, Asia and Americas. Distribution of the STs among the isolates could not be correlated to the hospital in which they were recovered or to the HIV status of the patients. The majority of the isolates belonged to the molecular type VNI; three belonged to the rare molecular type VNII and one to the VNB group, which until now had not been described in Europe. The results reveal that the Italian C. neoformans var. grubii population presents a distinct variability, displaying a high number of new genotypes, and probably recombines sexually.

Epidemiology and molecular characterization of Cryptococcus neoformans isolated from pigeon excreta in Mazandaran province, northern Iran

OBJECTIVE

The aims of this study were to verify the presence of Cryptococcus neoformans in pigeon excreta in Mazandaran province, Iran, to identify the varieties of the C. neoformans isolates using D1/D2 and IGS sequencing, and determining the presence of the two mating types: α and a.

MATERIALS AND METHODS

Four hundred pigeon droppings samples were collected from 15 different cities in Mazandaran province over a period of 1 year (February 2010-March 2011). Identification of C. neoformans was determined based on growing brown colonies on Niger seed agar (NSA) and biochemical characteristics. We used MATα and MATa specific primers for determining mating type and sequence analysis of the D1/D2 and intergenic spacer regions were done.

RESULTS

Out of 400 samples, 20 samples (5%) were positive for C. neoformans and all of these isolates were α mating types. Sequence analysis of polymerase chain reaction (PCR) amplicons of D1/D2 regions revealed that all of the isolates were C. neoformans var. grubii except two isolates that were C. neoformans var. neoformans.

CONCLUSION

Our results reinforced that the pigeon excreta is a favorable environment rich in nitrogen and supports the growth of C. neoformans and the pigeon could play an important role in spread of this organism.

Cryptococcus gattii: where do we go from here?

Infections caused by the emerging pathogen Cryptococcus gattii are increasing in frequency in North America. During the past decade, interest in the pathogen has continued to grow, not only in North America but also in other areas of the world where infections have recently been documented. This review synthesizes existing data and raises issues that remain to be addressed.

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

Cryptococcosis is an important systemic mycosis caused by members of the Cryptococcus neoformans species complex. This disease is potentially fatal in various animals, including koalas. We describe the long-term surveillance and treatment of subclinical cryptococcosis and nasal colonization of koalas by Cryptococcus neoformans and C. gattii. Of the 15 animals investigated through the use of samples obtained by nasal swabs, antigen titer measurements, and pathologic examination, C. neoformans was found associated with nine koalas and C. gattii with one animal. Nine koalas showed subclinical disease and one clinical infections and antigenemia. Treatment with fluconazole, itraconazole and amphotericin B upon detection of C. neoformans or C. gattii was not effective. The results of the present study showed that C. neoformans was the predominant species isolated from the nasal swab samples and the fungus might have naturally become associated with the koalas' nasal cavities at Kanazawa Zoological Gardens. The unclear treatment effectiveness might have been caused by a shorter treatment period that is routinely used and unstable itraconazole absorption. This investigation also underscores the need for identifying effective treatment regimens for subclinical cryptococcosis and efficient measures for eradicating C. neoformans and C. gattii in koalas.

Cryptococcus neoformans isolation from swallow (Hirundo rustica) excreta in Iran

Cryptococcus neoformans is an encapsulated yeast that can cause cryptococcosis, a life-threatening infection that mainly occurs in immunocompromised patients. The major environmental sources of C. neoformans have been shown to be soil contaminated with avian droppings. In the present study, we evaluated the isolation of C. neoformans from swallow (Hirundo rustica) excreta in two northern cities of Iran. Ninety-seven swallow droppings were evaluated and 498 yeast-like colonies were isolated and identified as Rhodotorula spp. (62.8%), Candida spp. (28.5%)and C. neoformans (8.7%). Cryptococcus neoformans was isolated from 5/97 (5.2%) of collected samples. Min-Max colony forming units (CFU) per one gram for the positive samples were 3-10 C. neoformans colonies. The total mean CFU per one gram for the positive samples was 4.8. The results of this study demonstrate that excreta of swallow may harbor different species of potentially pathogenic yeasts, mainly C. neoformans, and may be capable of disseminating these fungi in the environment.

Microbial Pathogens in the Fungal Kingdom

The fungal kingdom is vast, spanning ~1.5 to as many as 5 million species diverse as unicellular yeasts, filamentous fungi, mushrooms, lichens, and both plant and animal pathogens. The fungi are closely aligned with animals in one of the six to eight supergroups of eukaryotes, the opisthokonts. The animal and fungal kingdoms last shared a common ancestor ~1 billion years ago, more recently than other groups of eukaryotes. As a consequence of their close evolutionary history and shared cellular machinery with metazoans, fungi are exceptional models for mammalian biology, but prove more difficult to treat in infected animals. The last common ancestor to the fungal/metazoan lineages is thought to have been unicellular, aquatic, and motile with a posterior flagellum, and certain extant species closely resemble this hypothesized ancestor. Species within the fungal kingdom were traditionally assigned to four phyla, including the basal fungi (Chytridiomycota, Zygomycota) and the more recently derived monophyletic lineage, the dikarya (Ascomycota, Basidiomycota). The fungal tree of life project has revealed that the basal lineages are polyphyletic, and thus there are as many as eight to ten fungal phyla. Fungi that infect vertebrates are found in all of the major lineages, and virulence arose multiple times independently. A sobering recent development involves the species Batrachochytrium dendrobatidis from the basal fungal phylum, the Chytridiomycota, which has emerged to cause global amphibian declines and extinctions. Genomics is revolutionizing our view of the fungal kingdom, and genome sequences for zygomycete pathogens (Rhizopus, Mucor), skin-associated fungi (dermatophytes, Malassezia), and the Candida pathogenic species clade promise to provide insights into the origins of virulence. Here we survey the diversity of fungal pathogens and illustrate key principles revealed by genomics involving sexual reproduction and sex determination, loss of conserved pathways in derived fungal lineages that are retained in basal fungi, and shared and divergent virulence strategies of successful human pathogens, including dimorphic and trimorphic transitions in form. The overarching conclusion is that fungal pathogens of animals have arisen repeatedly and independently throughout the fungal tree of life, and while they share general properties, there are also unique features to the virulence strategies of each successful microbial pathogen.

Clonality and α-a recombination in the Australian Cryptococcus gattii VGII population--an emerging outbreak in Australia

BACKGROUND

Cryptococcus gattii is a basidiomycetous yeast that causes life-threatening disease in humans and animals. Within C. gattii, four molecular types are recognized (VGI to VGIV). The Australian VGII population has been in the spotlight since 2005, when it was suggested as the possible origin for the ongoing outbreak at Vancouver Island (British Columbia, Canada), with same-sex mating being suggested as the driving force behind the emergence of this outbreak, and is nowadays hypothesized as a widespread phenomenon in C. gattii. However, an in-depth characterization of the Australian VGII population is still lacking. The present work aimed to define the genetic variability within the Australian VGII population and determine processes shaping its population structure.

METHODOLOGY/PRINCIPAL FINDINGS

A total of 54 clinical, veterinary and environmental VGII isolates from different parts of the Australian continent were studied. To place the Australian population in a global context, 17 isolates from North America, Europe, Asia and South America were included. Genetic variability was assessed using the newly adopted international consensus multi-locus sequence typing (MLST) scheme, including seven genetic loci: CAP59, GPD1, LAC1, PLB1, SOD1, URA5 and IGS1. Despite the overall clonality observed, the presence of MATa VGII isolates in Australia was demonstrated for the first time in association with recombination in MATα-MATa populations. Our results also support the hypothesis of a "smouldering" outbreak throughout the Australian continent, involving a limited number of VGII genotypes, which is possibly caused by a founder effect followed by a clonal expansion.

CONCLUSIONS/SIGNIFICANCE

The detection of sexual recombination in MATα-MATa population in Australia is in accordance with the natural life cycle of C. gattii involving opposite mating types and presents an alternative to the same-sex mating strategy suggested elsewhere. The potential for an Australian wide outbreak highlights the crucial issue to develop active surveillance procedures.

Immunoproteomic approach to elucidating the pathogenesis of cryptococcosis caused by Cryptococcus gattii

Cryptococcosis caused by Cryptococcus gattii is a devastating disease of immunocompetent hosts with an incompletely understood pathogenesis. Utilizing an immunoproteomic approach in a naturally occurring koala model of disease, a number of key proteins and pathways are identified in the early and late pathogenesis of cryptococcosis for the first time. In particular, the thioredoxin system appears important in the pathogenesis of cryptococcosis caused by C. gattii VGII.

The emergence of Cryptococcus gattii in British Columbia and the Pacific Northwest

An unprecedented emergence of cryptococcal infections in animals and otherwise healthy humans was recognized in 1999 on the east coast of Vancouver Island, British Columbia. Unexpectedly, these infections were caused by Cryptococcus gattii, a species closely related to the AIDS-associated fungal pathogen Cryptococcus neoformans. Human cases have continued over the past 8 years and now total approximately 170 with eight deaths. Extensive environmental sampling, coupled with detailed molecular typing of isolates, revealed areas of permanent and transient colonization with primarily three genotypes of the fungus. C. gattii was found in air, soil, water, and in association with numerous tree species. Importantly, there is solid evidence for human-mediated dispersal of the pathogen, and C. gattii has now been detected in the environment on the mainland of British Columbia and in the Pacific Northwest. Associated animal and human cases are now being reported and further spread of the pathogen may be inevitable.

Attempted isolation of Blastomyces dermatitidis from the nares of dogs: Northern Wisconsin, USA

The nasal cavities of domestic animals may concentrate and allow isolation of environmentally acquired fungal pathogens. We obtained two swabs each from the nares of 110 asymptomatic, physically normal dogs from a veterinary practice in Eagle River, WI, USA, an area highly endemic for blastomycosis. Four of the tested dogs had past histories of blastomycosis. Samples were placed on yeast extract phosphate (Smith's) media at 20 degrees C but growth of Blastomyces dermatitidis was not observed on any of the 220 cultures. One dog developed cytologically confirmed B. dermatitidis one month following culture of its samples, 6 died of other illnesses, while 91/103 dogs completing follow-up have remained asymptomatic for three years. We did not observe nasal colonization by B. dermatitidis in this population of dogs with potential for sniffing and digging in an environment highly endemic for this fungus.

The expanding host tree species spectrum of Cryptococcus gattii and Cryptococcus neoformans and their isolations from surrounding soil in India

This study reports the widespread prevalence of Cryptococcus neoformans and Cryptococcus gattii in decayed wood inside trunk hollows of 14 species representing 12 families of trees and from soil near the base of various host trees from Delhi and several places in the Indian states of Uttar Pradesh, Haryana, Tamil Nadu and Chandigarh Union Territory. Of the 311 trees from which samples were obtained, 64 (20.5%) were found to contain strains of the C. neoformans species complex. The number of trees positive for C. neoformans var grubii (serotypeA) was 51 (16.3%), for C. gattii (serotype B) 24 (7.7%) and for both C. neoformans and C. gattii 11 (3.5%). The overall prevalence of C. neoformans species complex in decayed wood samples was 19.9% (111/556). There was no obvious correlation between the prevalence of these two yeast species and the species of host trees. The data on prevalence of C. gattii (24%) and C. neoformans (26%) in soil around the base of some host trees indicated that soil is another important ecologic niche for these two Cryptococcus species in India. Among our sampled tree species, eight and six were recorded for the first time as hosts for C. neoformans var grubii and C. gattii, respectively. A longitudinal surveillance of 8 host tree species over 0.7 to 2.5 years indicated long term colonization of Polyalthia longifolia, Mimusops elengi and Manilkara hexandra trees by C. gattii and/or C. neoformans. The mating type was determined for 153 of the isolates, including 98 strains of serotype A and 55 of serotype B and all proved to be mating type alpha (MAT alpha). Our observations document the rapidly expanding spectrum of host tree species for C. gattii and C. neoformans and indicate that decayed woods of many tree species are potentially suitable ecological niches for both pathogens.

Virulence in Cryptococcus species

Cryptococcus neoformans and Cryptococcus gattii are the cause of life-threatening meningoencephalitis in immunocompromised and immunocompetent individuals respectively. The increasing incidence of cryptococcal infection as a result of the AIDS epidemic, the recent emergence of a hypervirulent cryptococcal strain in Canada and the fact that mortality from cryptococcal disease remains high have stimulated intensive research into this organism. Here we outline recent advances in our understanding of C. neoformans and C. gattii, including intraspecific complexity, virulence factors, and key signaling pathways. We discuss the molecular basis of cryptococcal virulence and the interaction between these pathogens and the host immune system. Finally, we discuss future challenges in the study and treatment of cryptococcosis.

Screening of antigenemia and isolation of Cryptococcus neoformans and C. gattii from cloaca and crop of birds in the state of Paraná, Brazil

Cryptococcus neoformans and C. gattii are associated with dry bird excreta but rarely recovered from birds' digestive tract. The objective of the present study was (1) to verify the existence of C. neoformans and C. gattii in crop and cloaca of wildlife and captivity birds hypothesizing about a possible primary source of this yeast in the excreta, and (2) to determine the fungi's invasive capability in avian species through latex agglutination. For that purpose, 172 cloacal and 77 crop samples of domestic pigeon, Passerine, and Psittacine birds were collected. None of these samples was positive, suggesting that the yeast is not saprobiotic in the digestive tract of these birds. Only one out of 82 serum samples collected from pigeons and Psittacine birds was positive (title 1:2) showing that Cryptococcus sp. probably has a low invasive capability in birds, and is thus considered only a dry excreta colonizer.

Evidence of recombination in mixed-mating-type and alpha-only populations of Cryptococcus gattii sourced from single eucalyptus tree hollows

Disease caused by the pathogenic yeast Cryptococcus gattii begins with the inhalation of an infectious propagule. As C. gattii is heavily encapsulated, this propagule is most likely to be a basidiospore. However, most C. gattii strains are infertile in laboratory crosses, and population studies indicate that recombination and dispersal are very restricted. In addition, strains of the alpha mating type predominate, which would not be expected in a mating population. C. gattii comprises four genetically distinct molecular genotypes, designated VGI to VGIV. C. gattii molecular type VGI has a strong association with Eucalyptus camaldulensis and can be found in high numbers in E. camaldulensis hollows. Previous work on isolates obtained from E. camaldulensis suggested that environmental populations of C. gattii are highly fragmented, have limited ability to disperse, and are confined to individual tree hollows. In the current study, we examined large numbers of isolates from three separate hollows for evidence of recombination. In two hollows, the alpha and a mating types were present in approximately equal numbers. The third hollow had alpha cells only and was from a region where a isolates have never been found. Statistical analysis of multilocus genotypes revealed recombining subpopulations in the three Eucalyptus hollows. Recombination was equally present in the alpha-a and alpha-only populations. This is consistent with recent studies that have found evidence suggestive of alpha-alpha mating in C. gattii and Cryptococcus neoformans and raises the possibility this may be a widespread phenomenon, allowing these fungi to recombine despite a paucity of a mating partners.

Ecological niche of Cryptococcus neoformans var. grubii and Cryptococcus gattii in decaying wood of trunk hollows of living trees in Jabalpur City of Central India

Cryptococcus neoformans var. grubii and C. gattii were repeatedly isolated from decaying wood of trunk hollows in living trees growing in Jabalpur City in Central India. The isolation of C. gattii has been reported from decayed wood inside trunk hollow of Tamarindus indica (15.6%), Mangifera indica (2.2%), Pithecolobium dulce (12.5%), Syzygium cumini (14%), and one from bark of S. cumini. C. n. var. grubii was isolated from decaying wood debris of T. indica (4.4%), M. indica (13.3%), Terminalia arjuna (25%), S. cumini (2%), Cassia fistula (4.5%), and two from bark of S. cumini. The two species [corrected] never co-occurred in the same hollow. C. gattii [corrected] isolates belonged to serotype B. [corrected] The data strongly supported the colonization of the pathogen in decaying wood hollow of all six-tree species. Evidence of this was found by repeated isolation up to 820 days. P. dulce is being reported for the first time as natural habitat of C. gattii and T. arjuna and C. fistula as natural habitat for C. n. var. grubii. M. indica is being reported for the second time as the natural habitat of both species [corrected] (C. n. var. grubii and C. gattii). The population density of these pathogens from decaying wood debris of various tree species ranged between 0.5 x 10(3) cells/g and 6 x 10(5) cells/g. The seasonal variation has been seen in isolation of these pathogens. [corrected] Our result further reinforce the recently emerging evidence that the natural habitat of C. n. var. grubii and C. gattii is more generalized.

Characterization of environmental sources of the human and animal pathogen Cryptococcus gattii in British Columbia, Canada, and the Pacific Northwest of the United States

Cryptococcus gattii has recently emerged as a primary pathogen of humans and wild and domesticated animals in British Columbia, particularly on Vancouver Island. C. gattii infections are typically infections of the pulmonary and/or the central nervous system, and the incidence of infection in British Columbia is currently the highest reported globally. Prior to this emergence, the environmental distribution of and the extent of colonization by C. gattii in British Columbia were unknown. We characterized the environmental sources and potential determinants of colonization in British Columbia. C. gattii was isolated from tree surfaces, soil, air, freshwater, and seawater, and no seasonal prevalence was observed. The C. gattii concentrations in air samples were significantly higher during the warm, dry summer months, although potentially infectious propagules (<3.3 microm in diameter) were present throughout the year. Positive samples were obtained from many different areas of British Columbia, and some locations were colonization "hot spots." C. gattii was generally isolated from acidic soil, and geographic differences in soil pH may influence the extent of colonization. C. gattii soil colonization also was associated with low moisture and low organic carbon contents. Most of the C. gattii isolates recovered belonged to the VGIIa genetic subtype; however, sympatric colonization by the VGIIb strain was observed at most locations. At one sampling site, VGIIa, VGIIb, VGI, and the Cryptococcus neoformans serotype AD hybrid all were coisolated. Our findings indicate extensive colonization by C. gattii within British Columbia and highlight an expansion of the ecological niche of this pathogen.

Clinical and environmental isolates of Cryptococcus gattii from Australia that retain sexual fecundity

Cryptococcus gattii is a primary pathogenic yeast that causes disease in both animals and humans. It is closely related to Cryptococcus neoformans and diverged from a common ancestor approximately 40 million years ago. While C. gattii has a characterized sexual cycle dependent upon a dimorphic region of the genome known as the MAT locus, mating has rarely been observed in this species. In this study, we identify for the first time clinical (both human and veterinary) and environmental isolates from Australia that retain sexual fecundity. A collection of 120 isolates from a variety of geographic locations was analyzed for molecular type, mating type, and the ability to develop mating structures when cocultured with fertile tester strains. Nine isolates produced dikaryotic filaments with paired nuclei, fused clamp connections, and basidiospores. DNA sequence analysis of three genes (URA5, the MATalpha-specific SXI1alpha gene, and the MATa-specific SXI2a gene) revealed little or no variability in URA5 and SXI2a, respectively. However across the 108 MATalpha strains sequenced, the SXI1alpha gene was found to exist as 11 different alleles. Phylogenetic analysis found most variation to occur in the more fertile genotypes. Although some lineages of Australian C. gattii have retained the ability to mate, the majority of isolates were sterile, suggesting that asexuality is the dominant mode of propagation in these populations.

Isolation and characterization of Cryptococcus neoformans varieties recovered from natural sources in Bogotá, Colombia, and study of ecological conditions in the area

Cryptococcus neoformans, the etiological agent of cryptococcosis, has been associated with avian droppings and certain trees in different countries, including Colombia. C neoformans environmental isolates were obtained in urban areas in Bogotá, Colombia, and the strains recovered were phenotypically characterized. Attempts to determine the ecological conditions (micro- and macroclimatic) possibly related to their habitat were also undertaken. Four hundred and eighty samples from bark, soil around trunk bases, and detritus inside hollows of 32 trees were collected in three urban areas during a 5-month period, as well as 89 avian droppings samples from different places. Of plant samples, 6.7% collected from nine tree species yielded C. neoformans var. gattii, serotype B strains in 99% of the cases, and C. neoformans var. grubii, serotype A in 1%. The yeast was more frequently recovered from bark than from soil or detritus inside hollows, and from trees with hollows or rotted wood rather than from trees in which birds nest. C. neoformans was present with higher frequency and density in the rainy season than in the dry season; we found that slightly higher temperature and humidity values of the microhabitat, as compared to those of the environment, favored fungal occurrence, but the phenological state of the tree did not. Of dropping samples, 7.9% yielded C. neoformans strains, all of them C. neoformans var. grubii, serotype A. The yeast was obtained more frequently from dry droppings than from moist ones, but neither the sunlight exposure nor the site of collection of samples was correlated with this occurrence. Population density was significantly higher in droppings than in tree samples. Under laboratory conditions, isolates of different serotype showed similar capsular sizes. Water content and pH ranges were wide and did not show any significant difference between positive and negative samples.

Retrospective study of feline and canine cryptococcosis in Australia from 1981 to 2001: 195 cases

A retrospective study of 155 cats and 40 dogs diagnosed with cryptococcosis between 1981 and 2001 was undertaken. Age, sex, breed, clinical findings, feline immunodeficiency virus and feline leukaemia virus status (in cats), species of Cryptococcus causing disease and region of domicile were recorded. Associations between variables were tested. Male and female cats were affected equally. Age ranged from 1 to 16 years, with a preponderance of cats aged between 2 and 3 years. Siamese, Himalayan and Ragdoll breeds were over-represented. Rural cats were more frequently infected with Cryptococcus gattii. Retroviral infection was not identified as a predisposing condition and was not correlated with either species of Cryptococcus or physical findings. Most cats had signs of nasal cavity infection, which was typically localised for a substantial period before invasion of adjacent structures or dissemination. Male and female dogs were affected equally. A marked preponderance of young, large breed dogs was noted. Border Collies, Boxers, Dalmatians, Dobermann Pinschers, Great Danes and German Shepherds were over-represented. Cryptococcus species involved was not affected by place of domicile. Although nasal cavity involvement was important, the canine cohort had a greater propensity to develop secondary central nervous system involvement and disseminated disease than feline cases. There were no clinical findings in either cats or dogs which could be reliably used to distinguish disease caused by Cryptococcus neoformans variety grubii from disease caused by Cryptococcus gattii. Both Cryptococcus species appear to be primary pathogens of cats and dogs, with the upper respiratory tract presumed to be the predominant primary site of inoculation in most but not all cases.