The first reported case of central venous catheter-related fungemia caused by Cryptococcus liquefaciens

An Unusual High Prevalence of Cryptococcus (Naganishia) diffluens Colonization in Neonates Hospitalized in a Referral Neonatal Intensive Care Unit

BACKGROUND

Although the Candida species continue to be the most frequent colonizer of neonatal skin, a clear increase of colonization due to rare yeast-like fungi has been reported. In this study, we report an unusual high prevalence of Cryptococcus diffluens colonization in neonates admitted to the neonatal intensive care unit (NICU) over a 1-month period.

METHODS

From January 2020 to June 2021, the study included all neonates who were admitted to the NICU of Bu Ali Sina Hospital at least 28 days old. Skin swabs from different anatomical areas were collected. Sampling was done 3 times/week. Each sample was inoculated into Sabouraud Dextrose Agar containing chloramphenicol and CHROMagar Candida, separately. The plates were incubated at 30 °C and 35 °C, respectively. Identification of the isolates was molecularly confirmed. In vitro antifungal susceptibility testing of the isolates was performed against different antifungal agents using the Clinical Laboratory Standards Institute protocol.

RESULTS

Among 1026 samples collected from 78 neonates, 213 yeast isolates were recovered, of which the Candida species were the most common (77.5%), followed by C. diffluens (16.9%). During the study, 55 isolated yeasts were collected from December 26, 2020, to January 26, 2021, of which 65.5% were C. diffluens , while Candida spp. constituted 100% and 98.3% of the isolates before and after this period, respectively. The most frequent sources of C. diffluens were genital regions (27.8%). Of 36 C. diffluens isolates, 13.9%, 22.2%, 52.8%, and 83.3% were non-wild type to fluconazole, amphotericin B, itraconazole and 5-flucytosine, respectively.

CONCLUSIONS

We reported for the first time an unusual high prevalence of C. diffluens colonization in neonates hospitalized in NICU. Our findings also showed the high minimum inhibitory concentration of amphotericin B and 5-flucytosine against C. diffluens .

First report of environmental isolation of Cryptococcus and Cryptococcus-like yeasts from Boyacá, Colombia

The Cryptococcus genus comprises more than 100 species, of which C. neoformans and C. gattii are the leading cause of cryptococcosis. The distribution of C. gattii and C. neoformans species complexes has been extensively studied and widely reported globally. Other species such as Naganishia albida, Papiliotrema laurentii, and Papiliotrema flavescens have been reported as pathogenic yeasts. Since there are no reports of environmental isolation in the Boyacá region (Colombia), this study aimed to isolate and characterize Cryptococcus and Cryptococcus-like yeasts from pigeon feces, Eucalyptus, and olive trees distributed in the municipalities of Tunja and Ricaute Alto. The environmental data was recovered, and the isolations obtained were identified by microscopy, biochemical test, MALDI-TOF MS, URA5-RFLP, and sequencing of the ITS and LSU loci. For the 93 pigeon dropping samples collected in Tunja, 23 yielded to C. neoformans, 3 to N. globosa, 2 N. albida and 1 to P. laurentii. Of the 1188 samples collected from olive trees, 17 (1.43%) positive samples were identified as C. gattii species complex (4), C. neoformans species complex (2), P. laurentii (3), N. albida (2), N. globosa (5) and P. flavescens (1). Likewise, specimens of C. neoformans presented molecular type VNI and molecular type VNII; for C. gattii the molecular types found were VGIII and one VGIV by URA5-RFLP but VGIII by MALDI-TOF and sequencing of the ITS and LSU. Therefore, it can be concluded that the species of Cryptococcus, Naganishia and Papiliotrema genera, are present in the environment of Boyacá, and show a predilection for climate conditions that are typical of this region.

Cryptococcus liquefaciens isolated from the hand of a healthcare professional in a neonatal intensive care unit

Fungal infections are responsible for high morbidity and mortality in neonatal patients, especially in premature newborns. Infections in neonates caused by Cryptococcus spp. are rare, but it has occurred in an immunocompromised population. This study aims to describe the isolation of Cryptococcus liquefaciens from the hands of a health professional in a neonatal intensive care unit, and to evaluate the production of biofilm and virulence factors and susceptibility to antifungals. Antifungal susceptibility tests were performed according to Clinical and Laboratory Standard Institute document M27-A3. Thermotolerance virulence factors and DNase, phospholipase, proteinase, and hemolytic activities were verified through phenotypic tests; biofilm was evaluated by determining the metabolic activity and biomass. The isolate did not produce any of the tested enzymes and was susceptible to all antifungals (amphotericin B, fluconazole, and micafungin). The growth at 37 °C was very weak; however, the isolate showed a strong biomass production and low metabolic activity. This is the first report of C. liquefaciens isolated from the hands of a health professional. The isolate did not express any of the studied virulence factors in vitro, except for the low growth at 37 °C in the first 48 h, and the strong production of biofilm biomass. Cryptococcus liquefaciens can remain in the environment for a long time and is a human pathogen because it tolerates temperature variations. This report draws attention to the circulation of rare species in critical locations, information that may help in a fast and correct diagnosis and, consequently, implementation of an appropriate treatment.

Seven years of progress in determining fungal diversity and characterization of fungi isolated from the Japanese Experiment Module KIBO, International Space Station

The International Space Station (ISS) is a closed facility that orbits the earth carrying not only its crew but also microorganisms. We have participated in microbiota analysis projects for the Japanese Experiment Module KIBO (ISS; operations nomenclature: Microbe-I, II, III, and IV) and were in charge of fungal screening. The interior of KIBO was sampled using swabs and microbe detection sheets (MDSs) for fungal detection. The dominant genera obtained by culture were Aspergillus and Penicillium. DNA analyses of the fungal biota using a clone library showed that KIBO was dominated by Malassezia, a fungal inhabitant of human skin. Three fungal species, Aspergillus sydowii, Penicillium palitans, and Rhodotorula mucilaginosa, which grew under microgravity in KIBO were observed under a field emission-scanning electron microscope on the ground. No novel phenotypic characteristics were noted. The results of antifungal susceptibility testing of all isolates did not differ significantly from previous reports of corresponding fungi. In Microbe-I (August 2009), MDSs were culture negative, while in the next stages the CFU of MDSs were 10 for Microbe-II (February 2011), 24 for Microbe-III (October 2012), and 151 for Microbe-IV (February 2015). These results indicated that fungi inside KIBO are increasing and expanding over time, and therefore continuous surveillance is crucial.

Comparison of Cryptococcus gattii/neoformans Species Complex to Related Genera (Papiliotrema and Naganishia) Reveal Variances in Virulence Associated Factors and Antifungal Susceptibility

Cryptococcosis is an infectious disease of worldwide distribution, caused by encapsulated yeasts belonging to the phylum Basidiomycota. The genus Cryptococcus includes several species distributed around the world. The C. gattii/neoformans species complex is largely responsible for most cases of cryptococcosis. However, clinical series have been published of infections caused by Papiliotrema (Cryptococcus) laurentii and Naganishia albida (Cryptococcus albidus), among other related genera. Here, we examined the pathogenic potential and antifungal susceptibility of C. gattii/neoformans species complex (clades I and II) and related genera (Papiliotrema and Naganishia) isolated from environmental and clinical samples. P. laurentii (clade III), N. liquefasciens/N. albidosimilis (clade IV); and N. adeliensis/N. albida (clade V) strains produced higher levels of phospholipase and hemolysins, whereas the C. gattii/neoformans species complex strains (clades I and II) had markedly thicker capsules, produced more biofilm biomass and melanin, which are known virulence attributes. Interestingly, 40% of C. neoformans strains (clade II) had MICs above the ECV established for this species to amphotericin B. Several non-C. gattii/neoformans species complex (clades III to V) had MICs equal to or above the ECVs established for C. deuterogattii and C. neoformans for all the three antifungal drugs tested. Finally, all the non-C. gattii/neoformans clinical isolates (clades III to V) produced more melanin than the environmental isolates might reflect their particularly enhanced need for melanin during in vivo protection. It is very clear that C. gattii/neoformans species complex (clades I and II) strains, in general, show more similar virulence phenotypes between each other when compared to non-C. gattii/neoformans species complex (clades III to V) isolates. These observations together with the fact that P. laurentii and Naganishia spp. (clades III to V) strains were collected from the outside of a University Hospital, identify features of these yeasts important for environmental and patient colonization and furthermore, define mechanisms for infections with these uncommon pathogens.

Infections due to Rare Cryptococcus Species. A Literature Review

Infections due to rare Cryptococcus species (other than C. neoformans species complex, C. gattii species complex, C. albidus or C. laurentii) are barely reported. The aim of this work is to present a comprehensive literature review of all the papers describing infections due to these species referenced in the main databases (PubMed/MEDLINE, ScienceDirect, Scopus, and Google Scholar). Clinical and epidemiological data together with laboratory findings (identification and antifungal susceptibility) of each isolate were analyzed. Fifty-eight cryptococosis due to rare species were described in 46 papers between 1934-2018. These reports included 16 rare Cryptococcus spp. that were generally associated with nervous system infections and fungemias. Some species are non-capsulated and are not able to grow at 37 °C. Few species were identified by commercially available methods, making internal transcriber spacer (ITS) and D1/D2 regions sequencing mandatory. The most potent antifungal was amphotericin B (although some species showed high MIC values). The studied strains showed high MICs values to 5-fluorocytosine (all >64 µg/mL), echinocandins (all >8 µg/mL), and fluconazole (>80% of the MICs >4 µg/mL). Due to the scarcity of the data and the absence of guidelines for the treatment of these infections, this review could be informative and could help in the diagnosis and treatment of these infections.

Cryptococcus Species Other Than Cryptococcus neoformans and Cryptococcus gattii: Are They Clinically Significant?

Background

Cryptococcus spp is a major cause of opportunistic infections in immunocompromised patients, primarily due to Cryptococcus neoformans and Cryptococcus gattii. There are occasional reports of other Cryptococcus species causing invasive human disease. However, their epidemiology and clinical significance are not fully defined. We sought to describe cases with cultures positive for Cryptococcus species other than C neoformans and C gattii.

Methods

A retrospective descriptive analysis of clinical and laboratory data of patients with cultures growing Cryptococcus species other than C neoformans and C gattii from November 2011 to February 2019 was performed. Three Mayo Clinic sites in Arizona, Florida, and Minnesota were included.

Results

From 176 cases with a culture growing Cryptococcus spp, 54 patients (30%) had a culture for Cryptococcus other than C neoformans and C gattii in the study time frame. The most common species were Cryptococcus magnus, Cryptococcus laurentii, and Cryptococcus ater. The organisms were isolated and identified in culture of bronchoalveolar lavage (11), skin (11), urine (7), oral (4), sinus (3), intraoperative soft tissue (3), sputum (2), synovial fluid (2), cerebrospinal fluid (2), and intravenous catheter (2), among others (7).

Only 8 (15%) cases were considered to be potentially pathogenic, with 1 case of invasive disease. Antifungal treatment was fluconazole, itraconazole, and griseofulvin, for a mean systemic antifungal duration of 42 days.

Conclusions

This large series of patients with Cryptococcus spp other than C neoformans and C gattii suggests that these species rarely cause clinically significant infection in humans. Only 1 case of invasive disease was found.

Pulmonary cryptococcosis: A review of pathobiology and clinical aspects

Pulmonary cryptococcosis is an important opportunistic invasive mycosis in immunocompromised patients, but it is also increasingly seen in immunocompetent patients. The main human pathogens are Cryptococcus neoformans and C. gattii, which have a worldwide distribution. In contrast to cryptococcal meningitis, pulmonary cryptococcosis is still underdiagnosed because of limitations in diagnostic tools. It can mimic lung cancer, pulmonary tuberculosis, bacterial pneumonia, and other pulmonary mycoses both clinically and radiologically. Pulmonary nodules are the most common radiological feature, but these are not specific to pulmonary cryptococcosis. The sensitivity of culture of respiratory samples for Cryptococcus is poor and a positive result may also reflect colonisation. Cryptococcal antigen (CrAg) with lateral flow device is a fast and sensitive test and widely used on serum and cerebrospinal fluid, but sera from patients with pulmonary cryptococcosis are rarely positive in the absence of disseminated disease. Detection of CrAg from respiratory specimens might assist the diagnosis of pulmonary cryptococcosis but there are very few data. Molecular detection techniques such as multiplex reverse transcription polymerase chain reaction (RT-PCR) could also provide better sensitivity but these still require validation for respiratory specimens. The first line of treatment for pulmonary cryptococcosis is fluconazole, or amphotericin B and flucytosine for those with central nervous system involvement. Pulmonary cryptococcosis worsens the prognosis of cryptococcal meningitis. In this review, we summarize the biological aspects of Cryptococcus and provide an update on the diagnosis and management of pulmonary cryptococcosis.

The hidden pathogenic potential of environmental fungi

Invasive fungal infections are a growing threat to immunocompromised patients, highlighting the importance of monitoring fungal pathogens. Global warming (including climatic oscillations) may select for environmental species that have acquired thermotolerance, a key step toward pathogenesis to humans. Also, important virulence factors have developed in environmental fungi, because they are essential for yeast survival in the environment. Thus, fungi traditionally regarded as nonpathogenic to humans have virulence factors similar to those of their pathogenic relatives. Here, we highlight the emergence of saprophytic environmental fungi - including species of Cryptococcus, Aspergillus, Penicillium, Candida and Scedosporium - as new human pathogens. Emerging pathogens are, in some cases, resistant to the available antifungals, potentiating the threat of novel fungal diseases.

The environmental yeast Cryptococcus liquefaciens produces capsular and secreted polysaccharides with similar pathogenic properties to those of C. neoformans

Invasive fungal infections, including cryptococcosis, are a growing threat to immunocompromised patients. Although Cryptococcus neoformans and Cryptococcus gattii are the main agents of human cryptococcosis, opportunistic infections by environmental species, such as C. liquefaciens, have been observed recently. The main Cryptococcus virulence factor is the production and secretion of polysaccharides (PS). Previously, we showed that both species produce PS of similar composition. Here, we examined the ultrastructure and biological activity of capsular and secreted PS from C. liquefaciens, and yeast pathogenicity to an invertebrate host, in comparison with C. neoformans. Ultrastructural analysis by high-resolution microscopy showed that both species produce large and complex capsules. PS from both species had indistinguishable effects on phagocytosis levels, NO production and the secretion of a variety of immune mediators. Challenge with C. liquefaciens or C. neoformans led to complete lethality of G. mellonella larvae. Treatment with C. liquefaciens PS could not protect mice against infection with C. neoformans. We conclude that polysaccharides of the environmental yeast C. liquefaciens have strikingly similar ultrastructural and biological properties to those of C. neoformans, highlighting the importance of monitoring the emergence of new fungal pathogens for which thermotolerance may be an important transitional step towards pathogenesis in humans.

Fatal Case of Polymicrobial Meningitis Caused by Cryptococcus liquefaciens and Mycobacterium tuberculosis Complex in a Human Immunodeficiency Virus-Infected Patient

We describe a fatal case of polymicrobial meningitis in a human immunodeficiency virus-infected patient from Guatemala caused by Cryptococcus liquefaciens and Mycobacterium tuberculosis complex. Central nervous system infections caused concurrently by these species are extremely rare. This is also the first report of disseminated disease caused by C. liquefaciens.