Indoor Dust as a Source of Virulent Strains of the Agents of Cryptococcosis in the Rio Negro Micro-Region of the Brazilian Amazon

Abstract

Cryptococcosis, a potentially fatal mycosis in humans, is acquired via exposure to exogenous environmental sources. This study aimed to investigate the frequency, genetic diversity, and virulence of cryptococcal strains isolated from indoor dust in the Rio Negro micro-region of the Brazilian Amazon. A total of 8.9% of the studied houses were positive, recovering nine Cryptococcus neoformans VNI and 16 C. gattii VGII isolates, revealing an endemic pattern in domestic microenvironments. The International Society for Human and Animal Mycology (ISHAM) consensus multilocus sequence typing (MLST) scheme for the C. neoformans/C. gattii species complexes identified two sequence types (STs), ST93 and ST5, amongst C. neoformans isolates and six STs amongst C. gattii isolates, including the Vancouver Island Outbreak ST7 (VGIIa) and ST20 (VGIIb), the Australian ST5, and ST264, ST268 and ST445, being unique to the studied region. Virulence studies in the Galleria mellonella model showed that five C. gattii strains and one C. neoformans strain showed a similar pathogenic potential to the highly virulent Vancouver Island outbreak strain CDR265 (VGIIa). The findings of this study indicate that humans can be exposed to the agents of cryptococcosis via house dust, forming the basis for future studies to analyze the impact of early and continuous exposure to indoor dust on the development of subclinical or clinical infections.

Cryptococcus neoformans and Cryptococcus gattii Species Complexes in Latin America: A Map of Molecular Types, Genotypic Diversity, and Antifungal Susceptibility as Reported by the Latin American Cryptococcal Study Group

“…Taking advantage of the data analysis, unique nomenclature, and interlaboratory comparability of MLST, it was possible to gather 367 MLST profiles of C. neoformans and 400 of C. gattii isolates from Latin America, reported in 26 publications [ 20 , 32 , 61 , 66 , 68 , 73 , 75 , 79 , 81 , 84 , 87 , 90 , 91 , 98 , 100 , 106 , 109 , 117 , 123 , 124 , 128 , 138 , 139 , 140 , 141 , 142 ]. MLST studies with clinical and environmental C. neoformans isolates have been reported from Brazil (77.11%), Peru (12.53%), Colombia (9.54), and Argentina (0.82%), while MLST studies with clinical, environmental, and veterinary C. gattii isolates have been reported from Brazil (65.25%), Colombia (26.25%), Mexico (5%), Argentina (1%), Venezuela (1%), and Uruguay (0.75%), as well as Cuba, Guatemala, and Paraguay with one isolate each (0.25%).…”

Identification of Disease-Associated Cryptococcal Proteins Reactive With Serum IgG From Cryptococcal Meningitis Patients

“…We therefore hypothesize that latent pulmonary infection, as observed in IL-4Ra -/mice (75) and hypothesized in healthy individuals evidenced by reactivation of dormant cryptococcal infection (81,82), is sufficient to trigger basal production of anticryptococcal IgG and IgM antibodies. Alternatively, environmental exposure of humans to cryptococcal cells detectable in different reservoirs (3)(4)(5)(6) could trigger the observed production of anti-cryptococcal Igs. In contrast, dissemination of C. neoformans leading to systemic cryptococcal disease, as present in WT mice (75) and CM patients, leads to an increase in anti-cryptococcal IgG, but not IgM antibodies.…”

“…neoformans serotype A strain H99 cells were recovered from 10% skim milk stocks stored at -80°C and washed once with phosphate buffered saline (PBS). From cell suspension, 2x10 5 (human IgG analysis) or 5x10 5 (human IgM analysis, murine IgM and IgG analysis) cryptococcal cells were incubated with human serum samples diluted 1:10 in FACS buffer (3% FCS, 0.1% NaN 3 in PBS) for 30 min at 4°C. Cells were washed once with FACS buffer and once with PBS and incubated with Fixable Viability Dye eFluor ™ 780 (1:500 in PBS; ThermoFisher Scientific, Waltham, MA, USA) for 20 min at 4°C.…”

“…Cryptococcus neoformans, an encapsulated opportunistic fungal pathogen, is the main agent causing cryptococcosis, a fatal systemic disease (1). Cryptococcal infection occurs through inhalation of spores ubiquitously present in birds' droppings (2)(3)(4), house dust (5) and decaying wood (6). However, the most common clinical manifestation of cryptococcosis is not pulmonary, but disseminated disease manifesting mostly as cryptococcal meningitis (CM) (7).…”

Associations between Cryptococcus Genotypes, Phenotypes, and Clinical Parameters of Human Disease: A Review

“…C. neoformans VNI ST5 strains can cause infections in both HIV-infected and HIV-negative patients and are found in China, Vietnam, South America, Thailand, Korea, Laos, and USA [ 106 , 115 , 116 , 117 , 118 , 119 , 120 , 121 , 122 , 123 , 124 , 125 , 126 , 127 , 128 , 129 , 130 , 131 , 132 , 133 , 134 ]. In China and Vietnam, cryptococcosis is predominately caused by ST5 strains [ 116 , 119 , 121 , 123 , 124 , 133 ].…”