Global VGIIa isolates are of comparable virulence to the major fatal Cryptococcus gattii Vancouver Island outbreak genotype

The ongoing cryptococcosis outbreak on Vancouver Island, BC, Canada, is caused by two VGII sub-genotypes of the primary pathogen, Cryptococcus gattii: VGIIa isolates predominate, whereas VGIIb isolates are rare. Although higher virulence of the VGIIa genotype has been proposed, an unresolved key question is whether VGIIa isolates from other regions are also more virulent than VGIIb isolates. We report the relationship between genotype and virulence for a global collection of C. gattii VGIIa and VGIIb isolates (from Australia, Argentina, Brazil, Canada, Thailand and the USA). In vitro and in vivo virulence studies were conducted. At 37°C, growth [at 18 h: 0.2 optical density (OD) difference, p 0.026; at 36 h: 0.6 OD difference, p 0.036) and mean melanin production (OD = 0.25 vs. OD = 0.15, p 0.059] of VGIIa isolates was greater than that of VGIIb isolates. The inhibitory effect of high temperature on melanin production of VGIIa isolates was less than that of VGIIb isolates (OD = 0.36 vs. OD = 0.69; p 0.001). Capsule production at 37°C of VGIIa isolates was less than that of VGIIb isolates. All VGIIa isolates were fertile, whereas only 17% of VGIIb isolates were fertile (p <0.001). In vivo virulence studies using the BALB/c mice nasal inhalation model revealed that VGIIa isolates were more virulent than VGIIb isolates (p <0.001) independent of their clinical (p 0.003) or environmental origin (p <0.001). This study established a clear association between genotype and virulence of the primary fungal pathogen, C. gattii.     

Genetic Diversity of the Cryptococcus Species Complex Suggests that Cryptococcus gattii Deserves to Have Varieties

The Cryptococcus species complex contains two sibling taxa, Cryptococcus neoformans and Cryptococcus gattii. Both species are basidiomycetous yeasts and major pathogens of humans and other mammals. Genotyping methods have identified major haploid molecular types of C. neoformans (VNI, VNII, VNB and VNIV) and of C. gattii (VGI, VGII, VGIII and VGIV). To investigate the phylogenetic relationships among these haploid genotypes, we selected 73 strains from 2000 globally collected isolates investigated in our previous typing studies, representing each of these genotypes and carried out multigene sequence analyses using four genetically unlinked nuclear loci, ACT1, IDE, PLB1 and URA5. The separate or combined sequence analyses of all four loci revealed seven clades with significant support for each molecular type. However, three strains of each species revealed some incongruence between the original molecular type and the sequence-based type obtained here. The topology of the individual gene trees was identical for each clade of C. neoformans but incongruent for the clades of C. gattii indicating recent recombination events within C. gattii. There was strong evidence of recombination in the global VGII population. Both parsimony and likelihood analyses supported three major clades of C. neoformans (VNI/VNB, VNII and VNIV) and four major clades of C. gattii (VGI, VGII, VGIII and VGIV). The sequence variation between VGI, VGIII and VGIV was similar to that between VNI/VNB and VNII. MATa was for the first time identified for VGIV. The VNIV and VGII clades are basal to the C. neoformans or the C. gattii clade, respectively. Divergence times among the seven haploid monophyletic lineages in the Cryptococcus species complex were estimated by applying the hypothesis of the molecular clock. The genetic variation found among all of these haploid monophyletic lineages indicates that they warrant varietal status.     

Disseminated Cunninghamella bertholletiae infection with spinal epidural abscess in a kidney transplant patient: case report and literature review

Cunninghamella bertholletiae is a rare cause of invasive mucormycosis. We report the case of a 42‐year‐old Thai woman who suffered from disseminated C. bertholletiae infection. The patient developed dry cough, sharp shooting pain in the left buttock referred to the left leg, and fever 1 month after undergoing deceased‐donor kidney transplantation. Radiographic studies exhibited multiple pulmonary cavities, osteomyelitis of the sacral spine, epidural abscess along the lumbrosacral spine, and paravertebral soft tissue involvement. Surgical debridement of the epidural abscess concurrent with prolonged intravenous administration of amphotericin B resulted in a good outcome.