Analysis of oral yeast microflora in patients with oral squamous cell carcinoma.

BACKGROUND: Oral squamous cell carcinoma (OSCC) is the most common form of oral cancer, in this study, the association between OSCC and oral yeast carriage was investigated. FINDINGS: 20 patients having OSCC as well as 40 healthy controls were tested for the presence of yeasts in the oral cavity. Fungal burdens were examined by colony forming unit determinations, while the different yeast genera in patient samples were identified by matrix-associated laser desorption/ionization-time of flight-mass spectrometry. We found that the level of oral yeast carriage was significantly higher in patients with OSCC that was accompanied by a higher diversity of yeasts in the oral cavity of these patients. We also examined the extracellular enzyme production of isolated Candida spp.; however, we found that there was no association between the lipase/protease producing capacity of Candida strains and the higher colonisation rate of neoplastic epithelium. CONCLUSIONS: In conclusion, our results corroborate the findings of previous studies regarding the association between oral yeast carriage and epithelial carcinoma.

Differential sensitivity of the species of Candida parapsilosis sensu lato complex against statins.

Candida parapsilosis sensu stricto, Candida orthopsilosis and Candida metapsilosis are human fungal pathogens with clinical importance. The recently reclassified three closely related species have significant variation in virulence, clinical prevalence and susceptibility characteristics to different antifungal compounds. The aim of this study was to investigate the in vitro activity of atorvastatin and fluvastatin against C. metapsilosis, C. orthopsilosis and C. parapsilosis. Susceptibility tests showed that C. parapsilosis was the most sensitive while C. orthopsilosis was the least susceptible species to both drugs. On the basis of the differential sensitivity, we developed a simple, reliable and highly cost-effective plate assay to distinguish these closely related species. Applying this method, 54 isolates belonging to the C. parapsilosis sensu lato complex deposited in Szeged Microbial Collection could be sorted into the three species with 100 % probability.

Characterization of virulence properties in the C. parapsilosis sensu lato species.

The C. parapsilosis sensu lato group involves three closely related species, C. parapsilosis sensu stricto, C. orthopsilosis and C. metapsilosis. Although their overall clinical importance is dramatically increasing, there are few studies regarding the virulence properties of the species of the psilosis complex. In this study, we tested 63 C. parapsilosis sensu stricto, 12 C. metapsilosis and 18 C. orthopsilosis isolates for the ability to produce extracellular proteases, secrete lipases and form pseudohyphae. Significant differences were noted between species, with the C. metapsilosis strains failing to secrete lipase or to produce pseudohyphae. Nine different clinical isolates each of C. parapsilosis sensu stricto, C. orthopsilosis and C. metapsilosis were co-cultured with immortalized murine or primary human macrophages. C. parapsilosis sensu stricto isolates showed a significantly higher resistance to killing by primary human macrophages compared to C. orthopsilosis and C. metapsilosis isolates. In contrast, the killing of isolates by J774.2 mouse macrophages did not differ significantly between species. However, C. parapsilosis sensu stricto isolates induced the most damage to murine and human macrophages, and C. metapsilosis strains were the least toxic. Furthermore, strains that produced lipase or pseudohyphae were most resistant to macrophage-mediated killing and produced the most cellular damage. Finally, we used 9 isolates of each of the C. parapsilosis sensus lato species to examine their impact on the survival of Galleriamellonella larvae. The mortality rate of G. mellonella larvae infected with C. metapsilosis isolates was significantly lower than those infected with C. parapsilosis sensu stricto or C. orthopsilosis strains. Taken together, our findings demonstrate that C. metapsilosis is indeed the least virulent member of the psilosis group, and also highlight the importance of pseudohyphae and secreted lipases during fungal-host interactions.