Oral Candida albicans isolates from HIV-positive individuals have similar in vitro biofilm-forming ability and pathogenicity as invasive Candida isolates

Abstract

BackgroundCandida can cause mucocutaneous and/or systemic infections in hospitalized and immunosuppressed patients. Most individuals are colonized by Candida spp. as part of the oral flora and the intestinal tract. We compared oral and systemic isolates for the capacity to form biofilm in an in vitro biofilm model and pathogenicity in the Galleria mellonella infection model. The oral Candida strains were isolated from the HIV patients and included species of C. albicans, C. glabrata, C. tropicalis, C. parapsilosis, C. krusei, C. norvegensis, and C. dubliniensis. The systemic strains were isolated from patients with invasive candidiasis and included species of C. albicans, C. glabrata, C. tropicalis, C. parapsilosis, C. lusitaniae, and C. kefyr. For each of the acquired strains, biofilm formation was evaluated on standardized samples of silicone pads and acrylic resin. We assessed the pathogenicity of the strains by infecting G. mellonella animals with Candida strains and observing survival.ResultsThe biofilm formation and pathogenicity in Galleria was similar between oral and systemic isolates. The quantity of biofilm formed and the virulence in G. mellonella were different for each of the species studied. On silicone pads, C. albicans and C. dubliniensis produced more biofilm (1.12 to 6.61 mg) than the other species (0.25 to 3.66 mg). However, all Candida species produced a similar biofilm on acrylic resin, material used in dental prostheses. C. albicans, C. dubliniensis, C. tropicalis, and C. parapsilosis were the most virulent species in G. mellonella with 100% of mortality, followed by C. lusitaniae (87%), C. novergensis (37%), C. krusei (25%), C. glabrata (20%), and C. kefyr (12%).ConclusionsWe found that on silicone pads as well as in the Galleria model, biofilm formation and virulence depends on the Candida species. Importantly, for C. albicans the pathogenicity of oral Candida isolates was similar to systemic Candida isolates, suggesting that Candida isolates have similar biofilm-forming ability and virulence regardless of the infection site from which it was isolated.

Oral Candida colonization in HIV-infected patients in Londrina-PR, Brazil: antifungal susceptibility and virulence factors

“…On the other hand, biofilms are also established during host colonization, enabling the yeast to withstand removal by mechanical processes. The ability of oropharyngeal Candida isolates from HIV-infected individuals to form biofilm was described previously, and this characteristic was associated with higher virulence in experimental infection models [43,44].…”

Candida parapsilosis,Candida orthopsilosis, andCandida metapsilosisvirulence in the non-conventional hostGalleria mellonella

“…However, these differences could not be associated to differences in their growth rate. 35 Macrophages play an important role in the immune response by phagocytosing and killing microorganisms. [36][37][38] The ability of macrophages to internalize medically important fungal species as C. neoformans, C. krusei, Aspergillus spp., C. albicans, and also species belonging to C. parapsilosis spp.…”

Epidemiology, Antifungal Susceptibility, and Pathogenicity of Candida africana Isolates from the United Kingdom

“…Given the reduced formation of hyphae and slower growth of C. africana compared to C. albicans, as well as previous reports demonstrating that C. dubliniensis exhibits reduced pathogenicity compared to C. albicans in a variety of infection models (reviewed in references 15 and 14), we compared the virulence of isolates of C. albicans, C. africana, and C. dubliniensis in a systemic infection model using the insect larval model Galleria mellonella (34)(35)(36)(37). Although recent studies have failed to reveal differences in pathogenicity between mucosal and systemic isolates of key pathogenic yeast species in Galleria larvae (40), any such potential bias in the current study was avoided by comparing C. africana strains with C. albicans and C. dubliniensis isolates that had also been recovered from female genital samples. In preliminary experiments, and in agreement with previous reports (34), no significant larval killing was observed with any isolate when larvae were inoculated with 10 5 CFU/larva at any temperature (data not shown).…”