Antifungal Susceptibility In Vitro Determined by the Etest(r) for Candida Obtained from the Oral Cavity of Irradiated and Elderly Individuals

Abstract

This study aimed to evaluate the in vitro antifungal susceptibility of Candida species of head-and-neck-irradiated patients (Group 1), non-institutionalized (Group 2) and institutionalized elders (Group 3) using Etest® methodology. Candida was isolated from saliva and presumptively identified by CHROMagar Candida(r), confirmed by morphological criteria, carbohydrate assimilation (API 20C AUX®) and genetic typing (OPE 18). The collection was made from 29, 34 and 29 individuals (Groups 1, 2 and 3, respectively) with 67 isolates. Etest® strips (ketoconazole, itraconazole, fluconazole, amphotericin B and flucytosine) on RPMI (Roswell Park Memorial Institute) agar, on duplicate, were used to evaluate susceptibility. ATTC (American Type Culture Collection) 10231 (Candida albicans) was used as quality control. Among the 67 isolates of Candida species, most were susceptible to azoles, flucytosine and amphotericin B. None of the isolates showed resistance and dose-dependent susceptibility to amphotericin B. There were nine strains resistant to itraconazole, six to fluconazole and two to ketoconazole and ten dose-dependent, mainly to flucytocine. The highest MIC (minimum inhibitory concentration) to C. albicans, C. tropicalis, C. parapsilosis was 2.671 μg.mL-1, 8.104 μg.mL-1, 4.429 μg.mL-1, all for flucytosine. C. krusei and C. glabrata were associated with higher MIC for azoles and C. glabrata with higher MIC to flucytosine. In summary, susceptibility to all tested antifungal agents was evident. The isolates were more resistant to itraconazole and dose-dependent to flucytosine. A comparison of C. albicans in the three groups showed no outliers. Higher MIC was associated with C. krusei and C. glabrata.

Study of Microbial Interaction Formed by "Candida krusei" and "Candida glabrata": "In Vitro" and "In Vivo" Studies

“…Biofilms are defined as microbial communities encased in a matrix of extracellular polymeric substance (EPS), which display phenotypic features that differ from their planktonic or free-floating counterparts (3)(4)(5). It is known that C. glabrata exhibits intrinsically low susceptibility to azoles and develops resistance after exposure to these drugs (6) and C. krusei is naturally resistant to fluconazole, but in most cases, it is sensitive to voriconazole (cross-resistance is uncommon in this specie) (7,8), which complicates the treatment of candidiasis caused by this species. Because of that, it is important to know the behavior of these species when they grow together in a biofilm.…”

Synthesis, antifungal activity of caffeic acid derivative esters, and their synergism with fluconazole and nystatin against Candida spp.

“…to traditional antifungal drugs. The increasing microbial resistance rates may also be a result of long-term drug exposure or selection of strains with intrinsic resistance mechanisms (Fernandez-Ruiz et al, 2015;Freitas et al, 2015;Liao et al, 2015;Seifi et al, 2015;Ying et al, 2013). Therefore, the development of novel strategies to minimize the toxic effects of current antifungals and improve their effectiveness has been strongly encouraged.…”

Fungal contribution in chondroradionecrosis of the larynx

“…Lalla et al and Ramierez‐Amador et al also showed that oral fungal presence increased during radiotherapy for oral cavity and pharyngeal tumors. Emerging strains of Candida species that are resistant to antifungal medicines have been reported, perhaps establishing the need to determine the susceptibility of clinical isolates …”

“…Emerging strains of Candida species that are resistant to antifungal medicines have been reported, perhaps establishing the need to determine the susceptibility of clinical isolates. 22 Many of the current regimes for antifungal treatment of CRN are borrowed from the treatment of oral and oropharyngeal candidiasis. Recommendations range from nystatin and other topical therapies that are swallowed to systemic treatment for more severe infections.…”