Identification and antifungal susceptibility of a large collection of yeast strains isolated in Tunisian hospitals

Abstract

In this study, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used as a rapid method to identify yeasts isolated from patients in Tunisian hospitals. When identification could not be exstablished with this procedure, sequencing of the internal transcribed spacer with 5.8S ribosomal DNA (rDNA) (ITS1-5.8S-ITS2) and D1/D2 domain of large-subunit (LSU rDNA) were employed as a molecular approach for species differentiation. Candida albicans was the dominant species (43.37% of all cases), followed by C. glabrata (16.55%), C. parapsilosis (13.23%), C. tropicalis (11.34%), C. dubliniensis (4.96%), and other species more rarely encountered in human diseases such as C. krusei, C. metapsilosis, C. lusitaniae, C. kefyr, C. palmioleophila, C. guilliermondii, C. intermedia, C. orthopsilosis, and C. utilis. In addition, other yeast species were obtained including Saccharomyces cerevisiae, Debaryomyces hansenii (anamorph known as C. famata), Hanseniaspora opuntiae, Kodamaea ohmeri, Pichia caribbica (anamorph known as C. fermentati), Trichosporon spp. and finally a novel yeast species, C. tunisiensis. The in vitro antifungal activities of fluconazole and voriconazole were determined by the agar disk diffusion test and Etest, while the susceptibility to additional antifungal agents was determined with the Sensititre YeastOne system. Our results showed low incidence of azole resistance in C. albicans (0.54%), C. tropicalis (2.08%) and C. glabrata (4.28%). In addition, caspofungin was active against most isolates of the collection with the exception of two K. ohmeri isolates. This is the first report to describe caspofungin resistant isolates of this yeast.

Optimization and characterization of cold-active endoglucanase produced by Aspergillus terreus strain AKM-F3 grown on sugarcane bagasse

“…On the basis of the quantification results, a potent microfungus was selected and molecular identification was done using the D1/D2 region of the large subunit (LSU; 28S rDNA)-based molecular technique (Eddouzi et al, 2013). The gene sequence was used to carry out BLAST with the nr-database of the GenBank database.…”

The Ongoing Revolution of MALDI-TOF Mass Spectrometry for Microbiology Reaches Tropical Africa

“…Seven were identified only one time: A. flavus, Microsporum canis, Trichosporon asahii, Kodamaea ohmeri, C. africana (an emergent and rare pathogen described in 2001 for the first time), 13 C. nivariensis (an emergent and rare pathogen described in 2005 for the first time), 14 and C. utilis (an industrially important yeast that is rarely reported as a human pathogen, with approximately 10 reported cases found in a PubMed search on May 6, 2014). 15 Imprecise identification at the genus or family levels. Among 109 bacteria identified at the genus level (Table 5), most were from the genus Streptococcus (48 of 109; 44%), including 29 (26.6%) isolates with a misidentification between S. mitis, S. oralis, and S. pneumoniae.…”

Development of Two Molecular Approaches for Differentiation of Clinically Relevant Yeast Species Closely Related to Candida guilliermondii and Candida famata

“…The above-mentioned yeast species are likely to be confused with one another by conventional identification methods. In particular, isolates confused with C. famata were frequently misidentified, and C. famata was, in fact, very rare in clinical specimens (22,24,25,27).…”

“…The above-mentioned yeast species are likely to be confused with one another by conventional identification methods. In particular, isolates confused with C. famata were frequently misidentified, and C. famata was, in fact, very rare in clinical specimens (22,24,25,27).Currently, limited tools are available for molecular differentiation of these closely related yeast species. Molecular methods such as PCR-restriction fragment length polymorphism (RFLP), real-time PCR, Luminex techniques, electrophoretic karyotyping, and PCR with type-specific primers have been developed to distinguish some of these species, but other species were not involved in those studies (30-33).…”

“…Candida fermentati (the anamorph of Pichia caribbica), an emerging species that is very closely related to C. guilliermondii, has often been misidentified as C. guilliermondii using routine identification methods (22)(23)(24)(25)(26). Because of lower susceptibility to triazoles, Candida palmioleophila, which is often misidentified as Candida famata (the anamorph of Debaryomyces hansenii) or C. guilliermondii, has been emphasized in recent studies (24,25,27). Additionally, Debaryomyces nepalensis and Debaryomyces fabryi, two species that are closely related to C. famata, have been isolated from clinical samples, including blood (22,28,29), and also are potential pathogens.…”