Susceptibility testing of clinical isolates of Sporothrix globosa in Shandong, China

Abstract

Sporotrichosis is a subcutaneous mycosis caused by Sporothrix and is globally distributed. 1 The pathogen of the disease is a dimorphic fungus, which can produce different morphological characteristics under different temperature conditions. Dimorphism is usually seen as a mould at room temperature in the natural environment, when infecting mammalian hosts, it presents a yeast-like phase, which can adapt to human body temperature. 2 As a result of basic and clinical research in genetic, ecological and biological diversities of Sporothrix sporotrichosis, a new taxonomic classification in Sporothrix is recommended: the 'clinical clade' includes S brasiliensis, S schenckii, S globosa and S luriei, and the remaining Sporothrix are nested in an 'environmental clade'. Species within 'clinical clade' varies in susceptibility, virulence and geographic distribution, and some isolates have been reported to be insensitive to itraconazole and other antifungal agents. 3-5 Identification and antifungal susceptibility testing play an increasingly important role in guiding appropriate therapeutic decision-making. But so far, there is no standard technique for most dimorphic fungi to determine their in vitro susceptibilities. 6 Yeast is the infective form of the pathogen in humans; however, most studies have used the filamentous form of

5‐Aminolevulinic acid‐mediated photodynamic therapy has effective antifungal activity againstSporothrix globosain vitro

“…These results suggested that the yeast phase of S globosa was more sensitive to ALA‐PDT than the mycelial phase. This finding was very similar to the results of antifungal susceptibility testing in previous studies, in which the yeast phase of S globosa showed higher antifungal susceptibility than the mycelial phase, potentially because of differences in melanin content and cell wall structure 32,33 …”

Biological and Clinical Attributes of Sporothrix globosa, a Causative Agent of Sporotrichosis

“…There is disagreement about whether the drug sensitivity tests for S. globosa should be performed using yeast or mycelial phase. 115 Various reports used the yeast-like cells 116 according to the statement that these cells are the infective form, but still, the results obtained from using different growth phases of this morphology are considerably different. 115 …”

“… 115 Various reports used the yeast-like cells 116 according to the statement that these cells are the infective form, but still, the results obtained from using different growth phases of this morphology are considerably different. 115 …”

Old and New Insights into Sporothrix schenckii Complex Biology and Identification

“…Consistent with previous studies [ 49 ], a substantial presence of (extracellular) DNA in the S. schenckii biofilm ECM may not only contribute to the biofilm structure integrity but also to the biofilm-associated antifungal resistance in S. schenckii infections [ 48 ]. In this context, it is noteworthy that clinical isolates of Sporothrix species have increasingly been reported to be resistant to amphotericin B (AMB), azoles, and echinocandins [ 50 , 51 , 52 ]. The study by Rodrigues et al [ 53 ], determining the minimum inhibitory concentration (MIC) values for AMB, fluconazole (FLZ), itraconazole (ITZ), voriconazole (VRZ), posaconazole (PCZ), flucytosine (5FC), and caspofungin (CSF) of four pathogenic species ( S. schenckii sensu stricto , S. brasiliensis , S. globosa , and S. luriei ), showed that AMB, 5FC, CSF had no antifungal activity against any Sporothrix species.…”

“…It is still debated whether in vitro antifungal susceptibility testing should be performed on isolates in the mycelial or yeast phase [ 59 ]. However, it is noteworthy that in Bao et al’s study [ 50 ], a CLSI-adapted method, the Sensititre™ YeastOne™ assay, was used to test mycelium phase and yeast phase susceptibility of S. globosa isolates to echinocandins (anidulafungin, micafungin, and CSF), 5FC, azoles (PCZ, VRZ, ITZ, FLZ), and AMB. The authors found that ITZ was the most active antifungal drug against S. globosa , whereas the yeast phase of the same isolate was more susceptible than that of the mycelium phase, leading to consider the lower content of melanin present in the fungus’ yeast phase after repeated cultures as a possible explanation [ 50 ].…”