Aspergillus niger and its related species, known as Aspergillus section Nigri, are ubiquitously distributed across the globe and are often isolated from clinical specimens. In Japan, Aspergillus section Nigri is second most often isolated from clinical specimens following Aspergillus fumigatus. We determined the species of Aspergillus section Nigri isolated in Japan by DNA sequencing of partial -tubulin genes and investigated drug susceptibility by the CLSI M38-A2 method. The collection contained 20 Aspergillus niger, 59 Aspergillus welwitschiae, and 39 Aspergillus tubingensis strains. Drug susceptibility testing revealed 30 to 55% of A. niger, 6.8 to 18.6% of A. welwitschiae, and 79.5 to 89.7% of A. tubingensis isolates to be less susceptible (socalled resistant) to itraconazole (ITC) and/or voriconazole (VRC) according to the epidemiologic cutoff values (ECVs) proposed for A. niger previously. MIC distributions of ITC or VRC showed no remarkable differences between clinical and environmental isolates. When the cyp51A sequences were compared between susceptible and resistant strains, 18 amino acid mutations were specific for resistant isolates of A. niger and A. tubingensis; however, none of them were confirmed to be associated with azole resistance. Three nonrelated A. welwitschiae isolates possessed a partial deletion in cyp51A, likely attributable to being more susceptible to azoles than other isolates. One of five ITC-resistant A. tubingensis isolates showed higher expression of cyp51A than did susceptible strains. Our results show that cyp51A point mutations may have no association with azole resistance but that in some cases the overexpression of cyp51A may lead to the azole resistance in these species.
Sporotrichosis is a fungal infection caused by the Sporothrix species, which have distinct virulence profiles and geographic distributions. We performed a phylogenetic study in strains morphologically identified as Sporothrix schenckii from clinical specimens in Japan, which were preserved at the Medical Mycology Research Center, Chiba University. In addition, we examined the in vitro antifungal susceptibility and growth rate to evaluate their physiological features. Three hundred strains were examined using sequence analysis of the partial calmodulin gene, or polymerase chain reaction(PCR) method using newly designed species-specific primers; 291 strains were Sporothrix globosa and 9 strains were S. schenckii sensu stricto(in narrow sense, s. s.) . S. globosa strains were further clustered into two subclades, and S. schenckii s. s. strains were divided into three subclades. In 38 strains of S. globosa for which antifungal profiles were determined, 4 strains(11%)showed high minimal inhibitory concentration(MIC)value for itraconazole. All tested strains of S. schenckii s. s. and S. globosa showed low sensitivity for amphotericin B. These antifungals are used for treatment of sporotrichosis when infection is severe. S. schenckii s. s. grew better than S. globosa; wherein S. globosa showed restricted growth at 35℃ and did not grow at 37℃. Our molecular data showed that S. globosa is the main causal agent of sporotrichosis in Japan. It is important to determine the antifungal profiles of each case, in addition to accurate species-level identification, to strategize the therapy for sporotrichosis.
Polyhexamethylene biguanide hydrochloride (PHMB), an antimicrobial agent, has been widely used as a disinfectant in medical industries and public facilities. However, long-term use of any antimicrobial agent increases the risk of the microorganisms developing resistance. We aimed to examine the presence of microorganisms highly resistant to PHMB to address potential medical safety and public health concerns and devise strategies to prevent resistance development. We isolated and characterized a fungus from a 20% aqueous solution of PHMB and compared its microbiological characteristics and resistance profile with those of other major antimicrobial agents. Additionally, we sequenced the genome of the isolate to predict PHMB resistance-related genes. Based on the internal transcribed spacer (ITS) region of ribosomal DNA, the fungus was identified as Purpureocillium lilacinum. Although the P. lilacinum type and resistant strains showed similar morphology, the latter had extremely low PHMB susceptibility and was able to grow in the 20% aqueous solution of PHMB, which killed the type strain. Additionally, the minimum inhibitory concentration (MIC) of PHMB against the resistant strain was approximately four times higher than that against the type strain. In contrast, the MICs of four other antimicrobial agents and seven antifungal agents against the resistant strain were either less than or equal to those against the type strain. Furthermore, MICs of PHMB against four pathogenic filamentous fungi and two yeasts were significantly lower than those against the resistant strain. Despite its specific high resistance to PHMB, no gene homologous to fungal PHMB-resistant gene was found in the genome of the resistant strain. In summary, P. lilacinum was found to be significantly more resistant to PHMB than previously reported, suggesting an unidentified novel mechanism underlying drug resistance in the fungi.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.