Scedosporium apiospermum complex in cystic fibrosis; should we treat?

Scedosporiosis and lomentosporiosis: modern perspectives on these difficult-to-treat rare mold infections

SUMMARYAlthough Scedosporium species and Lomentospora prolificans are uncommon causes of invasive fungal diseases (IFDs), these infections are associated with high mortality and are costly to treat with a limited armamentarium of antifungal drugs. In light of recent advances, including in the area of new antifungals, the present review provides a timely and updated overview of these IFDs, with a focus on the taxonomy, clinical epidemiology, pathogenesis and host immune response, disease manifestations, diagnosis, antifungal susceptibility, and treatment. An expansion of hosts at risk for these difficult-to-treat infections has emerged over the last two decades given the increased use of, and broader population treated with, immunomodulatory and targeted molecular agents as well as wider adoption of antifungal prophylaxis. Clinical presentations differ not only between genera but also across the different Scedosporium species. L. prolificans is intrinsically resistant to most currently available antifungal agents, and the prognosis of immunocompromised patients with lomentosporiosis is poor. Development of, and improved access to, diagnostic modalities for early detection of these rare mold infections is paramount for timely targeted antifungal therapy and surgery if indicated. New antifungal agents (e.g., olorofim, fosmanogepix) with novel mechanisms of action and less cross-resistance to existing classes, availability of formulations for oral administration, and fewer drug-drug interactions are now in late-stage clinical trials, and soon, could extend options to treat scedosporiosis/lomentosporiosis. Much work remains to increase our understanding of these infections, especially in the pediatric setting. Knowledge gaps for future research are highlighted in the review.

Extracellularly Released Molecules by the Multidrug-Resistant Fungal Pathogens Belonging to the Scedosporium Genus: An Overview Focused on Their Ecological Significance and Pathogenic Relevance

The multidrug-resistant species belonging to the Scedosporium genus are well recognized as saprophytic filamentous fungi found mainly in human impacted areas and that emerged as human pathogens in both immunocompetent and immunocompromised individuals. It is well recognized that some fungi are ubiquitous organisms that produce an enormous amount of extracellular molecules, including enzymes and secondary metabolites, as part of their basic physiology in order to satisfy their several biological processes. In this context, the molecules secreted by Scedosporium species are key weapons for successful colonization, nutrition and maintenance in both host and environmental sites. These biologically active released molecules have central relevance on fungal survival when colonizing ecological places contaminated with hydrocarbons, as well as during human infection, particularly contributing to the invasion/evasion of host cells and tissues, besides escaping from the cellular and humoral host immune responses. Based on these relevant premises, the present review compiled the published data reporting the main secreted molecules by Scedosporium species, which operate important physiopathological events associated with pathogenesis, diagnosis, antimicrobial activity and bioremediation of polluted environments.

Comparative transcriptome analysis unveils the adaptative mechanisms of Scedosporium apiospermum to the microenvironment encountered in the lungs of patients with cystic fibrosis

Scedosporium species rank second among the filamentous fungi colonizing the lungs of patients with cystic fibrosis (CF). Apart from the context of immunodeficiency (lung transplantation), the colonization of the CF airways by these fungi usually remains asymptomatic. Why the colonization of the lower airways by Scedosporium species is fairly tolerated by CF patients while these fungi are able to induce a marked inflammatory reaction in other clinical contexts remains questionable. In this regards, we were interested here in exploring the transcriptional reprogramming that accompanies the adaptation of these fungi to the particular microenvironment encountered in the airways of CF patients. Cultivation of Scedosporium apiospermum in conditions mimicking the microenvironment in the CF lungs was shown to induce marked transcriptional changes. This includes notably the down-regulation of enzymes involved in the synthesis of some major components of the plasma membrane which may reflect the ability of the fungus to evade the host immune response by lowering the biosynthesis of some major antigenic determinants or inhibiting their targeting to the cell surface through alterations of the membrane fluidity. In addition, this analysis revealed that some genes encoding enzymes involved in the biosynthesis of some mycotoxins were down-regulated suggesting that, during the colonization process, S. apiospermum reduces the production of some toxic secondary metabolites to prevent exacerbation of the immune system response. Finally, a strong up-regulation of many genes encoding enzymes involved in the degradation of aromatic compounds was observed, suggesting that these catabolic properties would predispose the fungus to particular patterns of human pathogenicity. Together these data provide new insights into the adaptative mechanisms developed by S. apiospermum in the CF lungs, which should be considered for identification of potential targets for drug development, but also for the experimental conditions to be used in in vitro susceptibility testing of clinical isolates to current antifungals.

In vitro Interactions of Pseudomonas aeruginosa With Scedosporium Species Frequently Associated With Cystic Fibrosis

Members of the Scedosporium apiospermum species complex are the second most frequently isolated pathogens after Aspergillus fumigatus from cystic fibrosis (CF) patients with fungal pulmonary infections. Even so, the main risk factors for the infection are unrevealed. According to previous studies, bacterial infections might reduce the risk of a fungal infection, but an antibacterial therapy may contribute to the airway colonization by several fungal pathogens. Furthermore, corticosteroids, which are often used to reduce lung inflammation in children and adults with CF, are also proved to enhance the growth of A. fumigatus in vitro. Considering all the above discussed points, we aimed to test how Pseudomonas aeruginosa influences the growth of scedosporia and to investigate the potential effect of commonly applied antibacterial agents and corticosteroids on Scedosporium species. Direct interactions between fungal and bacterial strains were tested using the disk inhibition method. Indirect interactions via volatile compounds were investigated by the plate-in-plate method, while the effect of bacterial media-soluble molecules was tested using a modified cellophane assay and also in liquid culture media conditioned by P. aeruginosa. To test the effect of bacterial signal molecules, antibacterial agents and corticosteroids on the fungal growth, the broth microdilution method was used. We also investigated the germination ability of Scedosporium conidia in the presence of pyocyanin and diffusible signal factor by microscopy. According to our results, P. aeruginosa either inhibited or enhanced the growth of scedosporia depending on the culture conditions and the mode of interactions. When the two pathogens were cultured physically separately from each other in the plate-in-plate tests, the presence of the bacteria was able to stimulate the growth of several fungal isolates. While in direct physical contact, bacterial strains inhibited the fungal growth. This effect might be attributed to bacterial signal molecules, which also proved to inhibit the germination and growth of scedosporia. In addition, antibacterial agents showed growth-promoting, while corticosteroids exhibited growth inhibitory effect on several Scedosporium isolates. These data raise the possibility that a P. aeruginosa infection or a previously administered antibacterial therapy might be able to increase the chance of a Scedosporium colonization in a CF lung.

Fungal epidemiology in cystic fibrosis patients with a special focus on Scedosporium species complex

In this present study, for the first time, we evaluated the cystic fibrosis (CF) patients for the Scedosporium species and their antifungal susceptibility against eight antifungal agents. During one-year period, 90 Sputum samples were collected from Iranian CF patients. All samples were evaluated by direct microscopic examination, culture onto four different media including Malt extract agar, Inhibitory mold agar, Brain Heart Infusion and Scedo-Select III. The mold isolated fungi were identified by PCR-Sequencing of ITS and β-tubulin genes. In-vitro antifungal susceptibility was performed according to the Clinical & Laboratory Standards Institute (CLSI) M38-A2 guidelines. Out of 90 CF patients, 47 (52.2%) were male. The age of the patients ranged from 1 to 34 years (median of 15.84 ± 7.41 years). Overall, 3 (3.3%) cases were positive for Scedosporium spp. of which two isolates were characterized as Scedosporium boydii and one isolate as S. ellipsoideum. Among Aspergillus genus, A. flavus (29.4%) was the most prevalent species followed by A. tubingensis (24.7%), A. niger (17.0%) and A. fumigatus (14.5%). The minimum effective concentration ranges of micafungin, anidulafungin, and caspofungin were 0.008-0.031 μg/mL, 0.0625-0.25 μg/mL, and 0.0625-0.25 μg/mL, respectively. All isolates of Scedosporium species showed high minimum inhibitory concentration to the triazoles tested, except voriconazole. Our results showed that A. flavus and Scedosporium species are the most prevalent molds isolated from CF patient populations in Iran. Our findings have also showed that Scedo-Select III can be used as a reliable culture media for isolation of Scedosporium spp. in clinical samples.

Inhaled antibiotic use is associated with Scedosporium/Lomentospora species isolation in cystic fibrosis

INTRODUCTION

Prevalence of fungi has been rising in the cystic fibrosis (CF) population. Scedosporium species (spp) is the second most common mold seen in the CF respiratory tract. However, the characteristics associated with Scedosporium isolation and its clinical implications are poorly understood. The goal of this study was to determine clinical factors associated with Scedosporium spp to better understand the mechanisms that may contribute to the emergence of filamentous fungi in CF.

METHODS

We conducted a retrospective cohort study of subjects followed in the CF Foundation Patient Registry between January 1, 2010 and December 31, 2012. Patients under 6 years of age, history of solid organ transplantation, and insufficient respiratory culture data were excluded. We used a multivariable logistic regression model to determine demographic data and baseline disease characteristics, medications and co-infections associated with Scedosporium spp recovery in CF sputum.

RESULTS

Among 19 023 subjects, prevalence of Scedosporium spp was 615 (3.2%). Older age (odds ratio [OR] 1.16, 95% confidence interval [CI] 1.07, 1.26) and white race (OR 1.69, 95% CI 1.09, 2.63) were the demographic factors associated with Scedosporium spp isolation. Inhaled antibiotic use had a significant association with Scedosporium isolation (OR 2.01, 95% CI 1.61, 2.52). For every additional course of intravenous antibiotics, the odds of Scedosporium isolation increased by 8% (OR 1.08, 95% CI 1.03, 1.14).

CONCLUSIONS

The association between inhaled antibiotics and Scedosporium informs us that chronic inhaled antibiotics may be playing a role in Scedosporium isolation. Further investigation to better characterize this relationship is necessary.

Pulmonary Scedosporium apiospermum Infection with Pulmonary Tumorlet in an Immunocompetent Patient

Scedosporium apiospermum is an opportunistic fungus that can cause various types of infections, including localized infections and life-threatening disseminated infections, particularly in immunocompromised patients. Treatment is especially challenging due to its multidrug resistance. We herein report the case of a 73-year-old woman who was non-immunocompromised but developed S. apiospermum lung infection and a pulmonary tumorlet. To our knowledge, this is the first report of the coexistence of pulmonary S. apiospermum infection and tumorlet. The lung lesion was successfully treated by surgical excision without any antifungal agents, and no recurrence of the tumorlet or S. apiospermum infection has occurred.