Aspergillus flavus Infections in Children With Leukemia Despite Liposomal Amphotericin-B Prophylaxis

Occurrence and Case Fatality Rate of Invasive Aspergillosis in Children With Acute Leukemia: A Systematic Review and Meta-analysis

Invasive aspergillosis (IA) is a potentially life-threatening complication of childhood acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). We conducted a systematic review and meta-analyses of studies on acute leukemia in children aged 0-17 years since 2000. Findings were reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. We included 24 studies with 3661 ALL patients and 1728 AML patients. IA cumulative incidence varied (0%-10% for ALL and 0%-18% for AML) across the studies. Pooled cumulative IA incidences were estimated at 3.2% (95% CI: 1.8%-5.8%) in ALL and 5.2% (95% CI: 3.1%-8.6%) in AML, with corresponding case fatality rates of 13.3% (95% CI: 6.3%-25.9%), and 7.8% (95% CI: 0.7%-51.2%), respectively. Our analysis highlights the impact of IA in childhood leukemia, underscoring the need to address strategies for prevention, early detection, and treatment of IA in pediatric leukemia.

A single-source nosocomial outbreak of Aspergillus flavus uncovered by genotyping

During construction work (2017-2019), an increase in Aspergillus flavus infections was noted among pediatric patients, the majority of whom were receiving amphotericin B prophylaxis. Microsatellite genotyping was used to characterize the outbreak. A total of 153 A. flavus isolates of clinical and environmental origin were included. Clinical isolates included 140 from 119 patients. Eight patients were outbreak-related patients, whereas 111 were outbreak-unrelated patients from Danish hospitals (1994-2023). We further included four control strains. Nine A. flavus isolates were from subsequent air sampling in the outbreak ward (2022-2023). Typing followed Rudramurthy et al.(S. M. Rudramurthy, H. A. de Valk, A. Chakrabarti, J. Meis, and C. H. W. Klaassen, PLoS One 6:e16086, 2011, https://doi.org/10.1371/journal.pone.0016086). Minimum spanning tree (MST) and discriminant analysis of principal components (DAPC) were used for cluster analysis. DAPC analysis placed all 153 isolates in five clusters. Microsatellite marker pattern was clearly distinct for one cluster compared to the others. The same cluster was observed in an MST. This cluster included all outbreak isolates, air-sample isolates, and additional patient isolates from the outbreak hospital, previously undisclosed as outbreak related. The highest air prevalence of A. flavus was found in two technical risers of the outbreak ward, which were then sealed. Follow-up air samples were negative for A. flavus. Microsatellite typing defined the outbreak as nosocomial and facilitated the identification of an in-hospital source. Six months of follow-up air sampling was without A. flavus. Outbreak-related/non-related isolates were easily distinguished with DAPC and MST, as the outbreak clone's distinct marker pattern was delineated in both statistical analyses. Thus, it could be a variant of A. flavus, with a niche ability to thrive in the outbreak-hospital environment.

IMPORTANCE

Aspergillus flavus can cause severe infections and hospital outbreaks in immunocompromised individuals. Although lack of isogeneity does not preclude an outbreak, our study underlines the value of microsatellite genotyping in the setting of potential A. flavus outbreaks. Microsatellite genotyping documented an isogenic hospital outbreak with an internal source. This provided the "smoking gun" that prompted the rapid allocation of resources for thorough environmental sampling, the results of which guided immediate and relevant cleaning and source control measures. Consequently, we advise that vulnerable patients should be protected from exposure and that genotyping be included early in potential A. flavus outbreak investigations. Inspection and sampling are recommended at any site where airborne spores might disperse from. This includes rarely accessed areas where air communication to the hospital ward cannot be disregarded.

Inhibitory Mechanism of Pinosylvin Monomethyl Ether against Aspergillus flavus

Control of Aspergillus flavus is beneficial for the agricultural economy and food safety. Stilbenes exhibit antifungal properties through an unknown mechanism. Here, six stilbenes isolated from Cajanus cajan were screened for anti-A. flavus activity. Among them, pinosylvin monomethyl ether (PME) showed the strongest anti-A. flavus activity and has a broad antifungal spectrum with negligible hemolysis within the concentration range measured. PME inhibited the spore germination of A. flavus and the accumulation of aflatoxin B1. Mechanistic studies showed that PME could bind the cell membrane phospholipids, resulting in increased permeability and decreased fluidity. Further metabolic analysis showed that PME caused the lysis of cell membranes and subsequent collapse of spores, which resulted in a cell wall autolysis-like phenotype. Structure-activity relationship analysis revealed the importance of maintaining amphiphilicity harmony by substituent groups for the antifungal activity of stilbenes. Together, natural stilbenes are promising antifungal lead compounds worthy of further exploration and research for potential application in the food, pharmaceutical, and agricultural industries.