Penicillium species as a rare isolate in tracheal granulation tissue: a case series

Chronic postcataract endophthalmitis caused by Penicillium species in an immunocompetent patient

Objective

Penicillium species are abundant, generally saprophytic, and widely distributed in the environment. On rare occasions, they cause endophthalmitis in immunocompromised patients or in immunocompetent patients with uncontrolled diabetic mellitus or immunosuppressive agents. We report a case of endophthalmitis caused by Penicillium species in an immunocompetent patient without any disorders.

Case presentation

A 67-year-old woman presented with ocular pain, hyperemia, and blurred vision in her right eye. She was in an immunocompetent condition and had received cataract surgery without complications 3 months ago. Severe cell infiltration and a clump of 3 mm diameter were found in the anterior chamber of the right eye, and there was no abnormality in the posterior segment. Serum β-d-glucan was not elevated; bacterial culture, histological analysis, and PCR using aqueous humor did not detect any pathogen (28S rDNA 2.4×10² copies/mL). However, because the clinical findings suggested fungal endophthalmitis, anti-fungal medication was initiated. The inflammation was gradually resolved with contraction of the clump; however, it recurred 47 days after the initiation by discontinuation of antifungal medication. Examination of culture identified Penicillium species in samples from both the anterior chamber and the vitreous.

Conclusion

Chronic postoperative endophthalmitis by Penicillium species can occur in an immunocompetent patient without any systemic diseases.

Can filamentous fungi form biofilms?

The discovery of biofilm formation in bacteria and yeasts has led to a better understanding of microbial ecology and to new insights into the mechanisms of virulence and persistence of pathogenic microorganisms. However, it is generally assumed that filamentous fungi, some of which have a significant impact on our health or our economy, do not form biofilms. In contrast to this assumption, here we discuss recent findings supporting the hypothesis that surface-associated filamentous fungi can form biofilms. Based on these findings and on previous models for bacterial and yeast systems, we propose preliminary criteria and a model for biofilm formation by filamentous fungi.

Phagocytosis of Aspergillus fumigatus conidia by primary nasal epithelial cells in vitro

Background

Invasive aspergillosis, which is mainly caused by the fungus Aspergillus fumigatus, is an increasing problem in immunocompromised patients. Infection occurs by inhalation of airborne conidia, which are first encountered by airway epithelial cells. Internalization of these conidia into the epithelial cells could serve as a portal of entry for this pathogenic fungus.

Results

We used an in vitro model of primary cultures of human nasal epithelial cells (HNEC) at an air-liquid interface. A. fumigatus conidia were compared to Penicillium chrysogenum conidia, a mould that is rarely responsible for invasive disease. Confocal microscopy, transmission electron microscopy, and anti-LAMP1 antibody labeling studies showed that conidia of both species were phagocytosed and trafficked into a late endosomal-lysosomal compartment as early as 4 h post-infection. In double immunolabeling experiments, the mean percentage of A. fumigatus conidia undergoing phagocytosis 4 h post-infection was 21.8 ± 4.5%. Using combined staining with a fluorescence brightener and propidium iodide, the mean rate of phagocytosis was 18.7 ± 9.3% and the killing rate 16.7 ± 7.5% for A. fumigatus after 8 h. The phagocytosis rate did not differ between the two fungal species for a given primary culture. No germination of the conidia was observed until 20 h of observation.

Conclusion

HNEC can phagocytose fungal conidia but killing of phagocytosed conidia is low, although the spores do not germinate. This phagocytosis does not seem to be specific to A. fumigatus. Other immune cells or mechanisms are required to kill A. fumigatus conidia and to avoid further invasion.