Aspergillus in the Papanicolaou stain: morphology, fluorescence and diagnostic feasibility

Fluorescence of Candida in diagnosis of oral candidiasis

BACKGROUND

Many pathogenic fungi fluoresce in hematoxylin and eosin stained sections, and Papanicolaou (PAP)-stained smears under ultraviolet illumination. In theory, this phenomenon could aid in the diagnosis of common fungal infections without the delay which is usually associated with special stains.

OBJECTIVE

To evaluate the role of fluorescence as a rapid screening technique for oral infections caused by Candida organisms in exfoliative smears of oral candidiasis.

MATERIALS AND METHODS

Two smears and one swab were collected from each of 62 clinically diagnosed cases of oral candidiasis. Smears were stained with (PAP) and periodic acid-Schiff stain (PAS). Both smears were evaluated under light microscopy (LM). Later, PAP smears were observed under fluorescent microscopy (PAP-FM). The swab was inoculated on Sabouraud's agar plate. Each technique was evaluated for sensitivity and specificity.

RESULTS

It was found that the PAS-stained smears were more reliable for detection of Candida species than other methods (sensitivity = 100%; specificity = 66.7%). The PAP-LM and PAP-FM showed less sensitivity (67.9% and 85.7%) and specificity (66.7% and 33.3%), respectively. Combined results of both light and fluorescent microscopy of PAP (LM + FM) showed increased sensitivity (89.3%) but reduced specificity (16.7%).

CONCLUSION

PAP autofluorescence is less sensitive than PAS, still it accentuates the distinct morphological features of Candida.

Liquid-based cytopathology test as a novel method to identify Aspergillus in patients with pulmonary aspergillosis

Conventional cytopathology examination of respiratory samples can aid in identifying Aspergillus but with poor sensitivity, so this study aimed to assess the potential of the liquid-based cytopathology test (LCT) for improving the identification of Aspergillus in respiratory samples following Papanicolaou's or Special staining with Grocott's methenamine silver or periodic acid-Schiff staining. Paired bronchial brushing samples (n = 54) and sputum samples (n = 117) from 171 patients with pulmonary aspergillosis were prepared as slides using either conventional cytopathology or SurePath LCT. LCT slides were generally superior to conventional slides, showing smaller cell monolayer surface area, clearer background and more distinct stereoscopic cytological features. For Papanicolaou's staining, LCT-prepared slides allowed a higher positive rate of Aspergillus identification than conventional slides for bronchial brushing samples (59.25% vs. 20.37%, P < 0.05) and sputum samples (29.05% vs. 8.55%, P < 0.05). Similarly, Special staining of LCT-prepared slides showed a higher positive rate of Aspergillus identification for bronchial brushing samples (83.33% vs. 57.41%, P < 0.05) and sputum samples (43.59% vs. 19.66%, P < 0.05). This preliminary study suggests that LCT may be better than conventional slide preparation for identifying Aspergillus in respiratory samples from patients with pulmonary aspergillosis.

Fluorescence of fungi in superficial and deep fungal infections

BACKGROUND

Fluorescence of many fungi is noted when H&E stained sections are examined under a fluorescent microscope. In theory, this phenomenon could aid in the diagnosis of cutaneous and disseminated fungal infections without the delay associated with special stains. Seventy-six cases of superficial and deep fungal infections and 3 cases of protothecosis were studied to determine the clinical usefulness of this technique.

RESULTS

In most cases, fluorescence was noted, but was not intense. Fluorescence of fungi did not correlate with the age of the specimen. In most cases, organisms in H&E stained sections were more easily identified with routine light microscopy than with fluorescent microscopy.

CONCLUSION

This report suggests that in H&E stained skin specimens, fluorescent microscopy is of little benefit in the identification of fungal organisms.