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Histochemical observations on Pneumocystis carinii: selective demonstration of honeycomb forms
Abstract:
Histochemical investigations of pulmonary lesions indicated selective coloration of membranes of honeycomb stages of Pneumocystis carinii by the periodic acid--sodium bisulfite--resorcin-fuchsin reaction for basement membranes; mucus, fibrin and other deposits in respiratory pathways did not react. These membranes were colored selectively also by the picro-Sirius Red F3BA method for collagens; fungi in tissues from patients with candidiasis remained unstained. For simultaneous demonstration of honeycomb and cyst forms of Pneumocystis carinii, sections were prestained with Grocott's modification of Gomori's methenamine-silver nitrate technic and then treated with the periodic acid-Schiff (PAS) or picro-Sirius Red F3BA reaction. In contrast to other Gram-positive microorganisms, cysts of Pneumocystis carinii were immediately decolorized by acetone-ether mixtures; this indicates differences in the mode of dye binding. Frequently, only one stage of Pneumocystis carinii was found in a given area. Hence a combination of reactions showing different stages is recommended for studies of small tissue samples.
Insights
Histochemical stains selectively color Pneumocystis carinii membranes, aiding diagnosis. Combining methods is recommended for identifying both honeycomb and cyst stages in lung tissue samples.
Area of Science:
- Pulmonary Pathology
- Medical Mycology
- Histochemistry
Background:
- Pneumocystis carinii pneumonia (PCP) diagnosis relies on identifying the organism in respiratory samples.
- Traditional staining methods may not reliably detect all forms of Pneumocystis carinii.
Purpose of the Study:
- To evaluate the efficacy of specific histochemical stains for identifying Pneumocystis carinii.
- To determine optimal staining combinations for visualizing different Pneumocystis carinii life cycle stages.
Main Methods:
- Periodic acid-sodium bisulfite-resorcin-fuchsin (PARF) stain for basement membranes.
- Picro-Sirius Red F3BA stain for collagens.
- Grocott's methenamine-silver nitrate (GMS) stain.
- Periodic acid-Schiff (PAS) stain.
- Acetone-ether decolorization tests.
Main Results:
- PARF and Picro-Sirius Red F3BA selectively stained Pneumocystis carinii membranes, differentiating them from mucus and fibrin.
- GMS, PAS, or Picro-Sirius Red F3BA, when combined with GMS prestaining, visualized both honeycomb and cyst forms.
- Pneumocystis carinii cysts showed rapid decolorization with acetone-ether, unlike other Gram-positive organisms.
Conclusions:
- Specific histochemical stains offer selective visualization of Pneumocystis carinii structures.
- Combining multiple staining techniques is crucial for comprehensive detection of Pneumocystis carinii stages in limited tissue samples.
- Unique dye-binding properties of Pneumocystis carinii cysts warrant further investigation.