Microbiology Images - Infectious Agents of the Lower Respiratory Tract

Question 1

Answer 1

Actinomyces

Actinomycotic “sulfur granules” composed of numerous filamentous organisms with a dark granular center (hematoxylin-eosin, original magnification ×100).

Question 2

Answer 2

Actinomyces

Higher-power view of actinomycotic sulfur granule, with numerous filamentous bacteria evident in the periphery (Gram, original magnification ×400).

Question 3

Answer 3

Nocardia

Slender branching filamentous bacteria that are positive by modified acid-fast (Fite) stain (original magnification ×600).

Question 4

Answer 4

Cytomegalovirus

Enlarged infected cells with eosinophilic intranuclear viral inclusions and prominent halo (Papanicolaou, original magnification ×1000).

Question 5

Answer 5

Mycobacteria

Acid-fast bacillus stain highlights delicate rod-shaped mycobacteria (original magnification ×600).

Question 6

Answer 6

Herpesvirus

Multinucleation, chromatin margination, and nuclear molding are seen (Papanicolaou, original magnification ×600).

Question 7

Answer 7

Adenovirus

Infected bronchial cell with enlarged, smudgy nucleus (Papanicolaou, original magnification ×600).

Question 8

Answer 8

Pneumocystis jerovecii

Pale green, amorphous foamy casts (Papanicolaou, original magnification ×600).

Question 9

Answer 9

Pneumocystis jerovecii

Cup-shaped cysts measuring 5 to 7 μm with a central dark zone (Grocott methenamine silver, original magnification ×600).

Question 10

Answer 10

Pneumocystis jerovecii

Cysts are highlighted as negative images. Individual trophozoites (1.5 μm) are visible within the cysts, macrophages, or as free organisms (Diff-Quik, original magnification ×400).

Question 11

Answer 11

Aspergillus

Narrow, septate hyphae with acute angle branching (Grocott methenamine silver, original magnification ×400).

Question 12

Answer 12

Aspergillus

Aspergillus spp can also be visualized with Papanicolaou stain with a similar appearance to that with Grocott methenamine silver stain (Papanicolaou, original magnification ×400).

Question 13

Answer 13

Mucormycosis

Broad, ribbon-like pauciseptate hyphae with irregular branching (Papanicolaou, original magnification ×400).

Question 14

Answer 14

Histoplasma

Yeast structures (2–4 μm) within the cytoplasm of macrophages (Diff-Quik, original magnification ×400).

Question 15

Answer 15

Blastomyces

Large (8–15 μm) yeast forms showing a refractile cell wall and single, broad-based budding (Grocott methenamine silver, original magnification ×600).

Question 16

Answer 16

Coccidioides

Endospores containing variably sized thick-walled spherules (20–70 μm) (Grocott methenamine silver, original magnification ×400).

Question 17

Answer 17

Cryptococcus

Individual and clustered organisms with accentuated capsular halos (Diff-Quik, original magnification ×600).

Question 18

Answer 18

Cryptococcus

Grocott methenamine silver highlights the yeast forms ranging from 4 to 10 μm. Narrow-based budding is seen, as well as a clear halo around some yeast forms (original magnification ×600).

Question 19

Answer 19

Cryptococcus

Mucicarmine stain highlights the thick polysaccharide capsule (original magnification ×400).

Question 20

Answer 20

Cryptococcus

Periodic acid–Schiff stain highlights the thick polysaccharide capsule (original magnification ×400).