Textbook Question
Under what conditions can the saprophytes Aspergillus and Rhizopus cause infections?
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Ch. 24 - Microbial Diseases of the Respiratory System
Tortora14th EditionMicrobiology: An IntroductionISBN: 9780138200398
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Table of contents
- Ch. 1 - The Microbial World and You18
- Ch. 2 - Chemical Principles20
- Ch. 3 - Observing Microorganisms Through a Microscope18
- Ch. 4 - Functional Anatomy of Prokaryotic and Eukaryotic Cells21
- Ch. 5 - Microbial Metabolism20
- Ch. 6 - Microbial Growth20
- Ch. 7 - The Control of Microbial Growth20
- Ch. 8 - Microbial Genetics19
- Ch. 9 - Biotechnology & DNA Technology20
- Ch. 10 - Classification of Microorganisms15
- Ch. 11 - The Prokaryotes: Domains Bacteria and Archaea14
- Ch. 12 - The Eukaryotes: Fungi, Algae, Protozoa, and Helminths17
- Ch. 13 - Viruses, Viroids, and Prions20
- Ch. 14 - Principles of Disease and Epidemiology21
- Ch. 15 - Microbial Mechanisms of Pathogenicity19
- Ch. 16 - Innate Immunity: Nonspecific Defenses of the Host20
- Ch. 17 - Adaptive Immunity: Specific Defenses of the Host20
- Ch. 18 - Practical Applications of Immunology20
- Ch. 19 - Disorders Associated with the Immune System19
- Ch. 20 - Antimicrobial Drugs19
- Ch. 21 - Microbial Diseases of the Skin and Eyes21
- Ch. 22 - Microbial Diseases of the Nervous System19
- Ch. 23 - Microbial Diseases of the Cardiovascular and Lymphatic Systems20
- Ch. 24 - Microbial Diseases of the Respiratory System20
- Ch. 25 - Microbial Diseases of the Digestive System20
- Ch. 26 - Microbial Diseases of the Urinary and Reproductive Systems19
- Ch. 27 - Environmental Microbiology20
- Ch. 28 - Applied and Industrial Microbiology19
Tortora14th EditionMicrobiology: An IntroductionISBN: 9780138200398Not the one you use?Change textbook
Chapter 24, Problem 5
Match the following choices to the culture descriptions in questions 3 through 6:
a. Chlamydia
b. Coccidioides
c. Histoplasma
d. Mycobacterium
e. Mycoplasma
Microscopic examination of a lung biopsy shows ovoid cells in alveolar macrophages. You suspect these are the cause of the patient’s signs and symptoms, but your culture grows a filamentous organism.
Verified step by step guidance1
Step 1: Identify the key observations from the problem: microscopic examination shows ovoid cells inside alveolar macrophages, and the culture grows a filamentous organism.
Step 2: Recall that ovoid cells inside alveolar macrophages are characteristic of Histoplasma capsulatum, a dimorphic fungus that appears as small yeast cells (ovoid) within macrophages in tissue.
Step 3: Understand that Histoplasma grows as a filamentous mold (mycelial form) in culture at environmental temperatures, which explains the filamentous organism observed in culture.
Step 4: Compare the other options: Chlamydia is an obligate intracellular bacterium, Coccidioides forms spherules in tissue, Mycobacterium is an acid-fast bacterium, and Mycoplasma lacks a cell wall and does not form filaments or ovoid cells in macrophages.
Step 5: Conclude that the description matches Histoplasma (option c) because of the ovoid yeast cells in macrophages and filamentous growth in culture.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Intracellular Pathogens and Their Morphology
Some pathogens, like Histoplasma, exist as ovoid yeast cells inside alveolar macrophages, indicating an intracellular lifestyle. Recognizing the typical microscopic appearance of these organisms helps differentiate them from others and guides diagnosis.
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Types of Bacterial Cell Morphology
Dimorphic Fungi and Filamentous Growth
Dimorphic fungi, such as Histoplasma and Coccidioides, can grow as yeast in tissue and as filamentous molds in culture. This morphological switch is key for identification, as the filamentous form often appears in laboratory cultures despite yeast forms in the host.
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Correlation Between Microscopic Findings and Culture Results
Discrepancies between microscopic examination and culture morphology require understanding that some pathogens change form depending on environment. For example, seeing ovoid cells in tissue but filamentous growth in culture suggests a dimorphic fungus rather than bacteria or other microbes.
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Related Practice
Textbook Question
Match the following choices to the culture descriptions in questions 3 through 6:
a. Chlamydia
b. Coccidioides
c. Histoplasma
d. Mycobacterium
e. Mycoplasma
This pneumonia etiology requires cell culture.
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Textbook Question
List the causative agent, mode of transmission, and endemic area for the diseases histoplasmosis, coccidioidomycosis, blastomycosis, and Pneumocystis pneumonia.
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Textbook Question
Match the following choices to the culture descriptions in questions 3 through 6:
a. Chlamydia
b. Coccidioides
c. Histoplasma
d. Mycobacterium
e. Mycoplasma
Microscopic examination of a lung biopsy shows spherules.
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Textbook Question
Complete the following table.
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Textbook Question
A patient has been diagnosed as having pneumonia. Is this sufficient information to begin treatment with antimicrobial agents? Briefly discuss why or why not.
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