Ch. 21 - Microbial Diseases of the Skin and Eyes

Tortora - Microbiology: An Introduction 14th Edition

Tortora14th EditionMicrobiology: An IntroductionISBN: 9780138200398Not the one you use?Change textbook

Tortora 14th Edition

Ch. 21 - Microbial Diseases of the Skin and Eyes

Problem 7

Chapter 21, Problem 7

Use the following choices to answer the question given below.
a. Pseudomonas
b. Staphylococcus aureus
c. Scabies
d. Sporothrix
e. Virus
Nothing is seen in microscopic examination of a scraping from the patient’s rash.

Verified step by step guidance

Step 1: Understand the context of the problem, which involves identifying the likely cause of a rash when microscopic examination of a skin scraping shows no visible organisms.

Step 2: Review the given options: a. Pseudomonas (a bacterium), b. Staphylococcus aureus (a bacterium), c. scabies (a parasitic mite), d. Sporothrix (a fungus), e. virus (a non-cellular infectious agent).

Step 3: Recall that microscopic examination of a scraping typically reveals bacteria, fungi, or parasites if present in sufficient numbers, but viruses are too small to be seen under a light microscope without special staining or culture techniques.

Step 4: Consider that scabies mites are usually visible under the microscope in skin scrapings, as are fungal elements like Sporothrix, and bacteria like Pseudomonas or Staphylococcus aureus can often be detected or cultured.

Step 5: Conclude that if nothing is seen in the microscopic examination, the most likely cause is a virus, since viruses cannot be directly visualized by standard light microscopy in skin scrapings.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.

Video duration:

Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Microscopic Examination in Microbiology

Microscopic examination involves observing samples under a microscope to detect microorganisms like bacteria, fungi, or parasites. If nothing is seen, it may indicate the pathogen is too small, not present in the sample, or requires special staining techniques. Understanding the limitations of microscopy helps in interpreting negative results.

Characteristics of Common Pathogens

Different pathogens have distinct features; for example, bacteria like Staphylococcus aureus are visible under light microscopy, fungi like Sporothrix can be seen with special stains, while viruses are too small to be seen with standard microscopes. Recognizing these traits aids in identifying the likely cause of infection.

Diagnostic Challenges of Viral and Parasitic Infections

Viruses and some parasites, such as scabies mites, may not be visible in routine microscopic exams of skin scrapings. Viruses require molecular or culture methods for detection, and scabies mites may be missed if sampling is inadequate. Awareness of these challenges guides appropriate diagnostic approaches.

Recommended video:

Guided course

05:12

Persistent Viral Infections

Related Practice

Textbook Question

Identify the diseases based on the symptoms in the following chart.

views

Textbook Question

A patient has conjunctivitis. If you isolated Pseudomonas from the patient’s mascara, you would most likely conclude all of the following except that

a. The mascara was the source of the infection.

b. Pseudomonas is causing the infection.

c. Pseudomonas has been growing in the mascara.

d. The mascara was contaminated by the manufacturer.

e. All of the above are valid conclusions.

views

Textbook Question

You microscopically examine scrapings from a case of Acanthamoeba keratitis. You expect to see

a. Nothing.

b. Viruses.

c. Gram-positive cocci.

d. Eukaryotic cells.