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Ch. 25 - Microbial Diseases of the Digestive System
Tortora - Microbiology: An Introduction 14th Edition
Tortora14th EditionMicrobiology: An IntroductionISBN: 9780138200398Not the one you use?Change textbook
All textbooksTortora 14th EditionCh. 25 - Microbial Diseases of the Digestive SystemProblem 5
Chapter 25, Problem 5

Microscopic examination of a patient’s fecal culture shows comma-shaped bacteria. These bacteria require 2-4% NaCl to grow. The bacteria probably belong to the genus
a. Campylobacter.
b. Escherichia.
c. Salmonella.
d. Shigella.
e. Vibrio.

Verified step by step guidance
1
Step 1: Identify the shape of the bacteria described. The problem states the bacteria are comma-shaped, which is a curved rod shape often associated with certain genera.
Step 2: Consider the salt requirement for growth. The bacteria require 2-4% NaCl, indicating they are halophilic or salt-tolerant organisms.
Step 3: Recall the characteristics of the given genera: Campylobacter is curved but microaerophilic and does not require high salt; Escherichia, Salmonella, and Shigella are straight rods and do not require salt for growth; Vibrio species are comma-shaped and require or tolerate salt concentrations around 2-4%.
Step 4: Match the combination of comma-shaped morphology and salt requirement to the genus Vibrio, which is known for these features.
Step 5: Conclude that the bacteria most likely belong to the genus Vibrio based on the morphological and growth requirements described.

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Key Concepts

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

Bacterial Morphology

Bacterial morphology refers to the shape and arrangement of bacteria, which helps in their identification. Comma-shaped bacteria are curved rods, often described as vibrio-shaped, distinguishing them from straight rods or cocci. Recognizing shape is a primary step in classifying bacteria in clinical samples.
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Halophilic Growth Requirements

Some bacteria require specific salt concentrations to grow, known as halophilic bacteria. A requirement of 2-4% NaCl indicates moderate halophilicity, which is characteristic of certain genera like Vibrio. This growth condition helps differentiate bacteria that thrive in saline environments from those that do not.
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Genus Vibrio Characteristics

The genus Vibrio includes comma-shaped, gram-negative bacteria that are facultative anaerobes and require salt (NaCl) for growth. They are commonly found in marine or estuarine environments and are known pathogens causing diseases like cholera. Their unique morphology and salt requirement aid in their identification.
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Textbook Question

A cholera epidemic in Peru had all of the following characteristics. Which one led to the others?

a. Eating raw fish

b. Sewage contamination of water

c. Catching fish in contaminated water

d. Vibrio in fish intestine

e. Including fish intestines with edibles

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Textbook Question

Gastric ulcers are caused by

a. Stomach acid.

b. H. pylori.

c. Spicy food.

d. Acidic food.

e. Stress.

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E. coli bacteria are part of the normal microbiota of the intestines and can cause gastroenteritis. Explain why this one species is both beneficial and harmful.

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Identify the site colonized by the following organisms: E. granulosus, E. vermicularis, Giardia, H. pylori, hepatitis B virus, mumps virus, Rotavirus, Salmonella, Shigella, Streptococcus mutans, Trichinella spiralis, Trichuris.

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Define mycotoxin. Give an example of a mycotoxin.

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Explain how the following diseases differ and how they are similar: giardiasis, amebic dysentery, cyclosporiasis, and cryptosporidiosis.

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