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Ch. 1 - The Microbial World and You
Chapter 1, Problem 25.3a

Isolation of E. coli from a stool sample is diagnostic proof that the patient has
a. cholera.
b. E. coli gastroenteritis.
c. salmonellosis.
d. typhoid fever.
e. none of the above

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1
Understand the context: E. coli is a common bacterium found in the intestines of humans and animals. Its presence in a stool sample is not unusual.
Consider the diseases listed: Cholera, E. coli gastroenteritis, salmonellosis, and typhoid fever are all gastrointestinal diseases, but they are caused by different pathogens.
Identify the causative agents: Cholera is caused by Vibrio cholerae, salmonellosis by Salmonella species, and typhoid fever by Salmonella typhi.
Recognize that E. coli gastroenteritis is specifically caused by certain pathogenic strains of E. coli, such as ETEC, EPEC, EHEC, etc.
Conclude that the isolation of E. coli from a stool sample is diagnostic proof of E. coli gastroenteritis, as it directly involves pathogenic strains of E. coli.

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Key Concepts

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

E. coli Pathogenicity

Escherichia coli (E. coli) is a diverse group of bacteria, some strains of which are pathogenic and can cause gastrointestinal diseases. The pathogenic strains, such as Enterotoxigenic E. coli (ETEC) and Enterohemorrhagic E. coli (EHEC), are responsible for conditions like gastroenteritis. Understanding the specific strain involved is crucial for diagnosing the type of infection.
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Differential Diagnosis

Differential diagnosis is the process of distinguishing a particular disease or condition from others that present similar clinical features. In this case, the presence of E. coli in a stool sample must be differentiated from other gastrointestinal infections like cholera, salmonellosis, and typhoid fever, which have distinct causative agents and clinical presentations.
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Stool Culture Techniques

Stool culture techniques are laboratory methods used to isolate and identify pathogens from fecal samples. These techniques involve culturing the sample on selective media that favor the growth of specific bacteria, allowing for the identification of E. coli and other pathogens. Accurate culture results are essential for confirming the diagnosis and guiding appropriate treatment.
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