Which of the following is a bacterium commonly found in soil, water, and on the skin of healthy individuals?

• A. Escherichia coli
• B. Mycobacterium tuberculosis
• C. Pseudomonas aeruginosa
• D. Streptococcus pneumoniae

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the question is asking to identify a bacterium commonly found in soil, water, and on the skin of healthy individuals. This means the bacterium should be environmental and also part of normal human flora.
2. Step 2: Review the characteristics of each bacterium listed: Escherichia coli is primarily found in the intestines, Mycobacterium tuberculosis is a pathogen causing tuberculosis, Streptococcus pneumoniae is a respiratory pathogen, and Pseudomonas aeruginosa is known to inhabit soil, water, and skin.
3. Step 3: Recognize that Pseudomonas aeruginosa is an opportunistic pathogen widely distributed in the environment, including soil and water, and can colonize the skin of healthy individuals without causing disease.
4. Step 4: Compare the ecological niches of the bacteria to confirm that Pseudomonas aeruginosa fits the description best, as the others are either primarily pathogens or found in different body sites.
5. Step 5: Conclude that the bacterium commonly found in soil, water, and on the skin of healthy individuals is Pseudomonas aeruginosa.