Multiple Choice
Which group of bacteria is typically the first to colonize the upper respiratory tract in humans?
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1. Introduction to Microbiology
Members of the Bacterial World
Multiple Choice
Which of the following characteristics is most commonly associated with Staphylococcus aureus?
A
Coagulase positivity
B
Lack of catalase enzyme
C
Gram-negative rod morphology
D
Beta-hemolysis on MacConkey agar
Verified step by step guidance1
Step 1: Understand the general characteristics of Staphylococcus aureus. It is a Gram-positive bacterium, which means it retains the crystal violet stain and appears purple under a microscope.
Step 2: Recall that Staphylococcus aureus is catalase positive, meaning it produces the enzyme catalase that breaks down hydrogen peroxide into water and oxygen. Therefore, 'lack of catalase enzyme' is not a characteristic of S. aureus.
Step 3: Recognize that Staphylococcus aureus is coagulase positive. Coagulase is an enzyme that clots plasma, and this trait is commonly used to differentiate S. aureus from other Staphylococcus species.
Step 4: Note that Staphylococcus aureus is a coccus (spherical) bacterium, not a rod-shaped one, so 'Gram-negative rod morphology' does not apply.
Step 5: Understand that while S. aureus can exhibit beta-hemolysis on blood agar, MacConkey agar is selective for Gram-negative bacteria and does not support the growth of Gram-positive bacteria like S. aureus, so beta-hemolysis on MacConkey agar is not a relevant characteristic.
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