The bacterium Staphylococcus aureus is which type of bacteria?

JIPMER Nursing Officer-2024

Applied Microbiology & Infection control

Easy

Appeared in: JIPMER Nursing Officer-2024

Explanation

Mesophiles are bacteria that grow best in moderate temperatures, typically between 20°C and 45°C.
Staphylococcus aureus is a common human pathogen, and its optimal growth temperature is around 37°C (normal human body temperature).
Because its optimal growth temperature falls within the 20°C to 45°C range, S. aureus is classified as a mesophile.
Most medically significant bacteria that cause infections in humans are mesophiles, as they are adapted to thrive at body temperature.

Option B: Bacteria are classified by their optimal growth temperature. S. aureus does not have optimal growth in both the mesophile and psychrophile ranges; its optimum is clearly mesophilic.
Option C: Psychrophiles are cold-loving bacteria that thrive at temperatures below 20°C, such as in refrigerators. S. aureus does not grow optimally at these low temperatures.
Option D: Thermophiles are heat-loving bacteria that prefer temperatures above 45°C, often found in environments like hot springs. S. aureus cannot survive at these high temperatures.

Visual 1: Chart: A graph showing the growth rates of psychrophiles, mesophiles, and thermophiles across a temperature spectrum. The mesophile curve would peak at 37°C.
Visual 2: Infographic: A diagram illustrating the different temperature classifications of bacteria with common examples and their typical environments (e.g., refrigerator for psychrophiles, human body for mesophiles, hot spring for thermophiles).

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Bacterial classification based on optimal growth temperature as background academic context rather than a clinical decision trigger.
Understanding that S. aureus is a mesophile is critical for infection control. It explains why the human body is an ideal environment for this bacterium to cause infections, from skin infections to more severe conditions like pneumonia and sepsis.
This knowledge guides practices for handling clinical specimens. To prevent the overgrowth of contaminating mesophiles, samples are often refrigerated if they cannot be processed immediately.
What if the patient had a high fever of 40°C (104°F)? This temperature is still within the optimal range for a mesophile like S. aureus, allowing the infection to persist and potentially worsen. It is not high enough to inhibit bacterial growth.

How to Approach the Question

First, identify the key term in the question, which is 'Staphylococcus aureus'.
Next, understand the question is asking for its classification based on an environmental factor, which the options (Mesophile, Psychrophile, Thermophile) reveal to be temperature.
Recall or deduce the environment where S. aureus is commonly found. It's a major human pathogen, so it thrives in or on the human body.
Relate the human body environment to the temperature classifications. The normal human body temperature is approximately 37°C.
Match this temperature to the correct classification. Mesophiles thrive in moderate temperatures (20-45°C), which includes 37°C. Psychrophiles prefer cold, and thermophiles prefer heat.
Conclude that S. aureus must be a mesophile.

Concept Tested & Keywords

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