Which bacterium cannot survive in the presence of oxygen?

Appeared in: AIIMS CRE, SNO-2024

Explanation

The question asks to identify a bacterium that cannot survive in the presence of oxygen, which is the definition of an obligate anaerobe.
Clostridium botulinum is a classic example of an obligate anaerobe.
These organisms lack enzymes like superoxide dismutase and catalase, which are necessary to detoxify harmful reactive oxygen species formed in the presence of oxygen.
Therefore, oxygen is toxic to Clostridium botulinum, restricting its growth to anaerobic environments.

Option A: Staphylococcus aureus is a facultative anaerobe, meaning it can survive and grow in both the presence and absence of oxygen, although it prefers aerobic conditions.
Option C: Mycobacterium tuberculosis is an obligate aerobe. It strictly requires oxygen to survive and multiply, which is why tuberculosis most commonly affects the highly oxygenated apices of the lungs.
Option D: Bacillus subtilis is also an obligate aerobe. It requires oxygen for cellular respiration and cannot grow in its absence.

Visual 1: Diagram: Growth patterns in thioglycolate broth. This visual shows how different types of bacteria (obligate aerobes, obligate anaerobes, facultative anaerobes, etc.) grow in a special liquid medium. Obligate anaerobes like C. botulinum would be seen growing only at the bottom of the tube where there is no oxygen.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Bacterial classification based on oxygen requirements as background academic context rather than a clinical decision trigger.
Understanding bacterial oxygen requirements is crucial for diagnosing and treating infections. For example, specimens for anaerobic culture must be collected and transported in special oxygen-free containers.
Nurses play a key role in patient education about food safety, particularly the dangers of improperly canned homemade foods, which can create the perfect anaerobic environment for C. botulinum to produce its deadly toxin.
Recognizing the signs of botulism (e.g., descending paralysis, difficulty swallowing, blurred vision) is critical for early intervention, which includes supportive care and administration of antitoxin.

How to Approach the Question

First, analyze the question to identify the core requirement. The key phrase is 'cannot survive in the presence of oxygen'.
This phrase is the definition of an 'obligate anaerobe'. Your task is to identify the obligate anaerobe among the options.
Recall the classification of the bacteria listed in the options based on their oxygen needs.
Staphylococcus aureus is a facultative anaerobe.
Clostridium botulinum is an obligate anaerobe.
Mycobacterium tuberculosis and Bacillus subtilis are obligate aerobes.

Concept Tested & Keywords

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Practise the full AIIMS CRE, SNO-2024

Attempt every question from this paper in a timed mock, then review the full solution for each one.