Question:medium
Anaerobes are intrinsically resistant to which class of antibiotics?
Anaerobes are intrinsically resistant to which class of antibiotics?
Show Hint
Which antibiotic needs oxygen-dependent uptake that anaerobes cannot provide?
Updated On: Jun 24, 2026
- Beta lactam antibiotics
- Aminoglycosides
- Azithromycin
- Metronidazole
Show Solution
The Correct Option is B
Solution and Explanation
Step 1: Aminoglycosides need an oxygen-powered transport step to cross the bacterial membrane and reach the ribosome.
Step 2: Anaerobes, by definition, do not run aerobic oxidative metabolism, so they cannot energize this uptake; the antibiotic is effectively locked out.
Step 3: This is classic intrinsic resistance, a built-in trait of the organism rather than an acquired plasmid or mutation.
Step 4: By contrast metronidazole is actually activated inside anaerobes and is their drug of choice, so it is the opposite of the answer.
\[\boxed{\text{Aminoglycosides}}\]
Step 2: Anaerobes, by definition, do not run aerobic oxidative metabolism, so they cannot energize this uptake; the antibiotic is effectively locked out.
Step 3: This is classic intrinsic resistance, a built-in trait of the organism rather than an acquired plasmid or mutation.
Step 4: By contrast metronidazole is actually activated inside anaerobes and is their drug of choice, so it is the opposite of the answer.
\[\boxed{\text{Aminoglycosides}}\]
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