Which antibiotic is NOT used to treat giardiasis?

Which antibiotic is NOT used to treat giardiasis?

• A. Amoxicillin
• B. Metronidazole
• C. Tinidazole
• D. Nitazoxanide

Answer: (A)

Giardiasis is caused by a protozoan, and the drugs used to treat it are targeted to protozoal metabolism rather than bacterial cell walls. Amoxicillin is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis and has no activity against protozoa like Giardia. Because the organism is a eukaryotic parasite without a bacterial cell wall, amoxicillin won’t clear the infection. In contrast, metronidazole and tinidazole are nitroimidazoles that damage Giardia’s DNA, and nitazoxanide disrupts a parasite-specific energy pathway, all of which are effective against giardiasis. So the medication not appropriate for this infection is amoxicillin.

Giardiasis is caused by a protozoan, and the drugs used to treat it are targeted to protozoal metabolism rather than bacterial cell walls. Amoxicillin is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis and has no activity against protozoa like Giardia. Because the organism is a eukaryotic parasite without a bacterial cell wall, amoxicillin won’t clear the infection. In contrast, metronidazole and tinidazole are nitroimidazoles that damage Giardia’s DNA, and nitazoxanide disrupts a parasite-specific energy pathway, all of which are effective against giardiasis. So the medication not appropriate for this infection is amoxicillin.