Question
A 39-year-old man comes to the emergency room with fever, chills, and left lower leg pain for 2 days. He was recently discharged from the hospital after arthroscopic knee surgery. Physical examination shows an erythematous lesion with poorly defined margins over the left shin but no fluctuance. Treatment with an intravenous antibiotic is begun. Shortly after starting the infusion, the patient develops flushing, erythema, and pruritus of the upper body. The symptoms resolve after discontinuation of the infusion. Before the next dose with the same agent, the patient is given diphenhydramine and ranitidine and the antibiotic is subsequently given at a slower infusion rate without complications. The patient was most likely treated with an antibiotic that binds to which of the following?
| A. |
Topoisomerase II
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| B. |
30S subunit
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| C. |
Dihydrofolate reductase
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| D. |
D-alanyl-D-alanine
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Show Answer
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Correct Answer � D
Explanation
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Ans-D-D-alanyl-D-alanine
Topoisomerase II
Topoisomerase II and topoisomerase IV are inhibited by fluoroquinolones. These drugs have narrow indications for the treatment of skin and soft tissue infections, including surgical site infections following gastrointestinal surgery, infections resulting from bite wounds, and as empiric treatment in neutropenic patients. This patient does not meet any of these criteria. Moreover, ciprofloxacin is the only fluoroquinolone associated with red man syndrome and its occurrence is quite rare.
30S subunit
The 30S subunit of the bacterial ribosome is inhibited by several classes of antibiotics, including aminoglycoside, tetracycline, and glycylcycline drugs, all of which inhibit bacterial protein synthesis. None of these drugs are indicated for the treatment of moderate, nonpurulent skin and soft tissue infections. Furthermore, red man syndrome is not associated with these medications.
Dihydrofolate reductase
Dihydrofolate reductase is the target of trimethoprim, which is commonly administered along with sulfamethoxazole; TMP-SMX is sometimes used for treatment of moderate purulent skin and soft tissue infections. However, this patient’s examination does not show fluctuance, so a purulent infection is much less likely. Moreover, neither trimethoprim nor sulfamethoxazole cause red man syndrome; other toxicities, such as type 1 hypersensitivity reactions and Stevens-Johnson syndrome, are associated with these drugs.
D-alanyl-D-alanine
D-alanyl-D-alanine residues are bacterial cell wall precursors and the molecular target of vancomycin. Targeting of this highly conserved sequence is responsible for the broad spectrum of vancomycin activity against gram-positive species (including MRSA), which are the most common cause of cellulitis. Red man syndrome is an infusion rate-dependent effect and is a result of IgE-independent mast cell degranulation.
