A 24-year-old man presents to the emergency department with a 2-day history of fever, malaise, and boils on his right leg. He is a competitive swimmer and reports that he borrowed a teammate's razor to shave his legs before a swim meet. Past medical history is unremarkable. Physical examination shows 3 raised, erythematious, warm, lesions with a central point extruding pus. A Gram stain and culture are performed and reveal that the causative organism is a catalase-positive, Gram-positive coccus. The organism also tests positive for the MecA gene. The patient is prescribed oral linezolid to treat this patient.
Two days later, the patient develops spiking fevers, chills, nausea, and vomiting. He is admitted to the hospital and started on an intravenous antibiotic that acts against the bacterial cell wall.
Which of the following is a potential adverse effect of this intravenous antibiotic?
A) Flushing
B) Gray baby syndrome
C) Pseudomembranous colitis
D) Rhabdomyolysis
E) Tendon rupture
A) Flushing
Of the gram-positive cocci, only Staphylococcus aureus is both catalase positive and coagulase positive. A positive MecA gene means that this S. aureus has a mutant peptidoglycan transpeptidase (also known as penicillin binding protein) that does not bind to most beta-lactams, such penicillins and cephalosporins. Linezolid is prescribed and has a mechanism of action of binding to the 50S subunit of the bacterial ribosome and preventing the initiation complex. Outpatient therapy is unsuccessful, so the patient is prescribed an intravenous antibiotic with a different mechanism of action. Specifically, the drug cannot target peptidoglycan transpeptidase due to the resistance from MecA, so the only other mechanism that targets the bacterial cell wall is inhibiting the synthesis/polymerization of peptidoglycan. Vancomycin is the antibiotic and is only given intravenously for systemic infections. Adverse effects include nephrotoxicity, ototoxicity, thrombophlebitis, and diffuse flushing (red man syndrome).
Gray baby syndrome is a major complication of chloramphenicol when given to premature babies. Chloramphenicol functions at the 50S subunit of bacterial ribosomes. Pseudomembranous colitis is a possible adverse effect for clindamycin, which works at the 50S subunit of the bacterial ribosome. Rhabdomyolysis is a risk with daptomycin, especially when the patients are on statins. Daptomycin would be an effective treatment for MRSA skin infections, but it works by disrupting cell membranes by creating transmembrane K+ channels. Tendon rupture is a major complication of fluroquinolones, which inhibit prokaryotic topoisomerase II (also known as DNA gyrase).
Key Learning Point
Vancomycin targets the bacterial cell wall by inhibiting the synthesis/polymerization of peptidoglycan. Adverse effects of vancomycin include nephrotoxicity, ototoxicity, thrombophlebitis, and diffuse flushing.
