A 22-year-old man comes to the office due to a painful lesion on his upper back. The patient developed a small tender papule a few days ago that progressively enlarged and became red and painful. He has had 3 similar lesions on his upper back over the past 6 months, which were treated with incision and drainage and antibiotics. The patient has no other medical issues and takes no medications. He does not use tobacco, alcohol, or illicit drugs. On physical examination, there is a 3-cm tender pustule with surrounding erythema on his right upper back. Gram staining of purulent drainage from the lesion is shown below. Which of the following most likely predisposed this patient to recurrent infections?

Question

A 22-year-old man comes to the office due to a painful lesion on his upper back.  The patient developed a small tender papule a few days ago that progressively enlarged and became red and painful.  He has had 3 similar lesions on his upper back over the past 6 months, which were treated with incision and drainage and antibiotics.  The patient has no other medical issues and takes no medications.  He does not use tobacco, alcohol, or illicit drugs.  On physical examination, there is a 3-cm tender pustule with surrounding erythema on his right upper back.  Gram staining of purulent drainage from the lesion is shown below.  Which of the following most likely predisposed this patient to recurrent infections?

Quizplus · Accepted Answer

Staphylococcus aureus is a gram-positive bacterium that grows in grape-like clusters. Approximately 30% of individuals in the community-setting are colonized with S aureus. The pathogen is transmitted by direct contact, colonizes the anterior nares, and spreads to the skin. Defects in the mucosal or cutaneous barrier can lead to invasion. The most common manifestation is skin and soft-tissue abscess; patients usually develop a localized pustule that evolves over days into a painful nodule with a necrotic, purulent center and surrounding indurated erythema. Treatment with incision/drainage and oral antibiotics is usually curative of the localized infection. However, oral antibiotics do not eliminate S aureus colonization of the nares and skin so recurrent infections are common. Colonization with methicillin-sensitive S aureus (MSSA) is associated with a low risk of illness. In contrast, methicillin-resistant S aureus (MRSA) colonization is much more likely to cause disease due to expression of associated virulence factors (eg, leukocidin). (Choice B) Latent Mycobacterium tuberculosis is characterized by the presence of organisms in walled-off granulomas. Patients with latent tuberculosis are asymptomatic and most will never have reactivation of disease. Reactivation is classically characterized by the formation of apical, cavitary lesions in the lung, weight loss, and cough. (Choice C) Chlamydia trachomatis is an obligate intracellular organism that invades as a small elementary body and then evolves to the metabolically active reticulate body once inside host cells. Recurrent Chlamydia symptoms (eg, dysuria, purulent urethra discharge) in patients who have been adequately treated (eg, azithromycin) usually indicates a new infection due to continued high-risk behavior (eg, unprotected sex). (Choice D) Scabies is a skin mite (Sarcoptes scabiei) that causes intensely pruritic eruptions, particularly of the finger webs, wrists, axilla, areola, and genitalia. The mite burrows into the epidermis and lays eggs. Topical treatment with permethrin is usually curative, but recurrence can occur if close contacts and environmental harbors (eg, sheets) are not adequately treated. (Choice E) Clostridium difficile spores are hardy and resistant to heat and soap. Infection usually causes colitis with watery diarrhea, fever, and abdominal pain. Recurrent infection after treatment with oral antibiotics (eg, vancomycin) is common and may require a repeat pharmacologic treatment or, in some cases, fecal transplant. Educational objective: Staphylococcus aureus is the most common cause of skin and soft-tissue abscess (eg, furuncle). Treatment of the abscess with incision and drainage and antibiotics can eliminate the local infection but does not eliminate colonization of the anterior nares and skin. Therefore, recurrent infections are common.

A 22-Year-Old Man Comes to the Office Due to a Painful