WBR0062

Author	PageAuthor::William J Gibson (Reviewed by Yazan Daaboul)
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Microbiology, MainCategory::Pharmacology
Sub Category	SubCategory::Infectious Disease
Prompt	[[Prompt::A 22-year-old woman presents to her primary care physician with a complaint of a pruritic rash for the past 20 days associated with a new-onset low grade fever that started today. She visited another primary care physician when the rash first started and was reassured that her condition would most likely self-resolve within 1-2 weeks. However, she reports no relief of her symptoms since then. She denies exposure to any sick contacts or children. She recalls having previously been infected with varicella zoster virus as a child. The patient denies using any new washing detergents nor any known allergies. Three weeks ago, she returned from a vacation in South America where she stayed mostly at a massage spa. During the vacation, she remained indoors and enjoyed swimming and jacuzzi with her friends. On physical examination of the skin, a rash seen as shown in the image below. What is the treatment of choice for this patient's condition? ]]
Answer A	AnswerA::Acyclovir
Answer A Explanation	AnswerAExp::Acyclovir may be used to treat varicella zoster virus, which this patient has already been infected with and ought to be immune to, given her immunocompetent status.
Answer B	AnswerB::Moxifloxacin
Answer B Explanation	AnswerBExp::Moxifloxacin is a 4th generation fluoroquinolone that has no anti-pseudomonal activity.
Answer C	AnswerC::Erythromycin
Answer C Explanation	AnswerCExp::Erythromycin is a macrolide antibiotic that binds to the 23S rRNA of the 50S ribosomal subunit. It may be used to treat atypical pneumonias.
Answer D	AnswerD::Ciprofloxacin
Answer D Explanation	AnswerDExp::Ciprofloxacin is a 2nd generation fluoroquinolone antibiotic which blocks bacterial DNA topoisomerase. It has an anti-pseudomonal activity that may be used in prolonged cases of hot tub folliculitis.
Answer E	AnswerE::Ceftriaxone
Answer E Explanation	AnswerEExp::Ceftriaxone is a 3rd generation cephalosporin, a β-lactam antibiotic that inhibits cell wall synthesis. It has no anti-pseudomonal activity.
Right Answer	RightAnswer::D
Explanation	[[Explanation::“Hot tub folliculitis” is an infectious dermatologic disease caused by Pseudomonas aeruginosa. It manifests as a widespread, pruritic, papular, and erythematous rash like the one observed in this patient. Although varicella zoster virus and allergic conditions are in the differential diagnosis of hot tub folliculitis, the patient’s history suggests that she had been infected by Pseudomonas aeruginosa while exposed to public swimming pools and jacuzzis during her vacation. Prevention of hot tub folliculitis is optimally by adding and maintaining appropriate levels of chlorine in public swimming pools. Even showering after exposure might not prevent the infection. Pseudomonas aeruginosa is a gram-negative, oxidase-positive rod that causes several waterborne infections, such as external otitis (swimmer’s ear) and hot tub folliculitis. Pseudomonas aeruginosa also produces several pigments: A blue-green pigment called "pyocyanin", a yellow-green fluorescent pigment called "pyoverdin", and a red-brown pigment called "pyorubin". The organism can also be identified by its distinct "grape-like" odor. Generally, pseudomonal infections can be treated with aztreonam, or extended spectrum β-lactam antibiotics such as ticarcillin/clavulonate or piperacillin/tazobactam, some fluoroquinolones such as ciprofloxacin or ofloxacin, or even some 3rd and 4th generation cephalosporins, such as ceftazidime (3rd generation) and cefipime (4th generation). However, hot tub folliculitis is considered a particular case of pseudomonal infection that generally self-resolves within 1-2 weeks and requires no treatment except symptomatic relief. The indications to treat with antibiotics include: fever, constitutional symptoms, persistent infection, or immunocompromised status. Anti-pseudomonal antibiotics are required in such cases, including 3rd generation cephalosporin or fluoroquinolones with anti-pseudomonal activity, such as ciprofloxacin or ofloxacin. Educational Objective: Hot tub folliculitis is usually caused by P. aeruginosa infection after exposure to unchlorinated public swimming pools, hot tubs, and jacuzzis. It generally self-resolves within 1-2 weeks and requires only symptomatic relief. Use of antibiotics with anti-pseudomonal activity, such as ciprofloxacin or ofloxacin, is useful in prolonged cases of hot tub folliculitis, immunocompromised status, or cases complicated with fever and other constitutional symptoms. References: Malhotra PS, Fowlet Jr JF. Hot-tub folliculitis in Acneiform Eruptions in Dermatology: A Differential Diagnosis. Ed. Zeichner JA. Springer Science and Business Media, New York, 2014 First Aid 2014 page 138]]
Approved	Approved::Yes
Keyword	WBRKeyword::Microbiology, WBRKeyword::Dermatology, WBRKeyword::Bacteria, WBRKeyword::Infection, WBRKeyword::Rash, WBRKeyword::Folliculitis, WBRKeyword::Pseudomonas aeruginosa, WBRKeyword::Antibiotics, WBRKeyword::Drugs
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