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 the primary care office with a complaint of a pruritic rash of 20 days duration as shown in the image below, and new-onset low grade fever that started today. She visited another primary care physician when the rash first started and was reassured that the rash would most likely self-resolve within 1-2 weeks. However, she reports no relief of her symptoms. She denies any sick contacts or contact with children. She recalls having previously been infected with varicella zoster virus as a child. 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. She denies using any new washing detergents nor any known allergies. What is the treatment of choice for this patient's condition? ]]
Answer A	AnswerA::Acyclovir
Answer A Explanation	AnswerAExp::Acyclovir may to treat varicella zoster virus, which the woman has already been infected with and ought to be immune to.
Answer B	AnswerB::Tazobactam
Answer B Explanation	[[AnswerBExp::Tazobactam is not useful in P. aeruginosa infection because tazobactam has no activity on β-lactamase of P. aeruginosa. However, piperacillin, which is an extended-spectrum β-lactam antibiotic, is frequently added to tazobactam and has 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 is used to treat atypical pneumonias.
Answer D	AnswerD::Ciprofloxacin
Answer D Explanation	AnswerDExp::Ciprofloxacin is a 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 third generation cephalosporin which is also a beta-lactam-based drug and inhibits cell wall synthesis. It has no anti-pseudomonal activity.
Right Answer	RightAnswer::D
Explanation	[[Explanation::The patient in this vignette is presenting with a case of “hot tub folliculitis” caused by Pseudomonas aeruginosa. A widespread, pruritic, papular, erythematous rash like the one observed in this patient should focus a differential between chicken pox (Varicella zoster virus), folliculitis, and an allergic condition. In this case, the patient’s history provides a clear clue by suggesting that the patient had been infected by Pseudomonas aeruginosa while exposed to public swimming pools and jacuzzis. Prevention of hot tub folliculitis is optimally by adding and maintaining appropriate levels of chlorine in public swimming pools. Even showing 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 penicillins such as ticarcillin/clavulonate or piperacillin/tazobactam, some fluoroquinolones such as ciprofloxacin, 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 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, or persistent infection. Anti-pseudomonal antibiotics are required in such cases, including 3rd generation cephalosporin with anti-pseudomonal activity, or fluoroquinolone 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 and requires only symptomatic relief. Use of antibiotics with anti-pseudomonal activity, such as ciprofloxacin, ofloxacin, are useful in prolonged cases of hot tub folliculitis, 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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