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 new-onset pruritic rash of 8 days duration as shown in the image below. She visited another primary care physician when the rash first started and prescribed a topical antibiotic that she cannot recall its name. However, she reports no relief of her symptoms despite proper application. She denies any sick contacts or contact with children. She recalls having previously been infected with varicella zoster virus as a child. Ten days 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 is used primarily to treat UTIs and community acquired pneumonia.
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 is most commonly used against gram negative Neisseria Species.
Right Answer	RightAnswer::B
Explanation	[[Explanation::The patient in this vignette is presenting with a case of “hot tub folliculitis” caused by Pseudomonas aeruginosa. A widespread, pruritic, raised 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 soaked in a hot bathtub. Pseudomonas aeruginosa is a gram-negative, oxidase-positive rod that causes several water-bourne 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. 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). Educational Objective: Pseudomonal infections can be treated with aztreonam, or extended spectrum penicillins such as ticarcillin or piperacillin. References: 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
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::

Image [[WBRImage::|]] Caption WBRImageCaption::no-display Position [[WBRImagePlace::Prompt|]]