Bacterial Skin Infections Practice Questions

Q: A man presents with a rash on his flank with itching for the past 2 weeks. The patient has tried several over-the-counter medications, including lotrimin and hydrocortisone, without any improvement. In physical examination, the rash is seen on his palms and the sole of one foot, but no oral lesions are found. What is the likely diagnosis?

Secondary syphilis. ***Secondary syphilis*** - The rash presenting on the **palms and soles** is highly characteristic of **secondary syphilis**, which helps differentiate it from many other dermatological conditions. - The lack of improvement with antifungal (Lotrimin) and corticosteroid (hydrocortisone) treatments further supports a diagnosis other than a fungal infection or inflammatory dermatitis. *Tinea corporis* - This fungal infection typically presents as an **annular (ring-shaped) rash** with central clearing and well-demarcated borders, often on the trunk or limbs. - It would likely show some improvement, even if partial, with **Lotrimin (an antifungal medication)**, which is not the case here. *Pityriasis rosea* - This condition is characterized by an initial **"herald patch"** followed by smaller, oval, pinkish-red patches that often align along skin cleavage lines in a **"Christmas tree" pattern** on the trunk. - It typically spares the palms and soles, which are involved in this patient's presentation. *Contact dermatitis* - This is an inflammatory skin reaction due to contact with an allergen or irritant, presenting as **pruritic (itchy) erythematous (red) patches, possibly with vesicles or bullae**, limited to exposed areas. - While hydrocortisone might offer some relief, the presentation on palms and soles without clear exposure and the lack of response to treatment make it less likely.

Q: A 30-year-old man presents with generalized lymphadenopathy, palmar rash, and condylomata lata 2 months after being treated for primary syphilis. VDRL is positive at 1:128. Which of the following best explains the pathogenesis of these manifestations?

Hematogenous dissemination of spirochetes. Hematogenous dissemination of spirochetes - The manifestations described (generalized lymphadenopathy, palmar rash, and condylomata lata) are classic signs of secondary syphilis, which occurs due to widespread dissemination of T. pallidum through the bloodstream [1]. - The persistence of a high-titer VDRL after primary syphilis treatment further supports active infection with systemic involvement [1]. *Treatment failure* - While possible, treatment failure typically presents with persistent primary lesions or symptoms, not necessarily the characteristic widespread rash and lymphadenopathy of secondary syphilis, especially if the primary infection was reportedly 'treated'. - The specific array of symptoms points more definitively to a stage of syphilis where the pathogen has widely disseminated. *Reinfection with T. pallidum* - Reinfection would typically lead to a primary chancre, although atypical presentations can occur [1]. - The described generalized symptoms and high VDRL titer are more consistent with the secondary stage of a continuous infection rather than a new primary infection. *Immune complex deposition* - While immune complex deposition can play a role in some manifestations of syphilis (e.g., glomerulonephritis), it is not the primary mechanism for the widespread mucocutaneous lesions and lymphadenopathy characteristic of secondary syphilis. - The immune response to the disseminated spirochetes, rather than immune complex deposition, is largely responsible for the clinical findings. *Direct invasion of skin by spirochetes* - While spirochetes are present in skin lesions, the generalized nature of the rash and lymphadenopathy indicates a systemic process, which begins with hematogenous spread to various tissues, including the skin, rather than direct invasion being the sole or primary mechanism [1]. - Direct invasion alone wouldn't explain the systemic lymphadenopathy.

Q: A 24-year-old man presents with dysuria and urethral discharge 5 days after unprotected sexual intercourse. Gram stain of the discharge shows intracellular gram-negative diplococci. The patient reports penicillin allergy. Which of the following is the most appropriate empiric treatment?

Spectinomycin 2g IM single dose. ***Spectinomycin 2g IM single dose*** - **Spectinomycin** is an effective alternative treatment for **gonorrhea** in patients with severe **penicillin/cephalosporin allergies** [1], [2]. - It is administered as a **single intramuscular dose**, which is convenient for adherence. *Ciprofloxacin 500 mg orally single dose* - **Ciprofloxacin** is a fluoroquinolone that was previously used for gonorrhea, but **resistance is now widespread**, making it ineffective for empiric treatment [2]. - Current guidelines do not recommend fluoroquinolones for uncomplicated gonococcal infections due to high rates of **antimicrobial resistance** [2]. *Doxycycline 100 mg orally twice daily for 7 days* - **Doxycycline** is the primary treatment for **Chlamydia trachomatis**, not Neisseria gonorrhoeae [2]. - While co-infection is common, doxycycline alone would not adequately treat the **gonococcal infection** confirmed by Gram stain [3]. *Azithromycin 2g orally single dose* - A **2g dose of azithromycin** is sometimes used in specific situations, but it's increasingly associated with **gonococcal resistance**. - Current CDC guidelines recommend **azithromycin 1g** often in combination with ceftriaxone, reserving higher doses for specific cases or as second-line. *Ceftriaxone 250 mg IM single dose* - **Ceftriaxone** is the **first-line recommended treatment** for uncomplicated gonorrhea, but the patient has a reported **penicillin allergy** [2]. - While cross-reactivity between penicillins and cephalosporins is low, in severe allergies, an alternative like **spectinomycin** is preferred [1].

Q: A 25-year-old man presents with painless penile ulcer for 2 weeks. Physical examination reveals a firm, non-tender, clean-based ulcer with rolled edges. Dark-field microscopy of the lesion shows spirochetes. VDRL test is positive at 1:32 dilution. Which of the following is the most appropriate treatment?

Single dose of benzathine penicillin G 2.4 million units IM. ***Single dose of benzathine penicillin G 2.4 million units IM*** - This is the recommended treatment for **primary syphilis**, characterized by a **painless chancre** and **positive dark-field microscopy** and VDRL [1]. - The single dose is effective because primary syphilis is an early stage of the infection [1]. *Azithromycin 1g orally single dose* - This regimen is primarily used for the treatment of **Chlamydia trachomatis** infections. - It is not effective against **Treponema pallidum**, the causative agent of syphilis. *Three weekly doses of benzathine penicillin G 2.4 million units IM* - This multi-dose regimen is indicated for **late latent syphilis** or **syphilis of unknown duration**, not primary syphilis. - While penicillin is the correct drug, the duration of therapy is too long for an early-stage infection. *Doxycycline 100 mg orally twice daily for 14 days* - Doxycycline is an alternative treatment for **early syphilis** (primary, secondary, or early latent) in patients who are allergic to penicillin. - Given that penicillin is not contraindicated here, it is not the primary choice, and treatment with penicillin is more effective. *Ceftriaxone 250 mg IM single dose* - Ceftriaxone is a treatment for **gonorrhea**, not syphilis. - While it has some activity against *Treponema pallidum*, it is not the recommended first-line treatment for syphilis.

Q: A 45-year-old man presents with well-circumscribed, hypopigmented patches on his face and arms. The lesions are asymmetric and show decreased sensation to light touch. Microscopic examination of a skin biopsy stained with Fite stain shows acid-fast bacilli within macrophages in dermal nerve bundles. Which of the following is the most appropriate treatment?

Multidrug therapy with dapsone, rifampin, and clofazimine. ***Multidrug therapy with dapsone, rifampin, and clofazimine*** - The clinical presentation of **hypopigmented patches with decreased sensation**, along with the presence of **acid-fast bacilli (AFB) in dermal nerve bundles** on Fite stain, is characteristic of **leprosy** (Hansen's disease) [1]. - This specific regimen of **dapsone, rifampin, and clofazimine** is the standard and most effective **multidrug therapy (MDT)** for treating **multibacillary leprosy**, ensuring eradication of the pathogen and preventing drug resistance [1]. *Topical steroids* - **Topical steroids** are primarily used for inflammatory skin conditions like eczema or psoriasis and would not be effective against **bacterial infections** like leprosy [1]. - While steroids might be used as an adjunct to manage **leprosy reactions**, they do not treat the underlying bacterial infection [1]. *Oral terbinafine* - **Oral terbinafine** is an **antifungal medication** used to treat fungal infections, such as onychomycosis or ringworm. - It has no activity against the **acid-fast bacillus** responsible for leprosy. *Oral acyclovir* - **Oral acyclovir** is an **antiviral medication** used to treat viral infections, particularly those caused by herpesviruses. - It is completely ineffective against **bacterial infections** like leprosy. *Phototherapy* - **Phototherapy**, using ultraviolet light, is a treatment modality for certain skin conditions like psoriasis, vitiligo, or severe eczema. - It is not an effective treatment for **bacterial infections** and would not address the underlying pathology of leprosy.

Q: A patient with gonorrhea infection shows persistence of symptoms despite appropriate treatment with Ceftriaxone. Which of the following best explains this treatment failure?

Reinfection from untreated partner. ***Reinfection from untreated partner*** - The most common reason for persistent gonorrhea symptoms despite appropriate treatment is **re-exposure** to the infection from an **untreated sexual partner** [1]. - This highlights the importance of **partner notification and treatment** in managing sexually transmitted infections [1]. *Host immune deficiency* - While host immune status can influence the severity or recurrence of infections, a primary **immune deficiency** is a less common explanation for treatment failure of uncomplicated gonorrhea, especially with an effective antibiotic like ceftriaxone. - Gonorrhea is typically managed effectively with standard antibiotic regimens, even in individuals with common viral infections like HIV, unless there are severe, unmanaged coinfections or systemic immunosuppression. *Initial misdiagnosis* - An initial misdiagnosis could lead to persistent symptoms if the patient never had gonorrhea or had another co-infection that was not treated. However, the question states "gonorrhea infection" and "appropriate treatment with Ceftriaxone," implying the diagnosis was correct and the treatment regimen was standard. - This option does not explain why the **specific treatment for gonorrhea** failed, but rather suggests a fundamental error in the diagnostic process. *Development of new resistance during therapy* - Although **antibiotic resistance** in *Neisseria gonorrhoeae* is a growing concern, the development of *new* resistance mutations *during* a typical short course of effective ceftriaxone treatment for an initial infection is rare [1]. - More commonly, resistance profiles are established before treatment, or an existing resistant strain was acquired, rather than a new mutation arising and causing failure within the short therapeutic window.

Q: A 25-year-old man presents with multiple painful genital ulcers with undermined edges and suppurative lymphadenopathy. Gram stain shows 'school of fish' arrangement. What is the most appropriate initial treatment?

Azithromycin 1g single dose. ***Azithromycin 1g single dose*** - This presentation is highly suggestive of **chancroid**, caused by *Haemophilus ducreyi*. **Azithromycin 1g single dose** is a highly effective and convenient treatment as recommended by CDC guidelines. - The **"school of fish"** gram stain appearance and **painful genital ulcers with undermined edges** are classic features of chancroid [1], making azithromycin the most appropriate initial therapy. *Erythromycin 500mg QID for 7 days* - While **erythromycin** is an effective treatment for chancroid, the **multi-day regimen** makes it less convenient and potentially lowers adherence compared to a single-dose option. - This regimen is less preferred as a first-line initial treatment given the availability of single-dose options for chancroid. *Ceftriaxone 250mg IM single dose* - **Ceftriaxone IM** is the preferred treatment for uncomplicated **gonorrhea** and is also used for **syphilis**, but it is **not the primary treatment for chancroid**. - While it has some activity against *Haemophilus ducreyi*, azithromycin or ciprofloxacin are generally more effective and recommended for chancroid. *Doxycycline 100mg BD for 7 days* - **Doxycycline** is the treatment of choice for **chlamydia** and **syphilis**, but it is **not the recommended first-line treatment for chancroid**. - Its efficacy against *Haemophilus ducreyi* is not as reliable as macrolides or fluoroquinolones for chancroid.

Q: All of the following are manifestations of congenital syphilis except:-

Gumma. ***Gumma*** - **Gumma** is a manifestation of **tertiary syphilis** in adults, typically appearing years after the initial infection [1]. - While syphilis can be transmitted congenitally, **gummatous lesions** are not a characteristic finding in congenital syphilis [1]. *Olympian brow* - **Olympian brow** (also known as frontal bossing) is a feature of **congenital syphilis**, characterized by prominent frontal bones [2]. - It results from **periostitis** and abnormal bone development due to chronic infection in utero. *Interstitial keratitis* - **Interstitial keratitis** is a classic manifestation of **late congenital syphilis**, affecting the cornea [2]. - It presents as **bilateral corneal inflammation** leading to vision impairment, often appearing in childhood or adolescence. *Hutchinson's teeth* - **Hutchinson's teeth** are a pathognomonic sign of **congenital syphilis**, characterized by notched, peg-shaped, and widely spaced incisors. - This dental abnormality results from the treponemal infection disrupting the **enamel formation** during tooth development.

Question 1

A man presents with a rash on his flank with itching for the past 2 weeks. The patient has tried several over-the-counter medications, including lotrimin and hydrocortisone, without any improvement. In physical examination, the rash is seen on his palms and the sole of one foot, but no oral lesions are found. What is the likely diagnosis?

Accepted Answer

Secondary syphilis

Answer

Tinea corporis

Answer

Pityriasis rosea

Answer

Contact dermatitis

Question 2

A 45-year-old man presents with a 2-month history of painless testicular swelling. He reports being treated for syphilis 20 years ago. Examination reveals bilateral, non-tender testicular enlargement. Which of the following is the most likely diagnosis?

Accepted Answer

Gummatous orchitis

Answer

Hydrocele

Answer

Tuberculosis orchitis

Answer

Epididymitis

Answer

Testicular cancer

Question 3

A 30-year-old man presents with generalized lymphadenopathy, palmar rash, and condylomata lata 2 months after being treated for primary syphilis. VDRL is positive at 1:128. Which of the following best explains the pathogenesis of these manifestations?

Accepted Answer

Hematogenous dissemination of spirochetes

Answer

Treatment failure

Answer

Reinfection with T. pallidum

Answer

Immune complex deposition

Answer

Direct invasion of skin by spirochetes

Question 4

A 24-year-old man presents with dysuria and urethral discharge 5 days after unprotected sexual intercourse. Gram stain of the discharge shows intracellular gram-negative diplococci. The patient reports penicillin allergy. Which of the following is the most appropriate empiric treatment?

Accepted Answer

Spectinomycin 2g IM single dose

Answer

Ciprofloxacin 500 mg orally single dose

Answer

Doxycycline 100 mg orally twice daily for 7 days

Answer

Azithromycin 2g orally single dose

Answer

Ceftriaxone 250 mg IM single dose

Question 5

A 25-year-old man presents with painless penile ulcer for 2 weeks. Physical examination reveals a firm, non-tender, clean-based ulcer with rolled edges. Dark-field microscopy of the lesion shows spirochetes. VDRL test is positive at 1:32 dilution. Which of the following is the most appropriate treatment?

Accepted Answer

Single dose of benzathine penicillin G 2.4 million units IM

Answer

Azithromycin 1g orally single dose

Answer

Three weekly doses of benzathine penicillin G 2.4 million units IM

Answer

Doxycycline 100 mg orally twice daily for 14 days

Answer

Ceftriaxone 250 mg IM single dose

Question 6

A 45-year-old man presents with well-circumscribed, hypopigmented patches on his face and arms. The lesions are asymmetric and show decreased sensation to light touch. Microscopic examination of a skin biopsy stained with Fite stain shows acid-fast bacilli within macrophages in dermal nerve bundles. Which of the following is the most appropriate treatment?

Accepted Answer

Multidrug therapy with dapsone, rifampin, and clofazimine

Answer

Topical steroids

Answer

Oral terbinafine

Answer

Oral acyclovir

Answer

Phototherapy

Question 7

A patient with gonorrhea infection shows persistence of symptoms despite appropriate treatment with Ceftriaxone. Which of the following best explains this treatment failure?

Accepted Answer

Reinfection from untreated partner

Answer

Host immune deficiency

Answer

Initial misdiagnosis

Answer

Development of new resistance during therapy

Question 8

A 25-year-old male presents with purulent urethral discharge and dysuria for 3 days. Gram stain shows intracellular gram-negative diplococci. What is the most appropriate empirical treatment regimen according to current CDC guidelines?

Accepted Answer

Ceftriaxone 500mg IM single dose + Azithromycin 1g oral single dose

Answer

Azithromycin 2g oral single dose

Answer

Doxycycline 100mg oral twice daily for 7 days

Answer

Ceftriaxone 1g IM single dose

Question 9

A 25-year-old man presents with multiple painful genital ulcers with undermined edges and suppurative lymphadenopathy. Gram stain shows 'school of fish' arrangement. What is the most appropriate initial treatment?

Accepted Answer

Azithromycin 1g single dose

Answer

Erythromycin 500mg QID for 7 days

Answer

Ceftriaxone 250mg IM single dose

Answer

Doxycycline 100mg BD for 7 days

Question 10

All of the following are manifestations of congenital syphilis except:-

Accepted Answer

Gumma

Answer

Olympian brow

Answer

Interstitial keratitis

Answer

Hutchinson's teeth

Bacterial Skin Infections — MCQs

Bacterial Skin Infections — MCQs

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