Bacterial Skin Infections Practice Questions

Q: What is the most likely diagnosis for a patient presenting with a painful ulcer on the glans penis?

Chancroid. The diagnosis of genital ulcers is a high-yield topic for NEET-PG, primarily differentiated by the presence or absence of pain and the characteristics of the lesion. [1] ### **Why Chancroid is Correct** **Chancroid**, caused by the gram-negative coccobacillus *Haemophilus ducreyi*, is classically characterized by a **painful**, "soft" ulcer. [1] The pain is the hallmark clinical feature that distinguishes it from many other STIs. These ulcers often have ragged, undermined edges and a necrotic base (grayish-yellow exudate). They are frequently associated with painful, inflammatory inguinal lymphadenopathy (buboes) which may suppurate. ### **Why Other Options are Incorrect** * **Syphilis (Option A):** Primary syphilis presents as a **painless**, indurated (hard) ulcer with a clean base. [1] * **Chancre (Option D):** This is the clinical term for the primary lesion of syphilis. By definition, a classic chancre is **painless**. * **Lymphogranuloma Venereum (LGV) (Option B):** Caused by *Chlamydia trachomatis* (L1-L3), the primary lesion is a small, transient, **painless** papule or ulcer that often heals unnoticed before the painful "groove sign" (lymphadenopathy) develops. [1] ### **NEET-PG High-Yield Pearls** * **Mnemonic for Pain:** "You **do cry** (*H. ducreyi*) because it's **painful** (Chancroid)." * **School of Fish Appearance:** On Gram stain, *H. ducreyi* shows a characteristic "railroad track" or "school of fish" pattern. * **Donovanosis (Granuloma Inguinale):** Another differential; presents as beefy-red, **painless** ulcers that bleed on touch (pseudo-buboes). [1] Look for "Donovan bodies" (safety-pin appearance) on biopsy. * **Treatment of Chancroid:** Azithromycin (1g orally) or Ceftriaxone (250mg IM).

Q: A 23-year-old presented with a painless penile ulcer and painless lymphadenopathy. What is the diagnosis?

Syphilis. The clinical presentation of a **painless penile ulcer** (chancre) associated with **painless regional lymphadenopathy** is the classic hallmark of **Primary Syphilis**, caused by the spirochete *Treponema pallidum*. ### Why Syphilis is Correct: The primary chancre typically appears 3 weeks after exposure. It is characterized by a clean base, indurated (hard) edges, and a lack of exudate. Crucially, both the ulcer and the associated inguinal lymphadenopathy are **painless**, which distinguishes it from most other genital ulcerative diseases. ### Why Other Options are Incorrect: * **Chancroid (*Haemophilus ducreyi*):** Presents as a **painful** ulcer with a ragged, undermined edge and a necrotic base. The associated lymphadenopathy (bubo) is also exquisitely painful and may suppurate. * **Donovanosis (Granuloma Inguinale):** Caused by *Klebsiella granulomatis*. It presents as chronic, beefy-red, painless ulcers that bleed on touch. Notably, there is **no true lymphadenopathy**, though "pseudo-buboes" (subcutaneous granulation) may occur. * **Herpes (HSV-2):** Presents as multiple, small, **painful** vesicles that rupture to form shallow ulcers. It is often associated with systemic symptoms like fever and painful lymphadenopathy. ### High-Yield Clinical Pearls for NEET-PG: * **Hard Chancre:** Syphilis (Indurated). * **Soft Chancre:** Chancroid (Non-indurated). * **Diagnosis:** Dark-ground microscopy is the gold standard for primary syphilis (shows corkscrew motility). VDRL/RPR are screening tests but may be negative in the very early stages. * **Treatment:** Benzathine Penicillin G (2.4 million units IM) is the drug of choice.

Q: Which of the following is NOT involved in leprosy?

Central Nervous System (CNS). **Explanation:** The correct answer is **A. Central Nervous System (CNS)**. **Why CNS is not involved:** *Mycobacterium leprae* has a unique predilection for cooler areas of the body. The organism thrives at temperatures between **30°C and 33°C**. The Central Nervous System (brain and spinal cord) is protected by the blood-brain barrier and maintains a core body temperature of approximately **37°C**, which is inhibitory to the growth and survival of *M. leprae*. Therefore, leprosy characteristically spares the CNS. **Why the other options are involved:** * **Skin (C):** This is the most common site of involvement [1]. Lesions range from hypopigmented patches in Tuberculoid leprosy to diffuse infiltration and nodules (lepromas) in Lepromatous leprosy. * **Testis (B):** The testes are located outside the body cavity to maintain a lower temperature, making them a prime target. Involvement can lead to orchitis, testicular atrophy, and subsequent sterility or gynecomastia [1]. * **Cornea (D):** The anterior segment of the eye is cooler than the posterior segment. Leprosy frequently affects the cornea (keratitis), iris, and ciliary body, potentially leading to blindness [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Target Tissues:** *M. leprae* primarily affects the skin, peripheral nerves (especially the ulnar, common peroneal, and posterior tibial), anterior chamber of the eye, upper respiratory tract mucosa, and testes [1]. * **Nerve Involvement:** It is the most common cause of peripheral neuropathy worldwide. * **Immune Response:** The clinical spectrum depends on the host’s **Cell-Mediated Immunity (CMI)**; strong CMI leads to Tuberculoid (TT), while weak CMI leads to Lepromatous (LL) leprosy [1]. * **Cardinal Signs:** Hypopigmented patches with loss of sensation, thickened peripheral nerves, and a positive slit-skin smear [1].

Q: A farmer presents with a lesion on the leg. Which of the following is the most likely diagnosis?

Tuberculosis verrucosa cutis. ***Tuberculosis verrucosa cutis*** - **Farmer's occupation** creates high risk for inoculation injury with **Mycobacterium tuberculosis**, leading to this **verrucous, warty skin lesion** typically on exposed areas like legs. - Characterized by **hyperkeratotic, warty plaques** with minimal inflammation, often called "**prosector's wart**" when occurring in healthcare workers. *Verruca vulgaris* - Caused by **human papillomavirus (HPV)**, not associated with occupational farming activities or tuberculosis exposure. - Typically presents as **well-demarcated papules** with **black dots** (thrombosed capillaries), unlike the hyperkeratotic appearance of TVC. *Mycetoma* - Presents as **chronic granulomatous infection** with **multiple sinuses** discharging colored grains, not a single verrucous lesion. - Caused by **fungi or actinomycetes**, typically affecting the **foot** (Madura foot) rather than presenting as warty leg lesions. *Lichen planus hypertrophicus* - **Autoimmune condition** with **violaceous, polygonal papules** showing **Wickham's striae**, unrelated to occupational exposure. - Typically affects **flexural surfaces** and mucous membranes, not associated with farming or tuberculosis infection.

Q: Apple jelly nodules on diascopy are characteristic of which condition?

Lupus vulgaris. **Explanation:** **Lupus Vulgaris (Correct Answer):** Lupus vulgaris is the most common form of chronic, progressive cutaneous tuberculosis. It occurs in individuals with a high degree of cell-mediated immunity. The characteristic lesion is a reddish-brown plaque that expands peripherally. When a glass slide is pressed against the lesion (**diascopy**), the vascular congestion is blanched, revealing yellowish-brown, translucent foci known as **"apple jelly nodules."** These nodules represent the underlying granulomatous pathology (tubercles) in the dermis. **Incorrect Options:** * **Tinea versicolor:** A fungal infection caused by *Malassezia furfur*. It presents as hypo- or hyperpigmented scaly macules. Diagnosis is confirmed by a "spaghetti and meatballs" appearance on KOH mount or yellow-orange fluorescence under Wood’s lamp. * **Erythrasma:** A bacterial infection caused by *Corynebacterium minutissimum*. It typically involves intertriginous areas and shows a characteristic **coral-red fluorescence** under Wood’s lamp due to porphyrin production. * **Vitiligo:** An autoimmune condition causing depigmentation. Diascopy is not diagnostic; however, Wood’s lamp examination shows a bright "milk-white" fluorescence. **High-Yield Clinical Pearls for NEET-PG:** * **Diascopy:** Used to differentiate between purpura (extravasated blood, does not blanch) and erythema (dilated capillaries, blanches). * **Lupus Vulgaris Complication:** The most serious long-term complication is the development of **Squamous Cell Carcinoma** (Marjolin’s ulcer) within the scar. * **Other "Apple Jelly" associations:** While classic for Lupus Vulgaris, apple jelly nodules can also be seen in **Sarcoidosis** and **Leishmaniasis**.

Q: What is the recommended duration for the treatment of multibacillary leprosy?

12 months. **Explanation:** The treatment of Leprosy follows the World Health Organization (WHO) Multi-Drug Therapy (MDT) guidelines. The correct duration for **Multibacillary (MB) Leprosy** is **12 months**. **1. Why 12 months is correct:** In 1998, the WHO shortened the treatment duration for MB leprosy from 24 months to 12 months. This change was based on clinical trials showing that a 12-month regimen of Rifampicin, Clofazimine, and Dapsone was sufficient to achieve a cure and prevent relapse, while significantly improving patient compliance. **2. Analysis of Incorrect Options:** * **24 months (Option A):** This was the standard duration for MB leprosy prior to 1998. While some clinicians still consider it for patients with a very high Bacterial Index (BI >4+), it is no longer the standard WHO recommendation. * **18 months (Option B):** There is no standard WHO regimen for leprosy that lasts 18 months; this is a distractor. * **6 months (Option D):** This is the standard duration for **Paucibacillary (PB) Leprosy**, which involves fewer lesions and a lower bacterial load. **High-Yield Clinical Pearls for NEET-PG:** * **MB MDT Regimen:** Rifampicin (600mg once monthly, supervised), Clofazimine (300mg once monthly supervised + 50mg daily), and Dapsone (100mg daily). * **PB MDT Regimen:** Rifampicin (600mg once monthly) and Dapsone (100mg daily) for 6 months. * **Classification:** MB is defined by >5 skin lesions, >1 nerve involvement, or a positive skin smear. PB is 1–5 lesions and only 1 nerve involved. * **Accompanied MDT (A-MDT):** Providing the full course of treatment at the first visit to ensure completion in mobile populations.

Q: A farmer presents with a lesion on the leg. Which of the following is the most likely diagnosis?

Tuberculosis verrucosa cutis. ***Tuberculosis verrucosa cutis*** - Occurs through **inoculation** in individuals with high immunity to TB, commonly in **farmers** and **laborers** exposed to contaminated soil. - Presents as a **verrucous plaque** on extremities, typically the **legs or hands**, with characteristic **warty appearance**. *Verruca vulgaris* - Caused by **human papillomavirus (HPV)** and lacks specific **occupational association** with farming activities. - Usually appears as **discrete papules** with **black dots** (thrombosed capillaries), not large verrucous plaques. *Mycetoma* - Characterized by the **triad** of **tumefaction**, **sinuses**, and **grains** discharged from sinus tracts. - Involves **deeper subcutaneous tissues** and bone, presenting with significant **swelling** and **deformity**. *Lichen planus hypertrophicus* - Shows **violaceous polygonal papules** that are **pruritic** and typically affect **flexural surfaces**. - Lacks **occupational predisposition** and has different **morphological characteristics** compared to verrucous lesions.

Q: In a diagnosed lepromatous leprosy patient, treatment was started. After intake of the drug, skin lesions and fever develop within a few days. Which type of hypersensitivity reaction leads to this manifestation?

Type 3. **Explanation:** The clinical scenario describes **Erythema Nodosum Leprosum (ENL)**, also known as a **Type 2 Lepra Reaction**. This typically occurs in patients with Lepromatous Leprosy (LL) or Borderline Lepromatous (BL) leprosy, often triggered by the initiation of multidrug therapy (MDT). **Why Type 3 Hypersensitivity is Correct:** ENL is a classic example of a **Type 3 (Immune-complex mediated) hypersensitivity reaction**. The rapid killing of a high load of *Mycobacterium leprae* bacilli by drugs releases a large amount of bacterial antigens into the circulation. these antigens combine with circulating antibodies to form **immune complexes**, which deposit in blood vessel walls, activating the complement system and leading to systemic vasculitis. This manifests clinically as painful erythematous nodules, high-grade fever, malaise, and occasionally organ involvement (neuritis, arthritis, or iridocyclitis). **Why Incorrect Options are Wrong:** * **Type 4 (Delayed-type):** This is the mechanism behind **Type 1 Lepra Reactions (Reversal Reactions)**, seen in borderline cases. It involves a cell-mediated immune response, not immune complexes. * **Type 2 (Antibody-dependent):** This involves antibodies directed against antigens on specific cell surfaces (e.g., hemolytic anemia), which is not the pathology of ENL. * **Type 1 (Immediate):** This is IgE-mediated (e.g., anaphylaxis/urticaria) and is not associated with lepra reactions. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice for ENL:** **Thalidomide** is the most effective treatment. Oral corticosteroids are used for milder cases or when thalidomide is contraindicated. * **Type 1 Reaction vs. Type 2 Reaction:** Type 1 occurs in paucibacillary/borderline cases (Type 4 hypersensitivity); Type 2 occurs in multibacillary cases (Type 3 hypersensitivity). * **Clofazimine:** This component of MDT has anti-inflammatory properties that help prevent and treat ENL.

Q: What is the best method of treatment for ulnar nerve abscess in case of leprosy?

Incision and drainage. **Explanation:** The management of nerve involvement in leprosy is critical to prevent permanent disability. When a patient presents with a **nerve abscess** (most commonly involving the ulnar nerve), it represents a localized collection of caseous material within the nerve sheath. **1. Why Incision and Drainage (I&D) is correct:** A nerve abscess is a surgical emergency in the context of leprosy. The accumulation of pus increases **intraneural pressure**, which leads to rapid ischemia and irreversible destruction of nerve fibers. Medical management alone cannot evacuate the collection. Therefore, **longitudinal incision of the nerve sheath (epineurotomy) and drainage** of the abscess is the definitive treatment to decompress the nerve and preserve motor and sensory function. **2. Why other options are incorrect:** * **High dose steroids (Option A):** While steroids are the mainstay for treating *Type 1 reactions* (neuritis), they cannot drain a physical collection of pus. They are used post-operatively to reduce edema but are not the primary treatment for an abscess. [1] * **Thalidomide (Option C):** This is the drug of choice for *Type 2 reactions (Erythema Nodosum Leprosum)*. It has no role in treating a localized nerve abscess. * **High dose Clofazimine (Option D):** Clofazimine has anti-inflammatory properties used in chronic ENL, but it is ineffective for the acute mechanical compression caused by an abscess. [2] **Clinical Pearls for NEET-PG:** * **Most common nerve involved in Leprosy:** Ulnar nerve. * **Most common nerve involved in Nerve Abscess:** Ulnar nerve. * **Steroid of choice for Lepra reactions:** Prednisolone. * **Silent Neuritis:** Nerve damage occurring without overt symptoms of inflammation; also managed with steroids. * **Surgical indication:** If there is no improvement in nerve function after 4–6 weeks of optimal steroid therapy, surgical decompression is indicated.

Q: Which of the following tests is NOT used for the diagnosis of leprosy?

Lepromin test. In leprosy management, it is crucial to distinguish between **diagnosis** and **prognosis**. **Why Option A (Lepromin Test) is the correct answer:** The Lepromin test is **not** a diagnostic test. It cannot confirm if a patient has leprosy because it is often negative in the most severe form (lepromatous leprosy) and can be positive in healthy individuals due to cross-reactivity with BCG or environmental mycobacteria. Instead, it is used for: 1. **Classification:** To categorize leprosy into Tuberculoid (Positive) or Lepromatous (Negative). 2. **Prognosis:** To assess the patient’s cell-mediated immunity (CMI) against *M. leprae*. 3. **Assessment of Resistance:** To check the immune status of an individual. **Why the other options are incorrect (Diagnostic Methods):** * **Slit Skin Smear (B):** The gold standard for identifying Acid-Fast Bacilli (AFB) using Ziehl-Neelsen staining. It is essential for calculating the Bacteriological Index (BI). * **Fine Needle Aspiration Cytology (C):** A reliable tool for sampling cells from enlarged nerves or skin nodules to identify granulomas and bacilli. * **Skin Biopsy (D):** The definitive method for histopathological confirmation, showing characteristic nerve involvement and granuloma patterns. **High-Yield Clinical Pearls for NEET-PG:** * **Cardinal Signs:** Diagnosis is primarily clinical based on: (1) Hypopigmented patches with sensory loss, (2) Thickened peripheral nerves, and (3) Positive skin smears. * **Fernandez Reaction:** Early reading of Lepromin test (at 48 hours); indicates delayed hypersensitivity. * **Mitsuda Reaction:** Late reading (at 21 days); indicates cell-mediated immunity. * **Ridley-Jopling Scale:** The standard 5-group classification system based on clinical, immunological, and histopathological features.

Question 1

What is the most likely diagnosis for a patient presenting with a painful ulcer on the glans penis?

Accepted Answer

Chancroid

Answer

Syphilis

Answer

Lymphogranuloma venerum

Answer

Chancre

Question 2

A 23-year-old presented with a painless penile ulcer and painless lymphadenopathy. What is the diagnosis?

Accepted Answer

Syphilis

Answer

Chancroid

Answer

Donovanosis

Answer

Herpes

Question 3

Which of the following is NOT involved in leprosy?

Accepted Answer

Central Nervous System (CNS)

Answer

Testis

Answer

Skin

Answer

Cornea

Question 4

A farmer presents with a lesion on the leg. Which of the following is the most likely diagnosis?

Accepted Answer

Tuberculosis verrucosa cutis

Answer

Verruca vulgaris

Answer

Mycetoma

Answer

Lichen planus hypertrophicus

Question 5

Apple jelly nodules on diascopy are characteristic of which condition?

Accepted Answer

Lupus vulgaris

Answer

Tinea versicolor

Answer

Erythrasma

Answer

Vitiligo

Question 6

What is the recommended duration for the treatment of multibacillary leprosy?

Accepted Answer

12 months

Answer

24 months

Answer

18 months

Answer

6 months

Question 7

A farmer presents with a lesion on the leg. Which of the following is the most likely diagnosis?

Accepted Answer

Tuberculosis verrucosa cutis

Answer

Verruca vulgaris

Answer

Mycetoma

Answer

Lichen planus hypertrophicus

Question 8

In a diagnosed lepromatous leprosy patient, treatment was started. After intake of the drug, skin lesions and fever develop within a few days. Which type of hypersensitivity reaction leads to this manifestation?

Accepted Answer

Type 3

Answer

Type 4

Answer

Type 2

Answer

Type 1

Question 9

What is the best method of treatment for ulnar nerve abscess in case of leprosy?

Accepted Answer

Incision and drainage

Answer

High dose of steroid

Answer

Thalidomide

Answer

High dose of clofazamine

Question 10

Which of the following tests is NOT used for the diagnosis of leprosy?

Accepted Answer

Lepromin test

Answer

Slit skin smear

Answer

Fine needle aspiration cytology

Answer

Skin biopsy

Bacterial Skin Infections — MCQs

Bacterial Skin Infections — MCQs

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