Bacterial Skin Infections Practice Questions

Q: Erythematous lesions seen in the axilla with coral red fluorescence under a Wood's lamp indicate which of the following conditions?

Erythrasma. **Explanation:** The clinical presentation of erythematous, well-demarcated patches in intertriginous areas (like the axilla) showing **coral red fluorescence** under a Wood’s lamp is pathognomonic for **Erythrasma**. **1. Why Erythrasma is correct:** Erythrasma is a superficial bacterial infection caused by ***Corynebacterium minutissimum***. This organism produces **porphyrins** (specifically Coproporphyrin III) as a metabolic byproduct. When exposed to ultraviolet light (Wood’s lamp), these porphyrins emit a characteristic coral red glow. **2. Why other options are incorrect:** * **Tinea (Dermatophytosis):** While it presents with erythematous patches, it typically shows central clearing (annular) and active borders. Under Wood's lamp, most Tinea corporis/cruris do not fluoresce; only specific species like *Microsporum* (Tinea capitis) show bright green fluorescence. * **Lichen Planus:** This is an inflammatory condition characterized by the "6 Ps" (Planar, Purple, Polygonal, Pruritic, Papules, and Plaques). It does not show specific fluorescence. * **Vitiligo:** This is a depigmenting disorder. Under Wood’s lamp, it shows **milky-white** fluorescence due to the complete loss of melanin, which enhances the reflection of light. **High-Yield Clinical Pearls for NEET-PG:** * **Treatment of Choice:** Topical or oral **Erythromycin** (or Clindamycin). * **Common Sites:** Axilla, groin (most common), and toe webs (4th-5th space). * **Differential Diagnosis:** Often confused with Tinea cruris or Intertrigo; Wood's lamp is the gold standard for rapid bedside differentiation. * **Microscopy:** KOH mount will be negative for fungi, but Gram stain shows Gram-positive filamentous bacilli.

Q: Exacerbation of lesions in patients of borderline leprosy is seen in which type of reaction?

Type I lepra reaction. **Explanation:** **Type I Lepra Reaction (Delayed Hypersensitivity)** is the correct answer because it is specifically associated with **Borderline forms of leprosy** (BT, BB, and BL). It occurs due to a sudden change in the patient's cell-mediated immunity (CMI). Clinically, it manifests as the **exacerbation of existing lesions**, which become erythematous, edematous, and painful. New lesions may appear, and there is often associated acute neuritis (nerve tenderness and loss of function). **Analysis of Incorrect Options:** * **A. Erythema Nodosum Leprosum (ENL):** Also known as Type II lepra reaction, this is a humoral (Type III) hypersensitivity reaction seen primarily in **lepromatous (LL)** and occasionally **borderline lepromatous (BL)** leprosy. It presents with crops of tender, evanescent subcutaneous nodules, fever, and systemic symptoms, rather than the exacerbation of existing skin patches. * **C. Jarisch-Herxheimer Reaction:** This is a systemic inflammatory response seen following the initiation of antibiotic treatment for spirochetal infections (e.g., Syphilis, Leptospirosis), caused by the release of endotoxin-like products from dying organisms. It is not a feature of leprosy. * **D. Resolving Leprosy:** This refers to the healing phase where lesions become flatter, less erythematous, and lose their activity, which is the clinical opposite of an exacerbation. **High-Yield Clinical Pearls for NEET-PG:** * **Type I Reaction:** Can be "Upgrading" (Reversal reaction – shift toward Tuberculoid pole) or "Downgrading" (shift toward Lepromatous pole). * **Treatment of Choice:** Systemic Corticosteroids (Prednisolone) are the mainstay for both Type I and Type II reactions to prevent permanent nerve damage. * **Thalidomide:** Highly effective for Type II (ENL) but contraindicated in Type I and pregnancy.

Q: Satellite lesions are seen in which type of leprosy?

Borderline Tuberculoid Leprosy. **Explanation:** The presence of **satellite lesions** is a hallmark clinical feature of **Borderline Tuberculoid (BT) Leprosy**. In the Ridley-Jopling classification, BT leprosy represents a stage where the host's cell-mediated immunity (CMI) is significant but not as robust as in polar Tuberculoid leprosy. 1. **Why Borderline Tuberculoid (BT) is correct:** Satellite lesions are smaller, clinically similar lesions (macules or plaques) found in the immediate vicinity of a larger primary lesion. They indicate a degree of immunological instability and the beginning of hematogenous spread that the body is attempting to contain. 2. **Why other options are incorrect:** * **Tuberculoid Leprosy (TT):** Characterized by a single or very few (1–3) well-defined, anesthetic, hairless plaques. The CMI is very high, keeping the infection strictly localized; thus, satellite lesions are absent. * **Lepromatous Leprosy (LL):** Characterized by widespread, symmetrical, bilateral nodules or macules due to negligible CMI. The lesions are too numerous and generalized for "satellite" terminology to apply. * **Histoid Leprosy:** A variant of LL (often due to dapsone resistance) characterized by firm, shiny, hemispherical cutaneous nodules on normal-looking skin. It does not feature satellite lesions. **High-Yield Clinical Pearls for NEET-PG:** * **BT Leprosy** is the most common clinical type of leprosy seen in India. * **Nerve Involvement:** In BT, nerve involvement is asymmetrical and more extensive than in TT. * **Inverted Saucer Appearance:** Characteristic of **Borderline Borderline (BB)** leprosy. * **Swiss Cheese Appearance:** Histopathological feature of **Borderline Lepromatous (BL)** leprosy. * **Face:** If a lesion is on the face with satellite lesions, it is a strong indicator of BT leprosy.

Q: Which of the following conditions is characterized by 'honey-colored' crusts?

Impetigo. **Explanation:** **Impetigo** is the correct answer. It is a highly contagious, superficial bacterial skin infection most commonly caused by *Staphylococcus aureus* or *Streptococcus pyogenes*. The hallmark clinical feature of **Non-bullous Impetigo** (the most common form) is the formation of thin-walled vesicles or pustules that rupture to release an exudate, which dries into characteristic **"honey-colored" (golden) crusts**. These are typically found on the face, particularly around the nose and mouth. **Why the other options are incorrect:** * **Nummular eczema:** Characterized by coin-shaped, itchy, erythematous plaques. While they can ooze, they do not typically form the classic golden crusts seen in impetigo. * **Herpes zoster:** Presents as painful, dermatomal, grouped vesicles on an erythematous base. The crusts formed after vesicles rupture are usually hemorrhagic or dark, not honey-colored. * **Cutaneous diphtheria:** Caused by *Corynebacterium diphtheriae*, it typically presents as a "punched-out" ulcer with a greyish-white **pseudomembrane**, rather than superficial golden crusting. **High-Yield Clinical Pearls for NEET-PG:** * **Bullous Impetigo:** Always caused by *S. aureus* producing exfoliative toxins (ETA, ETB) that target **Desmoglein 1**. * **Ecthyma:** A deeper form of impetigo that extends into the dermis, resulting in "punched-out" ulcers covered with thick crusts. * **Treatment:** Topical **Mupirocin** or Retapamulin is the first-line treatment for localized lesions. * **Complication:** While impetigo can lead to Post-Streptococcal Glomerulonephritis (PSGN), it does *not* lead to Rheumatic Fever.

Q: A patient presents with bilateral tender lymphadenopathy and a history of sexual contact. The patient is a truck driver by profession. What is the probable causative agent?

Lymphogranuloma venereum. ### Explanation The clinical presentation of **bilateral tender lymphadenopathy** in a patient with a high-risk sexual history (often associated with mobile professions like truck driving) points toward **Lymphogranuloma venereum (LGV)** [1]. **1. Why LGV is the Correct Answer:** LGV is caused by **Chlamydia trachomatis (serotypes L1, L2, L3)**. The disease typically progresses through three stages. The second stage, the **inguinal syndrome**, is characterized by painful, often bilateral, inguinal lymphadenopathy [1]. A classic clinical sign is the **"Groove sign,"** where the inguinal ligament creates a depression between the inflamed superficial and deep inguinal nodes. **2. Why the Other Options are Incorrect:** * **Herpes simplex virus (HSV):** While HSV causes painful lymphadenopathy, it is almost always accompanied by **multiple, painful, grouped vesicles** or shallow ulcers [1]. The primary complaint here is the lymphadenopathy itself. * **Haemophilus ducreyi (Chancroid):** This causes a **painful, soft ulcer** with ragged edges [1]. While it causes tender lymphadenopathy (buboes), they are typically **unilateral** and prone to suppuration/rupture. * **Treponema pallidum (Syphilis):** Primary syphilis presents with a **painless** chancre and **painless, non-tender, rubbery** lymphadenopathy. **3. Clinical Pearls for NEET-PG:** * **Causative Agent:** *Chlamydia trachomatis* L1-L3. * **Diagnosis:** Nucleic Acid Amplification Test (NAAT) is the preferred method. * **Treatment of Choice:** **Doxycycline 100 mg BID for 21 days** [1]. (Note: Standard Chlamydia urethritis only requires 7 days). * **Esthiomene:** A chronic complication of LGV in females involving lymphatic obstruction leading to vulvar elephantiasis. * **Truck Drivers:** Frequently used in Indian medical exams as a social marker for high-risk sexual behavior and STIs [1].

Q: Which of the following is NOT a characteristic of the early eruption of secondary syphilis?

Intensely pruritic. Secondary syphilis, often called the **"Great Imitator,"** occurs due to the systemic hematogenous spread of *Treponema pallidum*. [1] **Why Option A is the Correct Answer:** The hallmark of the secondary syphilitic rash is that it is **non-pruritic** (not itchy); it is classically described as non-irritable. [1] In dermatology, most generalized rashes are itchy; however, syphilis is a classic exception. If a patient presents with a generalized maculopapular rash that does **not** itch, secondary syphilis should be the first differential diagnosis. **Analysis of Incorrect Options:** * **Option B (Papular/maculopapular):** This is the most common morphology. The rash typically begins as faint pink-to-red macules that evolve into papules. [1], [2] * **Option C (Symmetrical):** The eruption is characteristically widespread and bilaterally symmetrical, involving the trunk and extremities. [1] * **Option D (Pleomorphic):** Secondary syphilis is known for its variety. Lesions can be macular, papular, pustular, or squamous (psoriasiform) occurring simultaneously. [1] However, it **never** presents as vesicular or bullous lesions in adults (except in congenital syphilis). **High-Yield Clinical Pearls for NEET-PG:** * **Palm and Sole Involvement:** A maculopapular rash involving the palms and soles is a high-yield diagnostic clue for secondary syphilis. [1], [2] * **Condyloma Lata:** These are moist, flat-topped, highly infectious papules found in intertriginous areas (e.g., perianal region). [1] * **Lues Maligna:** A rare, severe form of secondary syphilis with necrotic lesions, usually seen in HIV-positive patients. * **Diagnosis:** Screening is done via **VDRL/RPR** (non-treponemal), and confirmation is via **FTA-ABS/TPHA** (treponemal).

Q: Which type of leprosy is characterized by these lesions?

Borderline tuberculoid leprosy. ***Borderline tuberculoid leprosy*** - Characterized by **hypopigmented/erythematous plaques** with **well-defined outer borders** and **less well-defined inner borders**, often with **satellite lesions**. - Shows **paucibacillary** infection with **partial cell-mediated immunity**, resulting in **asymmetric distribution** of lesions. *Tuberculoid leprosy* - Features **single or few lesions** with **sharply defined borders** and complete **anesthesia** within the lesion. - Has **strong cell-mediated immunity** with **no bacilli** found on skin smears, unlike the partial immunity in borderline forms. *Lepromatous leprosy* - Presents with **multiple symmetric nodules** and **infiltrated plaques** without clear borders. - Shows **multibacillary** infection with **poor cell-mediated immunity**, resulting in **bilateral symmetric** distribution. *Histoid leprosy* - Characterized by **firm nodular lesions** with a **histiocytic appearance** on histology. - Typically occurs as a **relapse** in treated lepromatous cases or in **untreated multibacillary** patients with high bacterial load.

Q: Wood's lamp examination in dermatology typically reveals a coral red fluorescence in which of the following conditions?

Erythrasma. **Explanation:** **Erythrasma** is the correct answer. It is a superficial bacterial infection caused by *Corynebacterium minutissimum*. The hallmark diagnostic feature under **Wood’s lamp examination** is a characteristic **coral-red fluorescence**. This occurs because the bacteria produce **coproporphyrin III**, which fluoresces when exposed to ultraviolet light (365 nm). Clinically, it presents as well-demarcated, reddish-brown, macerated plaques in intertriginous areas (axilla, groin, or toe webs). **Analysis of Incorrect Options:** * **Porphyria Cutanea Tarda (PCT):** While PCT involves porphyrins, Wood’s lamp examination of the **urine** (not the skin) typically shows a pink-orange or coral-red fluorescence. Skin lesions themselves do not typically show this fluorescence. * **Livedo Reticularis:** This is a vascular condition characterized by a reticulated (net-like) cyanotic pattern due to altered blood flow. It does not exhibit fluorescence under Wood’s lamp. * **Hypomelanosis (e.g., Vitiligo):** Wood’s lamp is used here to detect pigment loss. Depigmented areas (Vitiligo) appear **milky-white** and accentuated, while hypopigmented areas (Pityriasis versicolor) may show a pale yellow/gold fluorescence. **High-Yield Clinical Pearls for NEET-PG:** * **Tinea Versicolor:** Shows **yellowish-gold** fluorescence (due to *Malassezia*). * **Tinea Capitis (Microsporum):** Shows **bright greenish** fluorescence. * **Pseudomonas (Burn infections):** Shows **apple-green** fluorescence (due to pyoverdin). * **Treatment of Erythrasma:** Topical fusidic acid or clindamycin; oral Erythromycin for extensive cases.

Q: A 20-year-old male presents with multiple painful ulcers over the prepuce and glans, accompanied by suppurative lymphadenopathy, developing two weeks after unprotected sexual intercourse. What is the most probable diagnosis?

Chancroid. ### **Explanation** The clinical presentation of **painful ulcers** associated with **suppurative lymphadenopathy** (buboes) is the classic hallmark of **Chancroid**, caused by the Gram-negative coccobacillus *Haemophilus ducreyi* [1]. #### **Why Chancroid is Correct:** 1. **Painful Ulcers:** Unlike syphilis, the ulcers in chancroid are characteristically painful, soft, and often have ragged, undermined edges with a gray/yellow purulent base [1]. 2. **Suppurative Lymphadenopathy:** About 50% of patients develop painful inguinal lymphadenitis. These "buboes" are typically unilateral and frequently progress to suppuration (pus formation) and spontaneous rupture [1]. 3. **Incubation Period:** The 2-week timeline fits the typical 3–14 day incubation period of *H. ducreyi* [1]. #### **Why Other Options are Incorrect:** * **Herpes Simplex (HSV-2):** While painful, HSV presents as multiple small, superficial **vesicles** on an erythematous base that later rupture into shallow ulcers [1]. Lymphadenopathy is usually bilateral and non-suppurative. * **Molluscum Contagiosum:** Presents as **painless**, firm, pearly, umbilicated papules. It does not cause ulcers or suppurative lymphadenopathy. * **Syphilis (Primary):** Caused by *Treponema pallidum*, the classic chancre is **painless**, indurated (hard), and associated with painless, non-suppurative regional lymphadenopathy [1]. #### **NEET-PG High-Yield Pearls:** * **School of Fish Appearance:** On Gram stain, *H. ducreyi* shows a characteristic "railroad track" or "school of fish" pattern. * **The "P" Rule:** Remember **Chancroid = Painful** (Soft Chancre) vs. **Syphilis = Painless** (Hard Chancre). * **Treatment:** A single dose of **Azithromycin (1g orally)** or Ceftriaxone (250mg IM). * **Differential for Buboes:** If the lymphadenopathy is associated with a small, transient, *painless* ulcer, consider **Lymphogranuloma Venereum (LGV)** (Chlamydia trachomatis L1-L3) [1].

Q: What is the recommended treatment for granuloma inguinale?

Azithromycin. **Explanation:** **Granuloma Inguinale (Donovanosis)** is a chronic bacterial infection caused by the Gram-negative intracellular organism *Klebsiella granulomatis*. It is characterized by painless, beefy-red, vascular ulcerative lesions that bleed easily on contact. **Why Azithromycin is correct:** According to the current **CDC and WHO guidelines**, **Azithromycin (1g orally once a week or 500mg daily) for at least 3 weeks** is the first-line treatment of choice. It is preferred due to its high intracellular concentration, long half-life, and superior efficacy in achieving complete healing of the lesions compared to older regimens. Treatment must be continued until all lesions have completely epithelialized. **Analysis of Incorrect Options:** * **A. Tetracycline:** While Doxycycline (a tetracycline) is a recommended alternative, it is no longer the first-line agent due to the superior dosing convenience and safety profile of Azithromycin. * **C. Clarithromycin:** Although it belongs to the same Macrolide class as Azithromycin, it is not the standard protocol for Donovanosis and requires more frequent dosing. * **D. Streptomycin:** This was historically used but is now obsolete for this condition due to the risk of ototoxicity, nephrotoxicity, and the requirement for parenteral administration. **High-Yield Clinical Pearls for NEET-PG:** * **Pathognomonic Sign:** Presence of **Donovan bodies** (safety-pin appearance) within macrophages on a Giemsa or Wright stain. * **Clinical Presentation:** "Painless but progressive" ulcers; pseudobuboes (inguinal swelling due to granulation tissue, not lymphadenopathy). * **Alternative Regimens:** Doxycycline (100mg BID), Erythromycin, or Trimethoprim-Sulfamethoxazole. * **Pregnancy:** Azithromycin remains the drug of choice for pregnant women with Donovanosis.

Question 1

Erythematous lesions seen in the axilla with coral red fluorescence under a Wood's lamp indicate which of the following conditions?

Accepted Answer

Erythrasma

Answer

Tinea

Answer

Lichen planus

Answer

Vitiligo

Question 2

Exacerbation of lesions in patients of borderline leprosy is seen in which type of reaction?

Accepted Answer

Type I lepra reaction

Answer

Erythema nodosum leprosum (ENL)

Answer

Jarisch-Herxheimer reaction

Answer

Resolving leprosy

Question 3

Satellite lesions are seen in which type of leprosy?

Accepted Answer

Borderline Tuberculoid Leprosy

Answer

Tuberculoid Leprosy

Answer

Lepromatous Leprosy

Answer

Histoid Leprosy

Question 4

Which of the following conditions is characterized by 'honey-colored' crusts?

Accepted Answer

Impetigo

Answer

Nummular eczema

Answer

Herpes zoster

Answer

Cutaneous diphtheria

Question 5

A patient presents with bilateral tender lymphadenopathy and a history of sexual contact. The patient is a truck driver by profession. What is the probable causative agent?

Accepted Answer

Lymphogranuloma venereum

Answer

Herpes simplex virus

Answer

Haemophilus ducreyi

Answer

Treponema pallidum

Question 6

Which of the following is NOT a characteristic of the early eruption of secondary syphilis?

Accepted Answer

Intensely pruritic

Answer

Papular/maculopapular eruption

Answer

Symmetrical

Answer

Pleomorphic

Question 7

Which type of leprosy is characterized by these lesions?

Accepted Answer

Borderline tuberculoid leprosy

Answer

Tuberculoid leprosy

Answer

Lepromatous leprosy

Answer

Histoid leprosy

Question 8

Wood's lamp examination in dermatology typically reveals a coral red fluorescence in which of the following conditions?

Accepted Answer

Erythrasma

Answer

Porphyria cutanea tarda

Answer

Livedo reticularis

Answer

Hypomelanosis

Question 9

A 20-year-old male presents with multiple painful ulcers over the prepuce and glans, accompanied by suppurative lymphadenopathy, developing two weeks after unprotected sexual intercourse. What is the most probable diagnosis?

Accepted Answer

Chancroid

Answer

Herpes simplex

Answer

Molluscum contagiosum

Answer

Syphilis

Question 10

What is the recommended treatment for granuloma inguinale?

Accepted Answer

Azithromycin

Answer

Tetracycline

Answer

Clarithromycin

Answer

Streptomycin

Bacterial Skin Infections — MCQs

Bacterial Skin Infections — MCQs

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