Bacterial Skin Infections — MCQs

Bacterial Skin Infections Indian Medical PG Practice Questions and MCQs

Question 141: Which of the following is/are a clinical feature of lepromatous leprosy?

A. Leonine facies
B. Loss of libido and impotence
C. Saddle nose
D. All the above (Correct Answer)

Explanation: In **Lepromatous Leprosy (LL)**, there is a high bacterial load (multibacillary) due to a deficient cell-mediated immune response (Th2 response). This leads to hematogenous spread and extensive tissue infiltration by *Mycobacterium leprae*. **Explanation of Features:** * **Leonine Facies (Option A):** This "lion-like" appearance is a hallmark of LL. it results from diffuse infiltration of the facial skin, leading to thickening of the forehead, malar areas, and earlobes, along with the loss of eyebrows (**madarosis**). * **Loss of Libido and Impotence (Option B):** *M. leprae* has a predilection for cooler areas of the body, including the testes. Infiltration leads to **interstitial orchitis**, testicular atrophy, and subsequent primary hypogonadism, causing impotence and gynecomastia. * **Saddle Nose (Option C):** Chronic lepromatous rhinitis leads to infiltration and destruction of the nasal cartilage and the anterior nasal spine. This causes the bridge of the nose to collapse, resulting in a "saddle nose" deformity. Since all three features are characteristic of the systemic involvement seen in the lepromatous pole of the disease, **Option D** is the correct answer. **High-Yield Clinical Pearls for NEET-PG:** * **Glove and Stocking Anesthesia:** Unlike the asymmetrical patches in Tuberculoid Leprosy, LL presents with symmetrical sensory loss in distal extremities. * **Bacteriological Index (BI):** Usually high (4+ to 6+) in LL. * **Lepromin Test:** Consistently **negative** in LL (indicates poor cell-mediated immunity). * **Eye Involvement:** LL frequently involves the anterior segment, leading to iridocyclitis and secondary glaucoma.

Question 142: Which of the following tuberculides is characterized by involvement of sweat glands and hair follicles with non-caseating epithelioid granuloma?

A. Lichen scrofulosorum (Correct Answer)
B. Miliary tuberculosis
C. Papulonecrotic tuberculide
D. Lupus vulgaris

Explanation: **Explanation:** **Lichen scrofulosorum** is a rare, asymptomatic, "id" reaction (tuberculide) occurring in individuals with high immunity against *Mycobacterium tuberculosis*. It typically presents as clusters of tiny, lichenoid, skin-colored to reddish-brown papules on the trunk. * **Histopathology:** The hallmark is the presence of **non-caseating epithelioid cell granulomas** specifically localized around **adnexal structures**, such as hair follicles and sweat glands (perifollicular or periadnexal distribution). This anatomical localization is the key diagnostic feature. **Analysis of Incorrect Options:** * **Miliary Tuberculosis:** This is a form of primary cutaneous TB (not a tuberculide) resulting from hematogenous spread. Histology shows multiple small areas of necrosis and numerous acid-fast bacilli (AFB), unlike the paucibacillary nature of tuberculides. * **Papulonecrotic Tuberculide:** Characterized by dusky red papules that undergo central **necrosis** and heal with varioliform scarring. Histology shows wedge-shaped necrosis and vasculitis, not periadnexal non-caseating granulomas. * **Lupus Vulgaris:** The most common form of chronic cutaneous TB. Histology shows typical **tubercles** (caseating granulomas) in the upper dermis with marked epidermal changes (atrophy or pseudoepitheliomatous hyperplasia). It is not specifically associated with sweat gland involvement. **High-Yield Clinical Pearls for NEET-PG:** * **Tuberculides** (Lichen scrofulosorum, Papulonecrotic tuberculide, Erythema induratum) are hypersensitivity reactions where AFB are **absent** in lesions, but the Mantoux test is strongly positive. * Lichen scrofulosorum is most commonly seen in **children and adolescents** with systemic TB (usually nodal or skeletal). * **Treatment:** It responds rapidly to standard Anti-Tubercular Therapy (ATT).

Question 143: Which of the following conditions does not involve nerve damage?

A. Tuberculoid leprosy
B. Lepromatous leprosy
C. Indeterminate leprosy (Correct Answer)
D. Borderline tuberculoid leprosy

Explanation: In leprosy (Hansen’s disease), the degree of nerve involvement is dictated by the host's cell-mediated immunity (CMI). **Why Indeterminate Leprosy is the correct answer:** Indeterminate leprosy is the **earliest clinical stage** of the disease. It typically presents as a single, ill-defined, hypopigmented macule with preserved or only slightly impaired sensation. At this stage, the disease has not yet polarized into the Ridley-Jopling spectrum. Crucially, there is **no peripheral nerve trunk enlargement or damage** at this stage. It may either resolve spontaneously or progress to other forms depending on the patient's immune response. **Why the other options are incorrect:** * **Tuberculoid Leprosy (TT):** Characterized by a strong CMI response. This leads to intense inflammation and granuloma formation within nerves, causing **early, severe, and asymmetrical** nerve damage and enlargement. * **Lepromatous Leprosy (LL):** Characterized by low CMI and high bacillary load. Nerve involvement is **late, symmetrical, and progressive**, involving small dermal nerve twigs first and then major trunks. * **Borderline Tuberculoid (BT):** This is the most common clinical presentation. It involves significant nerve damage, often presenting with multiple enlarged nerves and a high risk of "reversal reactions" which further exacerbate nerve palsy. **High-Yield Clinical Pearls for NEET-PG:** * **Earliest sensation lost:** Temperature (Cold followed by Hot), then Touch, then Pain, and lastly Deep Pressure. * **Most commonly involved nerve:** Ulnar nerve (leads to claw hand). * **Cardinal signs of Leprosy:** Hypopigmented patches with loss of sensation, thickened peripheral nerves, and a positive skin smear for *M. leprae*. * **Indeterminate Leprosy Histology:** Shows non-specific lymphocytic infiltration around skin appendages and neurovascular bundles; Acid-Fast Bacilli (AFB) are usually very difficult to find.

Question 144: What is the recommended treatment for impetigo?

A. Dicloxacillin (Correct Answer)
B. Ciprofloxacin
C. Gentamicin
D. Amoxicillin and clavulanic acid

Explanation: **Explanation:** **1. Why Dicloxacillin is correct:** Impetigo is a highly contagious superficial bacterial skin infection primarily caused by **Staphylococcus aureus** (most common) and **Streptococcus pyogenes** (Group A Beta-hemolytic Strep). Since most *S. aureus* strains produce penicillinase (beta-lactamase), they are resistant to standard penicillin. **Dicloxacillin** is a penicillinase-resistant penicillin, making it an ideal first-line oral agent for localized or moderate impetigo. It effectively covers both *S. aureus* and *S. pyogenes*. **2. Analysis of Incorrect Options:** * **B. Ciprofloxacin:** This is a fluoroquinolone. While it has Gram-negative coverage, it is not the drug of choice for Gram-positive skin infections and is generally avoided in children (the primary demographic for impetigo) due to potential cartilage damage. * **C. Gentamicin:** This aminoglycoside is primarily effective against aerobic Gram-negative bacilli. It lacks sufficient efficacy against *Streptococcus* and is not used as monotherapy for impetigo. * **D. Amoxicillin and clavulanic acid:** While this combination is effective against beta-lactamase-producing bacteria, in the context of standard NEET-PG protocols, a narrow-spectrum penicillinase-resistant penicillin like **Dicloxacillin** or **Cephalexin** is traditionally preferred as the specific answer for non-MRSA staphylococcal skin infections. **3. High-Yield Clinical Pearls for NEET-PG:** * **Clinical Features:** Look for "honey-colored crusts" (Non-bullous) or thin-walled flaccid bullae (Bullous impetigo). * **Topical Treatment:** For very localized lesions, **Mupirocin** or **Retapamulin** ointment is the treatment of choice. * **Complications:** While impetigo can lead to **Post-Streptococcal Glomerulonephritis (PSGN)**, it does *not* cause Rheumatic Fever. * **Etiology:** Bullous impetigo is specifically caused by *S. aureus* producing exfoliative toxins (targeting Desmoglein 1).

Question 145: True about Lucio's phenomenon is:

A. Associated with tuberculoid leprosy
B. Occurs as a side effect of treatment of leprosy
C. Ischemic necrosis (Correct Answer)
D. Also known as type 2 Lepra reaction

Explanation: **Explanation:** **Lucio’s Phenomenon** is a rare, severe variant of Type 2 Lepra reaction specifically associated with **Diffuse Lepromatous Leprosy (of Lucio and Latapi)**. **Why Option C is Correct:** The underlying pathophysiology involves a massive invasion of the vascular endothelium by *Mycobacterium leprae*. This leads to **endothelial proliferation, necrotizing vasculitis, and thrombo-occlusion** of the dermal vessels. The resulting lack of blood supply causes **ischemic necrosis** of the skin, clinically manifesting as painful, jagged, purpuric macules that progress to necrotic ulcers (predominantly on the extremities). **Analysis of Incorrect Options:** * **Option A:** It is never seen in tuberculoid leprosy; it occurs exclusively in untreated, non-nodular diffuse lepromatous leprosy. * **Option B:** Unlike Erythema Nodosum Leprosum (ENL), which often occurs *after* starting Multi-Drug Therapy (MDT), Lucio’s phenomenon typically occurs in **untreated patients**. * **Option D:** While some classifications consider it a variant of Type 2 reaction, it is distinct from the classic Type 2 reaction (ENL). ENL is a Type III hypersensitivity (immune-complex mediated), whereas Lucio’s phenomenon is primarily a **thrombotic vasculopathy**. **High-Yield Clinical Pearls for NEET-PG:** * **Geographic distribution:** Most common in Mexico and Central America. * **Clinical sign:** Characterized by "Lucio’s leprosy" (diffuse infiltration of skin, loss of eyebrows/eyelashes, but no nodules). * **Histopathology:** Shows acid-fast bacilli (AFB) within the endothelial cells and thrombus formation. * **Treatment:** Standard MDT for Leprosy; systemic steroids have limited efficacy compared to their role in ENL.

Question 146: Tuberculides are seen in which of the following conditions?

A. Lupus vulgaris
B. Scrofuloderma
C. Lichen scrofulosorum (Correct Answer)
D. Erythema nodosum

Explanation: **Explanation:** **Tuberculides** are a group of skin eruptions that represent a hypersensitivity reaction to a distant, often occult, focus of *Mycobacterium tuberculosis* in a patient with high immunity. Unlike true cutaneous tuberculosis, tuberculides are characterized by the **absence** of bacilli in the skin lesions (paucibacillary/sterile) and a strongly positive Mantoux test. **Why Option C is Correct:** **Lichen scrofulosorum** is a classic example of a tuberculide. It typically presents in children and young adults as asymptomatic, skin-colored to reddish-brown, follicular papules grouped in discoid patterns on the trunk. It occurs in individuals with high cell-mediated immunity and usually responds rapidly to anti-tubercular therapy (ATT). **Analysis of Incorrect Options:** * **Lupus vulgaris (A) and Scrofuloderma (B):** These are forms of **True Cutaneous Tuberculosis**. In these conditions, the bacteria are physically present in the skin lesions (though they may be paucibacillary in Lupus Vulgaris). * **Erythema nodosum (D):** While it can be a manifestation of tuberculosis, it is a non-specific reactive septal panniculitis seen in various conditions (Sarcoidosis, Leprosy, Streptococcal infections). It is not classified as a "tuberculide" in the strict dermatological sense. **High-Yield Clinical Pearls for NEET-PG:** * **Classification of Tuberculides:** 1. **Lichen scrofulosorum:** Follicular papules (most common in children). 2. **Papulonecrotic tuberculide:** Symmetrical dusky-red papules with central necrosis, usually on extensors. 3. **Erythema induratum of Bazin:** Nodular lesions on the calves (posterior leg), often ulcerating. * **Key Differentiator:** True cutaneous TB (e.g., Lupus Vulgaris) has a positive culture/PCR from the lesion; Tuberculides have a negative culture but a strongly positive Mantoux test.

Question 147: Which of the following statements about Jacuzzi syndrome is true?

A. It is caused by Pneumococcus.
B. It is also known as hot tub folliculitis. (Correct Answer)
C. It is a progressive illness.
D. It is always a painless condition.

Explanation: **Explanation:** **Jacuzzi syndrome**, also known as **Hot Tub Folliculitis**, is a skin condition caused by the bacterium ***Pseudomonas aeruginosa***. This organism thrives in warm, alkaline water environments like hot tubs, whirlpools, and poorly maintained swimming pools. 1. **Why Option B is correct:** The term "Jacuzzi syndrome" is a direct synonym for hot tub folliculitis. The infection occurs when *Pseudomonas* invades the hair follicles, typically under areas covered by tight-fitting swimwear, which traps the contaminated water against the skin. 2. **Why other options are incorrect:** * **Option A:** It is caused by *Pseudomonas aeruginosa* (a Gram-negative rod), not *Pneumococcus* (a Gram-positive coccus). * **Option C:** It is generally a **self-limiting** illness. In most healthy individuals, the rash resolves spontaneously within 7 to 10 days without specific antibiotic treatment. * **Option D:** The lesions are typically **pruritic (itchy)** and can be **tender or painful**. They present as erythematous papules and pustules, often accompanied by malaise or low-grade fever. **High-Yield Clinical Pearls for NEET-PG:** * **Pathogen:** *Pseudomonas aeruginosa* (most common cause of Gram-negative folliculitis). * **Clinical Presentation:** "Diving suit distribution"—lesions are most concentrated in areas covered by bathing suits. * **Diagnosis:** Usually clinical; however, culture of the pus will grow *Pseudomonas*. * **Management:** Observation is key as it is self-limiting. For severe or persistent cases, oral **Ciprofloxacin** (anti-pseudomonal activity) may be used. * **Differential Diagnosis:** Should be distinguished from *Staphylococcal folliculitis*, which is not typically associated with hot tub use.

Question 148: Multidrug therapy is indicated for which of the following conditions?

A. Syphilis
B. Leprosy (Correct Answer)
C. Herpetiformis
D. Ichthyosis Vulgaris

Explanation: **Explanation:** **Multidrug Therapy (MDT)** is the cornerstone of treatment for **Leprosy** (Hansen’s Disease). The primary medical rationale for using MDT is to **prevent the emergence of drug resistance** in *Mycobacterium leprae*, particularly against Rifampicin. MDT also ensures a rapid clinical cure and reduces the duration of treatment. According to WHO guidelines, the regimen typically includes a combination of **Rifampicin, Dapsone, and Clofazimine** (for Multibacillary cases). **Analysis of Incorrect Options:** * **Syphilis:** Caused by *Treponema pallidum*, it is treated with **monotherapy**, specifically Benzathine Penicillin G (the drug of choice). Resistance to penicillin has not yet been documented in syphilis. * **Dermatitis Herpetiformis:** This is an autoimmune blistering disorder associated with gluten-sensitive enteropathy. The primary treatment is a **Gluten-Free Diet** and **Dapsone** (monotherapy) to control skin lesions. * **Ichthyosis Vulgaris:** This is a genetic keratinization disorder (Filaggrin mutation). It is managed with **topical emollients** and keratolytics (e.g., urea, lactic acid), not systemic antimicrobial therapy. **High-Yield Clinical Pearls for NEET-PG:** * **Paucibacillary (PB) Leprosy:** Treated for 6 months with Rifampicin and Dapsone. * **Multibacillary (MB) Leprosy:** Treated for 12 months with Rifampicin, Dapsone, and Clofazimine. * **Rifampicin** is the most bactericidal drug in the regimen and is administered once monthly under supervision. * **Clofazimine** is known for causing brownish-black skin discoloration and ichthyosis as side effects.

Question 149: Which of the following can lead to infiltration of ear lobules, loss of nails, and resorption of distal phalanges?

A. Tuberculoid leprosy
B. Lepromatous leprosy (Correct Answer)
C. Indeterminate leprosy
D. Any of the above

Explanation: **Explanation:** The correct answer is **Lepromatous Leprosy (LL)**. This clinical presentation is characteristic of the multibacillary end of the leprosy spectrum, where there is a high bacterial load due to deficient cell-mediated immunity (CMI). 1. **Why Lepromatous Leprosy is correct:** * **Infiltration of Ear Lobules:** In LL, *M. leprae* proliferates extensively in cooler areas of the body. Diffuse infiltration leads to thickening of the ear lobules (a classic early sign) and may eventually progress to "Leonine facies." * **Resorption of Distal Phalanges:** This occurs due to a combination of specific lepromatous osteitis, secondary pyogenic osteomyelitis (from neglected trauma to anesthetic limbs), and neurotrophic changes. * **Loss of Nails:** Chronic trophic changes and destruction of the nail matrix due to vascular compromise and repeated trauma lead to onychoatrophy or total nail loss. 2. **Why other options are incorrect:** * **Tuberculoid Leprosy (TT):** Characterized by strong CMI, few lesions (1-3), and early, severe nerve involvement. While it causes localized anesthesia, it does not typically present with diffuse infiltration of ear lobules or generalized resorption of phalanges. * **Indeterminate Leprosy:** This is the early, transitory stage of the disease. It presents as a single, ill-defined macule with slight sensory loss and never exhibits the chronic destructive features mentioned. **High-Yield Clinical Pearls for NEET-PG:** * **Ear Lobule:** The ear lobule is the site of choice for a slit-skin smear (SSS) because of its high bacterial density. * **Leonine Facies:** Caused by diffuse infiltration of the forehead, cheeks, and nose, along with **Madarosis** (loss of lateral 1/3rd of eyebrows). * **Internal Involvement:** LL is a systemic disease; it can involve the testes (leading to gynecomastia/sterility), the nasal septum (leading to saddle nose deformity), and the eyes.

Question 150: Bullous impetigo is caused by which bacterium?

A. Streptococcus
B. Staphylococcus (Correct Answer)
C. Staphylococcus
D. Yersinia pestis

Explanation: **Explanation:** **Bullous Impetigo** is a localized form of impetigo characterized by large, fragile, flaccid bullae. The correct answer is **Staphylococcus aureus** (specifically Phage Group II, types 71 and 55). **1. Why Staphylococcus is Correct:** The pathogenesis involves the production of **Exfoliative Toxins (ETA and ETB)** by *S. aureus*. These toxins act as "molecular scissors" that specifically target and cleave **Desmoglein-1**, a cell-adhesion molecule found in the desmosomes of the upper epidermis (stratum granulosum). This leads to acantholysis (loss of cell-to-cell adhesion), resulting in the formation of subcorneal blisters. **2. Why Other Options are Incorrect:** * **Streptococcus:** While *Streptococcus pyogenes* (Group A Strep) is the most common cause of **Non-bullous impetigo** (honey-colored crusts), it does not produce exfoliative toxins and therefore does not cause the bullous variant. * **Yersinia pestis:** This is the causative agent of the Plague. While it can cause cutaneous necrosis or "buboes," it is not associated with the superficial blistering seen in impetigo. **3. Clinical Pearls for NEET-PG:** * **Target Molecule:** Desmoglein-1 (Same target as Pemphigus Foliaceus). * **Nikolsky Sign:** Usually negative in bullous impetigo (unlike Staphylococcal Scalded Skin Syndrome, where it is positive). * **Staphylococcal Scalded Skin Syndrome (SSSS):** This is the systemic version of the same toxin-mediated process; however, in SSSS, the toxin spreads hematogenously, and cultures from the blisters are typically sterile. In bullous impetigo, the toxin acts locally, and cultures from the blister fluid will grow *S. aureus*. * **Treatment:** Topical Mupirocin for localized lesions; oral Dicloxacillin or Cephalexin for widespread cases.

Practice by Chapter

Impetigo

Practice Questions

Folliculitis, Furuncles, and Carbuncles

Practice Questions

Ecthyma

Practice Questions

Erysipelas and Cellulitis

Practice Questions

Staphylococcal Scalded Skin Syndrome

Practice Questions

Necrotizing Fasciitis

Practice Questions

Cutaneous Tuberculosis

Practice Questions

Leprosy

Practice Questions

Lyme Disease

Practice Questions

Syphilis

Practice Questions

Antibiotic Resistance in Dermatology

Practice Questions

Prophylaxis and Management

Practice Questions

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