Bacterial Skin Infections Practice Questions

Q: Blistering dactylitis is typically caused by which of the following?

Streptococcal infection. **Explanation:** **Blistering Dactylitis** is a localized superficial infection characterized by tense, fluid-filled blisters (bullae) over the volar fat pads of the distal phalanx of the fingers or toes. 1. **Why Option A is Correct:** The most common causative organism is **Group A Beta-hemolytic Streptococcus (Streptococcus pyogenes)**. Occasionally, *Staphylococcus aureus* may be co-isolated, but classic blistering dactylitis is traditionally associated with Streptococcus. The infection typically follows minor trauma or autoinoculation from the nasopharynx, leading to the formation of a characteristic oval bulla on an erythematous base. 2. **Why Other Options are Incorrect:** * **Option B (Staphylococcus):** While *S. aureus* can cause bullous impetigo, it is less frequently the primary isolate in the specific clinical presentation of volar dactylitis compared to Streptococcus. * **Option C (Tuberculosis):** Cutaneous TB (like Lupus Vulgaris) or TB of the bone (Spina Ventosa) can affect the digits, but they present as chronic nodules, ulcers, or "bottleneck" swelling, not acute superficial blisters. * **Option D (Sickle cell anaemia):** This is associated with **Hand-Foot Syndrome** (dactylitis) in infants, which is caused by microinfarction of the small bones, leading to painful, non-blistering inflammatory swelling. **Clinical Pearls for NEET-PG:** * **Target Population:** Most commonly seen in children (2–16 years). * **Clinical Feature:** Tense bullae containing seropurulent fluid over the **volar** aspect of the distal digit. * **Treatment:** Incision and drainage of the bulla followed by a course of oral antibiotics (e.g., Penicillinase-resistant penicillins or Cephalosporins). * **Differential Diagnosis:** Must be distinguished from herpetic whitlow (which presents with grouped vesicles and significant pain) and friction blisters.

Q: Leprosy does NOT affect the axilla, groin, and scalp because:

These are warmer regions of the body. **Explanation:** The causative organism of Leprosy, ***Mycobacterium leprae***, is an obligate intracellular bacterium with a unique temperature sensitivity. It thrives optimally at temperatures slightly lower than the core body temperature, specifically between **30°C and 33°C**. **1. Why Option A is correct:** The axilla, groin, and scalp are considered "warm zones" of the body because they are either well-insulated by skin folds (intertriginous areas) or have high vascularity and hair cover, maintaining a temperature close to the core body temperature (37°C). Because *M. leprae* cannot replicate efficiently at these higher temperatures, these areas are typically spared from clinical lesions. Conversely, the bacteria preferentially affect cooler areas like the nose, ears, and extensor surfaces of the limbs. **2. Why other options are incorrect:** * **Option B:** These areas are physiologically warmer, not colder. Colder regions (like the pinna of the ear) are actually the most common sites for finding the bacilli. * **Option C:** The scalp and groin are actually highly vascular areas. Blood supply does not dictate the distribution of leprosy; temperature does. * **Option D:** These regions have a rich sensory nerve supply. While leprosy is a disease of the nerves, the distribution of lesions is determined by the thermal requirements of the bacteria, not the density of the nerves. **NEET-PG High-Yield Pearls:** * **"Immune Privileged" Sites in Leprosy:** The midline of the back, axilla, groin, and scalp are often referred to as "spared areas." * **Diagnosis:** The **Ear lobe snip** is a classic site for Slit Skin Smear (SSS) because it is one of the coolest peripheral parts of the body. * **Target Organs:** *M. leprae* has a predilection for **peripheral nerves** (Schwann cells) and the **skin**.

Q: Lymphogranuloma venerum is characterized by all of the following except?

Metronidazole is an effective treatment.. **Lymphogranuloma Venereum (LGV)** is a sexually transmitted infection caused by **Chlamydia trachomatis serovars L1, L2, and L3**. ### Explanation of Options: * **Option C (Correct Answer):** Metronidazole is an antiprotozoal and anaerobic antibacterial agent; it has no activity against *Chlamydia*. The **first-line treatment for LGV is Doxycycline** (100 mg twice daily for 21 days). Erythromycin or Azithromycin are alternatives. * **Option A:** The primary lesion is typically a small, painless papule or ulcer that is transient and often goes unnoticed. It **heals rapidly without leaving a scar**, which distinguishes it from the scarring seen in Syphilis or Chancroid. * **Option B:** LGV is a systemic disease. Beyond local lesions, patients frequently present with **systemic symptoms** such as fever, chills, malaise, and myalgia, especially during the secondary stage (lymphatic spread) [1]. * **Option C:** The **"Groove Sign" (Greenblatt’s sign)** is a pathognomonic clinical finding. It occurs when the inguinal ligament divides matted, enlarged inguinal and femoral lymph nodes, creating a visible depression or "groove" between the two groups of nodes [1]. ### NEET-PG High-Yield Pearls: * **Stages:** 1° (Primary ulcer) → 2° (Inguinal syndrome/Buboes) → 3° (Anogenital syndrome/Strictures). * **Esthiomene:** A chronic complication involving hypertrophic ulceration and elephantiasis of the female external genitalia due to lymphatic obstruction. * **Diagnosis:** Nucleic Acid Amplification Test (NAAT) is the preferred diagnostic method. Frei’s test is a historical skin test (now obsolete). * **Proctocolitis:** Common in MSM (Men who have sex with men), presenting with rectal discharge, pain, and tenesmus [1].

Q: A 12-year-old child presents with a painless neck swelling in the supraclavicular region that started discharging after a few days. What is the most probable diagnosis?

Scrofuloderma. ### Explanation **Correct Answer: A. Scrofuloderma** **Concept:** Scrofuloderma (Tuberculosis colliquativa cutis) is a form of **cutaneous tuberculosis** that occurs due to the direct extension of an underlying tuberculous focus (most commonly a **cervical lymph node**) to the overlying skin. In this clinical scenario, the "painless neck swelling" represents a cold abscess of the lymph node. As the infection progresses, the skin breaks down, leading to the formation of a **discharging sinus** or ulcer with undermined edges. The supraclavicular and cervical regions are the most classic sites for this presentation in children. **Analysis of Incorrect Options:** * **B. Actinomycosis:** While it presents with discharging sinuses, it typically involves the **mandibular region** ("lumpy jaw"). The discharge characteristically contains **sulfur granules**, and the lesions are usually indurated (woody hard) rather than a simple painless swelling. * **C. Botryomycosis:** This is a chronic granulomatous bacterial infection (usually *S. aureus*) that mimics fungal infections. It typically affects the extremities and presents with nodules and sinuses, but is not the primary diagnosis for a pediatric supraclavicular neck mass. * **D. Fungal Mycetoma:** This is a chronic infection of the subcutaneous tissue, usually involving the **foot** (Madura foot). It presents with a triad of tumefaction, sinuses, and discharge of macroscopic grains. **High-Yield Clinical Pearls for NEET-PG:** * **Lupus Vulgaris:** The most common clinical variant of secondary cutaneous TB; characterized by "apple-jelly nodules" on diascopy. * **Scrofuloderma:** The most common form of cutaneous TB in children in India. * **Tuberculosis Verrucosa Cutis (TVC):** Also known as "Prosector’s wart," it occurs due to exogenous inoculation in individuals with high immunity. * **Histopathology:** Look for acid-fast bacilli (AFB) and caseating granulomas.

Q: What is the treatment for severe ulnar neuritis in borderline tuberculoid leprosy?

MDT plus steroids. **Explanation:** The correct answer is **MDT plus steroids**. In leprosy, **neuritis** (nerve inflammation) is often a manifestation of a **Type 1 Lepra Reaction** (Reversal Reaction), which is common in Borderline Tuberculoid (BT) leprosy. Severe ulnar neuritis indicates an acute inflammatory process that can lead to irreversible nerve damage and physical disability (e.g., claw hand) if not treated aggressively. 1. **Why MDT plus Steroids is correct:** While MDT (Rifampicin and Dapsone for BT) treats the underlying *Mycobacterium leprae* infection, it does not stop the acute immunological reaction damaging the nerve. **Systemic corticosteroids** (typically Prednisolone) are the gold standard to reduce edema and inflammation within the nerve sheath, thereby preventing permanent paralysis. 2. **Why other options are wrong:** * **MDT only:** Insufficient for neuritis; it kills bacilli but doesn't address the immune-mediated nerve destruction. * **Wait and watch:** Dangerous; delay in treatment leads to permanent nerve fibrosis and disability. * **MDT plus Thalidomide:** Thalidomide is the drug of choice for **Type 2 Lepra Reaction** (Erythema Nodosum Leprosum), which occurs in lepromatous poles, not Type 1 reactions seen in BT leprosy. **High-Yield Clinical Pearls for NEET-PG:** * **Type 1 Reaction:** Delayed hypersensitivity (Cell-mediated); seen in BT, BB, BL; treated with Steroids. * **Type 2 Reaction:** Humoral immunity (Arthus phenomenon); seen in BL, LL; treated with Thalidomide, Clofazimine, or Steroids. * **Silent Neuritis:** Nerve damage without pain/tenderness; also requires urgent steroid therapy. * **WHO MDT Duration (BT):** 6 months (Paucibacillary regimen).

Q: Which of the following is NOT a characteristic feature of Hutchinson's triad?

Cataract. **Explanation:** Hutchinson’s triad is a classic clinical presentation of **Late Congenital Syphilis** (symptoms appearing after 2 years of age). It is caused by the transplacental transmission of *Treponema pallidum*. **Why Cataract is the correct answer:** Cataract is **not** a component of Hutchinson’s triad. While congenital syphilis can cause various ocular issues, the specific ocular component of the triad is **Interstitial Keratitis**, which involves inflammation of the corneal stroma leading to scarring and potential blindness, rather than opacification of the lens (cataract). **Analysis of other options:** * **Interstitial Keratitis (Option A):** A hallmark of the triad, usually appearing between ages 5 and 15. It presents with ground-glass corneal edema. * **Notched Incisors (Option B):** Also known as **Hutchinson’s teeth**. These are permanent upper central incisors that are small, widely spaced, and peg-shaped with a central notch on the biting edge. * **Deafness (Option C):** Specifically, **Sensorineural hearing loss** caused by eighth cranial nerve (vestibulocochlear) involvement. It often develops suddenly around puberty. **High-Yield Clinical Pearls for NEET-PG:** * **Mulberry Molars:** Another dental finding in late congenital syphilis characterized by multiple rudimentary cusps on the first molars. * **Saber Shin:** Anterior bowing of the tibia due to periostitis. * **Clutton’s Joints:** Symmetrical painless swelling of the knees. * **Early Congenital Syphilis signs:** Snuffles (syphilitic rhinitis), palmoplantar rash, and condyloma lata. * **Drug of Choice:** Penicillin G remains the treatment of choice for all stages of syphilis.

Q: Which of the following organisms is responsible for vesicular eruptions and 'honey-coloured' crusts over the face?

Staphylococcus aureus. The clinical presentation described—**vesicular eruptions** progressing to **'honey-colored' crusts**—is the classic hallmark of **Impetigo Contagiosa** (Non-bullous impetigo). ### 1. Why Option B is Correct **Staphylococcus aureus** is currently the most common cause of non-bullous impetigo worldwide, followed by *Streptococcus pyogenes* (Group A Beta-hemolytic Strep). The pathogenesis involves the bacteria invading the superficial epidermis (subcorneal layer), leading to fragile vesicles that rupture easily. The dried exudate results in the characteristic "stuck-on" golden-yellow or honey-colored crusts, typically found on the face around the nose and mouth. ### 2. Why Other Options are Incorrect * **A. TB bacilli:** Cutaneous tuberculosis (e.g., Lupus vulgaris or Scrofuloderma) typically presents as chronic plaques, nodules, or cold abscesses, not acute vesicular eruptions with honey-colored crusts. * **C. Hansen's bacilli:** *Mycobacterium leprae* causes Leprosy, characterized by hypopigmented patches with loss of sensation or thickened nerves, rather than superficial crusting infections. * **D. Herpes zoster:** While it presents with vesicles, they are typically **grouped**, painful, and follow a **dermatomal distribution**. The crusts are usually hemorrhagic or serous, not classically "honey-colored." ### 3. NEET-PG High-Yield Pearls * **Bullous Impetigo:** Always caused by *S. aureus* (Phage group II). It is mediated by **Exfoliative Toxin A**, which targets **Desmoglein-1**. * **Ecthyma:** A deeper form of impetigo (extending into the dermis) that results in "punched-out" ulcers; often caused by *Streptococcus*. * **Complication:** While non-bullous impetigo can lead to **Post-Streptococcal Glomerulonephritis (PSGN)**, it does *not* lead to Rheumatic Fever. * **Treatment:** Topical **Mupirocin** is the drug of choice for localized lesions. For systemic involvement, use Cloxacillin or Amoxicillin-Clavulanate.

Q: All are features of lepromatous leprosy except?

Perforating Ulcer. **Explanation:** The correct answer is **D. Perforating Ulcer**. In Leprosy, **Perforating Ulcers** (trophic ulcers) are a hallmark of **Tuberculoid Leprosy (TT/BT)**. These occur due to anesthesia resulting from early, asymmetric, and severe nerve damage. In contrast, Lepromatous Leprosy (LL) is characterized by high bacterial load but delayed nerve damage; anesthesia occurs much later and is usually symmetrical (glove-and-stocking distribution), making trophic ulcers less characteristic of the early-to-mid clinical presentation of LL. **Analysis of Incorrect Options:** * **Gynaecomastia:** This is a classic feature of LL. It occurs due to testicular atrophy caused by direct *M. leprae* infiltration (orchitis), leading to a hormonal imbalance (decreased testosterone and increased estrogen). * **Madarosis:** This refers to the loss of eyebrows (specifically the lateral one-third). It is a common feature of LL due to the infiltration of lepromas into the hair follicles. * **Saddle nose:** In LL, the bacilli infiltrate the nasal mucosa and cartilage, leading to chronic rhinitis, crusting, and eventually destruction of the nasal septum, causing the bridge of the nose to collapse. **High-Yield Clinical Pearls for NEET-PG:** * **LL Hallmark:** Bilateral symmetrical lesions, Leonine facies, and "Glove and Stocking" anesthesia. * **TT Hallmark:** Asymmetrical, well-defined anesthetic patches with early nerve enlargement. * **Bacteriology:** LL is Multibacillary (BI 3+ to 6+), while TT is Paucibacillary (BI 0 to 1+). * **Internal Organ Involvement:** LL involves the reticuloendothelial system, liver, spleen, and testes; TT is limited to skin and nerves.

Question 1

Large bilateral painless effusions of the knees occurring in late congenital syphilis in patients between ages 8 to 18 are designated as?

Accepted Answer

Clutton's joints

Answer

Ramsey's joints

Answer

Charcot's joints

Answer

Mercer's joints

Question 2

Blistering dactylitis is typically caused by which of the following?

Accepted Answer

Streptococcal infection

Answer

Staphylococcus

Answer

Tuberculosis

Answer

Sickle cell anaemia

Question 3

Leprosy does NOT affect the axilla, groin, and scalp because:

Accepted Answer

These are warmer regions of the body

Answer

These are colder regions of the body

Answer

These areas have less blood supply

Answer

These areas have less sensory nerve supply

Question 4

Lymphogranuloma venerum is characterized by all of the following except?

Accepted Answer

Metronidazole is an effective treatment.

Answer

Primary lesions heal without scarring.

Answer

Commonly develop systemic infection.

Answer

Groove sign is seen characteristically.

Question 5

A 12-year-old child presents with a painless neck swelling in the supraclavicular region that started discharging after a few days. What is the most probable diagnosis?

Accepted Answer

Scrofuloderma

Answer

Actinomycosis

Answer

Botryomycosis

Answer

Fungal mycetoma

Question 6

What is the treatment for severe ulnar neuritis in borderline tuberculoid leprosy?

Accepted Answer

MDT plus steroids

Answer

Multidrug therapy (MDT) only

Answer

Wait and watch

Answer

MDT plus thalidomide

Question 7

Which of the following is NOT a characteristic feature of Hutchinson's triad?

Accepted Answer

Cataract

Answer

Interstitial keratitis

Answer

Notched incisors

Answer

Deafness

Question 8

A 45-year-old woman presents with a 2-year history of slowly progressive, minimally pruritic, confluent plaques involving the perioral and centrofacial areas. The eruption was preceded by oral mucosal plaques. On examination, multiple, confluent, fibrotic, scaly, hypopigmented plaques with central atrophy, peripheral hyperpigmentation, and crusts are noted in the involved areas. A skin biopsy demonstrates granulomatous inflammation. Which of the following would be true about this patient?

Accepted Answer

Cultures would grow Mycobacterium tuberculosis

Answer

Fungal culture would be positive

Answer

The patient is at risk of erythema nodosum leprosum

Answer

Visceral leishmaniasis should be ruled out

Question 9

Which of the following organisms is responsible for vesicular eruptions and 'honey-coloured' crusts over the face?

Accepted Answer

Staphylococcus aureus

Answer

TB bacilli

Answer

Hansen's bacilli

Answer

Herpes zoster

Question 10

All are features of lepromatous leprosy except?

Accepted Answer

Perforating Ulcer

Answer

Gynaecomastia

Answer

Madarosis

Answer

Saddle nose

Bacterial Skin Infections — MCQs

Bacterial Skin Infections — MCQs

On this page

Practice by Chapter

Want unlimited practice?