Bacterial Skin Infections Practice Questions

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.

Q: Lepra cells are seen in abundance in which type of leprosy?

Lepromatous leprosy. **Explanation:** The presence of **Lepra cells** (also known as **Virchow cells**) is a hallmark of **Lepromatous Leprosy (LL)**. These are large, foamy macrophages that have ingested a high number of *Mycobacterium leprae*. In LL, the patient exhibits a deficient Cell-Mediated Immunity (CMI), allowing the bacilli to multiply unchecked. The macrophages become "stuffed" with bacilli, which are often arranged in parallel clusters called **globi**. **Analysis of Options:** * **Lepromatous Leprosy (Correct):** Due to the Th2-dominant cytokine profile and poor CMI, there is a high bacillary load (multibacillary). Macrophages fail to kill the bacteria, leading to the formation of foamy Lepra cells. * **Tuberculoid Leprosy (Incorrect):** This pole is characterized by strong CMI (Th1 response). Bacilli are very rare (paucibacillary), and the histology shows well-formed granulomas with epithelioid cells and Langhans giant cells, rather than foamy Lepra cells. * **Histoid Leprosy (Incorrect):** A variant of LL characterized by spindle-shaped histiocytes arranged in a storiform pattern. While it has a high bacillary load, the characteristic cell is the spindle cell, not the classic foamy Lepra cell. * **Indeterminate Leprosy (Incorrect):** This is an early stage where the immune response hasn't polarized. Histology usually shows only non-specific perineural inflammation. **NEET-PG High-Yield Pearls:** * **Grenz Zone:** A clear subepidermal zone of uninvolved dermis seen in Lepromatous and Histoid leprosy (absent in Tuberculoid). * **Fite-Faraco Stain:** A modified acid-fast stain used to visualize *M. leprae* in tissue sections. * **Globi:** Masses of acid-fast bacilli held together by a mucoid material called **glis**. * **Ridley-Jopling Classification:** The standard 5-group classification based on the immunological spectrum of the disease.

Q: What is the most important cytokine for type II lepra reaction?

TNF alpha. **Explanation:** **Type II Lepra Reaction (Erythema Nodosum Leprosum - ENL)** is a classic example of a **Type III Hypersensitivity reaction** (Immune-complex mediated). It typically occurs in patients with multibacillary leprosy (lepromatous or borderline lepromatous) where there is a high bacterial load. **Why TNF-alpha is the correct answer:** TNF-alpha (Tumor Necrosis Factor-alpha) is the central mediator in the pathogenesis of ENL. During the reaction, there is a massive systemic release of TNF-alpha from activated macrophages and monocytes. This cytokine is responsible for the systemic symptoms (fever, malaise) and the acute inflammatory skin lesions. The clinical effectiveness of **Thalidomide** in treating Type II reactions is specifically due to its potent ability to inhibit TNF-alpha synthesis. **Analysis of Incorrect Options:** * **IL-1 and IL-6:** While these are pro-inflammatory cytokines that may be elevated during systemic inflammation, they are secondary mediators and not the primary drivers or therapeutic targets specific to ENL. * **IFN-gamma:** This is the hallmark cytokine of **Type 1 Lepra Reaction** (Reversal Reaction), which involves a Type IV Delayed Hypersensitivity response and a shift toward a Th1 immune profile. **High-Yield Clinical Pearls for NEET-PG:** * **Type I Reaction:** Type IV Hypersensitivity; involves IFN-gamma and IL-2; treated with Steroids. * **Type II Reaction (ENL):** Type III Hypersensitivity; involves TNF-alpha; treated with **Thalidomide** (drug of choice) or Clofazimine. * **Clinical Presentation of ENL:** Tender evanescent subcutaneous nodules, fever, arthralgia, and iridocyclitis. * **Trigger:** Often precipitated by the initiation of Multidrug Therapy (MDT).

Q: Which of the following statements regarding Botryomycosis is FALSE?

It mainly affects the viscera.. ### **Explanation: Botryomycosis** Botryomycosis is a rare, chronic, granulomatous bacterial infection that clinically mimics fungal infections (like actinomycosis or eumycetoma) but is caused by non-filamentous bacteria. **1. Why Option B is the Correct Answer (The False Statement):** Botryomycosis primarily affects the **integumentary system (skin and subcutaneous tissue)** in approximately 75% of cases. While a visceral form exists (affecting lungs, liver, or brain), it is much less common and typically occurs in severely immunocompromised patients. Therefore, stating that it "mainly" affects the viscera is incorrect. **2. Analysis of Other Options:** * **Option A (Chronic granulomatous disease):** This is **true**. Histologically, it is characterized by a granulomatous inflammatory response surrounding bacterial grains (Splendore-Hoeppli phenomenon). * **Option C (Staphylococcus aureus):** This is **true**. *Staphylococcus aureus* is the most common causative agent (40% of cases), followed by *Pseudomonas aeruginosa*, *E. coli*, and *Proteus*. * **Option D (Sinuses and purulent discharge):** This is **true**. The clinical hallmark is the presence of nodules, abscesses, and multiple draining sinuses that discharge pus containing "grains" (clusters of bacteria). **3. NEET-PG Clinical Pearls:** * **The "Grains":** Unlike Actinomycosis (which has sulfur granules), Botryomycosis grains are composed of masses of **true bacteria** held together by a polysaccharide matrix. * **Splendore-Hoeppli Phenomenon:** An eosinophilic, glassy material surrounding the bacterial colonies seen on H&E stain; it represents an antigen-antibody complex. * **Predisposing Factors:** Often linked to trauma, foreign bodies, or altered host immunity (e.g., Diabetes, HIV). * **Treatment:** Long-term culture-specific antibiotics and occasionally surgical debridement.

Q: Which of the following is NOT true of erysipelas?

Common in tropics. **Explanation:** **Erysipelas** is a distinct superficial form of cellulitis with prominent lymphatic involvement. 1. **Why Option D is the Correct Answer:** Erysipelas is **not** more common in the tropics; it is actually more prevalent in **temperate climates**. In contrast, other pyodermas like impetigo are more frequently seen in tropical, humid environments. This makes Option D the false statement and thus the correct answer. 2. **Analysis of Other Options:** * **Option A (Streptococcal infection):** This is true. The primary causative agent is **Group A Beta-hemolytic Streptococci** (*Streptococcus pyogenes*). Unlike cellulitis, *Staphylococcus aureus* is a rare cause of erysipelas. * **Option B (Contagious and infectious):** This is true. It is an acute infectious process that can spread through autoinoculation or direct contact, especially if there is a break in the skin barrier (e.g., tinea pedis, fissures). * **Option C (Margins are raised):** This is a hallmark feature. Because the infection is superficial (upper dermis), it presents with a **sharply demarcated, raised, and indurated border** (Milian’s ear sign). This distinguishes it from cellulitis, which has ill-defined, non-raised borders. **Clinical Pearls for NEET-PG:** * **Classic Appearance:** "St. Anthony’s Fire" – characterized by a fiery red, painful, shiny, and edematous plaque. * **Milian’s Ear Sign:** Involvement of the pinna (ear) suggests erysipelas because the ear lacks deep subcutaneous tissue, making cellulitis impossible at that site. * **Treatment of Choice:** Parenteral or oral **Penicillin** remains the gold standard. * **Predisposing Factor:** Chronic lymphedema is the most significant risk factor for recurrent erysipelas.

Q: A 12-year-old child with intellectual disability presents with multiple, painful, shiny white discharging lesions around the anus. What is the most probable diagnosis?

Syphilitic condyloma. **Explanation:** The clinical presentation of multiple, painful, shiny white discharging lesions in the perianal region of a child is highly suggestive of **Condyloma Lata**, a hallmark of **Secondary Syphilis**. **Why Syphilitic Condyloma is correct:** Condyloma lata are hypertrophic, papular lesions found in moist intertriginous areas (like the anus or axilla). They are characterized by a "flat-topped," "moist," or "shiny white" appearance due to maceration and are highly infectious, teeming with *Treponema pallidum*. In a child with intellectual disability, this presentation should raise immediate suspicion of sexual abuse leading to an acquired sexually transmitted infection. **Why other options are incorrect:** * **Lupus Vulgaris:** This is a chronic form of cutaneous tuberculosis characterized by "apple-jelly nodules" on diascopy. It typically presents on the face and neck, not as acute discharging perianal lesions. * **Carcinoma:** Squamous cell carcinoma of the anus usually presents as a hard, indurated, non-healing ulcer or mass in older adults, rather than multiple moist lesions in a child. * **Hemorrhoids:** These are vascular cushions. While they can cause pain and bleeding, they do not present as "shiny white discharging" infectious papules. **NEET-PG High-Yield Pearls:** * **Condyloma Lata vs. Condyloma Acuminata:** Lata is flat-topped and moist (Secondary Syphilis); Acuminata is cauliflower-like and warty (HPV 6, 11). * **Dark-field Microscopy:** The gold standard for immediate diagnosis of Condyloma Lata, showing motile spirochetes. * **Screening:** Always perform a VDRL/RPR test. In pediatric cases, a thorough social evaluation for potential abuse is mandatory.

Question 1

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 2

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 3

All are features of lepromatous leprosy except?

Accepted Answer

Perforating Ulcer

Answer

Gynaecomastia

Answer

Madarosis

Answer

Saddle nose

Question 4

Lepra cells are seen in abundance in which type of leprosy?

Accepted Answer

Lepromatous leprosy

Answer

Tuberculoid leprosy

Answer

Histoid leprosy

Answer

Intermediate leprosy

Question 5

What is the most important cytokine for type II lepra reaction?

Accepted Answer

TNF alpha

Answer

IL 1

Answer

IL 6

Answer

INF gamma

Question 6

Which of the following statements regarding Botryomycosis is FALSE?

Accepted Answer

It mainly affects the viscera.

Answer

It is a chronic granulomatous disease.

Answer

The causative organism is Staphylococcus aureus.

Answer

It presents with sinuses and purulent discharge.

Question 7

Which of the following statements about leprosy classification is true?

Accepted Answer

In paucibacillary leprosy, the bacterial index is less than 2.

Answer

A bacterial index of 2+ indicates two different sites.

Answer

Seven sites are needed for classification.

Answer

Various sites are needed for classification.

Question 8

A 28-year-old female presented with a syphilitic chancre and was treated with Inj. Benzathine penicillin G, 2.4 million units intramuscularly as a single dose. After initial treatment, she was screened at 6-month intervals and was found to be still seropositive. Which of the following treatment regimens would you recommend?

Accepted Answer

Inj. Benzathine penicillin G, 2.4 million units intramuscularly, weekly for 3 weeks

Answer

Inj. Benzathine penicillin G, 2.4 million units intramuscularly, single dose

Answer

Inj. Benzathine penicillin G, 2.4 million units intramuscularly, twice daily for 1 week

Answer

Inj. Benzathine penicillin G, 2.4 million units intramuscularly, twice weekly for 3 weeks

Question 9

Which of the following is NOT true of erysipelas?

Accepted Answer

Common in tropics

Answer

Streptococcal infection

Answer

Contagious and infectious

Answer

Margins are raised

Question 10

A 12-year-old child with intellectual disability presents with multiple, painful, shiny white discharging lesions around the anus. What is the most probable diagnosis?

Accepted Answer

Syphilitic condyloma

Answer

Lupus vulgaris

Answer

Carcinoma

Answer

Hemorrhoids

Bacterial Skin Infections — MCQs

Bacterial Skin Infections — MCQs

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