Bacterial Skin Infections Practice Questions

Q: What is the drug of choice for Lymphogranuloma venereum (LGV)?

Doxycycline. **Lymphogranuloma venereum (LGV)** is a sexually transmitted infection caused by the **L1, L2, and L3 serovars of *Chlamydia trachomatis***. It typically presents in three stages: a painless primary lesion, a painful secondary stage characterized by regional lymphadenopathy (the "Groove sign"), and a tertiary stage involving chronic inflammation and proctocolitis [1]. 1. **Why Doxycycline is correct:** **Doxycycline (100 mg orally twice daily for 21 days)** is the established **drug of choice** for LGV. Tetracyclines are highly effective against intracellular organisms like *Chlamydia* [1]. The extended 3-week duration is necessary to ensure complete eradication and prevent the late-stage complications of lymphatic destruction and fibrosis. 2. **Why the other options are incorrect:** * **Ampicillin:** This is a beta-lactam antibiotic. *Chlamydia* lacks a traditional peptidoglycan cell wall, making cell-wall synthesis inhibitors like Ampicillin ineffective. * **Erythromycin:** While Erythromycin (500 mg four times daily for 21 days) is an effective alternative for patients who cannot tolerate tetracyclines (e.g., pregnant women), it is not the first-line treatment due to gastrointestinal side effects and a more frequent dosing schedule. * **Ceftriaxone:** This is the drug of choice for *Neisseria gonorrhoeae* and Chancroid, but it has no clinical activity against *C. trachomatis* [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Groove Sign:** Pathognomonic for LGV; it refers to the inguinal ligament dividing matted, enlarged matted lymph nodes (inguinal and femoral). * **Alternative in Pregnancy:** Erythromycin base is the preferred treatment for LGV in pregnant and lactating women. * **Azithromycin:** While a single dose of Azithromycin (1g) treats uncomplicated urethritis/cervicitis (*Serovars D-K*), it is **not** the first-line recommendation for LGV; Doxycycline remains superior for the L-serovars.

Q: Which of the following statements about Donovanosis is true?

Caused by Calymmatobacterium granulomatis. **Explanation:** **Donovanosis** (Granuloma Inguinale) is a chronic, progressive bacterial infection of the genital and perianal region. 1. **Why Option A is Correct:** The causative agent is **_Klebsiella granulomatis_** (formerly known as **_Calymmatobacterium granulomatis_**). It is a Gram-negative, pleomorphic, intracellular bacillus. The hallmark of diagnosis is the identification of **Donovan bodies** (safety-pin appearance) within large mononuclear cells (macrophages) on a tissue smear stained with Giemsa or Wright stain. 2. **Why Other Options are Incorrect:** * **Option B:** Lymphadenopathy is typically **absent**. However, the disease causes subcutaneous granulation tissue that mimics lymph node enlargement, known as **"Pseudobubo."** * **Option C:** The drug of choice is **Azithromycin** (1g weekly or 500mg daily for at least 3 weeks). Penicillin is ineffective as the organism is an intracellular Gram-negative rod. * **Option D:** Donovanosis is characterized by **painless**, beefy-red, friable ulcers with exuberant granulation tissue. Painful ulcers are characteristic of Chancroid or Herpes Simplex. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Appearance:** "Beefy red" ulcers that bleed easily on touch. * **Pathognomonic Sign:** Donovan bodies (Intracellular safety-pin appearance). * **Key Distinction:** Unlike Syphilis or Chancroid, it does not involve true regional lymph nodes. * **Common Sites:** Prepuce/frenulum in males; labia/fourchette in females.

Q: Which drug is used in the management of steroid-resistant lepra reactions?

Thalidomide. **Explanation:** The correct answer is **Thalidomide**. **Why Thalidomide is correct:** Lepra reactions are immunologically mediated inflammatory episodes occurring during the course of leprosy. **Type 2 Lepra Reaction (Erythema Nodosum Leprosum - ENL)** is a Type III hypersensitivity reaction characterized by painful nodules, fever, and systemic symptoms. While systemic corticosteroids are the first-line treatment, **Thalidomide** is the drug of choice for **steroid-resistant or steroid-dependent ENL**. Its efficacy is attributed to its potent inhibition of **Tumor Necrosis Factor-alpha (TNF-α)** and its ability to modulate T-cell responses. **Why other options are incorrect:** * **Clofazimine:** While it has anti-inflammatory properties and is used to prevent recurrences of ENL, it is slower acting than Thalidomide and is primarily used as part of Multi-Drug Therapy (MDT) or as a steroid-sparing agent. * **Dapsone & Rifampicin:** These are bactericidal/bacteriostatic components of MDT used to kill *Mycobacterium leprae*. They do not have significant acute anti-inflammatory properties and, in some cases, the initiation of these drugs can actually trigger a lepra reaction due to the release of antigens from dying bacilli. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Thalidomide:** TNF-α inhibitor. * **Teratogenicity:** Thalidomide is famous for causing **Phocomelia** (seal-like limbs). It is strictly contraindicated in pregnancy and requires the "S.T.E.P.S." program for risk management. * **Type 1 Reaction:** A Type IV hypersensitivity (Reversal reaction); managed primarily with steroids, NOT Thalidomide. * **Drug of Choice for ENL:** Mild (NSAIDs), Severe (Steroids), Steroid-resistant (Thalidomide).

Q: Which of the following statements about impetigo is FALSE?

It produces scars on healing.. ### Explanation **1. Why Option C is the Correct (False) Statement:** Impetigo is a **superficial** bacterial infection of the skin, specifically involving the **epidermis** (subcorneal layer). Because the infection does not penetrate the basement membrane or involve the dermis, it **heals without scarring**. Any residual changes are usually limited to temporary post-inflammatory hyperpigmentation. If an infection deepens to involve the dermis (becoming Ecthyma), it will result in scarring. **2. Analysis of Incorrect Options:** * **Option A:** This is **True**. *Staphylococcus aureus* is currently the most common cause of both bullous and non-bullous impetigo worldwide. *Streptococcus pyogenes* (Group A Beta-hemolytic Strep) is the second most common cause, often seen in non-bullous cases. * **Option B:** This is **True**. Non-bullous impetigo caused by "nephritogenic" strains of *S. pyogenes* can lead to **Post-Streptococcal Glomerulonephritis (PSGN)**. Notably, unlike pharyngitis, skin infections do **not** predispose to Rheumatic Fever. * **Option D:** This is incorrect because Option C is a false statement. **3. High-Yield Clinical Pearls for NEET-PG:** * **Non-bullous Impetigo (Impetigo Contagiosa):** Characterized by "honey-colored crusts." Most common form. * **Bullous Impetigo:** Always caused by *S. aureus*. It is mediated by **Exfoliative Toxin A**, which targets **Desmoglein-1** (similar to Pemphigus Foliaceus). * **Ecthyma:** Often described as a "deep form of impetigo" that produces "punched-out ulcers" and **does** result in scarring. * **Treatment:** Topical Mupirocin is the drug of choice for localized lesions. Systemic antibiotics (e.g., Cloxacillin or Amoxicillin-Clavulanate) are used for extensive cases.

Q: Which condition is caused by Corynebacterium minutissimum?

Erythrasma. **Explanation:** **Erythrasma** is a superficial bacterial infection caused by **Corynebacterium minutissimum**, a Gram-positive, non-spore-forming bacillus. It typically presents as well-demarcated, reddish-brown, scaly patches in intertriginous areas (axilla, groin, and toe webs). The hallmark of this condition is the production of **coproporphyrin III** by the bacteria, which results in a characteristic **coral-red fluorescence** under Wood’s lamp examination. **Analysis of Incorrect Options:** * **A. Erysipelas:** A superficial cutaneous cellulitis with prominent lymphatic involvement, primarily caused by **Group A Beta-hemolytic Streptococci** (*S. pyogenes*). It presents as a bright red, edematous, "orange-peel" (peau d'orange) plaque with sharply defined borders. * **C. Erysipeloid disease:** An occupational zoonotic infection (common in fishermen and butchers) caused by **Erysipelothrix rhusiopathiae**. It typically presents as a violaceous, painful lesion on the hands. * **D. Scrum pox:** A form of **Herpes Simplex Virus (HSV-1)** infection spread through skin-to-skin contact, commonly seen among rugby players (also known as Herpes gladiatorum). **High-Yield Clinical Pearls for NEET-PG:** * **Wood’s Lamp:** Coral-red fluorescence is the pathognomonic diagnostic feature for Erythrasma. * **Treatment of Choice:** Topical Fusidic acid or Clindamycin for localized cases; Oral **Erythromycin** or Clarithromycin for extensive involvement. * **Differential Diagnosis:** Often confused with Tinea cruris (which has a central clearing and active border) or Intertrigo (candidal). Erythrasma lacks the satellite lesions seen in Candidiasis.

Q: Symmetrical multiple lesions are seen in which type of leprosy?

Lepromatous. **Explanation:** The distribution and number of lesions in leprosy are determined by the host's **Cell-Mediated Immunity (CMI)**. 1. **Why Lepromatous (LL) is correct:** In Lepromatous Leprosy, the host has **minimal or absent CMI** against *Mycobacterium leprae*. This allows for uncontrolled hematogenous spread of the bacilli, resulting in **numerous, small, and symmetrically distributed** lesions. These lesions are typically macules, papules, or nodules (lepromas) with ill-defined borders and a shiny surface. 2. **Why other options are incorrect:** * **Tubercular (TT):** Characterized by **strong CMI**, which limits the disease. Lesions are typically **solitary or very few (1-3)** and are **asymmetrical** with well-defined margins and complete anesthesia. * **Borderline (BT/BB/BL):** These represent the unstable middle of the spectrum. While Borderline Lepromatous (BL) can show many lesions, they are usually **asymmetrical** compared to the "mirror-image" symmetry seen in polar LL. * **Neuritic:** This is a pure neural form involving peripheral nerves without any visible skin lesions. **High-Yield Clinical Pearls for NEET-PG:** * **Symmetry Rule:** The closer a patient is to the Lepromatous pole (LL), the more symmetrical and numerous the lesions become. * **Leonine Facies:** Seen in LL due to diffuse infiltration of the face and loss of eyebrows (**Madarosis**). * **Grenz Zone:** A characteristic histological feature of LL where a clear band of dermis separates the epidermis from the underlying lepromatous infiltrate. * **Bacteriological Index (BI):** Highest in LL (strongly positive), while TT is typically paucibacillary (BI = 0).

Q: What is the primary management for a patient with a Type I lepra reaction presenting with severe neuritis?

Systemic corticosteroid. **Explanation:** **1. Why Systemic Corticosteroids are the Correct Choice:** Type I Lepra Reaction (Reversal Reaction) is a **Type IV hypersensitivity reaction** characterized by an increase in cell-mediated immunity. When it involves **severe neuritis** (nerve pain, tenderness, or new sensory/motor loss), it is a medical emergency. **Systemic corticosteroids** (e.g., Prednisolone) are the gold standard because they rapidly suppress the inflammatory response, reducing endoneural edema and preventing permanent nerve damage and subsequent physical disability. **2. Why Other Options are Incorrect:** * **Thalidomide (A):** This is the drug of choice for **Type II Lepra Reaction** (Erythema Nodosum Leprosum), particularly chronic or recurrent cases. It is ineffective in Type I reactions. * **Clofazimine (B):** While it has anti-inflammatory properties and is used in managing Type II reactions (ENL), its onset of action is too slow for acute, severe neuritis in Type I reactions. * **Dapsone (C):** This is a bacteriostatic component of Multi-Drug Therapy (MDT) for *M. leprae*. It does not treat the immunological reaction and must be continued alongside steroids, not used as a primary treatment for the reaction itself. **3. High-Yield Clinical Pearls for NEET-PG:** * **Type I Reaction:** Occurs in Borderline leprosy (BT, BB, BL). Clinical signs include existing skin lesions becoming erythematous and edematous. * **Steroid Regimen:** Usually started at 40–60 mg/day of Prednisolone, tapered over 12–24 weeks. * **Silent Neuritis:** Always screen for nerve thickening and sensory loss even without pain; it also requires immediate steroid therapy. * **MDT:** Never stop Multi-Drug Therapy during a lepra reaction.

Q: Which of the following anti-leprosy drugs is used in the treatment of type 2 lepra reactions?

Clofazimine. **Explanation:** **Type 2 Lepra Reaction (Erythema Nodosum Leprosum - ENL)** is a Type III hypersensitivity reaction occurring primarily in multibacillary (BL/LL) leprosy [3]. It is characterized by painful erythematous nodules, fever, arthralgia, and neuritis [1]. **Why Clofazimine is correct:** While primarily an anti-mycobacterial agent, **Clofazimine** possesses significant **anti-inflammatory and immunosuppressive properties**. In the management of Type 2 reactions, it is used as a "steroid-sparing agent." It is particularly useful in chronic, steroid-dependent ENL cases. It works by inhibiting neutrophil chemotaxis and the hexose monophosphate shunt. Note that it is *not* effective for Type 1 reactions. **Why the other options are incorrect:** * **Dapsone:** This is a bacteriostatic drug that inhibits folate synthesis [2]. It has no anti-inflammatory role and is continued as part of MDT during a reaction but does not treat the reaction itself. * **Rifampicin:** This is a potent bactericidal drug [2]. Like Dapsone, it is continued during reactions to treat the underlying infection but does not possess the anti-inflammatory properties required to suppress ENL. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice (DOC) for Type 2 Reaction:** Systemic **Corticosteroids** (Prednisolone) are the first-line treatment. * **DOC for Severe/Recurrent Type 2 Reaction:** **Thalidomide** (most effective, but contraindicated in pregnancy due to phocomelia). * **Clofazimine Side Effect:** Characteristic **reddish-black skin discoloration** and ichthyosis. * **Type 1 Reaction (Reversal Reaction):** A Type IV hypersensitivity reaction [1]; Clofazimine is **not** used here; treatment is primarily Steroids.

Question 1

All statements regarding the diagnosis and classification of leprosy are true, except?

Accepted Answer

A 'plus 2' mean indicates the presence of 2 bacilli in 2 smears.

Answer

At least 7 skin smears should be examined.

Answer

A paucibacillary leprosy classification has a bacterial index less than 2.

Answer

A multibacillary leprosy classification has a bacterial index greater than or equal to 2.

Question 2

A 65-year-old woman has developed thick, erythematous nodules on her ears and nose with significant associated sensory loss. The nodules have grown slowly over many years. Biopsy of the lesions shows dermal granulomas with giant cells but no acid-fast bacteria. Cultures on blood agar and Lowenstein-Jensen medium show no growth. What is the most likely diagnosis?

Accepted Answer

Tuberculoid leprosy

Answer

Cutaneous leishmaniasis

Answer

Onchocerciasis

Answer

Rhinoscleroma

Question 3

What is the drug of choice for Lymphogranuloma venereum (LGV)?

Accepted Answer

Doxycycline

Answer

Ampicillin

Answer

Erythromycin

Answer

Ceftriaxone

Question 4

Which of the following statements about Donovanosis is true?

Accepted Answer

Caused by Calymmatobacterium granulomatis

Answer

Lymphadenopathy is remarkable and diagnostic

Answer

Penicillin is the drug of choice

Answer

Characterized by painful genital ulcers

Question 5

Which drug is used in the management of steroid-resistant lepra reactions?

Accepted Answer

Thalidomide

Answer

Clofazamine

Answer

Dapsone

Answer

Rifampicin

Question 6

Which of the following statements about impetigo is FALSE?

Accepted Answer

It produces scars on healing.

Answer

It is mostly caused by Staphylococcus aureus or Streptococcus pyogenes, or both.

Answer

It can predispose to post-streptococcal glomerulonephritis.

Answer

All of the above statements are true.

Question 7

Which condition is caused by Corynebacterium minutissimum?

Accepted Answer

Erythrasma

Answer

Erysipelas

Answer

Erysipeloid disease

Answer

Scrum pox

Question 8

Symmetrical multiple lesions are seen in which type of leprosy?

Accepted Answer

Lepromatous

Answer

Borderline

Answer

Neuritic

Answer

Tubercular

Question 9

What is the primary management for a patient with a Type I lepra reaction presenting with severe neuritis?

Accepted Answer

Systemic corticosteroid

Answer

Thalidomide

Answer

Clofazimine

Answer

Dapsone

Question 10

Which of the following anti-leprosy drugs is used in the treatment of type 2 lepra reactions?

Accepted Answer

Clofazimine

Answer

Dapsone

Answer

Rifampicin

Answer

None of the above

Bacterial Skin Infections — MCQs

Bacterial Skin Infections — MCQs

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