Bacterial Skin Infections Practice Questions

Q: Type-II lepra reaction is found in which classification of leprosy?

Lepromatous (LL). **Explanation:** Type-II Lepra Reaction, also known as **Erythema Nodosum Leprosum (ENL)**, is a Type-III hypersensitivity reaction (immune-complex mediated). It occurs exclusively in patients with a high bacillary load and low cell-mediated immunity (CMI). **Why Lepromatous (LL) is correct:** In the Ridley-Jopling classification, **Lepromatous (LL)** and **Borderline Lepromatous (BL)** leprosy are characterized by an abundance of *Mycobacterium leprae* (high Bacteriological Index). When treatment begins or during physiological stress, there is a massive release of antigens. These antigens combine with circulating antibodies to form immune complexes that deposit in tissues, leading to the systemic inflammatory features of ENL. **Why the other options are incorrect:** * **Tuberculoid (TT) and Borderline Tuberculoid (BT):** These poles have high CMI and very few bacilli (paucibacillary). Because there is an insufficient antigenic load to form significant immune complexes, Type-II reactions do not occur. Instead, these types are prone to **Type-I (Reversal) Reactions**, which are Type-IV hypersensitivity reactions. * **Borderline (BB):** While BB can occasionally transition toward the lepromatous pole, it is most classically associated with severe Type-I reactions due to its immunological instability. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Features:** Characterized by tender, evanescent, erythematous nodules, fever, lymphadenopathy, arthritis, and iridocyclitis. * **Drug of Choice:** **Thalidomide** is the gold standard for Type-II reactions. Steroids and Clofazimine are also used. * **Timing:** Unlike Type-I reactions (which often occur shortly after starting MDT), Type-II reactions can occur before, during, or even years after completing treatment. * **Key Lab Finding:** Neutrophilic leukocytosis and increased ESR/CRP.

Q: Cell-mediated immunity is maximally suppressed in which of the following conditions?

Lucio's Leprosy (LL). ### Explanation The clinical spectrum of Leprosy (Hansen’s Disease) is determined by the host's **Cell-Mediated Immunity (CMI)** against *Mycobacterium leprae*. This spectrum ranges from high resistance (Tuberculoid) to negligible resistance (Lepromatous). **Why Lucio’s Leprosy (LL) is correct:** Lucio’s Leprosy is a variant of **Lepromatous Leprosy (LL)**. In the LL pole, there is a **selective anergy** (complete absence of CMI) specifically against *M. leprae* antigens. This leads to uncontrolled bacillary multiplication, high bacterial indices, and a negative Lepromin test. While the humoral (antibody) response is exaggerated, it is ineffective at killing the intracellular bacilli, making LL the state of maximum CMI suppression. **Analysis of Incorrect Options:** * **Tuberculoid (TT):** This represents the opposite pole where CMI is **maximal**. The body effectively contains the infection, resulting in few lesions and a strongly positive Lepromin test. * **Borderline Tuberculoid (BT):** CMI is present but slightly diminished compared to TT. It is an unstable clinical state but far from the total suppression seen in LL. * **Indeterminate:** This is the early stage of the disease where the immune response has not yet polarized. CMI is not yet "suppressed"; it is simply evolving. **High-Yield Clinical Pearls for NEET-PG:** * **Th1 vs. Th2:** TT is associated with a **Th1 response** (IL-2, IFN-γ), while LL is associated with a **Th2 response** (IL-4, IL-5, IL-10). * **Lepromin Test:** It is a measure of CMI, not a diagnostic test. It is **Positive in TT** and **Negative in LL**. * **Lucio’s Phenomenon:** A rare, severe necrotizing vasculitis seen specifically in Lucio’s Leprosy, characterized by painful, jagged ulcerations. * **Foam Cells (Virchow cells):** Characteristic histological finding in LL due to macrophages laden with lepra bacilli.

Q: What is the drug of choice in Type I Lepra reaction with severe neuritis?

Systemic steroid. **Explanation:** **Type I Lepra Reaction (Reversal Reaction)** is a Delayed Type Hypersensitivity (Type IV) reaction occurring in borderline cases of leprosy. It is characterized by acute inflammation of existing skin lesions and, more critically, **acute neuritis** (nerve pain, tenderness, and loss of function). **Why Systemic Steroids are the Correct Choice:** The primary goal in managing Type I reactions, especially with **severe neuritis**, is to rapidly suppress cell-mediated inflammation to prevent permanent nerve damage and physical disability. **Systemic Corticosteroids (e.g., Prednisolone)** are the gold standard because they provide rapid anti-inflammatory and immunosuppressive action. The standard regimen usually starts at 40–60 mg/day, tapered over several months. **Analysis of Incorrect Options:** * **B. Clofazimine:** While it has anti-inflammatory properties and is used in Type II reactions (ENL) to help taper steroids, it is too slow-acting for the acute management of severe neuritis in Type I reactions. * **C. Thalidomide:** This is the **drug of choice for Type II Lepra Reaction (ENL)**. It is ineffective in Type I reactions because it does not address the Type IV hypersensitivity mechanism. * **D. Chloroquine:** This is a third-line agent occasionally used for mild Type II reactions (ENL) but has no role in managing Type I reactions or acute neuritis. **High-Yield Clinical Pearls for NEET-PG:** * **Type I Reaction:** Type IV Hypersensitivity; occurs in BT, BB, BL; key feature is **Neuritis**; DOC: **Steroids**. * **Type II Reaction (ENL):** Type III Hypersensitivity; occurs in BL, LL; key feature is **Erythema Nodosum** (tender nodules); DOC: **Thalidomide** (Steroids are also used, but Thalidomide is specific). * **Nerve Involvement:** If a patient on MDT develops new sensory/motor loss without skin changes, suspect "Silent Neuritis"—this also requires urgent systemic steroids.

Q: Which sexually transmitted infection is characterized by painful genital ulcers and lymphadenopathy?

Chancroid. **Explanation:** The clinical presentation of painful genital ulcers associated with painful inguinal lymphadenopathy (buboes) is the hallmark of **Chancroid**, caused by the Gram-negative coccobacillus *Haemophilus ducreyi*. **1. Why Chancroid is correct:** Chancroid presents as one or more deep, ragged, and exquisitely **painful** ulcers with a gray/yellow purulent base. A key diagnostic feature is the development of painful, unilateral or bilateral inflammatory inguinal lymphadenopathy, which may suppurate and form a "bubo." **2. Why other options are incorrect:** * **Syphilis (*Treponema pallidum*):** Characterized by a **painless**, indurated ulcer (hard chancre) and painless regional lymphadenopathy. * **Herpes (HSV-2):** Presents as multiple small, painful **vesicles** that rupture to form shallow ulcers. While painful, the primary lesion starts as a vesicle, unlike the necrotic ulcer of Chancroid. * **Donovanosis (*Klebsiella granulomatis*):** Characterized by **painless**, beefy-red, velvety ulcers that bleed easily on touch. There is typically no true lymphadenopathy (though "pseudobuboes" may occur). **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic:** "You *do cry* with *ducreyi*" (because it is painful). * **Microscopy:** *H. ducreyi* shows a classic **"School of fish"** or "Railroad track" appearance on Gram stain. * **Culture:** Requires enriched media like **Mueller-Hinton agar** with vancomycin. * **Treatment:** Azithromycin (1g orally) or Ceftriaxone. * **Differential:** Always rule out Syphilis and HIV in patients presenting with genital ulcers, as Chancroid increases the risk of HIV transmission.

Q: Bubos with multiple sinuses discharging into inguinal lymph nodes are seen in which condition?

Lymphogranuloma Venereum (LGV). ### Explanation **Correct Answer: C. Lymphogranuloma Venereum (LGV)** **Why it is correct:** Lymphogranuloma Venereum is caused by **Chlamydia trachomatis (serovars L1, L2, L3)**. The hallmark of the "inguinal syndrome" in LGV is painful, inflammatory lymphadenopathy (buboes). These buboes often involve both the inguinal and femoral nodes, separated by the inguinal ligament—a clinical sign known as the **Groove Sign**. As the infection progresses, the buboes undergo suppuration and form **multiple discharging sinuses** (often described as a "pepper pot" appearance) [1]. This chronic inflammation can eventually lead to lymphatic obstruction and elephantiasis of the genitalia. **Why the other options are incorrect:** * **A. Chancroid:** Caused by *Haemophilus ducreyi*. While it presents with painful buboes, they are typically **unilocular** (single) and tend to rupture into a single large ulcerated area rather than multiple chronic sinuses [1]. * **B. Granuloma Inguinale (Donovanosis):** Caused by *Klebsiella granulomatis*. This condition is characterized by **painless, beefy-red ulcers** that bleed on touch. It does not involve true lymphadenopathy; instead, it causes "pseudobuboes" (granulomatous nodules in the subcutaneous tissue) [1]. * **C. Syphilis:** Primary syphilis presents with a painless chancre and **painless, firm, non-suppurative** regional lymphadenopathy. They do not form discharging sinuses. **High-Yield Clinical Pearls for NEET-PG:** * **Groove Sign:** Pathognomonic for LGV (though present in only 15-20% of cases). * **Donovan Bodies:** Safety-pin appearance in tissue smears, diagnostic for Granuloma Inguinale. * **School of Fish Appearance:** Characteristic Gram stain finding for Chancroid. * **Esthiomene:** Chronic hypertrophic ulceration and edema of the vulva seen in late-stage LGV. * **Treatment of choice for LGV:** Doxycycline (100 mg BID for 21 days).

Q: A skin smear is negative in which type of leprosy?

Neuritic. **Explanation:** The **Slit Skin Smear (SSS)** is a diagnostic tool used to detect Acid-Fast Bacilli (*Mycobacterium leprae*). The presence or absence of bacilli depends on the host’s cell-mediated immunity (CMI). **Why Neuritic Leprosy is the correct answer:** In **Pure Neuritic Leprosy**, the pathology is strictly confined to the peripheral nerves. Since there are no visible skin lesions (patches or nodules), a skin smear will naturally be negative for bacilli. Diagnosis in these cases usually requires a nerve biopsy or clinical evidence of nerve thickening and sensory loss. **Analysis of Incorrect Options:** * **Indeterminate Leprosy:** This is the earliest stage. While bacilli are very sparse and often difficult to find, the smear is not *categorically* negative by definition; however, it is usually paucibacillary. * **Lepromatous Leprosy (LL):** This represents the polar end with low CMI. It is **multibacillary**, meaning the skin smear is strongly positive with a high Bacteriological Index (BI) and presence of globi. * **Borderline Leprosy:** This spectrum (BT, BB, BL) shows varying degrees of positivity. While Borderline Tuberculoid (BT) is often smear-negative, the "Borderline" category as a whole includes types (like BL) that are smear-positive. **High-Yield Clinical Pearls for NEET-PG:** * **Bacteriological Index (BI):** Measures the density of bacilli (0 to 6+). * **Morphological Index (MI):** Measures the percentage of solid-staining (viable) bacilli; useful for monitoring treatment response. * **Sites for SSS:** Usually taken from 4–6 sites, including both earlobes and active lesions. * **Ridley-Jopling Classification:** Pure Neuritic leprosy is not formally part of this 5-group scale but is a recognized clinical entity in the Indian classification.

Q: Cutaneous lesions may be produced by the following mycobacteria, except?

M. intracellulare. **Explanation:** The correct answer is **M. intracellulare**. While many mycobacteria are known to cause skin manifestations, *Mycobacterium intracellulare* (part of the *Mycobacterium avium* complex or MAC) primarily causes pulmonary disease, especially in immunocompromised patients or those with underlying lung pathology. It is rarely associated with primary cutaneous lesions. **Analysis of Options:** * **M. Leprae (Option B):** This is the causative agent of **Leprosy (Hansen’s Disease)**. It is a classic dermatological pathogen that presents with a spectrum of skin lesions ranging from hypopigmented patches (Tuberculoid) to diffuse nodules and infiltration (Lepromatous). * **M. marinum (Option C):** Known as the cause of **"Swimming Pool Granuloma"** or "Fish Tank Granuloma." It typically enters through abrasions and presents as a localized nodule or a series of nodules following a sporotrichoid distribution (along lymphatics). * **M. tuberculosis (Option D):** Cutaneous tuberculosis is well-documented. It presents in various forms depending on the host's immunity and mode of infection, such as **Lupus Vulgaris** (most common chronic form), **Scrofuloderma** (extension from underlying nodes), and **Warty Tuberculosis (Tuberculosis Verrucosa Cutis)**. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cutaneous TB in India:** Lupus Vulgaris. * **Apple-jelly nodules:** Pathognomonic sign seen on diascopy in Lupus Vulgaris. * **Buruli Ulcer:** Caused by *M. ulcerans*. * **Sporotrichoid spread:** Besides *M. marinum*, it is also seen in Sporotrichosis, Nocardiosis, and Leishmaniasis. * **MAC (M. avium-intracellulare):** Most common systemic opportunistic bacterial infection in AIDS patients (CD4 <50), usually presenting with fever and weight loss rather than skin lesions.

Q: Which of the following structures is affected during the development of a furuncle?

Sebaceous gland. **Explanation:** A **furuncle** (commonly known as a boil) is a deep-seated, painful, inflammatory nodule that develops from a preceding folliculitis. It is almost always caused by *Staphylococcus aureus*. **Why the Sebaceous Gland is correct:** The pathophysiology of a furuncle involves the **pilosebaceous unit**. It starts as an infection of the hair follicle that extends deep into the dermis and involves the associated **sebaceous gland**. The infection leads to follicular abscess formation and perifollicular necrosis. Since the sebaceous gland is an integral anatomical component of the pilosebaceous unit, it is the primary structure affected during the development of the lesion. **Analysis of Incorrect Options:** * **A. Sweat gland:** Infections of the eccrine sweat glands are rare. Infection of the apocrine sweat glands (found in axillae/groin) is characteristic of *Hidradenitis suppurativa*, not a simple furuncle. * **C. Holocrine gland:** While a sebaceous gland *is* a type of holocrine gland (based on its method of secretion), in clinical dermatology and NEET-PG exams, the anatomical term **"Sebaceous gland"** is the specific and preferred answer for the site of a furuncle. **High-Yield Clinical Pearls for NEET-PG:** * **Carbuncle:** A cluster of interconnected furuncles that drain through multiple follicular openings. It most commonly occurs on the nape of the neck or back. * **Predisposing Factors:** Diabetes mellitus, obesity, and immunocompromised states. * **Danger Triangle of the Face:** Furuncles in this area (nose/upper lip) can lead to **Cavernous Sinus Thrombosis** via the facial and ophthalmic veins. * **Treatment:** Incision and drainage (I&D) is the mainstay for fluctuant lesions; systemic antibiotics (e.g., Cloxacillin) are used for associated cellulitis or systemic symptoms.

Q: A female presents with a 3 cm painless ulcer with raised edges on the labia majora. What is the most common cause?

Syphilis. **Explanation:** The clinical presentation of a **painless, indurated ulcer with raised edges** (often described as a "button-like" consistency) is the classic hallmark of a **Chancre**, which is the primary lesion of **Syphilis**, caused by *Treponema pallidum*. **Why Syphilis is correct:** Primary syphilis typically manifests as a single, firm, painless ulcer at the site of inoculation. The "raised edges" and lack of tenderness are key diagnostic features [1]. In females, these are often found on the labia majora, labia minora, or cervix. **Why the other options are incorrect:** * **Gonorrhea:** Typically presents as a purulent vaginal or urethral discharge (cervicitis/urethritis) rather than a discrete ulcer [2]. * **Herpes (HSV-2):** Characterized by **painful**, multiple, shallow, vesicular or ulcerative lesions on an erythematous base [1]. They are rarely painless or indurated. * **Chlamydia trachomatis:** While Serotypes L1-L3 cause *Lymphogranuloma Venereum (LGV)*, the initial ulcer is usually small, transient, and often goes unnoticed. The dominant feature of LGV is painful inguinal lymphadenopathy (Buboes) [3]. **NEET-PG High-Yield Pearls:** * **Painful vs. Painless Ulcers:** Remember the mnemonic **"H is for Hurt"** (Herpes and Hemophilus ducreyi/Chancroid are painful). Syphilis and LGV are generally painless. * **Donovanosis (Granuloma Inguinale):** Caused by *Klebsiella granulomatis*; presents as a painless, beefy-red, velvety ulcer that bleeds on touch (Donovan bodies on biopsy) [3]. * **Investigation of Choice:** Dark-field microscopy is the gold standard for primary syphilis; VDRL/RPR are screening tests (may be negative in early primary stage). * **Treatment:** Benzathine Penicillin G (2.4 million units IM) remains the drug of choice.

Question 1

Type-II lepra reaction is found in which classification of leprosy?

Accepted Answer

Lepromatous (LL)

Answer

Borderline (BB)

Answer

Borderline tuberculoid (BT)

Answer

Tuberculoid (TT)

Question 2

Cell-mediated immunity is maximally suppressed in which of the following conditions?

Accepted Answer

Lucio's Leprosy (LL)

Answer

Borderline Tuberculoid (BT)

Answer

Tuberculoid (TT)

Answer

Indeterminate

Question 3

What is the drug of choice in Type I Lepra reaction with severe neuritis?

Accepted Answer

Systemic steroid

Answer

Clofazimine

Answer

Thalidomide

Answer

Chloroquine

Question 4

Which sexually transmitted infection is characterized by painful genital ulcers and lymphadenopathy?

Accepted Answer

Chancroid

Answer

Syphilis

Answer

Herpes

Answer

Donovanosis

Question 5

Bubos with multiple sinuses discharging into inguinal lymph nodes are seen in which condition?

Accepted Answer

Lymphogranuloma Venereum (LGV)

Answer

Chancroid

Answer

Granuloma Inguinale

Answer

Syphilis

Question 6

A 25-year-old male student presents with a rash. He denies headache, fever, or myalgia. A slightly pruritic maculopapular rash is noted over the abdomen, trunk, palms of the hands, and soles of the feet. Inguinal, occipital, and cervical lymphadenopathy is also noted. Hypertrophic, flat, wart-like lesions are noted around the anal area. Laboratory studies show: Hct: 40%, Hgb: 14 g/dL, WBC: 13,000/mL with a differential of 50% segmented neutrophils and 50% lymphocytes. Which of the following is the most useful laboratory test in this patient?

Accepted Answer

Rapid Plasma Reagin (RPR) test

Answer

Human papillomavirus (HPV) serology

Answer

Nucleic acid amplification test for Chlamydia

Answer

Blood cultures

Question 7

A skin smear is negative in which type of leprosy?

Accepted Answer

Neuritic

Answer

Indeterminate

Answer

Lepromatous

Answer

Borderline

Question 8

Cutaneous lesions may be produced by the following mycobacteria, except?

Accepted Answer

M. intracellulare

Answer

M. Leprae

Answer

M. marinum

Answer

M. tuberculosis

Question 9

Which of the following structures is affected during the development of a furuncle?

Accepted Answer

Sebaceous gland

Answer

Sweat gland

Answer

Holocrine gland

Answer

None of the above

Question 10

A female presents with a 3 cm painless ulcer with raised edges on the labia majora. What is the most common cause?

Accepted Answer

Syphilis

Answer

Gonorrhea

Answer

Herpes

Answer

Chlamydia trachomatis

Bacterial Skin Infections — MCQs

Bacterial Skin Infections — MCQs

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