Bacterial Skin Infections Practice Questions

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.

Q: Globi is seen in which type of leprosy?

Lepromatous. ### Explanation **Correct Answer: B. Lepromatous** **Why it is correct:** In **Lepromatous Leprosy (LL)**, the patient exhibits a deficient cell-mediated immunity (CMI) against *Mycobacterium leprae*. This allows for the uncontrolled multiplication of bacilli within macrophages. These macrophages, heavily laden with bacilli and lipids, are termed **Virchow cells** (or foam cells). When these bacilli aggregate into dense, cigar-shaped bundles or large spherical masses held together by a waxy matrix (glis), they are called **Globi**. Globi are a hallmark of high bacterial load (multibacillary status) and are characteristically seen in LL and Borderline Lepromatous (BL) cases. **Why other options are incorrect:** * **A. Tuberculoid (TT):** In TT, the patient has strong CMI. This results in well-formed granulomas that effectively contain or eliminate the bacilli. Consequently, bacilli are rare or absent (paucibacillary), and Globi are never seen. * **D. Borderline Tuberculoid (BT):** Similar to TT, the CMI is relatively strong. While a few bacilli may be found, they do not aggregate into Globi. * **C. Borderline (BB):** While BB has more bacilli than the tuberculoid end, the classic formation of massive Globi is specifically the defining feature of the lepromatous pole (LL) where the Bacteriological Index (BI) is highest (5+ to 6+). **High-Yield Clinical Pearls for NEET-PG:** * **Fite-Faraco Stain:** The specific modification of the Ziehl-Neelsen stain used to identify *M. leprae* (which is less acid-fast than *M. tuberculosis*). * **Bacteriological Index (BI):** A logarithmic scale (0 to 6+) used to quantify density; Globi are typically seen when the BI is >4+. * **Grenz Zone:** A clear subepidermal band of uninvolved dermis seen in LL, separating the epidermis from the underlying lepromatous infiltrate. * **Lepromin Test:** Strongly positive in TT (strong CMI) and negative in LL (absent CMI).

Q: A 34-year-old HIV-positive male, a truck driver, presented with small painless nodules and a sexual history 15 days prior. Subsequently, the nodules ruptured, forming open, fleshy, oozing lesions that developed into beefy red ulcers in the genital region. What is the most likely diagnosis?

Klebsiella granulomatis. **Explanation:** The clinical presentation of **beefy red, painless, fleshy ulcers** in the genital region is the hallmark of **Granuloma Inguinale (Donovanosis)**, caused by **Klebsiella granulomatis** (formerly *Calymmatobacterium granulomatis*). [1] **Why Option A is correct:** The incubation period (typically 1–4 weeks) and the progression from painless nodules to highly vascular, "beefy red" ulcers that bleed easily on contact (friable) are classic features. [1] Unlike many other STIs, Donovanosis is characterized by the **absence of significant inguinal lymphadenopathy** (though "pseudobuboes"—subcutaneous granulation tissue—may occur). [1] **Why other options are incorrect:** * **B. Chlamydia trachomatis (L1-L3):** Causes Lymphogranuloma Venereum (LGV). It typically presents with a transient, small, painless papule followed by painful, massive inguinal lymphadenopathy (the "Groove sign"). [1] * **C. Neisseria gonorrhea:** Primarily causes urethritis (purulent discharge) rather than genital ulcers. [2] * **D. Haemophilus ducreyi:** Causes Chancroid. These ulcers are characteristically **painful**, soft, and often associated with painful inflammatory inguinal buboes. [1] **NEET-PG High-Yield Pearls:** * **Pathognomonic Finding:** Presence of **Donovan Bodies** (safety-pin appearance) within macrophages on Giemsa or Wright stain. * **Clinical Appearance:** Often described as "velvety" or "serpiginous" ulcers. * **Treatment of Choice:** Azithromycin (1g once weekly or 500mg daily) for at least 3 weeks or until lesions heal. * **Risk Group:** Frequently seen in tropical regions and among individuals with high-risk sexual behavior (e.g., long-distance truck drivers).

Question 1

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

Accepted Answer

Chancroid

Answer

Syphilis

Answer

Herpes

Answer

Donovanosis

Question 2

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 3

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 4

A skin smear is negative in which type of leprosy?

Accepted Answer

Neuritic

Answer

Indeterminate

Answer

Lepromatous

Answer

Borderline

Question 5

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

Accepted Answer

M. intracellulare

Answer

M. Leprae

Answer

M. marinum

Answer

M. tuberculosis

Question 6

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 7

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

Question 8

The skin lesions of secondary syphilis include all of the following except?

Accepted Answer

Vesicles and bullae

Answer

Macules

Answer

Nodules

Answer

Papulosquamous lesions

Question 9

Globi is seen in which type of leprosy?

Accepted Answer

Lepromatous

Answer

Tuberculoid

Answer

Borderline

Answer

Borderline tuberculoid

Question 10

A 34-year-old HIV-positive male, a truck driver, presented with small painless nodules and a sexual history 15 days prior. Subsequently, the nodules ruptured, forming open, fleshy, oozing lesions that developed into beefy red ulcers in the genital region. What is the most likely diagnosis?

Accepted Answer

Klebsiella granulomatis

Answer

Chlamydia trachomatis

Answer

Neisseria gonorrhea

Answer

Haemophilus ducreyi

Bacterial Skin Infections — MCQs

Bacterial Skin Infections — MCQs

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