Bacterial Skin Infections Practice Questions

Q: A 3-year-old child presents with multiple isolated lesions on the face and neck. Physical examination reveals lesions up to 4 cm in diameter with golden crusts, and in other areas, small blisters and weeping are observed. What is the most likely diagnosis?

Impetigo. **Explanation:** The clinical presentation of a young child with **golden-yellow (honey-colored) crusts** on the face and neck is the classic hallmark of **Impetigo**, specifically the non-bullous variety. This is a highly contagious superficial bacterial infection of the epidermis, most commonly caused by *Staphylococcus aureus* or *Streptococcus pyogenes*. The "weeping" and small blisters (vesicles) represent the early stage before the exudate dries into the characteristic crust. **Why other options are incorrect:** * **Aphthous ulcers:** These are painful, shallow ulcers found on the **oral mucosa** (inside the mouth), not on the external skin of the face with crusting. * **Erysipelas:** This is a deeper infection (upper dermis) characterized by a **sharply demarcated**, bright red, edematous, and painful plaque, often accompanied by fever. It does not typically present with isolated honey-colored crusts. * **Herpes simplex I:** While it can cause vesicles on the face, they are usually **grouped (herpetiform)** on an erythematous base and are often associated with tingling or burning pain. While they can crust, the classic "golden crust" of impetigo is distinct. **High-Yield Clinical Pearls for NEET-PG:** * **Etiology:** *S. aureus* is now the most common cause of both bullous and non-bullous impetigo. * **Bullous Impetigo:** Caused by Staphylococcal **exfoliative toxins (ETA, ETB)** targeting Desmoglein 1. * **Complication:** Non-bullous impetigo (Streptococcal) can lead to **Post-Streptococcal Glomerulonephritis (PSGN)**, but notably, it does *not* lead to Rheumatic Fever. * **Treatment:** Topical **Mupirocin** is the drug of choice for localized lesions. For systemic involvement, use oral Cloxacillin or Amoxicillin-Clavulanate.

Q: Gonococcal vaginitis occurs in:

Children. **Explanation:** The correct answer is **Children**. The anatomical and physiological characteristics of the female genital tract change significantly from birth through puberty, which dictates the site of gonococcal infection. **1. Why Children?** In prepubertal girls (children), the vaginal mucosa is thin, atrophic, and lined with **columnar or cuboidal epithelium**. Additionally, the vaginal pH is neutral or alkaline due to the absence of estrogen and *Lactobacillus*. This environment is highly susceptible to *Neisseria gonorrhoeae*, leading to **primary gonococcal vulvovaginitis**. In this age group, the infection is often a result of non-sexual transmission (fomites) or, importantly, must raise suspicion of child sexual abuse. **2. Why other options are incorrect:** * **Adults and Adolescents:** In post-pubertal females, increased estrogen levels cause the vaginal lining to thicken into **stratified squamous epithelium**, which is resistant to gonococcal invasion. In these groups, gonorrhea primarily causes **cervicitis** (infection of the endocervix) rather than vaginitis. * **Infants:** Newborns possess maternal estrogen for the first few weeks of life, which temporarily cornifies the vaginal epithelium, providing protection against primary vaginitis. **Clinical Pearls for NEET-PG:** * **Site of Infection:** In adult females, the **endocervix** is the most common site of gonococcal infection. * **Gold Standard Diagnosis:** Culture on **Thayer-Martin medium** (chocolate agar with antibiotics). * **Treatment:** Due to rising resistance, the current recommendation is typically a single dose of IM Ceftriaxone [1]. * **Key Concept:** If a child presents with gonococcal vulvovaginitis, clinicians must prioritize ruling out **sexual abuse**.

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

The scrotum and hands are the most common sites affected.. **Erysipelas** is a distinct clinical variant of cellulitis characterized by its superficial nature and sharp demarcation. ### **Explanation of Options** * **Why D is the correct answer (The False Statement):** The most common site for erysipelas is the **lower limbs** (approx. 80%), followed by the **face** (butterfly distribution). The scrotum and hands are rarely involved. In contrast, Fournier’s gangrene is the necrotizing infection typically associated with the scrotum. * **Option A:** This is true. Erysipelas is an acute inflammatory condition specifically involving the **upper/outer dermis**. This superficial location results in the characteristic "raised" edge and "orange-peel" (peau d'orange) texture. * **Option B:** This is true. The infection characteristically involves the **superficial lymphatics**, leading to prominent lymphatic obstruction and regional lymphadenopathy. * **Option C:** This is true. The primary causative agent is **Group A Beta-hemolytic Streptococci (Streptococcus pyogenes)**. The rapid spread and systemic symptoms (fever, chills) are mediated by bacterial **exotoxins**. ### **High-Yield Clinical Pearls for NEET-PG** * **Milian’s Ear Sign:** A classic clinical sign where erysipelas involves the pinna (ear). Since the pinna lacks deep dermis/subcutaneous tissue, true cellulitis cannot occur there, making erysipelas the definitive diagnosis. * **Clinical Appearance:** Characterized by a "shiny, red, edematous, and tender plaque" with **sharply defined borders** (unlike cellulitis, which has diffuse borders). * **Drug of Choice:** Oral or IV **Penicillin** remains the treatment of choice due to the high sensitivity of *S. pyogenes*. * **Predisposing Factors:** Lymphedema, tinea pedis (serving as a portal of entry), and venous insufficiency.

Q: Which of the following is a characteristic feature of Borderline leprosy?

Inverted saucer appearance. **Explanation:** The **Inverted Saucer Appearance** is a pathognomonic clinical feature of **Borderline Tuberculoid (BT)** or **Borderline Borderline (BB)** leprosy. This refers to a characteristic plaque where the center is elevated and erythematous, while the edges slope outwards, resembling an upside-down saucer. This occurs due to the immunological instability of the borderline spectrum, where the body attempts to contain the infection, leading to localized inflammation and edema within the lesion. **Analysis of Incorrect Options:** * **B. Erythema Nodosum Leprosum (ENL):** This is a Type 2 Lepra Reaction, which is classically seen in **Lepromatous Leprosy (LL)** or occasionally in Borderline Lepromatous (BL) cases, but not typically in the pure borderline spectrum. * **C. Hypopigmented plaques all over the body:** While hypopigmented patches occur in leprosy, "all over the body" (generalized, symmetrical distribution) is a hallmark of **Lepromatous Leprosy (LL)**. Borderline lesions are usually asymmetrical and fewer in number. * **D. Glove and stocking sensory symptoms:** This pattern of distal, symmetrical sensory loss is characteristic of **Lepromatous Leprosy (LL)** due to diffuse nerve involvement. In Borderline leprosy, nerve involvement is typically asymmetrical and localized to specific nerve trunks. **High-Yield Clinical Pearls for NEET-PG:** * **Punch-out lesions:** Another term for the appearance of BB leprosy where the central area looks "punched out" but is actually a zone of clearing. * **Immune Status:** Borderline leprosy is the most **immunologically unstable** form; it can "upgrade" toward the Tuberculoid pole or "downgrade" toward the Lepromatous pole. * **Satellite Lesions:** Small clinical lesions found near a larger plaque, highly suggestive of **Borderline Tuberculoid (BT)** leprosy.

Q: Which of the following drugs is not used in the management of lepra reactions?

Rifampicin. ### Explanation The management of leprosy involves two distinct components: killing the bacilli (*Mycobacterium leprae*) and managing immunological complications known as **Lepra Reactions**. **Why Rifampicin is the correct answer:** Rifampicin is a potent bactericidal drug used in the Multi-Drug Therapy (MDT) for leprosy to kill the organism. However, it has **no anti-inflammatory or immunomodulatory properties**. In fact, during a lepra reaction, MDT (including Rifampicin) is usually continued to ensure the infection remains under control, but Rifampicin itself does not treat the reaction. **Analysis of Incorrect Options:** * **Clofazimine:** This drug is unique because it possesses both **leprostatic** and **anti-inflammatory** properties. It is specifically used in the management of Type 2 Lepra Reaction (ENL), especially in chronic or steroid-dependent cases. * **Thalidomide:** This is the **drug of choice for Type 2 Lepra Reaction (ENL)**. It acts by inhibiting TNF-alpha. Note: It is strictly contraindicated in pregnancy due to its high teratogenic potential (phocomelia). * **Chloroquine:** While primarily an antimalarial, Chloroquine has mild anti-inflammatory properties and is used as an adjuvant in treating mild cases of Type 2 Lepra Reaction. **Clinical Pearls for NEET-PG:** * **Type 1 Reaction (Reversal Reaction):** Delayed hypersensitivity (Type IV). Treatment: Corticosteroids (Drug of Choice). * **Type 2 Reaction (Erythema Nodosum Leprosum - ENL):** Immune complex-mediated (Type III). Treatment: Thalidomide (DOC), Corticosteroids, Clofazimine, or Chloroquine. * **Rule of Thumb:** Never stop MDT during a lepra reaction; add anti-inflammatory drugs to the existing regimen.

Q: A young male presented with a hypoesthetic patch on the right forearm. On examination, a thickened peripheral nerve was palpable. Skin biopsy histopathology shows well-formed epithelioid granulomas with Langhans giant cells, dense lymphocytic infiltrate, and perineural infiltration. What is the most likely diagnosis?

Tuberculoid Leprosy. ***Tuberculoid Leprosy*** - The combination of a **hypoesthetic patch** with a **palpable thickened nerve** is pathognomonic for tuberculoid leprosy, representing the **TT pole** of Hansen's disease. - Histopathology shows **well-formed epithelioid granulomas** with **Langhans giant cells** and **perineural infiltration**, characteristic of the strong cell-mediated immune response in tuberculoid leprosy. *Lepromatous Leprosy* - Clinical presentation includes **multiple symmetrical lesions** without significant nerve thickening or hypoesthesia in early stages. - Histopathology shows **foamy macrophages** (Virchow cells) filled with **acid-fast bacilli** and **no true granuloma formation** due to poor cell-mediated immunity. *Lymphoma* - Would present with **lymphadenopathy** and **B-symptoms** (fever, night sweats, weight loss) rather than isolated hypoesthetic patches. - Histopathology would show **malignant lymphoid cells** with **monoclonal proliferation**, not granulomatous inflammation with nerve involvement. *Histiocytosis* - Typically presents with **multiple organ involvement** including bone lesions, skin rash, and hepatosplenomegaly in children. - Histopathology shows **Langerhans cells** with **Birbeck granules** and positive **CD1a/CD68** staining, distinct from epithelioid granulomas.

Q: Erythematous lesions seen in the axilla with coral red fluorescence under a Wood's lamp indicate which of the following conditions?

Erythrasma. **Explanation:** The clinical presentation of erythematous, well-demarcated patches in intertriginous areas (like the axilla) showing **coral red fluorescence** under a Wood’s lamp is pathognomonic for **Erythrasma**. **1. Why Erythrasma is correct:** Erythrasma is a superficial bacterial infection caused by ***Corynebacterium minutissimum***. This organism produces **porphyrins** (specifically Coproporphyrin III) as a metabolic byproduct. When exposed to ultraviolet light (Wood’s lamp), these porphyrins emit a characteristic coral red glow. **2. Why other options are incorrect:** * **Tinea (Dermatophytosis):** While it presents with erythematous patches, it typically shows central clearing (annular) and active borders. Under Wood's lamp, most Tinea corporis/cruris do not fluoresce; only specific species like *Microsporum* (Tinea capitis) show bright green fluorescence. * **Lichen Planus:** This is an inflammatory condition characterized by the "6 Ps" (Planar, Purple, Polygonal, Pruritic, Papules, and Plaques). It does not show specific fluorescence. * **Vitiligo:** This is a depigmenting disorder. Under Wood’s lamp, it shows **milky-white** fluorescence due to the complete loss of melanin, which enhances the reflection of light. **High-Yield Clinical Pearls for NEET-PG:** * **Treatment of Choice:** Topical or oral **Erythromycin** (or Clindamycin). * **Common Sites:** Axilla, groin (most common), and toe webs (4th-5th space). * **Differential Diagnosis:** Often confused with Tinea cruris or Intertrigo; Wood's lamp is the gold standard for rapid bedside differentiation. * **Microscopy:** KOH mount will be negative for fungi, but Gram stain shows Gram-positive filamentous bacilli.

Q: Exacerbation of lesions in patients of borderline leprosy is seen in which type of reaction?

Type I lepra reaction. **Explanation:** **Type I Lepra Reaction (Delayed Hypersensitivity)** is the correct answer because it is specifically associated with **Borderline forms of leprosy** (BT, BB, and BL). It occurs due to a sudden change in the patient's cell-mediated immunity (CMI). Clinically, it manifests as the **exacerbation of existing lesions**, which become erythematous, edematous, and painful. New lesions may appear, and there is often associated acute neuritis (nerve tenderness and loss of function). **Analysis of Incorrect Options:** * **A. Erythema Nodosum Leprosum (ENL):** Also known as Type II lepra reaction, this is a humoral (Type III) hypersensitivity reaction seen primarily in **lepromatous (LL)** and occasionally **borderline lepromatous (BL)** leprosy. It presents with crops of tender, evanescent subcutaneous nodules, fever, and systemic symptoms, rather than the exacerbation of existing skin patches. * **C. Jarisch-Herxheimer Reaction:** This is a systemic inflammatory response seen following the initiation of antibiotic treatment for spirochetal infections (e.g., Syphilis, Leptospirosis), caused by the release of endotoxin-like products from dying organisms. It is not a feature of leprosy. * **D. Resolving Leprosy:** This refers to the healing phase where lesions become flatter, less erythematous, and lose their activity, which is the clinical opposite of an exacerbation. **High-Yield Clinical Pearls for NEET-PG:** * **Type I Reaction:** Can be "Upgrading" (Reversal reaction – shift toward Tuberculoid pole) or "Downgrading" (shift toward Lepromatous pole). * **Treatment of Choice:** Systemic Corticosteroids (Prednisolone) are the mainstay for both Type I and Type II reactions to prevent permanent nerve damage. * **Thalidomide:** Highly effective for Type II (ENL) but contraindicated in Type I and pregnancy.

Q: Satellite lesions are seen in which type of leprosy?

Borderline Tuberculoid Leprosy. **Explanation:** The presence of **satellite lesions** is a hallmark clinical feature of **Borderline Tuberculoid (BT) Leprosy**. In the Ridley-Jopling classification, BT leprosy represents a stage where the host's cell-mediated immunity (CMI) is significant but not as robust as in polar Tuberculoid leprosy. 1. **Why Borderline Tuberculoid (BT) is correct:** Satellite lesions are smaller, clinically similar lesions (macules or plaques) found in the immediate vicinity of a larger primary lesion. They indicate a degree of immunological instability and the beginning of hematogenous spread that the body is attempting to contain. 2. **Why other options are incorrect:** * **Tuberculoid Leprosy (TT):** Characterized by a single or very few (1–3) well-defined, anesthetic, hairless plaques. The CMI is very high, keeping the infection strictly localized; thus, satellite lesions are absent. * **Lepromatous Leprosy (LL):** Characterized by widespread, symmetrical, bilateral nodules or macules due to negligible CMI. The lesions are too numerous and generalized for "satellite" terminology to apply. * **Histoid Leprosy:** A variant of LL (often due to dapsone resistance) characterized by firm, shiny, hemispherical cutaneous nodules on normal-looking skin. It does not feature satellite lesions. **High-Yield Clinical Pearls for NEET-PG:** * **BT Leprosy** is the most common clinical type of leprosy seen in India. * **Nerve Involvement:** In BT, nerve involvement is asymmetrical and more extensive than in TT. * **Inverted Saucer Appearance:** Characteristic of **Borderline Borderline (BB)** leprosy. * **Swiss Cheese Appearance:** Histopathological feature of **Borderline Lepromatous (BL)** leprosy. * **Face:** If a lesion is on the face with satellite lesions, it is a strong indicator of BT leprosy.

Question 1

A 3-year-old child presents with multiple isolated lesions on the face and neck. Physical examination reveals lesions up to 4 cm in diameter with golden crusts, and in other areas, small blisters and weeping are observed. What is the most likely diagnosis?

Accepted Answer

Impetigo

Answer

Aphthous ulcers

Answer

Erysipelas

Answer

Herpes simplex I

Question 2

Gonococcal vaginitis occurs in:

Accepted Answer

Children

Answer

Adults

Answer

Infants

Answer

Adolescents

Question 3

Which of the following is NOT true regarding erysipelas?

Accepted Answer

The scrotum and hands are the most common sites affected.

Answer

It is an acute spreading inflammation of the outer dermis.

Answer

Superficial lymphatics are typically involved.

Answer

The rash is primarily due to exotoxin produced by Streptococcus pyogenes.

Question 4

Which of the following is a characteristic feature of Borderline leprosy?

Accepted Answer

Inverted saucer appearance

Answer

Erythema Nodosum Leprosum

Answer

Presence of hypopigmented plaques all over the body

Answer

Glove and stocking sensory symptoms

Question 5

Which of the following drugs is not used in the management of lepra reactions?

Accepted Answer

Rifampicin

Answer

Chloroquine

Answer

Clofazimine

Answer

Thalidomide

Question 6

A young male presented with a hypoesthetic patch on the right forearm. On examination, a thickened peripheral nerve was palpable. Skin biopsy histopathology shows well-formed epithelioid granulomas with Langhans giant cells, dense lymphocytic infiltrate, and perineural infiltration. What is the most likely diagnosis?

Accepted Answer

Tuberculoid Leprosy

Answer

Lepromatous Leprosy

Answer

Lymphoma

Answer

Histiocytosis

Question 7

A young female presented to the hospital OPD with suspected chlamydial infection. She was prescribed oral doxycycline for 2 weeks. After 3 weeks, she came to the hospital again with a mucopurulent cervicitis. On questioning, she admitted that she took the drug only for 3 days. What should be done next?

Accepted Answer

Treat her with a single oral dose of Azithromycin

Answer

Rewrite the original prescription for oral doxycycline

Answer

Treat her with an intravenous dose of amoxicillin

Answer

Write a prescription for oral erythromycin for 10 days

Question 8

Erythematous lesions seen in the axilla with coral red fluorescence under a Wood's lamp indicate which of the following conditions?

Accepted Answer

Erythrasma

Answer

Tinea

Answer

Lichen planus

Answer

Vitiligo

Question 9

Exacerbation of lesions in patients of borderline leprosy is seen in which type of reaction?

Accepted Answer

Type I lepra reaction

Answer

Erythema nodosum leprosum (ENL)

Answer

Jarisch-Herxheimer reaction

Answer

Resolving leprosy

Question 10

Satellite lesions are seen in which type of leprosy?

Accepted Answer

Borderline Tuberculoid Leprosy

Answer

Tuberculoid Leprosy

Answer

Lepromatous Leprosy

Answer

Histoid Leprosy

Bacterial Skin Infections — MCQs

Bacterial Skin Infections — MCQs

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