Bacterial Skin Infections Practice Questions

Q: Which drug is NOT used in Type 1 Lepra reaction?

Thalidomide. **Explanation:** The management of Lepra reactions is a high-yield topic in NEET-PG. To answer this correctly, one must distinguish between Type 1 and Type 2 reactions. **Why Thalidomide is the Correct Answer:** **Thalidomide** is the drug of choice for **Type 2 Lepra Reaction** (Erythema Nodosum Leprosum/ENL). It acts by inhibiting TNF-alpha. However, it has **no role in Type 1 reactions**, which are delayed-type hypersensitivity (Type IV) reactions involving a change in cell-mediated immunity. Using Thalidomide in Type 1 reactions is ineffective and clinically inappropriate. **Analysis of Incorrect Options:** * **Antileprotics (A):** In Type 1 reactions, Multi-Drug Therapy (MDT) should **never be stopped**. If the reaction occurs during treatment, MDT is continued; if it occurs after completion, it is not restarted unless a relapse is suspected. * **Analgesics (B):** These are used for symptomatic relief of nerve pain and joint aches associated with the inflammation in Type 1 reactions. * **Corticosteroids (C):** Systemic steroids (like Prednisolone) are the **mainstay of treatment** for Type 1 reactions. they are essential to prevent permanent nerve damage and manage acute neuritis. **High-Yield Clinical Pearls for NEET-PG:** * **Type 1 Reaction (Reversal Reaction):** Seen in Borderline cases (BT, BB, BL). Characterized by "upgrading" or "downgrading" of lesions (erythema, edema) and **neuritis**. * **Type 2 Reaction (ENL):** Seen in Multibacillary cases (BL, LL). Characterized by tender evanescent nodules, fever, and systemic involvement. * **Drug of Choice Summary:** * Type 1: **Corticosteroids**. * Type 2: **Thalidomide** (except in women of childbearing age due to teratogenicity/Phocomelia) or **Clofazimine**.

Q: What is the early reaction of the Lepromin test known as?

Fernandez reaction. The **Lepromin test** is a skin test used to measure the cell-mediated immunity (CMI) of a patient against *Mycobacterium leprae*. It is not a diagnostic test for leprosy but is used for classification and prognosis. ### Explanation of the Correct Answer The **Fernandez reaction** is the **early reaction** observed in the Lepromin test. It occurs **48 to 72 hours** after the intradermal injection of lepromin. It is a Type IV (delayed-type) hypersensitivity reaction to the soluble bacterial proteins. A positive Fernandez reaction indicates that the individual has been previously sensitized to *M. leprae* antigens. ### Why Other Options are Incorrect * **Late Mitsuda reaction (Option A):** This is the **late reaction** observed **3 to 4 weeks** after the injection. It represents a granulomatous response to the bacillary components of the lepromin. It is highly positive in Tuberculoid leprosy (TT) and negative in Lepromatous leprosy (LL). * **Early Mitsuda reaction (Option C):** This is a misnomer. The Mitsuda reaction is inherently a late-phase reaction. * **First lepromin reaction (Option D):** This is not a standard medical term used to describe the phases of the Lepromin test. ### High-Yield Clinical Pearls for NEET-PG * **Prognostic Value:** A positive Mitsuda reaction indicates strong CMI and a better prognosis (Tuberculoid end of the spectrum). * **Classification:** Lepromin test is **Negative** in Lepromatous Leprosy (LL) due to anergy and **Positive** in Tuberculoid Leprosy (TT). * **Antigen Types:** * *Lepromin H (Hayashi):* Derived from human leproma. * *Lepromin A (Armadillo):* Derived from armadillo-grown bacilli (more commonly used today). * **Memory Aid:** **F**ernandez = **F**ast (48-72 hours); **M**itsuda = **M**onth (approx. 3-4 weeks).

Q: What is the treatment of choice for erythrasma?

Clarithromycin. **Explanation:** **Erythrasma** is a superficial bacterial infection caused by ***Corynebacterium minutissimum***, a Gram-positive rod. It typically presents as well-demarcated, reddish-brown, macerated plaques in intertriginous areas (axilla, groin, and toe webs). 1. **Why Clarithromycin is correct:** While topical therapy (like Fusidic acid or Clindamycin) is effective for localized disease, **oral Clarithromycin (1g single dose)** or Erythromycin is considered the systemic treatment of choice. Macrolides effectively target the protein synthesis of *C. minutissimum*. Clarithromycin is often preferred over Erythromycin due to better patient compliance and fewer gastrointestinal side effects. 2. **Why other options are incorrect:** * **Doxycycline:** While it has activity against some Gram-positive bacteria, it is not the first-line agent for Erythrasma. It is more commonly used for acne, rosacea, or rickettsial infections. * **Gentamicin:** This is an aminoglycoside primarily used for Gram-negative aerobic infections. It is not effective against the causative agent of erythrasma. * **Moxifloxacin:** This is a broad-spectrum fluoroquinolone. While it might show efficacy, it is "overkill" and not the standard of care, reserved for more complex respiratory or skin/soft tissue infections. **High-Yield Clinical Pearls for NEET-PG:** * **Wood’s Lamp Examination:** The most characteristic diagnostic feature is **Coral-red fluorescence**, caused by the production of **Coproporphyrin III** by the bacteria. * **Differential Diagnosis:** Often confused with Tinea cruris (which has a central clearing and active border) or Intertrigo. * **KOH Mount:** Will be negative for fungal hyphae, helping rule out dermatophytosis.

Q: Lepra cells seen in leprosy are:

Vacuolated Histiocytes. ### Explanation **Correct Answer: C. Vacuolated Histiocytes** In Leprosy (Hansen’s Disease), particularly in the **lepromatous (LL) pole**, there is a deficient cell-mediated immune (CMI) response. This allows *Mycobacterium leprae* to multiply uncontrollably within macrophages. These macrophages ingest the bacilli but are unable to digest them. As the bacilli multiply and undergo fatty degeneration, the cytoplasm of the macrophage becomes filled with lipids and clusters of bacilli (globi), giving it a characteristic **foamy or vacuolated appearance**. These modified macrophages are specifically termed **Lepra cells** or **Virchow cells**. **Analysis of Incorrect Options:** * **A. Lymphocytes:** While present in the granulomas of Tuberculoid Leprosy (TT) due to a strong CMI, they do not transform into the characteristic foamy Lepra cells. * **B. Plasma cells:** These are part of the chronic inflammatory infiltrate but are not the primary host cells for *M. leprae*. * **D. Neutrophils:** These are cells of acute inflammation. While they may be seen in Type 2 Lepra Reactions (Erythema Nodosum Leprosum), they are not the defining cellular feature of the disease pathology. **High-Yield Clinical Pearls for NEET-PG:** * **Grenz Zone:** A clear subepidermal zone of uninvolved dermis seen in Lepromatous Leprosy, separating the epidermis from the dermal infiltrate (Lepra cells). * **Globi:** Large clumps of acid-fast bacilli (AFB) found inside Lepra cells, often visualized using the **Fite-Faraco stain** (a modified Ziehl-Neelsen stain). * **Ridley-Jopling Classification:** Lepra cells are the hallmark of the Lepromatous (LL) end of the spectrum, where the Bacterial Index (BI) is highest. * **Histoid Leprosy:** A variant of LL characterized by spindle-shaped histiocytes resembling a dermatofibroma.

Q: Four split skin smears from a single patient show the following results: Two samples contain 10 bacilli per 100 high power fields (hpf), and two samples contain over 1000 bacilli per average fields. What is the bacteriological index?

3.5. To solve this question, we must first determine the **Bacteriological Index (BI)** for each individual smear using Ridley’s Logarithmic Scale and then calculate the average. ### 1. Understanding the Calculation The BI is calculated based on the density of *M. leprae* in skin smears: * **1+**: 1–10 bacilli per 100 high power fields (hpf) * **2+**: 1–10 bacilli per 10 hpf * **3+**: 1–10 bacilli per average field * **4+**: 10–100 bacilli per average field * **5+**: 100–1000 bacilli per average field * **6+**: >1000 bacilli per average field **Step-by-step calculation for this patient:** * **Smears 1 & 2:** 10 bacilli/100 hpf = **1+** (each) * **Smears 3 & 4:** >1000 bacilli/avg field = **6+** (each) * **Total BI Sum:** 1 + 1 + 6 + 6 = **14** * **Average BI:** 14 ÷ 4 (total sites) = **3.5** ### 2. Why Other Options are Incorrect * **B (4.5), C (5.5), D (6.5):** These values result from incorrect application of the Ridley scale or mathematical errors in averaging. For instance, a BI of 6.5 is impossible as the maximum scale value is 6. ### 3. High-Yield Clinical Pearls for NEET-PG * **Sites for Smear:** Usually taken from 4–6 sites (e.g., both earlobes, two lesions, and the nasal mucosa). * **BI vs. MI:** While **BI** measures the total bacterial load (living and dead), the **Morphological Index (MI)** measures the percentage of solid-staining (viable) bacilli. * **WHO Classification:** * **Paucibacillary (PB):** BI < 2 at all sites. * **Multibacillary (MB):** BI ≥ 2 at any site (though clinically, any positive smear is now treated as MB). * **Treatment Duration:** MB Leprosy requires 12 months of MDT (Rifampicin, Dapsone, Clofazimine), while PB requires 6 months (Rifampicin, Dapsone).

Q: Which of the following are clinical features of Erythema nodosum leprosum?

Fever. **Erythema Nodosum Leprosum (ENL)**, also known as a **Type 2 Lepra Reaction**, is a systemic immune-complex mediated (Type III hypersensitivity) reaction occurring primarily in lepromatous (LL) and borderline lepromatous (BL) leprosy. ### **Explanation of Options** * **A. Fever (Correct):** ENL is a multi-systemic inflammatory syndrome. **Fever** is the most common and characteristic constitutional symptom, often accompanied by malaise and prostration. It signifies the acute systemic nature of the immune response against released *M. leprae* antigens. * **B. Hepatitis:** While ENL can cause multi-organ involvement (like nephritis or orchitis), clinically significant hepatitis is not a standard or defining feature of the reaction. * **C. Joint Pain:** Although arthralgia can occur in ENL, "Fever" is considered the hallmark systemic sign in standard medical examinations. In many MCQ formats, if forced to choose the most definitive systemic feature, fever takes precedence. * **D. Skin Eruptions:** While ENL presents with painful, evanescent subcutaneous nodules, the term "skin eruptions" is too non-specific. The question specifically tests the recognition of the **systemic** inflammatory markers of the reaction. ### **Clinical Pearls for NEET-PG** * **Mechanism:** Type III Hypersensitivity (Immune-complex deposition). * **Classic Presentation:** Tender, erythematous, evanescent (short-lived) nodules appearing in crops, usually on the pretibial surface and face. * **Associated Features:** Neuritis, dactylitis, iridocyclitis, orchitis, and lymphadenopathy. * **Drug of Choice:** **Thalidomide** is the most effective treatment for ENL. Prednisolone and Clofazimine are also used. * **Trigger:** Often precipitated by starting Multi-Drug Therapy (MDT), pregnancy, or stress.

Q: A 7-year-old child presents with a hypo-pigmented anesthetic patch on the face. What is the most probable diagnosis?

Intermediate leprosy. ### Explanation The diagnosis of **Indeterminate Leprosy** is based on the classic clinical triad of leprosy: a hypopigmented patch, loss of sensation, and (potentially) nerve involvement. **1. Why Indeterminate Leprosy is Correct:** In the context of pediatric dermatology and the NEET-PG exam, a **hypopigmented patch with anesthesia** (loss of sensation) is pathognomonic for leprosy. Indeterminate leprosy is the earliest clinical stage, often seen in children. It typically presents as a single, ill-defined, hypopigmented macule. While sensation may be only slightly diminished in early stages, the presence of anesthesia definitively points toward a mycobacterial infection affecting the dermal nerves. **2. Why Other Options are Incorrect:** * **Pityriasis alba:** Common in children; presents as multiple, ill-defined, scaly hypopigmented patches on the face. Crucially, **sensation is intact**, and it is often associated with atopy. * **Nevus anemicus:** A congenital vascular anomaly where the area appears pale due to localized hypersensitivity to catecholamines (vasoconstriction). Sensation is normal, and the patch **disappears on diascopy** (pressure with a glass slide) or rubbing. * **Nevus achromicus (Nevus Depigmentosus):** A stable, congenital hypopigmented birthmark. It has **normal sensation** and does not change in size or pigment over time. **Clinical Pearls for NEET-PG:** * **Earliest sign of Leprosy:** Usually a solitary hypopigmented macule (Indeterminate). * **First sensation lost:** Temperature (Cold/Hot), followed by Touch, Pain, and Deep Pressure. * **Face involvement:** In children, the face is a common site for leprosy due to increased exposure to the environment/vectors. * **Histopathology:** Indeterminate leprosy shows non-specific lymphocytic infiltration around dermal appendages and nerves; Acid-Fast Bacilli (AFB) are rarely found.

Question 1

Which drug is NOT used in Type 1 Lepra reaction?

Accepted Answer

Thalidomide

Answer

Antileprotics

Answer

Analgesics

Answer

Corticosteroids

Question 2

What is the early reaction of the Lepromin test known as?

Accepted Answer

Fernandez reaction

Answer

Late Mitsuda reaction

Answer

Early Mitsuda reaction

Answer

First lepromin reaction

Question 3

A 30-year-old pregnant female in her third trimester (36 weeks) presents with fever, swollen lymph nodes, sore throat, and a characteristic rash on her palms and soles. A serological screening test was positive. Which of the following abnormalities is most likely to be found in the newborn child?

Accepted Answer

Congenital syphilis (Hutchinson's triad: interstitial keratitis, notching of incisors, and neurosyphilis)

Answer

Congenital rubella syndrome (Deafness, cataracts, and cardiac defects)

Answer

Congenital toxoplasmosis (Chorioretinitis, hydrocephalus, and intracranial calcifications)

Answer

Congenital cytomegalovirus infection (Microcephaly, chorioretinitis, and hearing loss)

Question 4

Which of the following is NOT a characteristic feature of impetigo?

Accepted Answer

Microscopic feature is the accumulation of lymphocytes beneath the stratum corneum.

Answer

A superficial bacterial infection commonly due to Staphylococcus aureus.

Answer

Blister formation is due to bacterial production of a toxin that cleaves Desmoglein 1.

Answer

Typically involves exposed skin, mainly hands and face.

Question 5

What is the treatment of choice for erythrasma?

Accepted Answer

Clarithromycin

Answer

Doxycycline

Answer

Gentamicin

Answer

Moxifloxacin

Question 6

Lepra cells seen in leprosy are:

Accepted Answer

Vacuolated Histiocytes

Answer

Lymphocytes

Answer

Plasma cells

Answer

Neutrophils

Question 7

Four split skin smears from a single patient show the following results: Two samples contain 10 bacilli per 100 high power fields (hpf), and two samples contain over 1000 bacilli per average fields. What is the bacteriological index?

Accepted Answer

3.5

Answer

4.5

Answer

5.5

Answer

6.5

Question 8

All of the following are true regarding the treatment of Syphilis, except:

Accepted Answer

Late latent syphilis is treated with 2.4 million units of Benzathine penicillin administered once.

Answer

The only acceptable treatment for syphilis in pregnancy is penicillin.

Answer

Early latent syphilis is treated with 2.4 million units of Benzathine penicillin administered once.

Answer

Neurosyphilis is treated with Aqueous penicillin G 18-24 million units intravenously daily.

Question 9

Which of the following are clinical features of Erythema nodosum leprosum?

Accepted Answer

Fever

Answer

Hepatitis

Answer

Joint pain

Answer

Skin eruptions

Question 10

A 7-year-old child presents with a hypo-pigmented anesthetic patch on the face. What is the most probable diagnosis?

Accepted Answer

Intermediate leprosy

Answer

Pityriasis alba

Answer

Nevus anemicus

Answer

Nevus achromicus

Bacterial Skin Infections — MCQs

Bacterial Skin Infections — MCQs

On this page

Practice by Chapter

Want unlimited practice?