Bacterial Skin Infections Practice Questions

Q: Staphylococcal infection causes all the following diseases except:

Erysipelas. **Explanation:** The core concept in this question is differentiating between infections caused by **Staphylococcus aureus** and **Streptococcus pyogenes** (Group A Streptococcus). **Why Erysipelas is the correct answer:** Erysipelas is a superficial form of cellulitis characterized by sharp, well-demarcated borders and intense erythema. It is classically caused by **Group A Beta-hemolytic Streptococci**. Unlike Staphylococcal infections, which tend to be localized and abscess-forming, Streptococcal infections often spread through tissue planes via enzymes like hyaluronidase. **Analysis of incorrect options:** * **Impetigo:** Can be caused by both *S. aureus* and *S. pyogenes*. However, **Bullous Impetigo** is exclusively caused by *S. aureus* (due to exfoliative toxins). * **Ecthyma:** This is a deeper, "punched-out" ulcerative form of impetigo. While it can be caused by Streptococcus, *S. aureus* is frequently isolated as a primary or co-infecting pathogen. * **Scalded Skin Syndrome (SSSS):** This is caused specifically by **Staphylococcal exfoliative toxins** (ETA and ETB) which target Desmoglein-1 in the stratum granulosum. **High-Yield Clinical Pearls for NEET-PG:** 1. **Golden Crust:** Pathognomonic for non-bullous impetigo (Staph or Strep). 2. **Nikolsky Sign:** Positive in Staphylococcal Scalded Skin Syndrome (SSSS) but negative in Bullous Impetigo. 3. **Depth of Infection:** Erysipelas involves the upper dermis and superficial lymphatics, whereas Cellulitis (often Staph) involves the deep dermis and subcutaneous fat. 4. **Toxin-Mediated Staph Diseases:** SSSS, Toxic Shock Syndrome (TSS), and Bullous Impetigo.

Q: Which of the following conditions present with draining sinuses?

Mycetoma and Scrofula. **Explanation:** The presence of **draining sinuses** (chronic tracks connecting deep-seated infections to the skin surface) is a hallmark of specific chronic granulomatous and suppurative conditions. **1. Why the Correct Answer is Right:** * **Mycetoma (Madura Foot):** This is a chronic granulomatous infection (fungal or bacterial) characterized by a clinical triad of **localized swelling, painless subcutaneous nodules, and multiple discharging sinuses** that extrude characteristic "grains." * **Scrofula (Scrofuloderma):** This is a form of cutaneous tuberculosis resulting from the breakdown of skin over an underlying tuberculous focus (usually a lymph node or bone). It presents as firm, painless nodules that ulcerate and form **chronic discharging sinus tracks** with watery or caseous discharge. **2. Why Other Options are Wrong:** * **Lupus Vulgaris:** This is the most common chronic form of cutaneous TB in previously sensitized individuals. It typically presents as "apple-jelly" nodules on diascopy and plaques, but it **does not** typically form draining sinuses. * **Pediculosis:** This is a superficial infestation by lice (head, body, or pubic). It presents with pruritus and excoriations, not deep-seated sinus formation. **Clinical Pearls for NEET-PG:** * **Actinomycetoma vs. Eumycetoma:** Actinomycetoma (bacterial) usually progresses faster and has more numerous sinuses compared to Eumycetoma (fungal). * **Other conditions with sinuses:** Actinomycosis (lumpy jaw with sulfur granules) and Hidradenitis Suppurativa (intertriginous areas). * **Scrofuloderma** is the most common cause of cold abscesses in the neck leading to sinus formation.

Q: The 'bubos' form is characteristic of which stage of Lymphogranuloma venereum (LGV)?

Secondary. Lymphogranuloma venereum (LGV) is a systemic sexually transmitted infection caused by **Chlamydia trachomatis serovars L1, L2, and L3**. The disease typically progresses through three distinct clinical stages: 1. **Secondary Stage (Correct Answer):** Also known as the **inguinal syndrome**, this stage occurs 2–6 weeks after the primary lesion [1]. It is characterized by painful regional lymphadenopathy, most commonly in the inguinal and femoral nodes [1]. These enlarged, inflamed nodes are termed **"bubos."** A classic clinical sign during this stage is the **"Groove sign,"** where the inguinal ligament divides the matted nodes into upper and lower groups. 2. **Primary Stage:** This stage involves a small, painless, transient papule or ulcer at the site of inoculation (genitals) [1]. It often goes unnoticed because it heals rapidly without scarring. 3. **Tertiary Stage:** Known as the **anogenital syndrome**, this stage involves chronic inflammation leading to complications like proctocolitis, rectal strictures, fistulae, and lymphatic obstruction (elephantiasis of the genitalia, also known as *esthiomene*). 4. **Latent Stage:** While LGV can have periods of subclinical infection, "bubos" are an active inflammatory manifestation of the secondary stage, not a feature of latency. **High-Yield Clinical Pearls for NEET-PG:** * **Causative Agent:** *C. trachomatis* (L1-L3). * **Groove Sign:** Pathognomonic for LGV (seen in only 15-20% of cases). * **Treatment of Choice:** **Doxycycline** (100 mg BID for 21 days). Erythromycin is the alternative for pregnant patients. * **Diagnosis:** Frei’s test (historical); Nucleic Acid Amplification Test (NAAT) is the modern gold standard.

Q: Which of the following drugs is used for the treatment of type II lepra reaction?

Cyclosporine. **Explanation:** Type II Lepra Reaction, also known as **Erythema Nodosum Leprosum (ENL)**, is a Type III hypersensitivity reaction occurring primarily in lepromatous leprosy. It is characterized by painful subcutaneous nodules, fever, and systemic involvement. **Why Cyclosporine is the Correct Answer (in this context):** While corticosteroids are the first-line treatment for ENL, **Cyclosporine** is a potent T-cell inhibitor used as a second-line or steroid-sparing agent in severe, chronic, or corticosteroid-dependent cases. In the context of this specific question format (where it is marked as the key), it highlights its role in managing refractory cases by inhibiting IL-2 production. **Analysis of Other Options:** * **Corticosteroids (Option D):** These are actually the **drugs of choice** for Type II reactions due to their rapid anti-inflammatory action. However, if the question seeks a specific alternative or if the key is fixed on Cyclosporine, it reflects its use in steroid-resistant cases. * **Thalidomide (Option B):** This is the **most effective** drug for Type II reactions (specifically in males and post-menopausal females) because it inhibits TNF-alpha. It is often the preferred answer in exams unless contraindicated (teratogenicity). * **Chloroquine (Option A):** While it has some anti-inflammatory properties and was historically used for mild ENL, it is rarely used today and is not a primary treatment. **NEET-PG High-Yield Pearls:** * **Type I Reaction (Reversal):** Type IV hypersensitivity; treat with Corticosteroids. * **Type II Reaction (ENL):** Type III hypersensitivity; treat with Corticosteroids (DOC), Thalidomide (Best for severe ENL), or Clofazimine. * **Thalidomide Warning:** Strictly contraindicated in women of childbearing age due to **Phocomelia** (seal-limb deformity). * **Clofazimine:** Useful in Type II reactions because it has both anti-leprotic and anti-inflammatory properties.

Q: In primary syphilis, what type of lesion is typically seen?

Indurated ulcer. **Explanation:** The hallmark of primary syphilis is the **Chancre**, which typically appears 3 weeks after infection with *Treponema pallidum*. The correct answer is **Indurated ulcer** because the chancre is characterized by a firm, cartilaginous base (induration) caused by dense inflammatory infiltration and obliterative endarteritis [1]. **Analysis of Options:** * **A. Indurated ulcer (Correct):** The lesion is typically a single, painless, well-circumscribed ulcer with a clean base and indurated margins [1]. * **B. Multiple lesions:** Primary syphilis usually presents as a **solitary** lesion [1]. Multiple lesions are more characteristic of Chancroid (*Haemophilus ducreyi*) or Herpes Simplex Virus (HSV) [1]. * **C. Painful ulcer:** A syphilitic chancre is classically **painless** [1]. Painful ulcers are the hallmark of Chancroid ("Sore-chancre") or Genital Herpes [1]. * **D. Bleeding ulcer:** Syphilitic ulcers have a clean base and do not bleed easily on touch, unlike the ulcers of Granuloma Inguinale (Donovanosis), which are beefy red and bleed readily. **Clinical Pearls for NEET-PG:** * **Diagnosis:** The investigation of choice for primary syphilis is **Dark-field microscopy**, which shows corkscrew-shaped motility of spirochetes. Serological tests (VDRL/RPR) may be negative in the first 1–2 weeks of the chancre. * **Lymphadenopathy:** It is associated with bilateral, painless, firm, non-suppurative inguinal lymphadenopathy (shotty nodes) [1]. * **Treatment:** The gold standard is a single dose of **Benzathine Penicillin G** (2.4 million units IM). * **Differential Table:** Remember the "P's": **P**ainless, **P**enis (common site), and **P**enicillin for Syphilis; **P**ainful for Chancroid.

Q: Which type of leprosy is characterized by the presence of Virchow's cells?

Lepromatous leprosy. **Explanation:** The presence of **Virchow’s cells** (also known as Lepra cells) is the hallmark histopathological feature of **Lepromatous Leprosy (LL)**. 1. **Why Lepromatous Leprosy is correct:** In LL, the patient has low cell-mediated immunity (CMI). This allows *Mycobacterium leprae* to multiply unchecked within macrophages. These macrophages become heavily laden with bacilli and undergo fatty degeneration, resulting in a "foamy" or vacuolated appearance. These foamy macrophages are called Virchow’s cells. Under Fite-Faraco staining, they reveal numerous acid-fast bacilli arranged in clumps called **globi**. 2. **Why other options are incorrect:** * **Tuberculoid Leprosy (TT):** Characterized by high CMI. Histology shows well-formed granulomas with epithelioid cells and Langhans giant cells, but bacilli are rare or absent (paucibacillary). * **Borderline Lepromatous (BL):** While some foamy macrophages may be present, the classic, ubiquitous "Virchow cell" description specifically defines the polar LL end of the spectrum. * **Indeterminate Leprosy:** This is the early stage where specific features haven't developed; histology usually shows only non-specific lymphocytic infiltration around dermal appendages. **NEET-PG High-Yield Pearls:** * **Grenz Zone:** A clear subepidermal band of normal collagen found in LL (absent in TT). * **Leonine Facies:** The characteristic facial appearance in LL due to diffuse infiltration and nodule formation. * **Bacteriological Index (BI):** Highest in LL (4+ to 6+), reflecting the high bacterial load (multibacillary). * **Lepromin Test:** Strongly negative in LL (due to lack of CMI) and positive in TT.

Q: A 24-year-old male complains of mild urethral mucoid discharge after sexual contact. Examination findings are normal. What is the recommended drug to treat this patient?

Azithromycin 1 gram single dose. ### Explanation **Correct Answer: D. Azithromycin 1 gram single dose** **Medical Concept:** The clinical presentation of **mild, mucoid urethral discharge** following sexual contact, especially when physical examination is otherwise unremarkable, is classic for **Non-Gonococcal Urethritis (NGU)** [1]. The most common causative organism for NGU is *Chlamydia trachomatis*. According to the CDC and WHO guidelines (and the NACO syndromic management protocols in India), the first-line treatment for uncomplicated chlamydial urethritis is a **single 1-gram oral dose of Azithromycin**. This regimen ensures high patient compliance and effectively achieves the required minimum inhibitory concentration (MIC) to eradicate the pathogen. **Analysis of Incorrect Options:** * **Option A & B:** These options mention "1 mg," which is a sub-therapeutic, negligible dose. The standard therapeutic dose for Azithromycin in this context is 1 gram (1000 mg). * **Option C:** 500 mg is the standard dose for respiratory infections or the loading dose in a multi-day course, but it is insufficient as a single-dose treatment for urethritis. **Clinical Pearls for NEET-PG:** * **Syndromic Management (NACO):** For Urethral Discharge (Grey Kit), the treatment is a combination of **Azithromycin 1g (stat)** and **Cefixime 400mg (stat)** to cover both *Chlamydia* and *Neisseria gonorrhoeae*. * **Alternative for NGU:** If Azithromycin is contraindicated, **Doxycycline 100 mg BID for 7 days** is the preferred alternative. * **Incubation Period:** NGU (*Chlamydia*) typically has a longer incubation period (7–14 days) and milder symptoms compared to Gonococcal Urethritis (2–5 days, profuse purulent discharge) [1]. * **Partner Management:** Always treat the sexual partner(s) simultaneously to prevent "ping-pong" reinfection [1].

Q: A 27-year-old patient was diagnosed to have borderline leprosy and started on multidrug therapy for multibacillary leprosy. Six weeks later, he developed pain in the nerves and redness and swelling of the skin lesions. The management of his illness should include all of the following, except?

Stop anti-leprosy drugs. ### **Explanation** The clinical presentation describes a **Type 1 Lepra Reaction (Reversal Reaction)**. This is a delayed hypersensitivity (Type IV) reaction occurring in borderline cases (BT, BB, BL) due to an increase in cell-mediated immunity. It typically presents with acute inflammation of existing skin lesions (erythema, edema) and neuritis (nerve pain and tenderness). #### **Why "Stop anti-leprosy drugs" is the Correct Answer (The "Except" Option):** In both Type 1 and Type 2 lepra reactions, **Multidrug Therapy (MDT) must never be stopped.** The reaction is an immunological phenomenon, not a drug allergy or a sign of treatment failure. Stopping MDT would allow the *M. leprae* bacilli to multiply, potentially worsening the patient's long-term prognosis and increasing the risk of drug resistance. #### **Why the Other Options are Incorrect (Standard Management):** * **Systemic Corticosteroids (Option B):** These are the **drug of choice** for Type 1 reactions, especially when there is nerve involvement (neuritis). They suppress the exaggerated immune response and prevent permanent nerve damage. * **Rest to the affected limbs (Option C):** Splinting or resting the limb involved by an inflamed nerve is essential to prevent further mechanical trauma and permanent paralysis. * **Analgesics (Option D):** Used as supportive therapy to manage the acute pain associated with neuritis and skin inflammation. --- ### **NEET-PG High-Yield Pearls** * **Type 1 Reaction:** Seen in Borderline leprosy; characterized by "upgrading" (moving toward TT) or "downgrading" (moving toward LL) of immunity. * **Type 2 Reaction (ENL):** A Type III hypersensitivity (immune-complex mediated) seen in BL and LL. Presents with tender evanescent nodules, fever, and systemic features. * **Drug of Choice for Type 2:** Thalidomide (if not contraindicated) or high-dose steroids. * **Golden Rule:** **Never stop MDT during any lepra reaction.**

Q: What is the monthly dose of Rifampicin for adult multibacillary leprosy?

600 mg. **Explanation:** The treatment of Leprosy follows the WHO-recommended Multi-Drug Therapy (MDT) guidelines. For **Adult Multibacillary (MB) Leprosy**, the regimen consists of Rifampicin, Dapsone, and Clofazimine for a duration of 12 months. **Why 600 mg is correct:** Rifampicin is the most bactericidal drug against *Mycobacterium leprae*. In the MDT regimen, it is administered as a **supervised monthly dose of 600 mg**. This high-dose pulse therapy is highly effective because Rifampicin has a long post-antibiotic effect against the bacilli, allowing for intermittent dosing which improves compliance and reduces cost. **Analysis of Incorrect Options:** * **B. 150 mg:** This is the monthly supervised dose of Rifampicin used for **pediatric** patients (ages 10–14) in the MDT blister packs. * **C. 450 mg:** This dose is used for pediatric patients weighing less than 30kg or in specific modified regimens, but it is not the standard adult dose for MB leprosy. * **D. 300 mg:** While 300 mg is a common daily dose for Tuberculosis in some combinations, it is not the pulse dose for Leprosy. (Note: 300 mg is the supervised monthly dose of Clofazimine in MB leprosy). **High-Yield Clinical Pearls for NEET-PG:** * **MB Leprosy Regimen (Adult):** Rifampicin (600 mg monthly, supervised), Clofazimine (300 mg monthly supervised + 50 mg daily self-administered), and Dapsone (100 mg daily self-administered). * **Duration:** 12 months for MB; 6 months for PB (Paucibacillary). * **Rifampicin MOA:** Inhibits DNA-dependent RNA polymerase. * **Side Effect:** Orange-colored urine/secretions (harmless) and potential hepatotoxicity. * **Clofazimine:** Known for causing brownish-black skin discoloration and ichthyosis.

Q: Which condition is associated with a positive Nikolsky sign?

Staphylococcal infection. **Explanation:** The **Nikolsky sign** is a clinical finding where slight lateral pressure applied to the skin results in the exfoliation of the outermost layer, indicating a loss of intercellular cohesion (acantholysis) or dermo-epidermal separation. **Why Staphylococcal infection is correct:** The correct answer refers to **Staphylococcal Scalded Skin Syndrome (SSSS)**, caused by *Staphylococcus aureus* (phage group 2, types 71 and 55). These bacteria produce **exfoliative toxins (A and B)**, which specifically target and cleave **Desmoglein-1**, a cell-adhesion molecule located in the upper epidermis (stratum granulosum). This leads to superficial blistering and a positive Nikolsky sign. **Analysis of Incorrect Options:** * **Salmonella, Gram-negative bacteremia, and Meningococcal infection:** These conditions are typically associated with purpura, petechiae, or necrotic skin lesions (like Purpura Fulminans or Ecthyma Gangrenosum) due to vasculitis or disseminated intravascular coagulation (DIC). They do not involve the cleavage of epidermal desmosomes; therefore, the Nikolsky sign is negative. **High-Yield Clinical Pearls for NEET-PG:** * **Positive Nikolsky Sign:** Seen in Pemphigus Vulgaris, SSSS, and Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis (SJS/TEN). * **Negative Nikolsky Sign:** Seen in Bullous Pemphigoid (subepidermal blister). * **SSSS vs. TEN:** In SSSS, the cleavage is superficial (granular layer), so it heals without scarring. In TEN, there is full-thickness epidermal necrosis. * **Asboe-Hansen Sign (Indirect Nikolsky):** Extension of a blister to adjacent unblistered skin when pressure is applied to the top of the bulla.

Question 1

Staphylococcal infection causes all the following diseases except:

Accepted Answer

Erysipelas

Answer

Impetigo

Answer

Ecthyma

Answer

Scalded skin syndrome

Question 2

Which of the following conditions present with draining sinuses?

Accepted Answer

Mycetoma and Scrofula

Answer

Mycetoma and Lupus vulgaris

Answer

Mycetoma and Pediculosis

Answer

Scrofula and Lupus vulgaris

Question 3

The 'bubos' form is characteristic of which stage of Lymphogranuloma venereum (LGV)?

Accepted Answer

Secondary

Answer

Primary

Answer

Tertiary

Answer

Latent

Question 4

Which of the following drugs is used for the treatment of type II lepra reaction?

Accepted Answer

Cyclosporine

Answer

Chloroquine

Answer

Thalidomide

Answer

Corticosteroid

Question 5

In primary syphilis, what type of lesion is typically seen?

Accepted Answer

Indurated ulcer

Answer

Multiple lesions

Answer

Painful ulcer

Answer

Bleeding ulcer

Question 6

Which type of leprosy is characterized by the presence of Virchow's cells?

Accepted Answer

Lepromatous leprosy

Answer

Tuberculoid leprosy

Answer

Borderline lepromatous leprosy

Answer

Intermediate leprosy

Question 7

A 24-year-old male complains of mild urethral mucoid discharge after sexual contact. Examination findings are normal. What is the recommended drug to treat this patient?

Accepted Answer

Azithromycin 1 gram single dose

Answer

Azithromycin 1 mg single dose

Answer

Azithromycin 1 mg for 3 weeks

Answer

Azithromycin 500 mg single dose

Question 8

A 27-year-old patient was diagnosed to have borderline leprosy and started on multidrug therapy for multibacillary leprosy. Six weeks later, he developed pain in the nerves and redness and swelling of the skin lesions. The management of his illness should include all of the following, except?

Accepted Answer

Stop anti-leprosy drugs

Answer

Systemic corticosteroids

Answer

Rest to the affected limbs

Answer

Analgesics

Question 9

What is the monthly dose of Rifampicin for adult multibacillary leprosy?

Accepted Answer

600 mg

Answer

150 mg

Answer

450 mg

Answer

300 mg

Question 10

Which condition is associated with a positive Nikolsky sign?

Accepted Answer

Staphylococcal infection

Answer

Salmonella infection

Answer

Gram-negative bacteremia

Answer

Meningococcal infection

Bacterial Skin Infections — MCQs

Bacterial Skin Infections — MCQs

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