Bacterial Skin Infections — MCQs
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Which condition is shown in the image below?
Identify the lesion shown in the image.
A 25-year-old male cattle-herd presented with skin lesion on the left knee of 2 years duration. The lesion initially started as itchy papule, which later enlarged to form a painful verrucous plaque with purulent discharge. Routine blood investigations and chest radiographs were within normal limits. Mantoux test measured 17 × 15 mm in size. Ten percent potassium hydroxide smear preparation was negative for fungus. Radiographs showed only soft-tissue swelling without bony involvement. Biopsy of lesion was performed as shown below. What is the diagnosis?
All are correct about the image shown except:
Which of the following toxins will produce the condition shown below?
A patient came with the complaint shown below one month after an extramarital sexual contact. He has no pain. Which one of the following statements is true?
All are correct about the condition shown in the image except: (Recent NEET Pattern 2016-17)
A child presents with skin lesions that started as vesicles and pustules, which ruptured leaving characteristic crusting. A Gram stain of the lesion is shown. The diagnosis is:
A 35-year-old obese woman presents with recurrent lesions in both axilla in summer season. Wood lamp examination is shown. The diagnosis is:
The following image is diagnostic of which STD?
Bacterial Skin Infections Indian Medical PG Practice Questions and MCQs
Question 161: Which condition is shown in the image below?
- A. Staphylococcal scalded skin syndrome (Correct Answer)
- B. Reiter syndrome
- C. Toxic epidermal necrolysis
- D. Stevens-Johnson syndrome
Explanation: ***Staphylococcal scalded skin syndrome*** - This image clearly depicts **widespread superficial blistering and peeling of the skin**, characteristic of Staphylococcal scalded skin syndrome (SSSS). - SSSS is caused by **exfoliative toxins** produced by *Staphylococcus aureus* that cleave desmoglein-1, leading to **intraepidermal cleavage** and skin sloughing, particularly prevalent in infants and young children due to immature renal clearance of toxins and lack of protective antibodies. *Stevens-Johnson syndrome* - Stevens-Johnson syndrome (SJS) is a severe **mucocutaneous reaction** typically triggered by medications, involving **less than 10% total body surface area (TBSA)** with targetoid lesions and significant mucous membrane involvement. - While it involves blistering, the **peeling in SJS is not as widespread or superficial** as depicted in the image, and mucous membrane involvement (e.g., eyes, mouth, genitals) is a prominent feature absent in the visual context provided. *Reiter syndrome* - Reiter syndrome, now known as **reactive arthritis**, is a seronegative spondyloarthropathy characterized by the triad of **arthritis, urethritis, and conjunctivitis**, often following a genitourinary or gastrointestinal infection. - It does **not involve diffuse skin blistering or exfoliation** as shown in the image; skin manifestations, if present, tend to be specific mucocutaneous lesions like circinate balanitis or keratoderma blennorrhagicum. *Toxic epidermal necrolysis* - Toxic epidermal necrolysis (TEN) is a severe, life-threatening immunological reaction, primarily drug-induced, characterized by **extensive epidermal necrosis and detachment** affecting **over 30% TBSA**. - While TEN involves widespread epidermal sloughing, it typically involves **full-thickness epidermal necrosis**, leading to a positive Nikolsky sign with large flaccid bullae and sheets of skin detachment, which is typically deeper and more severe than the superficial exfoliation seen in SSSS.
Question 162: Identify the lesion shown in the image.
- A. Furuncle (Correct Answer)
- B. Impetigo
- C. Carbuncle
- D. Erysipelas
Explanation: ***Furuncle*** - The image displays a **solitary, painful, pus-filled nodule** surrounded by an area of erythema, which is characteristic of a furuncle, originating from a **hair follicle infection**. - Furuncles typically present as a **deep, tender inflammatory nodule** that eventually points and may drain pus. *Impetigo* - Impetigo typically presents as **superficial, crusty lesions**, often with a characteristic **honey-colored crust**, which is not the primary feature shown here. - It usually involves the **epidermis** and is less deep than the lesion pictured. *Carbuncle* - A carbuncle is a **collection of coalescing furuncles**, forming a deeper and broader infection with multiple draining heads, which is not depicted in this image. - It is typically **larger** and causes more systemic symptoms than a single furuncle. *Erysipelas* - Erysipelas is a **superficial cellulitis** characterized by a well-demarcated, raised, red, warm, and painful rash, often involving the face. - It typically does not involve a central **pustule or abscess formation** as clearly seen in the image.
Question 163: A 25-year-old male cattle-herd presented with skin lesion on the left knee of 2 years duration. The lesion initially started as itchy papule, which later enlarged to form a painful verrucous plaque with purulent discharge. Routine blood investigations and chest radiographs were within normal limits. Mantoux test measured 17 × 15 mm in size. Ten percent potassium hydroxide smear preparation was negative for fungus. Radiographs showed only soft-tissue swelling without bony involvement. Biopsy of lesion was performed as shown below. What is the diagnosis?
- A. Tuberculosis verrucosa cutis (Correct Answer)
- B. Verruca vulgaris
- C. Epidermodysplasia verruciformis
- D. Madura foot
Explanation: ***Tuberculosis verrucosa cutis*** - The patient's occupation as a **cattle-herd** implies exposure to *Mycobacterium bovis* or *M. tuberculosis*. The verrucous, painful lesion with purulent discharge, in context of a **positive Mantoux test** and absence of systemic disease, points to cutaneous tuberculosis, specifically *Tuberculosis verrucosa cutis*. - The biopsy showing **granulomatous inflammation with giant cells** and likely **acid-fast bacilli** (though not explicitly stated, this is characteristic for this condition) confirms the diagnosis. *Verruca vulgaris* - This is a common **viral wart** caused by Human Papillomavirus (HPV), typically presenting as a hyperkeratotic papule or nodule, but rarely with purulent discharge or significant pain, and is not associated with a strong Mantoux reaction. - Histologically, verruca vulgaris would show **koilocytic atypia**, hyperkeratosis, and acanthosis, not granulomatous inflammation. *Epidermodysplasia verruciformis* - This is a rare, lifelong genetic disorder characterized by **widespread skin lesions** ranging from flat, reddish-brown macules to verrucous plaques, often aggravated by sun exposure and associated with specific HPV types. - It would not typically present as a single, painful, purulent lesion with a positive Mantoux test, and its histology also differs significantly from granuloma formation. *Madura foot* - **Madura foot (mycetoma)** is a chronic granulomatous infection of the skin and subcutaneous tissue, typically affecting the feet, caused by certain fungi or bacteria. It is characterized by extensive swelling, multiple sinuses, and grain discharge. - Though it can present with verrucous lesions and purulent discharge, the negative potassium hydroxide (KOH) smear for fungus in this case makes it less likely, and the strong Mantoux reaction points away from a fungal etiology.
Question 164: All are correct about the image shown except:
- A. Convoluted folds of facial skin
- B. Loss of eyebrows
- C. Keratitis
- D. Type 1 lepra reaction (Correct Answer)
Explanation: ***Type 1 lepra reaction (CORRECT - NOT present in image)*** - The image depicts **lepromatous leprosy** with features such as **leonine facies**, loss of eyebrows, and damage to the nasal cartilage, which are chronic manifestations of the disease. - A Type 1 lepra reaction, or **reversal reaction**, is an acute immunological reaction characterized by inflammation of existing skin lesions and nerves, and does not present as the chronic, diffuse facial changes shown. - This is the **EXCEPT answer** because Type 1 lepra reaction is **NOT demonstrated** in this image. *Convoluted folds of facial skin (Present in image)* - The image clearly shows **thickened**, **furrowed facial skin** with prominent **nodules** (leproma), characteristic of advanced lepromatous leprosy. - These deep folds and nodular infiltrations contribute to the appearance of **leonine facies**, a classic sign of this condition. *Loss of eyebrows (Present in image)* - The patient exhibits a visible **loss of the lateral portions of the eyebrows**, known as **madarosis**, which is a common finding in lepromatous leprosy due to infiltration of hair follicles by *Mycobacterium leprae*. - This **alopecia** affects both eyebrows, and can also extend to eyelashes and other facial hair. *Keratitis (Present in image)* - The patient's left eye appears **closed** or severely affected, and there are signs suggestive of chronic ocular involvement, consistent with **keratitis** often seen in advanced leprosy. - **Lagophthalmos** (inability to close the eyelids completely) due to facial nerve damage can lead to corneal exposure and subsequent keratitis, which is a frequent complication in leprosy.
Question 165: Which of the following toxins will produce the condition shown below?
- A. Leukocidin
- B. TSST-1
- C. ETA and ETB (Correct Answer)
- D. Serum opacity factor
Explanation: ***ETA and ETB*** - The image shows a child with widespread **blistering and epidermal exfoliation**, characteristic of **Staphylococcal Scalded Skin Syndrome (SSSS)**. - SSSS is caused by **exfoliative toxins A (ETA)** and **exfoliative toxins B (ETB)** produced by *Staphylococcus aureus*, which target **desmoglein-1** in the stratum granulosum, leading to intraepidermal cleavage and skin peeling. *Leukocidin* - **Leukocidin** is a cytotoxin produced by *Staphylococcus aureus* that targets and destroys **leukocytes**, particularly neutrophils and macrophages. - It does not directly cause the widespread epidermal blistering and exfoliation seen in the image. *TSST-1* - **Toxic Shock Syndrome Toxin-1 (TSST-1)** is a superantigen produced by *Staphylococcus aureus* that causes **Toxic Shock Syndrome**, characterized by fever, rash, hypotension, and multi-organ failure. - While it can manifest with a diffuse erythematous rash followed by desquamation, it does not typically cause the prominent blistering and extensive epidermal peeling seen in the image. *Serum opacity factor* - **Serum opacity factor** is an enzyme produced by some strains of **Group A Streptococcus** (not *Staphylococcus aureus*) that degrades serum lipoproteins. - It is associated with **rheumatic fever** and **acute glomerulonephritis** but plays no direct role in skin blistering or exfoliation.
Question 166: A patient came with the complaint shown below one month after an extramarital sexual contact. He has no pain. Which one of the following statements is true?
- A. It is caused by Haemophilus ducreyi
- B. A single dose of 2.4 million units of benzathine penicillin IM is the treatment (Correct Answer)
- C. He is likely to develop arthritis of the knee
- D. Examination of the groin will reveal a characteristic groove sign
Explanation: ***A single dose of 2.4 million units of benzathine penicillin IM is the treatment*** - The image depicts a **painless genital ulcer**, which is characteristic of a **chancre** in **primary syphilis**. The patient's history of extramarital sexual contact one month prior and the absence of pain further support this diagnosis. - The standard treatment for primary syphilis is a **single intramuscular dose of 2.4 million units of benzathine penicillin G**. *It is caused by Haemophilus ducreyi* - **Haemophilus ducreyi** causes **chancroid**, which presents as a **painful genital ulcer** with a ragged, undermined border. - The patient in the question specifically states he has **no pain**, making chancroid an unlikely diagnosis. *He is likely to develop arthritis of the knee* - Arthritis of the knee is **not a typical presentation nor a common complication** of primary syphilis. - While syphilis can cause various systemic manifestations in its later stages (secondary or tertiary), including arthralgias or synovitis in some cases, **primary syphilis is characterized by the chancre itself**, not arthritis. *Examination of the groin will reveal a characteristic groove sign* - The **groove sign** (Rollet's sign) is a characteristic clinical finding in **lymphogranuloma venereum (LGV)**, which involves inguinal lymphadenopathy that is separated by the inguinal ligament, forming a visible "groove". - This sign is **not associated with primary syphilis**, which typically causes firm, non-tender inguinal lymphadenopathy but not the groove sign.
Question 167: All are correct about the condition shown in the image except: (Recent NEET Pattern 2016-17)
- A. Epidermolysin mediated
- B. Staphylococcal scalded skin syndrome
- C. Caused by gram positive cocci in clusters
- D. Necrotising Fasciitis (Correct Answer)
Explanation: ***Necrotising Fasciitis*** - The image shows widespread superficial blistering and peeling of the skin, resembling a burn, which is characteristic of **Staphylococcal Scalded Skin Syndrome (SSSS)**, not necrotizing fasciitis. - **Necrotizing fasciitis** is a deeper, rapidly spreading infection of the subcutaneous tissue and fascia, characterized by severe pain, dusky skin, bullae, and crepitus, which is not depicted here. *Epidermolysin mediated* - **Staphylococcal Scalded Skin Syndrome (SSSS)** is indeed caused by **exotoxins (epidermolysins A and B)** produced by *Staphylococcus aureus* strains, which target desmoglein 1, leading to widespread epidermal detachment. - These epidermolysins act as **superantigens**, causing a systemic toxic effect without direct bacterial invasion of the skin at affected sites. *Staphyloccocal scalded skin syndrome* - The image is pathognomonic for **Staphylococcal Scalded Skin Syndrome (SSSS)**, characterized by generalized erythema, flaccid blisters, and epidermal exfoliation, particularly in infants and young children. - The peeling skin suggests a **positive Nikolsky sign**, where slight rubbing of the skin causes the epidermis to separate from the dermis, a hallmark of SSSS. *Caused by gram positive cocci in clusters* - **Staphylococcal Scalded Skin Syndrome (SSSS)** is caused by specific strains of **Gram-positive cocci in clusters**, namely *Staphylococcus aureus*, which produce exfoliative toxins. - These bacteria are commonly found on the skin and mucous membranes and are responsible for a variety of skin and soft tissue infections.
Question 168: A child presents with skin lesions that started as vesicles and pustules, which ruptured leaving characteristic crusting. A Gram stain of the lesion is shown. The diagnosis is:
- A. Ecthyma
- B. Erythrasma
- C. Impetigo contagiosa (Correct Answer)
- D. Bullous impetigo
Explanation: ***Impetigo contagiosa*** - The image on the left shows clustered **vesicles and pustules** that have ruptured, leaving honey-colored crusts, which are characteristic of non-bullous impetigo, also known as impetigo contagiosa. - The image on the right displays a Gram stain with numerous Gram-positive **cocci in chains** (streptococci) and possibly in clusters (staphylococci), consistent with the bacterial etiologies of impetigo. *Ecthyma* - Ecthyma is a more severe form of impetigo, characterized by **ulcerative lesions** that extend into the dermis, often with a "punched-out" appearance and a violaceous border. - While it can start as vesicles or pustules, the distinguishing feature is the presence of deep ulceration, which is not clearly depicted as the primary lesion type here. *Erythrasma* - Erythrasma is a superficial skin infection caused by *Corynebacterium minutissimum*, typically presenting as **reddish-brown patches** with fine scales in intertriginous areas. - It shows **coral-red fluorescence** under Wood's lamp, and microscopic examination would reveal Gram-positive rods, not cocci. *Bullous impetigo* - Bullous impetigo is characterized by **flaccid bullae** (large blisters) that may rupture to form erosions, caused by *Staphylococcus aureus* producing exfoliative toxins. - The image primarily shows smaller vesicles and pustules with crusting, rather than the large, prominent bullae distinct to bullous impetigo.
Question 169: A 35-year-old obese woman presents with recurrent lesions in both axilla in summer season. Wood lamp examination is shown. The diagnosis is:
- A. Ecthyma
- B. Erythrasma (Correct Answer)
- C. Impetigo contagiosa
- D. Bullous impetigo
Explanation: ***Erythrasma*** - Erythrasma is a superficial bacterial infection caused by **Corynebacterium minutissimum**, which commonly presents as red-brown patches in intertriginous areas like the axilla, especially in obese individuals and warm, humid conditions (summer season). - The distinctive **coral-red fluorescence under Wood's lamp** is due to porphyrin production by the bacteria, which is a classic diagnostic feature of erythrasma, as shown in the image. *Ecthyma* - Ecthyma is a deeper form of impetigo characterized by **ulcerative lesions with a thick, adherent crust** that extend into the dermis. - It is typically caused by *Streptococcus pyogenes* and sometimes *Staphylococcus aureus*, and would not exhibit coral-red fluorescence under Wood's lamp. *Impetigo contagiosa* - Impetigo contagiosa (non-bullous impetigo) presents with **honey-colored crusted lesions**, usually on the face and extremities. - While also a bacterial skin infection, it is typically caused by *Staphylococcus aureus* or *Streptococcus pyogenes* and does not show coral-red fluorescence under Wood's lamp. *Bullous impetigo* - Bullous impetigo is characterized by **flaccid bullae** (blisters) that rupture to form thin, varnish-like crusts, primarily caused by *Staphylococcus aureus* producing exfoliative toxins. - Similar to other forms of impetigo, it does not produce the coral-red fluorescence under Wood's lamp.
Question 170: The following image is diagnostic of which STD?
- A. Herpes simplex
- B. LGV (Correct Answer)
- C. Chancroid
- D. Donovanosis
Explanation: ***LGV*** - The image shows significant **inguinal lymphadenopathy** and **swelling** in the groin region, suggestive of buboes commonly seen in Lymphogranuloma Venereum (LGV). - LGV, caused by *Chlamydia trachomatis* serovars L1, L2, or L3, characteristically presents with unilateral or bilateral painful **inguinal lymph nodes** (buboes) that can rupture to form fistulas. *Herpes simplex* - Herpes simplex typically presents with painful **vesicles** or **ulcers** on erythematous bases, which often recur. - While it can cause inguinal lymphadenopathy, the prominent, large, fluctuant swelling visible in the image is not typical of primary herpes infection. *Chancroid* - Chancroid presents as one or more **painful, soft chancres** with irregular, undermined borders and a purulent base. - It also causes painful inguinal lymphadenopathy, but the primary lesion (soft chancre) is usually more prominent than the diffuse swelling seen here. *Donovanosis* - Donovanosis (granuloma inguinale) is characterized by **painless, beefy red, friable ulcerative lesions** that tend to bleed easily and slowly enlarge. - While it can cause pseudobuboes due to subcutaneous granulomas, the image does not show the typical ulcerative lesions associated with Donovanosis.
Practice by Chapter
Impetigo
Practice Questions
Folliculitis, Furuncles, and Carbuncles
Practice Questions
Ecthyma
Practice Questions
Erysipelas and Cellulitis
Practice Questions
Staphylococcal Scalded Skin Syndrome
Practice Questions
Necrotizing Fasciitis
Practice Questions
Cutaneous Tuberculosis
Practice Questions
Leprosy
Practice Questions
Lyme Disease
Practice Questions
Syphilis
Practice Questions
Antibiotic Resistance in Dermatology
Practice Questions
Prophylaxis and Management
Practice Questions
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