Bacterial Skin Infections Practice Questions

Q: Identify the lesion shown in the image.

Furuncle. ***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.

Q: 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?

Tuberculosis verrucosa cutis. ***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.

Q: All are correct about the image shown except:

Type 1 lepra reaction. ***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.

Q: Which of the following toxins will produce the condition shown below?

ETA and ETB. ***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.

Q: All are correct about the condition shown in the image except: (Recent NEET Pattern 2016-17)

Necrotising Fasciitis. ***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.

Q: 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:

Impetigo contagiosa. ***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.

Q: A 35-year-old obese woman presents with recurrent lesions in both axilla in summer season. Wood lamp examination is shown. The diagnosis is:

Erythrasma. ***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.

Q: The following image is diagnostic of which STD?

LGV. ***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.

Question 1

Which condition is shown in the image below?

Accepted Answer

Staphylococcal scalded skin syndrome

Answer

Reiter syndrome

Answer

Toxic epidermal necrolysis

Answer

Stevens-Johnson syndrome

Question 2

Identify the lesion shown in the image.

Accepted Answer

Furuncle

Answer

Impetigo

Answer

Carbuncle

Answer

Erysipelas

Question 3

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?

Accepted Answer

Tuberculosis verrucosa cutis

Answer

Verruca vulgaris

Answer

Epidermodysplasia verruciformis

Answer

Madura foot

Question 4

All are correct about the image shown except:

Accepted Answer

Type 1 lepra reaction

Answer

Convoluted folds of facial skin

Answer

Loss of eyebrows

Answer

Keratitis

Question 5

Which of the following toxins will produce the condition shown below?

Accepted Answer

ETA and ETB

Answer

Leukocidin

Answer

TSST-1

Answer

Serum opacity factor

Question 6

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?

Accepted Answer

A single dose of 2.4 million units of benzathine penicillin IM is the treatment

Answer

It is caused by Haemophilus ducreyi

Answer

He is likely to develop arthritis of the knee

Answer

Examination of the groin will reveal a characteristic groove sign

Question 7

All are correct about the condition shown in the image except: (Recent NEET Pattern 2016-17)

Accepted Answer

Necrotising Fasciitis

Answer

Epidermolysin mediated

Answer

Staphylococcal scalded skin syndrome

Answer

Caused by gram positive cocci in clusters

Question 8

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:

Accepted Answer

Impetigo contagiosa

Answer

Ecthyma

Answer

Erythrasma

Answer

Bullous impetigo

Question 9

A 35-year-old obese woman presents with recurrent lesions in both axilla in summer season. Wood lamp examination is shown. The diagnosis is:

Accepted Answer

Erythrasma

Answer

Ecthyma

Answer

Impetigo contagiosa

Answer

Bullous impetigo

Question 10

The following image is diagnostic of which STD?

Accepted Answer

LGV

Answer

Herpes simplex

Answer

Chancroid

Answer

Donovanosis

Bacterial Skin Infections — MCQs

Bacterial Skin Infections — MCQs

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