Bacterial Skin Infections Practice Questions

Q: A 30-year-old male patient presents with painful genital lesion after unprotected sexual intercourse. He is non cooperative during genital manipulation done to take culture specimen. All are true about the condition shown except:

Granulomatous lesion associated with endarteritis. ***Granulomatous lesion associated with endarteritis*** - This histopathological description is characteristic of **syphilitic chancre** (primary syphilis) or **gumma** (tertiary syphilis), NOT chancroid - Syphilis shows **granulomatous inflammation** with **obliterative endarteritis** (inflammation and narrowing of blood vessels) - **Chancroid** lesions are **non-granulomatous**, showing acute inflammatory infiltrate with lymphocytes, plasma cells, and neutrophils - This is the feature that is **NOT true** about chancroid, making it the correct answer to this "except" question *Phagedenic ulcer* - TRUE for chancroid - refers to rapidly destructive and spreading ulcers - Severe chancroid can present with extensive tissue destruction and sloughing - The aggressive nature of *Haemophilus ducreyi* infection can lead to phagedenic (rapidly spreading) ulceration *Autoinoculation* - TRUE for chancroid - the infection commonly spreads from existing lesions to other parts of the patient's body through direct contact - Results in multiple or satellite lesions around the primary ulcer - This is a well-recognized feature of *H. ducreyi* infection *Azithromycin single dose treatment* - TRUE for chancroid - **Azithromycin 1g orally as a single dose** is a **recommended first-line treatment** for chancroid - CDC and WHO guidelines support single-dose azithromycin as effective therapy - Other treatment options include ceftriaxone 250mg IM single dose, ciprofloxacin 500mg BD for 3 days, or erythromycin 500mg TDS for 7 days

Q: What is the diagnosis based on the image shown below?

Donovanosis. ***Donovanosis*** - The image displays genital lesions characterized by **slowly progressive, painless, nodular, ulcerative lesions** which bleed easily on contact, typical of Donovanosis. - This condition is caused by *Klebsiella granulomatis* and often presents with **beefy-red, friable granulation tissue** on the genitals or perineum. *Syphilis* - Primary syphilis typically presents as a **single, painless ulcer (chancre)** with a clean base and sharply demarcated, indurated borders. - While an ulcer is present in the image, its **granulomatous and friable appearance** does not align with a syphilitic chancre. *Chancroid* - Chancroid is characterized by **multiple, painful, soft ulcers** with ragged, undermined edges and a grayish, purulent base. - The lesion in the image appears to be a **painless, proliferative, and highly vascular** type, which is not characteristic of chancroid. *Lymphogranuloma Venereum* - LGV usually begins as a **small, transient, painless papule or vesicle** that often goes unnoticed, followed by painful inguinal lymphadenopathy (buboes). - The prominent **granulomatous ulceration** seen in the image is not the primary presentation of LGV, which is more focused on lymphatic involvement and systemic symptoms.

Q: The lesion shown in the image is:

Vernix caseosa. ***Vernix caseosa*** - The image shows a **thick, whitish, cheese-like substance** covering the scalp, which is characteristic of **vernix caseosa** on a neonate. - **Vernix caseosa** is a natural protective waxy or cheese-like white substance found on the skin of newborn human babies. *Atopic dermatitis* - **Atopic dermatitis** typically presents with **eczematous, itchy, red, and inflamed skin lesions**, often in flexural areas, which is not consistent with the image. - It usually involves **dry skin, lichenification, and excoriations**, not the thick, cheese-like coating seen here. *Seborrheic dermatitis* - While seborrheic dermatitis can involve the scalp, it typically appears as **greasy, yellowish scales** on an erythematous base, often referred to as "cradle cap" in infants. - The texture and widespread, thick white appearance in the image are less consistent with typical seborrheic dermatitis. *Urticarial dermatitis* - **Urticarial dermatitis** is characterized by the presence of **wheals (hives)**, which are transient, itchy, raised erythematous lesions with well-defined borders. - The image does not show classic **urticarial wheals**; instead, it depicts a continuous, thick, protective layer.

Q: Identify which of the following tests is being done?

Diascopy. ***Diascopy*** - The image shows a glass slide or a transparent object being pressed against a skin lesion to observe changes in color and **vascular blanching**, which is characteristic of diascopy. - This diagnostic technique helps differentiate between **erythema caused by vasodilation** (which blanches) and **erythema caused by extravasated red blood cells,** such as in purpura (which does not blanch). *Pathergy Test* - The pathergy test involves **pricking the skin with a sterile needle** and observing the development of a papule or pustule at the site after 24-48 hours. - This test is primarily used to diagnose **Behçet's disease** and is not represented by the action shown in the image. *Patch test* - A patch test is used to diagnose **allergic contact dermatitis** by applying specific allergens to the skin under patches for 48 hours and then observing the reaction. - It does not involve pressing a glass slide against a lesion as depicted in the image. *Dermoscopy* - Dermoscopy is a non-invasive technique that uses a handheld device with magnification and a light source to examine skin lesions, particularly moles, for patterns indicative of **melanoma** or other skin cancers. - It involves direct visualization through a dermoscope, not simple pressure with a glass slide.

Q: A 25-year-old woman presents with skin lesion on left supra-orbital margin. Eye examination is within normal limits. CXR done was normal. Diascopy shows apple jelly nodules. The image shows presence of:

Lupus vulgaris. ***Lupus vulgaris*** - The presence of **apple-jelly nodules** on diascopy is a classic and highly characteristic feature of **lupus vulgaris**, a type of cutaneous tuberculosis. - The lesion's location on the **supra-orbital margin** is a common site for this chronic, progressive skin infection. *Lupus pernio* - **Lupus pernio** is typically associated with **sarcoidosis**, presenting as violaceous plaques on the nose, cheeks, ears, and fingers. - It does not show **apple-jelly nodules** on diascopy. *Erythema marginatum* - **Erythema marginatum** is a transient, non-pruritic rash with red margins and clear centers, classically associated with **acute rheumatic fever**. - It does not manifest as nodular lesions or show translucency on diascopy. *Leprosy* - **Leprosy** can cause various skin lesions, but **apple-jelly nodules** on diascopy are not typical of its presentation; instead, thickened nerves and sensory loss are key features. - While it can affect the face, the specific description of diascopy findings points away from leprosy.

Q: A child presents with the skin lesions shown in the image. The most likely diagnosis is:

Impetigo contagiosa. ***Impetigo contagiosa*** - The image shows **honey-colored crusted lesions** around the mouth, which are highly characteristic of **impetigo contagiosa (non-bullous impetigo)**. - This form of impetigo is typically caused by *Staphylococcus aureus* or *Streptococcus pyogenes* and primarily affects superficial layers of the epidermis. *Bullous impetigo* - Characterized by **flaccid bullae** (blisters) that rupture to leave a thin, varnish-like crust, rather than the thick honey-colored crusts seen here. - It is exclusively caused by **Staphylococcus aureus** strains producing exfoliative toxins. *Ritter disease* - Also known as **Staphylococcal Scalded Skin Syndrome (SSSS)**, this condition involves widespread **erythema and exfoliation** resembling a burn. - It is a severe, systemic illness with widespread skin involvement, not localized crusted lesions like those pictured. *Ecthyma* - This is a more **deep-seated skin infection** that penetrates into the dermis, characterized by **"punched-out" ulcers** with thick, adherent crusts and often leaves scars. - While also caused by *Staphylococcus aureus* and/or *Streptococcus pyogenes*, its lesions are typically more severe and destructive than what is depicted.

Q: Which of the following is the most appropriate treatment for the skin condition shown in the image?

Selenium sulphide. ***Selenium sulphide*** - The image shows **pityriasis versicolor** (tinea versicolor), characterized by hypopigmented/hyperpigmented macules with fine **branny scaling** caused by **Malassezia furfur**. - **Selenium sulphide** is the **first-line topical treatment** for pityriasis versicolor, effectively eliminating the causative yeast organism. *Terbinafine* - **Terbinafine** has **limited topical efficacy** for pityriasis versicolor compared to selenium sulphide or ketoconazole. - While it's an effective antifungal for **dermatophytes**, it's not the preferred agent for **Malassezia** infections. *Tacrolimus* - **Tacrolimus** is a **calcineurin inhibitor** used primarily for **atopic dermatitis** and inflammatory skin conditions. - The image shows a **fungal infection** (pityriasis versicolor), not an inflammatory eczematous condition requiring immunosuppression. *Erythromycin* - **Erythromycin** is a **macrolide antibiotic** used for bacterial infections, not fungal conditions. - Pityriasis versicolor is caused by a **yeast organism** (**Malassezia furfur**), requiring antifungal treatment, not antibiotics.

Q: The following image shows:

Acantholytic cell. ***Acantholytic cell*** - The image displays characteristics of an **acantholytic cell**, particularly with its **rounder shape** and visible nucleus, surrounded by a distinct halo or separated from adjacent cells. - These cells result from the loss of cohesion between **keratinocytes** due to the breakdown of desmosomes, a hallmark feature in conditions like **Pemphigus vulgaris**. *Acanthocyte* - An **acanthocyte** is a red blood cell with **spiculated projections** (thorn-like processes) on its surface, often seen in liver disease or abetalipoproteinemia. - The cell in the image does not resemble a red blood cell and lacks the characteristic spiky projections. *Acanthosis* - **Acanthosis** refers to the **thickening of the stratum spinosum** (prickle cell layer) in the epidermis. - This is a **histopathological finding** visible at a tissue level, not a characteristic of an individual cell. *Anaplastic cell* - An **anaplastic cell** is typically a **highly undifferentiated malignant cell** with features like pleomorphism, prominent nucleoli, and abnormal mitotic figures. - While these cells can be irregular, the cell in the image specifically points to loss of intercellular adhesion rather than general cellular malignancy and dedifferentiation.

Q: A child presents with the following lesion in the neck folds. The gram stain from the lesion is shown below. Comment on the diagnosis.

Erythrasma. **Erythrasma** - The image shows a **reddish-brown, finely wrinkled lesion** in an intertriginous area (neck folds), consistent with erythrasma. - The gram stain reveals **long, filamentous Gram-positive bacilli**, characteristic of *Corynebacterium minutissimum*, the causative agent of erythrasma. *Impetigo contagiosa* - This typically presents as **honey-colored crusted lesions** or vesicles, often caused by *Staphylococcus aureus* or *Streptococcus pyogenes*. - Gram stain would show **Gram-positive cocci** (clusters for staph, chains for strep), not filamentous bacilli. *Scrofuloderma* - This is a form of **cutaneous tuberculosis**, typically presenting as **nontender subcutaneous nodules** that eventually ulcerate and discharge caseous material. - Diagnosis is confirmed by identifying acid-fast bacilli or histology showing granulomas; the gram stain and lesion appearance are not consistent. *Scrum pox* - This is a **viral skin infection** (often herpes simplex virus) seen in wrestlers, presenting as **vesicular or ulcerative lesions**. - It would not show filamentous Gram-positive bacilli on a bacterial gram stain.

Q: A patient has the following rash in the groin. Which of the following cannot be a cause?

Aspergillus. ***Aspergillus*** - **Aspergillus** is a **mold (filamentous fungus)**, NOT a dermatophyte, and therefore **cannot cause tinea cruris** (jock itch). - Dermatophytes (Trichophyton, Microsporum, Epidermophyton) are specialized fungi that digest keratin and cause superficial skin infections with characteristic ringworm patterns. - Aspergillus typically causes invasive infections in immunocompromised patients (invasive aspergillosis), allergic bronchopulmonary aspergillosis (ABPA), or rarely deep cutaneous infections in severely immunocompromised individuals—not superficial groin rashes. - **Key distinction:** Tinea cruris = dermatophyte infection; Aspergillus = opportunistic mold *Microsporum* - **Microsporum** species are dermatophytes that CAN cause tinea cruris, though less commonly than Trichophyton and Epidermophyton. - *M. canis* is the most common species, typically causing **tinea capitis** (scalp) and **tinea corporis** (body), but can extend to the groin area. - While not the most frequent cause, it remains a possible etiology and should not be excluded. *Epidermophyton* - **Epidermophyton floccosum** is one of the **most common causes** of tinea cruris. - Presents with itchy, erythematous, scaling patches with well-defined, elevated borders in the inguinal folds. - Thrives in warm, moist environments, making the groin an ideal location. - **Classic presentation:** bilateral involvement with central clearing and advancing scaly borders. *Trichophyton* - **Trichophyton rubrum** is the **MOST common** cause of tinea cruris worldwide, followed by **T. mentagrophytes**. - Causes characteristic pruritic, erythematous, annular or serpiginous lesions with raised, scaly borders. - T. rubrum accounts for the majority of dermatophyte infections in the groin, feet, and nails.

Question 1

A 30-year-old male patient presents with painful genital lesion after unprotected sexual intercourse. He is non cooperative during genital manipulation done to take culture specimen. All are true about the condition shown except:

Accepted Answer

Granulomatous lesion associated with endarteritis

Answer

Phagedenic ulcer

Answer

Azithromycin single dose treatment

Answer

Autoinoculation

Question 2

What is the diagnosis based on the image shown below?

Accepted Answer

Donovanosis

Answer

Syphilis

Answer

Chancroid

Answer

Lymphogranuloma Venereum

Question 3

The lesion shown in the image is:

Accepted Answer

Vernix caseosa

Answer

Atopic dermatitis

Answer

Seborrheic dermatitis

Answer

Urticarial dermatitis

Question 4

Identify which of the following tests is being done?

Accepted Answer

Diascopy

Answer

Pathergy Test

Answer

Patch test

Answer

Dermoscopy

Question 5

A 25-year-old woman presents with skin lesion on left supra-orbital margin. Eye examination is within normal limits. CXR done was normal. Diascopy shows apple jelly nodules. The image shows presence of:

Accepted Answer

Lupus vulgaris

Answer

Lupus pernio

Answer

Erythema marginatum

Answer

Leprosy

Question 6

A child presents with the skin lesions shown in the image. The most likely diagnosis is:

Accepted Answer

Impetigo contagiosa

Answer

Bullous impetigo

Answer

Ritter disease

Answer

Ecthyma

Question 7

Which of the following is the most appropriate treatment for the skin condition shown in the image?

Accepted Answer

Selenium sulphide

Answer

Terbinafine

Answer

Tacrolimus

Answer

Erythromycin

Question 8

The following image shows:

Accepted Answer

Acantholytic cell

Answer

Acanthocyte

Answer

Acanthosis

Answer

Anaplastic cell

Question 9

A child presents with the following lesion in the neck folds. The gram stain from the lesion is shown below. Comment on the diagnosis.

Accepted Answer

Erythrasma

Answer

Impetigo contagiosa

Answer

Scrofuloderma

Answer

Scrum pox

Question 10

A patient has the following rash in the groin. Which of the following cannot be a cause?

Accepted Answer

Aspergillus

Answer

Microsporum

Answer

Epidermophyton

Answer

Trichophyton

Bacterial Skin Infections — MCQs

Bacterial Skin Infections — MCQs

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