Bacterial Skin Infections Practice Questions

Q: Which of the following statements about impetigo is false?

Primarily caused by a viral infection. ***Primarily caused by a viral infection*** - Impetigo is a **bacterial skin infection**, not viral, primarily caused by *Staphylococcus aureus* or *Streptococcus pyogenes*. - This statement is **false** because viruses are not the causative agents of impetigo. *Commonly presents with honey-colored crusts* - The characteristic clinical sign of impetigo, especially non-bullous impetigo, is the presence of **vesicles** and **pustules** that rupture and form **honey-colored crusts**. - This is a true and common presentation of impetigo, making the statement correct. *Can be caused by Staphylococcus aureus* - *Staphylococcus aureus* is indeed one of the **primary bacterial pathogens** responsible for causing impetigo, particularly bullous impetigo. - This statement is true, as *S. aureus* infection is a well-established cause of impetigo. *It predisposes to glomerulonephritis* - Impetigo caused by certain strains of *Streptococcus pyogenes* can lead to **post-streptococcal glomerulonephritis** (PSGN), a serious renal complication. - This statement is true, highlighting a significant potential complication of impetigo.

Q: What is the initial clinical manifestation of Treponema pallidum infection in primary syphilis?

Primary chancre. ***Primary chancre*** - *Treponema pallidum* is the causative agent of syphilis, and the **primary chancre** is the initial clinical manifestation at the site of inoculation. - A **chancre** is a painless, indurated ulcer with a clean base that develops 10-90 days after infection, typically on the genitals, rectum, or mouth. - This represents the hallmark of **primary syphilis** and is the first clinical sign of *T. pallidum* infection. *Secondary rash* - A **secondary rash** is a manifestation of **secondary syphilis**, occurring several weeks to months after the primary chancre heals. - This disseminated stage occurs as spirochetes spread throughout the body, but it is not the initial clinical manifestation. *Neurosyphilis* - **Neurosyphilis** refers to infection of the central nervous system by *Treponema pallidum*, which can occur at any stage but typically represents **tertiary syphilis**. - This is a severe complication but not the initial clinical manifestation of the infection. *Dark-field microscopy* - **Dark-field microscopy** is a diagnostic laboratory technique used to visualize motile *Treponema pallidum* directly from chancre exudate. - This is a diagnostic method, not a clinical manifestation of the infection.

Q: The explosive and widespread form of secondary syphilis in immune-compromised individuals is known as:

Lues maligna. ***Lues maligna*** - This is an **aggressive, ulcerative, and widespread** form of secondary syphilis that typically occurs in **immunocompromised individuals**, such as those with HIV. - It presents with **necrotic lesions** that have a characteristic punched-out or crater-like appearance. *Condylomata lata* - These are **moist, flat-topped, wart-like lesions** that appear in the anogenital region and other moist intertriginous areas. - While a manifestation of secondary syphilis, they are not typically described as "explosive and widespread" in the same ulcerative way as lues maligna. *Mucous patches* - These are **painless, gray-white lesions** found on the mucous membranes of the mouth, pharynx, genitals, and rectum during secondary syphilis. - They are highly infectious but do not represent the aggressive, widespread, and ulcerative form seen in immunocompromised individuals. *Lupus vulgaris* - This is a form of **cutaneous tuberculosis**, not syphilis, caused by Mycobacterium tuberculosis. - It presents as chronic, progressive nodules and plaques that can lead to significant tissue destruction, but it is entirely unrelated to syphilis.

Q: In acquired syphilis, what is the characteristic lesion that develops in the primary stage?

The characteristic lesion is a chancre, a painless ulcer.. ***The characteristic lesion is a chancre, a painless ulcer [1].*** - The **chancre** is the hallmark lesion of **primary syphilis**, developing at the site of *Treponema pallidum* entry [1]. - It is a **painless, indurated ulcer with raised borders**, typically occurring 10-90 days after exposure and resolving spontaneously. *The infection is most infectious in the secondary stage.* - While primary syphilis with its chancre is infectious, the **secondary stage is characterized by widespread dissemination of spirochetes**, making it the most infectious stage [1]. - The **maculopapular rash** and **condylomata lata** of secondary syphilis contain a high bacterial load [1]. *Causes secondary uveitis.* - **Uveitis** can occur in syphilis, but it is more characteristic of **secondary syphilis**, not primarily associated with the primary stage lesion itself. - Ocular involvement in secondary syphilis can include **uveitis**, retinitis, and optic neuritis, due to systemic dissemination. *Interstitial keratitis is a recognized feature of tertiary syphilis.* - **Interstitial keratitis** is typically a manifestation of **congenital syphilis** or sometimes late **tertiary syphilis**, not a primary stage presentation. - It involves inflammation of the cornea without primary involvement of the epithelium or endothelium, leading to vision impairment.

Q: A 16-year-old student reported for the evaluation of multiple hypopigmented macules on the trunk and limbs. Which of the following tests is not useful in making a diagnosis of leprosy?

Lepromin test. ***Lepromin test*** - The **lepromin test** is a measure of cell-mediated immunity to *Mycobacterium leprae* antigens, specifically used for classification of leprosy type and prognosis NOT for diagnosing the disease. - A positive lepromin test indicates a strong cell-mediated immune response, typical of **tuberculoid leprosy**, while a negative test is seen in **lepromatous leprosy**. *Sensation testing* - **Sensory loss** (hypoesthesia or anesthesia) within the hypopigmented lesions is a key diagnostic feature of leprosy due to nerve involvement. - This test is a crucial clinical tool to differentiate leprosy from other causes of hypopigmentation. *Slit smears* - **Slit skin smears** are used to detect and quantify acid-fast bacilli in skin lesions, providing a bacterial index for diagnosis and classification. - The presence of **acid-fast bacilli** confirms the diagnosis of leprosy and helps categorize it into paucibacillary or multibacillary forms. *Skin biopsy* - A **skin biopsy** of a suspected lesion can reveal characteristic histological changes, such as granuloma formation or nerve damage, confirming leprosy. - It aids in differentiating leprosy from other **granulomatous diseases** and is essential for definitive diagnosis when clinical features are ambiguous.

Q: A 6-year-old child presents with lesions on the face, covered with honey-colored crusts, and pruritus is present. The possible cause is:

Impetigo. ***Impetigo*** - **Impetigo** is a common bacterial skin infection, particularly in children, characterized by the classic **honey-colored crusts** and **pruritus (itching)**. - It is typically caused by *Staphylococcus aureus* or *Streptococcus pyogenes* and often affects the face, especially around the nose and mouth. *Herpes* - Herpes simplex virus (HSV) infections manifest as **vesicles (blisters) on an erythematous base** that can rupture and form shallow ulcers, but typically do not present with honey-colored crusts. - Herpes lesions are often painful and can recur in the same location. *Chickenpox* - Chickenpox (varicella) is a viral infection characterized by a **pruritic rash of macules, papules, vesicles, and crusts** appearing in various stages across the body, not primarily honey-colored crusts on the face. - Lesions typically resolve within 1-2 weeks, leaving no scarring unless scratched and secondarily infected. *Molluscum contagiosum* - Molluscum contagiosum presents as **small, flesh-colored, dome-shaped papules with a central umbilication**, caused by a poxvirus. - These lesions are usually asymptomatic or mildly itchy and do not typically form honey-colored crusts.

Q: Erythema chronicum migrans is associated with which of the following conditions?

Lyme disease. ***Lyme disease*** - **Erythema chronicum migrans** (ECM) is the characteristic expanding annular rash seen in the early localized stage of **Lyme disease**. - It results from infection with **Borrelia burgdorferi**, transmitted by **Ixodes ticks**. *Glucagonoma* - This is a pancreatic neuroendocrine tumor that secretes **glucagon**. - It is classically associated with **necrolytic migratory erythema**, a distinct rash, not erythema chronicum migrans. *Gastrinoma* - A gastrinoma is a tumor that secretes **gastrin**, leading to **Zollinger-Ellison syndrome**, characterized by severe peptic ulcer disease. - It is not associated with skin rashes like erythema chronicum migrans. *Phaeochromocytoma* - This is a tumor of the adrenal medulla that secretes **catecholamines**, causing symptoms like hypertension, palpitations, and headaches. - It does not present with erythema chronicum migrans or other characteristic skin rashes.

Q: What is the best method of treatment for an ulnar nerve abscess in a case of leprosy?

Incision and drainage. ***Incision and drainage*** - An abscess, by definition, is a localized collection of **pus** that requires drainage for resolution and to prevent further tissue damage. - In the setting of an ulnar nerve abscess due to leprosy, surgical **incision and drainage** is the definitive treatment to remove the infected material and alleviate pressure on the nerve. *High doses of steroid* - Steroids are primarily used in leprosy to manage **nerve inflammation** and **reversal reactions**, not pre-formed pus collections like an abscess. - Using steroids alone for an abscess can suppress the immune response, potentially worsening the infection and delaying healing. *Thalidomide* - **Thalidomide** is most commonly used for severe type 2 leprosy reactions (**erythema nodosum leprosum**) due to its anti-inflammatory and immunomodulatory effects. - It does not have a role in directly treating a localized abscess, which requires physical drainage. *High dose of clofazimine* - **Clofazimine** is an anti-leprosy drug used as part of multi-drug therapy for treating the underlying *Mycobacterium leprae* infection. - While essential for treating leprosy, it will not resolve a pre-existing abscess, which is a collection of pus that needs to be mechanically drained.

Question 1

Which of the following statements about impetigo is false?

Accepted Answer

Primarily caused by a viral infection

Answer

Can be caused by Staphylococcus aureus

Answer

Commonly presents with honey-colored crusts

Answer

It predisposes to glomerulonephritis

Question 2

What is the initial clinical manifestation of Treponema pallidum infection in primary syphilis?

Accepted Answer

Primary chancre

Answer

Secondary rash

Answer

Neurosyphilis

Answer

Dark-field microscopy

Question 3

A 35-year-old female presented with multiple inverted saucer-shaped ulcers over the body, with sensations near normal. The SSS test was positive, and the lepromin test was negative. What is the most appropriate management for this patient?

Accepted Answer

T.Rifampicin 600 mg and T.Clofazimine 300 mg once a month, T.Clofazimine 50 mg daily, and T.Dapsone 100 mg daily for 12 months.

Answer

T.Rifampicin 600 mg and T.Clofazimine 300 mg once a month, T.Clofazimine 100 mg daily, and T.Dapsone 100 mg daily for 12 months.

Answer

T.Rifampicin 600 mg and T.Clofazimine 300 mg once a month, T.Clofazimine 50 mg daily, and T.Dapsone 100 mg daily for 6 months.

Answer

T.Rifampicin 600 mg and T.Clofazimine 300 mg once a month, T.Clofazimine 50 mg daily, and T.Dapsone 1000 mg daily for 12 months.

Question 4

The explosive and widespread form of secondary syphilis in immune-compromised individuals is known as:

Accepted Answer

Lues maligna

Answer

Condylomata lata

Answer

Mucous patches

Answer

Lupus vulgaris

Question 5

In acquired syphilis, what is the characteristic lesion that develops in the primary stage?

Accepted Answer

The characteristic lesion is a chancre, a painless ulcer.

Answer

Causes secondary uveitis.

Answer

The infection is most infectious in the secondary stage.

Answer

Interstitial keratitis is a recognized feature of tertiary syphilis.

Question 6

A 16-year-old student reported for the evaluation of multiple hypopigmented macules on the trunk and limbs. Which of the following tests is not useful in making a diagnosis of leprosy?

Accepted Answer

Lepromin test

Answer

Slit smears

Answer

Sensation testing

Answer

Skin biopsy

Question 7

A 6-year-old child presents with lesions on the face, covered with honey-colored crusts, and pruritus is present. The possible cause is:

Accepted Answer

Impetigo

Answer

Herpes

Answer

Chickenpox

Answer

Molluscum contagiosum

Question 8

Erythema chronicum migrans is associated with which of the following conditions?

Accepted Answer

Lyme disease

Answer

Glucagonoma

Answer

Gastrinoma

Answer

Phaeochromocytoma

Question 9

What is the best method of treatment for an ulnar nerve abscess in a case of leprosy?

Accepted Answer

Incision and drainage

Answer

High dose of clofazimine

Answer

Thalidomide

Answer

High doses of steroid

Question 10

A 12-year-old child presents with 4 lesions of leprosy on their back and four lesions on their left arm. What should be the treatment for this child?

Accepted Answer

Rifampicin 450 mg once monthly + Dapsone 50 mg daily + Clofazimine 50 mg alternate day

Answer

Rifampicin 300 mg once monthly + Dapsone 25 mg daily

Answer

Rifampicin 450 mg once monthly + Dapsone 50 mg daily

Answer

Rifampicin 600 mg once monthly + Dapsone 100 mg daily

Bacterial Skin Infections — MCQs

Bacterial Skin Infections — MCQs

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