Folliculitis, Furuncles, and Carbuncles — MCQs
A child of 7-8 years of age presents with scalp swelling and alopecia. What is the most appropriate diagnostic investigation?
Which of the following disorders would be more likely associated with Staphylococcus saprophyticus rather than Staphylococcus aureus?
A child presents with complaints of fever, rash, body ache, and throat ache. He had a history of thorn prick injury a week back. What antibiotics would you give empirically to this child?
What is the causative organism for the condition depicted in the image?
Best diagnostic test for fungal skin infection –
Female treated for Urinary tract infection now has vaginal discharge. The most likely organism is?
A young child of 7 years of age is seen with indurated ulcers, lymphadenopathy and fever. The likely treatment is:
Which of the following conditions is caused by Staphylococcus aureus?
Which feature best differentiates folliculitis from furuncle?
A 35-year-old obese woman presents with recurrent lesions in both axilla in summer season. Wood lamp examination is shown. The diagnosis is:
Folliculitis, Furuncles, and Carbuncles Indian Medical PG Practice Questions and MCQs
Question 1: A child of 7-8 years of age presents with scalp swelling and alopecia. What is the most appropriate diagnostic investigation?
- A. KOH staining of the scrapings (Correct Answer)
- B. Blood culture
- C. PAS staining
- D. Gram staining
Explanation: ***KOH staining of the scrapings*** - This presentation is highly suggestive of **tinea capitis**, a fungal infection of the scalp. **Potassium hydroxide (KOH) staining** of hair and scalp scrapings is the primary diagnostic method to identify fungal elements (hyphae and spores). - KOH dissolves keratinous material, making it easier to visualize the **fungal hyphae or spores** under a microscope. *Blood culture* - **Blood culture** is used to diagnose **systemic infections**, particularly bacterial or fungal infections that have entered the bloodstream. - It is **not indicated** for the initial diagnosis of localized skin and hair infections like tinea capitis. *PAS staining* - **Periodic acid–Schiff (PAS) staining** is primarily used for **histopathological examination** of tissue biopsies to detect fungi or other carbohydrates. - While it can identify fungi in tissue sections, it is **not the first-line diagnostic investigation** for tinea capitis, which typically uses direct microscopic examination of scrapings. *Gram staining* - **Gram staining** is a differential staining technique used to classify **bacteria** based on their cell wall properties (Gram-positive or Gram-negative). - It is **not effective** for identifying fungal organisms, which have different cell wall compositions.
Question 2: Which of the following disorders would be more likely associated with Staphylococcus saprophyticus rather than Staphylococcus aureus?
- A. Burns
- B. Tension pneumothorax
- C. Osteomyelitis
- D. Acute cystitis (Correct Answer)
Explanation: ***Acute cystitis*** - **Staphylococcus saprophyticus** is a common cause of **urinary tract infections (UTIs)**, particularly acute cystitis, in young sexually active women. - This bacterium has a high affinity for **uroepithelial cells**, facilitating its colonization and subsequent infection of the bladder. *Tension pneumothorax* - A **tension pneumothorax** is a medical emergency characterized by air accumulation in the pleural space, leading to lung collapse and mediastinal shift. - It is typically caused by trauma or iatrogenic factors, not directly by bacterial infection from either *Staphylococcus saprophyticus* or *Staphylococcus aureus*. *Burns* - Burn wounds are highly susceptible to bacterial colonization and infection, with **Staphylococcus aureus** being a primary pathogen in this context. - *Staphylococcus saprophyticus* is rarely associated with burn wound infections. *Osteomyelitis* - **Osteomyelitis**, an infection of the bone, is most frequently caused by **Staphylococcus aureus** via hematogenous spread or direct inoculation. - *Staphylococcus saprophyticus* is not a common pathogen in osteomyelitis.
Question 3: A child presents with complaints of fever, rash, body ache, and throat ache. He had a history of thorn prick injury a week back. What antibiotics would you give empirically to this child?
- A. Amoxicillin+ clavulanate (Correct Answer)
- B. Ceftriaxone
- C. Vancomycin
- D. Meropenem
Explanation: ***Amoxicillin + clavulanate*** - This combination provides **broad-spectrum coverage** against common skin flora including **Staphylococcus aureus**, **Streptococcus species**, and **anaerobes** that can be introduced by thorn prick injuries. - The **beta-lactamase inhibitor (clavulanate)** extends coverage to beta-lactamase producing organisms commonly found in skin infections. - Covers **Streptococcus pyogenes** which could explain the throat ache, making it ideal for this child with both skin infection and pharyngitis symptoms. - Most appropriate **first-line empiric therapy** for pediatric skin and soft tissue infections with systemic symptoms. *Ceftriaxone* - While this **third-generation cephalosporin** has good coverage against many gram-negative bacteria and some gram-positive organisms including **MSSA (methicillin-sensitive S. aureus)**, it is typically **reserved for parenteral therapy** in more severe infections. - For this clinical scenario, amoxicillin-clavulanate is preferred because it provides better **beta-lactamase coverage**, can be given orally, and covers both aerobic and anaerobic organisms relevant to thorn prick injuries. - Would be considered if the patient required **hospitalization** or failed first-line therapy. *Vancomycin* - This antibiotic is primarily used for serious infections caused by **multi-drug resistant gram-positive bacteria**, particularly **methicillin-resistant Staphylococcus aureus (MRSA)**. - Given the history of a thorn prick without specific risk factors for MRSA (no prior MRSA infection, hospital exposure, or failed beta-lactam therapy), there is **no indication for empiric vancomycin use**. - Using vancomycin empirically without specific indication contributes to **antibiotic resistance** and is not guideline-recommended. *Meropenem* - A **carbapenem** antibiotic reserved for **severe, life-threatening infections** caused by multi-drug resistant organisms or in cases of **septic shock** with unknown etiology. - The clinical presentation does not suggest severe sepsis, necrotizing fasciitis, or resistant pathogen requiring such broad coverage. - Empiric use in this scenario would represent **inappropriate antimicrobial stewardship** and promote development of carbapenem-resistant organisms.
Question 4: What is the causative organism for the condition depicted in the image?
- A. Staphylococci (Correct Answer)
- B. Candidal infection
- C. Streptococcus
- D. Actinomycetes
Explanation: ***Staphylococci*** - The image shows **impetigo** with **crusted lesions**, consistent with **_Staphylococcus aureus_** infection. - **Staphylococcus aureus** is a major causative organism of impetigo, particularly **bullous impetigo**, and commonly produces the characteristic **honey-colored crusts** seen in non-bullous forms as well. - This superficial bacterial skin infection is highly contagious and responds well to topical or systemic antibiotics. *Candidal infection* - **Candidal infections** (e.g., candidiasis) typically present as **erythematous patches** with satellite lesions, or white plaques in mucosal areas, which is not consistent with the image. - This fungal infection is often seen in immunocompromised individuals or in warm, moist skin folds, not as crusted superficial lesions. *Streptococcus* - While **_Streptococcus pyogenes_** can also cause impetigo (especially non-bullous impetigo), the clinical presentation in the image is most consistent with **staphylococcal infection**. - Streptococcal infections may present similarly but can also cause other conditions like cellulitis or erysipelas with distinct features. *Actinomycetes* - **Actinomycosis** is a rare, chronic bacterial infection that forms **abscesses and sinus tracts**, often with "sulfur granules," which is distinct from the superficial skin lesions shown. - This infection usually involves deeper tissues and presents as a chronic, indolent infection, unlike the acute superficial presentation of impetigo.
Question 5: Best diagnostic test for fungal skin infection –
- A. KOH test (Correct Answer)
- B. Diascopy
- C. Patch test
- D. Wood's lamp
Explanation: ***Correct: KOH test*** - The **potassium hydroxide (KOH) test** is the **most common and rapid method** for diagnosing dermatophyte infections. - It involves dissolving keratinous material to visualize **fungal hyphae** and **spores** under a microscope. - KOH test is **quick, inexpensive, and can be performed in any outpatient setting**, making it the best first-line diagnostic test. *Incorrect: Diascopy* - **Diascopy** is used to determine if a lesion is **vascular** (erythematous and blanches) or **non-vascular** (purpuric and does not blanch). - It involves pressing a glass slide against the lesion and observing color changes. - This test is not relevant for fungal identification. *Incorrect: Patch test* - A **patch test** is used to identify **allergic contact dermatitis** by applying specific allergens to the skin and observing for a delayed hypersensitivity reaction. - It is not designed to detect or diagnose fungal infections. *Incorrect: Wood's lamp* - A **Wood's lamp** emits ultraviolet light and is used to detect certain skin conditions that fluoresce. - While it can help diagnose some fungal infections like **Tinea capitis** caused by *Microsporum* species (which fluoresces green), it is **not a definitive diagnostic test** for all fungal infections. - Many common dermatophytes do not fluoresce, leading to false negatives.
Question 6: Female treated for Urinary tract infection now has vaginal discharge. The most likely organism is?
- A. Candida (Correct Answer)
- B. Trichomonas
- C. Ureaplasma urealyticum
- D. Chlamydia
Explanation: ***Candida*** - Antibiotic treatment for a **urinary tract infection** can disrupt the normal vaginal flora, leading to an overgrowth of **Candida albicans**, which is a common cause of vaginal discharge. - This often presents as **vulvovaginal candidiasis** with thick, white, "cottage cheese-like" discharge and intense pruritus. *Trichomonas* - **Trichomonas vaginalis** is a sexually transmitted infection (STI) that causes greenish-yellow, frothy vaginal discharge with a foul odor [1]. - While it can cause vaginal discharge, it is less likely to be directly precipitated by antibiotic use for a UTI compared to candidiasis. *Ureaplasma urealyticum* - **Ureaplasma urealyticum** can cause non-gonococcal urethritis and cervicitis, and sometimes vaginal discharge, but it is not typically associated with a flare-up following antibiotic treatment for a UTI. - It is often considered part of the normal genitourinary flora or an opportunistic pathogen. *Chlamydia* - **Chlamydia trachomatis** is a common sexually transmitted bacterium [2] that can cause cervicitis, leading to vaginal discharge, often mucopurulent and subtle [1]. - It would not typically emerge as a direct consequence or overgrowth due to antibiotic treatment for a UTI, unlike fungal infections.
Question 7: A young child of 7 years of age is seen with indurated ulcers, lymphadenopathy and fever. The likely treatment is:
- A. Excise the lesion
- B. Symptomatic treatment
- C. I.V. fluids
- D. Systemic antibiotics (Correct Answer)
Explanation: ***Systemic antibiotics*** - This clinical triad of **indurated ulcers, lymphadenopathy, and fever** in a child is highly suggestive of **ulceroglandular tularemia** (Francisella tularensis), **cat-scratch disease** (Bartonella henselae), or **atypical mycobacterial infection**. - **Tularemia** presents with a painful ulcer at the inoculation site with regional lymphadenopathy and systemic symptoms - treated with **streptomycin or gentamicin**. - **Cat-scratch disease** may present similarly after feline contact - treated with **azithromycin**. - **Atypical mycobacteria** (M. marinum) cause "swimming pool granuloma" with similar features - requiring **clarithromycin and rifampicin**. - **Systemic antibiotic therapy is essential** to prevent complications and disease progression. *Symptomatic treatment* - **Symptomatic treatment alone is inadequate** for bacterial infections presenting with indurated ulcers and lymphadenopathy. - While fever and pain management may be adjunctive, **definitive antimicrobial therapy is required** for these infectious conditions. - Failure to treat appropriately can lead to **systemic dissemination** and serious complications. *Excise the lesion* - **Surgical excision is not the primary treatment** for infectious ulcers with lymphadenopathy. - Excision may be considered for **localized atypical mycobacterial lymphadenitis** that fails medical therapy, but is not first-line. - The presence of **systemic symptoms (fever)** indicates need for medical rather than surgical management. *I.V. fluids* - **Intravenous fluids are supportive therapy** for dehydration, not definitive treatment. - The clinical presentation requires **antimicrobial therapy**, not just hydration. - IV fluids may be needed as adjunctive therapy if the child is unable to maintain oral hydration, but do not address the underlying infection.
Question 8: Which of the following conditions is caused by Staphylococcus aureus?
- A. Corynebacterium minutissimum infection
- B. Haemophilus ducreyi infection
- C. Propionibacterium acnes infection
- D. Bullous impetigo (Correct Answer)
Explanation: ***Bullous impetigo*** - Bullous impetigo is a superficial skin infection characterized by **blisters (bullae)**, and is specifically caused by **Staphylococcus aureus** producing exfoliative toxins. - The toxins produced by *S. aureus* cause intraepidermal cleavage, leading to the formation of the characteristic **flaccid bullae**. *Corynebacterium minutissimum infection* - *Corynebacterium minutissimum* causes **erythrasma**, a chronic superficial skin infection characterized by well-demarcated reddish-brown patches, often in intertriginous areas. - It does not cause bullous impetigo and is typically diagnosed by its coral-red fluorescence under a **Wood's lamp**. *Haemophilus ducreyi infection* - *Haemophilus ducreyi* is the causative agent of **chancroid**, a sexually transmitted infection characterized by painful genital ulcers with a necrotic base and often accompanied by swollen, tender regional lymph nodes. - It is not associated with skin blistering or bullous impetigo. *Propionibacterium acnes infection* - *Propionibacterium acnes* (now *Cutibacterium acnes*) is a bacterium commonly implicated in **acne vulgaris**, contributing to inflammation and comedone formation within hair follicles. - It causes inflammatory lesions like papules, pustules, nodules, and cysts, rather than bullous lesions.
Question 9: Which feature best differentiates folliculitis from furuncle?
- A. Depth of involvement (Correct Answer)
- B. Age of presentation
- C. Causative organism
- D. Site of occurrence
Explanation: ***Depth of involvement*** - **Folliculitis** is a superficial infection involving only the **hair follicle ostium**. - A **furuncle** (boil) is a deeper infection that extends into the **dermis** and subcutaneous tissue, often originating from a hair follicle. *Age of presentation* - Both conditions can occur at **any age**, although certain types of folliculitis (e.g., hot tub folliculitis) might be more common in specific age groups due to exposure. - Age itself is **not a distinguishing factor** in terms of disease pathology or differentiation. *Causative organism* - Both folliculitis and furuncles are **most commonly caused by *Staphylococcus aureus***. - While other organisms can sometimes cause folliculitis (e.g., *Pseudomonas* for hot tub folliculitis), the primary causative agent is similar for both. *Site of occurrence* - Both folliculitis and furuncles typically occur in **hair-bearing areas** of the body. - The site of occurrence does not inherently differentiate between a superficial infection of the follicle and a deeper, more extensive infection.
Question 10: 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.
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