Infectious Diseases Practice Questions

Q: A 40-year-old diabetic patient presents with proptosis of one eye and a black eschar over the palate. What is the likely causative organism?

Mucor. ### Explanation The clinical presentation of **proptosis** and a **black necrotic eschar** on the palate in a **diabetic patient** (especially one in ketoacidosis) is the classic triad for **Rhinocerebral Mucormycosis** [1]. **Why Mucor is the correct answer:** Mucormycosis is caused by fungi of the order Mucorales (e.g., *Rhizopus*, *Mucor*). These fungi are **angioinvasive**, meaning they invade blood vessel walls, leading to thrombosis, tissue ischemia, and necrosis [1]. This necrosis manifests clinically as a characteristic **black eschar** on the nasal mucosa or palate. The infection spreads rapidly from the sinuses to the orbit (causing proptosis and ophthalmoplegia) and eventually to the brain. **Why the other options are incorrect:** * **Pseudomonas:** While it can cause "Malignant Otitis Externa" in diabetics (involving the ear canal and skull base), it does not typically present with a palatal eschar or acute rhino-orbital syndrome. * **Candida:** Usually causes superficial infections like oral thrush (white plaques) or systemic candidiasis. It is not angioinvasive enough to cause rapid tissue necrosis and eschar formation [2]. * **E. coli:** A common cause of urinary tract infections and sepsis in diabetics, but it does not have a predilection for the paranasal sinuses or cause necrotic facial lesions. **High-Yield Clinical Pearls for NEET-PG:** * **Risk Factors:** Uncontrolled Diabetes Mellitus (Ketoacidosis), Neutropenia, and Iron overload (Deferoxamine use) [1]. * **Diagnosis:** KOH mount or biopsy showing **broad, ribbon-like, non-septate hyphae** with **right-angle (90°) branching**. * **Management:** Immediate surgical debridement + Intravenous **Liposomal Amphotericin B** [1]. (Note: Azoles like Fluconazole are ineffective; Posaconazole/Isavuconazole are alternatives).

Q: A 20-year-old male was admitted with fever, headache and retro-orbital pain with rash. The tourniquet test is positive. What is the diagnosis?

Dengue hemorrhagic fever. ***Dengue hemorrhagic fever***- The combination of high fever, **headache**, **retro-orbital pain**, and rash is characteristic of classic Dengue fever (breakbone fever) [1].- A **positive tourniquet test** suggests increased capillary fragility, which, along with the other symptoms, strongly indicates progression toward **Dengue hemorrhagic fever (DHF)** [1].*Malaria*- Malaria is characterized by cyclical fever patterns (such as tertian or quartan), often associated with severe chills and sweats, which are not mentioned here.- It typically does not cause prominent retro-orbital pain or lead to a positive **tourniquet test** as a primary finding.*Measles*- Measles is typically preceded by a prodrome including cough, coryza, and conjunctivitis, followed by the appearance of **Koplik spots** (buccal lesions).- The rash starts on the face and spreads downwards, and while fever is present, the key combination of **retro-orbital pain** and a positive tourniquet test is not characteristic.*Japanese encephalitis*- This is primarily a **neuroinvasive disease** transmitted by Culex mosquitoes, leading to symptoms like altered mental status, seizures, and focal neurological deficits.- Simple fever, headache, and rash without significant encephalopathy make this diagnosis less likely, and it is not typically associated with the **tourniquet test**.

Q: A woman presents with sudden-onset high-grade fever, hypotension, diffuse rash, and a history of using a tampon for an extended period. What is the most likely diagnosis?

Toxic Shock Syndrome. Toxic Shock Syndrome - This diagnosis is defined by the sudden onset of **high fever**, **hypotension** (shock), and a **diffuse erythematous rash** (often described as sunburn-like), strongly supported by the history of prolonged **tampon use** (a common source for *Staphylococcus aureus* producing **TSST-1** superantigen). [1] - TSS is a life-threatening illness caused by toxins that induce massive cytokine release, leading rapidly to shock and potential multi-organ failure. [1] Septic shock - While TSS is a specific diagnosis within the broader category of **sepsis/septic shock**, the acute presentation with the classic **diffuse rash** and clear association with prolonged tampon use makes TSS the most accurate diagnosis. - Septic shock is a general condition of infection-induced circulatory failure but lacks the specific **sunburn-like rash** and classic toxin etiology that defines TSS. Pelvic Inflammatory Disease - PID typically presents with **lower abdominal pain**, **cervical motion tenderness**, and purulent vaginal discharge, rather than rapid-onset systemic shock and generalized diffuse rash. - Although PID is an ascending infection often causing fever, it rarely leads to the swift and profound **hypotension** and multi-organ dysfunction characteristic of TSS. Streptococcal pharyngitis - This infection primarily presents with **sore throat**, fever, and sometimes exudates on the tonsils; it is locally confined and generally does not cause sudden, severe **hypotension** or systemic collapse. - While *Streptococcus pyogenes* can also cause a toxic shock syndrome, simple pharyngitis lacks the multi-system involvement, hypotensive crisis, and definitive association with **tampon usage** seen in this presentation. [1]

Q: A patient presents with fever after returning from a forest trip. On examination, a black eschar is noted on the abdomen. Which of the following is the most likely diagnosis and its drug of choice?

Doxycycline. ***Doxycycline (Scrub Typhus)*** - The clinical presentation of fever following a forest trip, along with a characteristic **black eschar** (tache noire), is highly suggestive of **scrub typhus**, a rickettsial infection caused by *Orientia tsutsugamushi*. - **Doxycycline** is the drug of choice for rickettsial diseases, including scrub typhus, as it effectively inhibits protein synthesis in these obligate intracellular bacteria. - The diagnosis is scrub typhus, and doxycycline is the first-line treatment with rapid clinical response typically within 24-48 hours. *Penicillin* - Penicillin targets bacterial **cell wall synthesis** and is primarily effective against gram-positive organisms like *Streptococcus* and *Staphylococcus*. - It is ineffective against intracellular pathogens like *Orientia tsutsugamushi*, which lack a typical peptidoglycan cell wall targeted by penicillins. *Ceftriaxone* - Ceftriaxone is a third-generation cephalosporin used for a wide range of bacterial infections, such as meningitis and community-acquired pneumonia, but it is not the standard treatment for rickettsial diseases. - Clinical trials have shown that tetracyclines like doxycycline result in faster defervescence and better outcomes for scrub typhus compared to cephalosporins. *Artesunate* - Artesunate is a potent **antimalarial** drug used for treating severe malaria caused by *Plasmodium* species. - While malaria can cause fever after travel, it does not produce a necrotic eschar, which is a key diagnostic feature distinguishing scrub typhus from malaria.

Q: A patient presents with blackish discoloration of the nasal cavity and posterior buccal mucosa. He has a history of high-dose steroid use. What is the most appropriate drug for treatment?

Amphotericin B. ***Amphotericin B*** - The patient's signs (**blackish discoloration** of the nasal and buccal mucosa) coupled with profound immunosuppression (high-dose steroids) strongly suggest **Rhinocerebral mucormycosis**, an aggressive angioinvasive fungal infection caused by **Mucorales** [2]. - **Amphotericin B** (liposomal formulation preferred) is the drug of choice for empirical and definitive treatment of life-threatening mucormycosis due to its potent fungicidal activity against **Zygomycetes** [2]. - Early surgical debridement combined with Amphotericin B therapy is essential for optimal outcomes [2]. *Fluconazole* - **Fluconazole** has no reliable activity against **Mucorales** (causative agents of mucormycosis) [3]. - It is primarily used for *Candida* and *Cryptococcus* infections, completely lacking the spectrum needed for this severe angioinvasive process [1][3]. *Itraconazole* - **Itraconazole** is typically ineffective against **Mucorales** and is generally reserved for endemic mycoses (*Histoplasma, Blastomyces*) or step-down therapy for *Aspergillus* [3]. - It does not achieve adequate fungicidal activity needed for aggressive invasive fungal sinusitis. *Griseofulvin* - **Griseofulvin** is indicated only for **dermatophytosis** (superficial tinea infections of skin, hair, and nails). - It has no role or efficacy in treating severe, systemic, or angioinvasive fungal infections like mucormycosis.

Q: A patient with known rheumatic heart disease is now found to have a 1–2 cm aneurysm on imaging. What is the most appropriate next step in management?

IV antibiotics. ***IV antibiotics*** - In a patient with **rheumatic heart disease (RHD)**, the finding of an aneurysm on imaging should raise strong suspicion for a **mycotic aneurysm**, especially given the increased risk of **infective endocarditis (IE)** in RHD patients [1]. - **Mycotic aneurysms** are infected arterial wall dilations that occur as a complication of IE, resulting from septic emboli or direct bacterial invasion of the vessel wall [2]. - **First-line management** consists of **prolonged IV antibiotics** (4-6 weeks) targeting the causative organism, along with close monitoring for aneurysm expansion or rupture. - Blood cultures, echocardiography, and infectious disease consultation are essential components of the workup [1]. *Aspirin lifelong* - While **aspirin** is important for long-term secondary prevention in RHD patients to reduce thromboembolic risk, it is **not the immediate priority** when an aneurysm is discovered. - In the setting of a **mycotic aneurysm**, aspirin may actually **increase bleeding risk** if the aneurysm ruptures and should be used cautiously [3]. - Long-term antiplatelet therapy would be considered after the acute infectious complication is addressed. *Aspirin + Clopidogrel* - **Dual antiplatelet therapy (DAPT)** is reserved for acute coronary syndromes or post-percutaneous coronary intervention, not for routine management of aneurysms in RHD. - In the context of a potential **mycotic aneurysm**, DAPT would significantly increase the risk of **catastrophic bleeding** without providing benefit. *Aspirin for 3 weeks* - Short-term aspirin therapy does not address the underlying pathology of a **mycotic aneurysm**, which requires targeted antimicrobial therapy. - This duration is insufficient for either treating the infection or providing adequate long-term vascular protection in RHD.

Q: CSF shows abundant PMNs with low sugar and elevated proteins. Diagnosis is?

Acute bacterial meningitis. ***Acute bacterial meningitis*** - The findings of abundant **Polymorphonuclear leukocytes (PMNs)**, **low CSF glucose** (due to bacterial consumption), and **elevated protein** are the classic triad for an acute bacterial infection of the meninges [1]. - A high PMN count indicates an acute inflammatory response, and the profound hypoglycemia and marked protein elevation distinguish it from most viral etiologies [1]. *Tubercular Meningitis* - While also associated with **low CSF glucose** and **elevated protein**, the predominant cell type is typically **lymphocytic** (mononuclear cells), not PMNs [3]. - The CSF often appears xanthochromic, and organisms like *M. tuberculosis* generally cause a subacute or chronic presentation rather than the acute presentation suggested by abundant PMN presence [3]. *Viral encephalitis* - CSF analysis usually reveals a **lymphocytic pleocytosis** (a higher proportion of lymphocytes), not a PMN predominance. - Glucose levels are typically **normal**, and protein elevation is usually mild to moderate, not markedly elevated. *Viral meningitis* - Similar to viral encephalitis, viral meningitis primarily causes a **lymphocytic pleocytosis** with a transient PMN phase early on, which quickly shifts to lymphocytes [2]. - The defining feature differentiating it from bacterial or tubercular meningitis is the **normal CSF glucose** level and milder protein elevation [2].

Q: What is the management of undulant fever?

Doxycycline plus rifampicin. ***Doxycycline plus rifampicin***- This is the **standard and preferred oral combination regimen** for treating **Brucellosis** (undulant fever), typically administered for 6 weeks [1].- The combination is crucial because it uses antibiotics that penetrate macrophages and have a **synergistic effect**, significantly reducing the risk of relapse compared to monotherapy.*Doxycycline*- **Doxycycline** is the cornerstone of treatment due to its excellent **intracellular penetration**, but **monotherapy** is associated with high rates of **relapse**.- It must be combined with a second agent (like **rifampicin** or **streptomycin**) to achieve adequate cure rates and prevent recurrence.*Doxycycline with azithromycin*- While macrolides like **azithromycin** show *in vitro* activity against *Brucella*, clinical data supporting this combination as a first-line treatment are generally lacking.- This combination is **less effective** and not recommended by major professional guidelines compared to regimens using **rifampicin** or aminoglycosides.*Doxycycline plus ceftriaxone*- **Ceftriaxone** (a third-generation cephalosporin) is used primarily for complicated brucellosis, especially **neurobrucellosis** (often added to the standard regimen).- It is **not recommended** as part of the standard initial **oral** regimen for uncomplicated brucellosis due to inferior efficacy compared to rifampicin.

Q: A patient presents with fever and altered sensorium. Peripheral smear shows multiple ring stages. Best treatment is?

Artesunate. Artesunate - The clinical presentation of fever and altered sensorium, along with a peripheral smear showing multiple ring stages (characteristic of P. falciparum), indicates severe malaria [1]. Intravenous artesunate is the recommended first-line treatment [1]. - Artesunate is a potent and rapidly acting artemisinin derivative that quickly reduces the parasite burden, leading to lower mortality rates compared to quinine in severe malaria cases [1]. Primaquine - Primaquine is primarily used to eradicate the dormant liver stages (hypnozoites) of P. vivax and P. ovale to prevent relapse, not for treating acute, severe falciparum malaria. - It is ineffective against the asexual erythrocytic stages of P. falciparum and can cause severe hemolysis in patients with G6PD deficiency. Quinine - Quinine is a second-line agent for severe malaria and is only used if artesunate is unavailable, due to its inferior efficacy and greater toxicity [1]. - Its use is associated with adverse effects known as cinchonism (tinnitus, headache, nausea) and can cause severe hypoglycemia and cardiac arrhythmias [1]. Chloroquine - Widespread resistance of P. falciparum to chloroquine makes it an ineffective choice for treating this infection in most malaria-endemic regions. - Chloroquine is typically reserved for the treatment of uncomplicated malaria caused by chloroquine-sensitive species like P. malariae, _P. ovale, or P. vivax (in areas without resistance).

Q: A 38-year-old male presents with a one-week history of fever, headache, retro-orbital pain, and myalgia. Skin examination reveals multiple purpura and petechiae on the left shoulder, trunk, and legs. Similar cases have been reported linked to increased incidence of mosquito breeding. What is the most common neurological complication associated with this condition?

Encephalopathy. ***Encephalopathy***- **Encephalopathy** is the most frequent neurological complication in severe **Dengue fever**, often resulting from systemic factors like **shock**, **hypoxia**, **hepatic dysfunction**, or **hyponatremia** rather than direct viral invasion [1].- The presented symptoms (fever, retro-orbital pain, myalgia, hemorrhagic signs/purpura) are classic for severe Dengue, where multorgan failure and systemic derangements frequently lead to altered consciousness [1].*Guillain-Barré Syndrome*- **GBS** is a **post-infectious** demyelinating condition that typically manifests after recovery from the acute viral illness, presenting as progressive, ascending paralysis.- While Dengue is a recognized trigger for GBS, it is much less common than acute encephalopathy occurring during the febrile or critical phase of the illness.*Stroke*- **Stroke** (ischemic or hemorrhagic) can occur in severe dengue due to complications like **vasculitis**, **coagulopathy**, or profound **thrombocytopenia**, leading to focal neurological deficits.- Although the hemorrhagic signs (purpura/petechiae) indicate a risk for bleeding complications, stroke is generally less common than systemic **encephalopathy** in the overall spectrum of dengue neuro-complications [1].*Encephalitis*- **Encephalitis** refers to inflammation of the brain caused by **direct viral invasion** of the central nervous system by the Dengue virus.- While possible, primary dengue encephalitis due to neurotropism is considered a relatively rare neurological manifestation compared to secondary **dengue-associated encephalopathy** [1].

Question 1

A 40-year-old diabetic patient presents with proptosis of one eye and a black eschar over the palate. What is the likely causative organism?

Accepted Answer

Mucor

Answer

Pseudomonas

Answer

Candida

Answer

E. coli

Question 2

A 20-year-old male was admitted with fever, headache and retro-orbital pain with rash. The tourniquet test is positive. What is the diagnosis?

Accepted Answer

Dengue hemorrhagic fever

Answer

Malaria

Answer

Japanese encephalitis

Answer

Measles

Question 3

A woman presents with sudden-onset high-grade fever, hypotension, diffuse rash, and a history of using a tampon for an extended period. What is the most likely diagnosis?

Accepted Answer

Toxic Shock Syndrome

Answer

Septic shock

Answer

Pelvic Inflammatory Disease

Answer

Streptococcal pharyngitis

Question 4

A patient presents with fever after returning from a forest trip. On examination, a black eschar is noted on the abdomen. Which of the following is the most likely diagnosis and its drug of choice?

Accepted Answer

Doxycycline

Answer

Ceftriaxone

Answer

Penicillin

Answer

Artesunate

Question 5

A patient presents with blackish discoloration of the nasal cavity and posterior buccal mucosa. He has a history of high-dose steroid use. What is the most appropriate drug for treatment?

Accepted Answer

Amphotericin B

Answer

Fluconazole

Answer

Griseofulvin

Answer

Itraconazole

Question 6

A patient with known rheumatic heart disease is now found to have a 1–2 cm aneurysm on imaging. What is the most appropriate next step in management?

Accepted Answer

IV antibiotics

Answer

Aspirin for 3 weeks

Answer

Aspirin lifelong

Answer

Aspirin + Clopidogrel

Question 7

CSF shows abundant PMNs with low sugar and elevated proteins. Diagnosis is?

Accepted Answer

Acute bacterial meningitis

Answer

Viral encephalitis

Answer

Tubercular Meningitis

Answer

Viral meningitis

Question 8

What is the management of undulant fever?

Accepted Answer

Doxycycline plus rifampicin

Answer

Doxycycline

Answer

Doxycycline plus ceftriaxone

Answer

Doxycycline with azithromycin

Question 9

A patient presents with fever and altered sensorium. Peripheral smear shows multiple ring stages. Best treatment is?

Accepted Answer

Artesunate

Answer

Chloroquine

Answer

Primaquine

Answer

Quinine

Question 10

A 38-year-old male presents with a one-week history of fever, headache, retro-orbital pain, and myalgia. Skin examination reveals multiple purpura and petechiae on the left shoulder, trunk, and legs. Similar cases have been reported linked to increased incidence of mosquito breeding. What is the most common neurological complication associated with this condition?

Accepted Answer

Encephalopathy

Answer

Stroke

Answer

Encephalitis

Answer

Guillain-Barré Syndrome

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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