Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 1261: A 65-year-old male presents with fever, chills, and a productive cough with rust-colored sputum. What is the most likely diagnosis?

A. TB
B. Klebsiella pneumonia
C. Pneumocystis pneumonia
D. Pneumococcal Pneumonia (Correct Answer)

Explanation: Pneumococcal Pneumonia - This presentation with fever, chills, and rust-colored sputum is classic for pneumococcal pneumonia, caused by Streptococcus pneumoniae [1]. [2] - The rust color results from the presence of hemolyzed red blood cells from the inflamed alveoli [3]. TB - While TB can cause fever and cough, the sputum is typically mucoid or purulent, and sometimes hemoptysis (frank blood) is seen, but not usually rust-colored [4]. - TB symptoms tend to be more chronic, including night sweats and weight loss, which are not mentioned here. Klebsiella pneumonia - Klebsiella pneumoniae typically causes severe pneumonia, often in individuals with alcoholism or diabetes [1]. - It classically presents with currant jelly sputum, which is distinct from rust-colored sputum [2]. Pneumocystis pneumonia - Pneumocystis jirovecii pneumonia (PCP) primarily affects immunocompromised individuals, particularly those with HIV [4]. - Symptoms are usually more insidious, involving dyspnea, non-productive cough, and hypoxia, and sputum is not typically rust-colored [4].

Question 1262: Fever and haemorrhagic rash are seen in all except which of the following?

A. Dengue fever
B. Rift Valley fever
C. Sand fly fever (Correct Answer)
D. Lassa fever

Explanation: ***Sand fly fever*** - **Sand fly fever**, also known as phlebotomus fever, is typically characterized by an acute onset of fever, headache, myalgia, and malaise. - While it can cause a rash, it is generally **non-hemorrhagic** and petechiae or purpura are uncommon. *Dengue fever* - **Dengue fever** is well-known for causing **hemorrhagic manifestations**, ranging from petechiae and purpura to severe bleeding [1]. - The classic presentation includes high fever, severe headache, retro-orbital pain, and a generalized rash which can become hemorrhagic [1]. *Lassa fever* - **Lassa fever** is a severe viral hemorrhagic fever caused by the Lassa virus [2]. - It often progresses to include a **hemorrhagic rash** along with organ damage and generalized bleeding tendencies [2]. *Rift Valley fever* - **Rift Valley fever** is another viral hemorrhagic fever that can cause a spectrum of symptoms including fever and, in severe cases, **hemorrhagic manifestations** such as petechiae, ecchymoses, and epistaxis. - Ocular and neurological complications are also characteristic of severe disease.

Question 1263: Which of the following is a chronic complication of malaria?

A. Nephrotic syndrome
B. Pneumonia
C. Hodgkin's disease
D. Splenomegaly (Correct Answer)

Explanation: Splenomegaly - Chronic malaria, especially Plasmodium falciparum infections, leads to persistent erythrocytic sequestration in the spleen. - This prolonged immune response and destruction of infected red blood cells contribute to significant and often palpable enlargement of the spleen [1]. Nephrotic syndrome - While malaria can cause kidney complications, nephrotic syndrome is more commonly associated with specific types of malaria, particularly Plasmodium malariae, and is often considered a direct acute or subacute complication rather than a widespread chronic sequela of all malaria types. - The primary chronic complication that affects a broader range of malaria cases is splenomegaly. Pneumonia - Pneumonia is an acute respiratory infection that can occur as a co-infection or complication in severely ill malaria patients. - It is not considered a chronic complication of malaria itself, but rather an acute opportunistic infection or secondary issue. Hodgkin's disease - There is no direct, established link between chronic malaria infection and the development of Hodgkin's disease [2]. - While other infections (e.g., EBV) are associated with certain lymphomas, malaria is not known to be a direct causative agent or chronic complication leading to Hodgkin's lymphoma [2].

Question 1264: Fecal leucocytes are absent in all of the following, except:

A. Cryptosporidiosis
B. Clostridium perfringes infection
C. Giardiasis
D. Campylobacter infection (Correct Answer)

Explanation: ***Campylobacter infection*** - This infection causes **inflammatory diarrhea**, leading to the presence of **fecal leucocytes** as a response to intestinal tissue invasion. - The inflammatory process results in disruption of the intestinal mucosa, attracting **neutrophils** and other inflammatory cells to the stool. *Giardiasis* - **Giardia lamblia** infection typically causes **non-inflammatory diarrhea** by interfering with nutrient absorption in the small intestine. - Due to the non-invasive nature of the pathogen, **fecal leucocytes** are generally **absent** in the stool. *Cryptosporidiosis* - **Cryptosporidium parvum** primarily causes **non-inflammatory watery diarrhea** by adhering to and damaging the microvilli of the intestinal epithelium. - While it can cause flattening of the villi, it does not typically lead to significant tissue invasion or the presence of **fecal leucocytes**. *Clostridium perfringens infection* - This bacterium causes **food poisoning** mainly through the production of **toxins** that affect the intestinal lining. - The diarrhea is typically **non-inflammatory**, and **fecal leucocytes** are usually **absent** because there is no significant host immune cell invasion.

Question 1265: A most common cause of nongonococcal septic arthritis is

A. Staphylococcus aureus (Correct Answer)
B. Pseudomonas aeruginosa
C. Streptococcus species
D. Haemophilus influenzae

Explanation: ***Staphylococcus aureus*** - **_Staphylococcus aureus_** is the most common cause of **nongonococcal septic arthritis** in adults and children [1]. - This organism can invade joints via **hematogenous spread** or direct inoculation following trauma or surgery [1]. *Pseudomonas aeruginosa* - **_Pseudomonas aeruginosa_** is a common cause of septic arthritis in **IV drug users** and individuals with **puncture wounds** through shoes [1]. - It is not the most common overall cause of nongonococcal septic arthritis. *Streptococcus species* - Various **_Streptococcus species_** (e.g., *S. pyogenes*, *S. pneumoniae*) can cause septic arthritis, particularly in elderly individuals or those with underlying conditions [1]. - However, they are **less frequent** causes compared to *Staphylococcus aureus* [1]. *Haemophilus influenzae* - **_Haemophilus influenzae_** was a common cause of septic arthritis in **children** before the widespread introduction of the hib vaccine. - Its incidence has significantly decreased in vaccinated populations and is now rare in adults.

Question 1266: An 34-year-old male HIV patient on c-A presents with seizures and a unilateral facial nerve palsy. The CT scan shows a ring-enhancing lesion. What is the best treatment?

A. Albendazole with dexamethasone
B. Amphotericin B
C. ATT with steroids
D. Sulphadiazine, pyrimethamine and Leucovorin (Correct Answer)

Explanation: ***Sulphadiazine, pyrimethamine and Leucovorin*** - This combination is the standard **first-line treatment for cerebral toxoplasmosis**, which is strongly suggested by the clinical presentation (HIV patient, seizures, facial nerve palsy) and the imaging findings of **multiple ring-enhancing lesions**. - **Leucovorin** is added to prevent bone marrow suppression caused by pyrimethamine. *Albendazole with dexamethasone* - **Albendazole** is primarily used for **neurocysticercosis**, which typically presents with cystic lesions, not necessarily ring-enhancing, and the patient's HIV status makes toxoplasmosis more likely. - While **dexamethasone** may be used to reduce brain edema, it's adjunctive and not the primary antimicrobial treatment for toxoplasmosis. *Amphotericin B* - **Amphotericin B** is the mainstay treatment for **cryptococcal meningitis** and other severe fungal infections, which usually present with symptoms of meningitis and different imaging findings (e.g., hydrocephalus, gelatinous pseudocysts). - It is not effective against **Toxoplasma gondii**. *ATT with steroids* - **ATT (Anti-Tubercular Therapy)** with steroids is the treatment for **CNS tuberculosis**, which can present with ring-enhancing lesions. - However, the typical presentation for CNS tuberculosis in HIV patients often includes basilar meningitis, multiple tuberculomas, or abscesses, and toxoplasmosis is a far more common cause of ring-enhancing lesions in HIV patients with CD4 counts < 100 cells/µL.

Question 1267: Risk of pneumococcal meningitis is seen in whom?

A. Post splenectomy patient (Correct Answer)
B. Patient undergone neurosurgical intervention
C. Patient following cardiac surgery
D. Patient with hypoplasia of lung

Explanation: ***Post splenectomy patient*** - Patients who have undergone a **splenectomy** are at a significantly increased risk of developing severe infections, particularly by **encapsulated bacteria** like *Streptococcus pneumoniae*. - The **spleen plays a crucial role** in filtering bacteria from the blood and producing antibodies. Without it, the body's ability to clear pneumococci is severely impaired, leading to a higher risk of systemic infections, including meningitis. *Patient undergone neurosurgical intervention* - Neurosurgical interventions can increase the risk of meningitis, but usually it involves **nosocomial infections** or organisms introduced during the procedure (e.g., *Staphylococcus aureus*, gram-negative rods). - While possible, the risk of **pneumococcal meningitis** specifically is not as uniquely or significantly elevated as in splenectomized patients due to an underlying immune deficiency related to bacterial clearance. *Patient following cardiac surgery* - Patients undergoing cardiac surgery are at risk for various postoperative complications, including infections (e.g., **surgical site infections**, **endocarditis**). - However, routine cardiac surgery does not inherently predispose patients to a significantly increased risk of **pneumococcal meningitis** specifically, as their immune response to encapsulated bacteria is generally intact. *Patient with hypoplasia of lung* - **Hypoplasia of the lung** refers to incomplete development of the lung tissue, leading to reduced lung function. - While it may increase susceptibility to **respiratory infections** due to compromised lung mechanics, it does not directly impair the systemic immune response to encapsulated bacteria like *Streptococcus pneumoniae* in a way that specifically elevates the risk of meningitis to the same extent as asplenia.

Question 1268: A female presents with symptoms and signs suggestive of meningitis, and MRI reveals a ring-enhancing lesion in the frontotemporal region, while CSF grows Gram-positive bacilli. Other findings are minimally abnormal. Which of the following organisms is the most likely etiological agent?

A. Listeria monocytogenes (Correct Answer)
B. Streptococcus pneumoniae
C. Staphylococcus aureus
D. Haemophilus influenzae

Explanation: ***Listeria monocytogenes*** - This is a **Gram-positive bacillus** known to cause **meningitis**, especially in immunocompromised individuals, pregnant women, and the elderly [1]. - While not exclusively, *Listeria* can cause **brain abscesses** which might present as **ring-enhancing lesions** on MRI. *Streptococcus pneumoniae* - *Streptococcus pneumoniae* is a common cause of **bacterial meningitis**, but it is a **Gram-positive coccus**, not a bacillus [1]. - While it can cause complications like cerebritis or abscesses, its Gram stain morphology differentiates it from the given scenario [1]. *Staphylococcus aureus* - *Staphylococcus aureus* is a **Gram-positive coccus** that can cause meningitis, often associated with neurosurgical procedures or trauma. - Its typical presentation is as a coccus in clusters, not as a bacillus as described in the question. *Haemophilus influenzae* - *Haemophilus influenzae* is a **Gram-negative coccobacillus**, which contradicts the finding of a Gram-positive bacillus in the CSF. - Although it causes meningitis, especially in unvaccinated children, its Gram stain morphology rules it out in this case.

Question 1269: Which of the following statements regarding giardiasis is false?

A. Metronidazole is the drug of choice
B. Absence of fever
C. Diarrhea with steatorrhea
D. Bloody diarrhea (Correct Answer)

Explanation: Bloody diarrhea - **Giardiasis** is caused by the flagellate **_Giardia lamblia_**, which colonizes the small intestine and disrupts nutrient absorption, leading to **non-bloody diarrhea** [1]. - The parasite does not invade the intestinal wall, so **bloody stools are not a typical feature**; their presence suggests other infectious agents or conditions [1]. *Diarrhea with steatorrhea* - **_Giardia lamblia_ infection** impairs fat absorption in the small intestine, leading to the characteristic **fatty, foul-smelling stools known as steatorrhea**. - This malabsorption is due to damage to the brush border of enterocytes and disruption of bile salt metabolism. *Metronidazole is the drug of choice* - **Metronidazole** is indeed the **first-line treatment** for giardiasis, highly effective against the parasitic trophozoites. - Other effective alternatives include **tinidazole** and **nitazoxanide**, depending on regional resistance patterns and patient factors. *Absence of fever* - **Giardiasis** typically causes **gastrointestinal symptoms** such as diarrhea, abdominal cramps, and bloating, without systemic signs like fever [1]. - The absence of fever helps differentiate giardiasis from invasive infections that cause inflammatory responses.

Question 1270: Which of the following is a characteristic symptom of Bacillus cereus food poisoning?

A. Abdominal cramps
B. Vomiting (emetic type) (Correct Answer)
C. Fever (uncommon)
D. Diarrhea (diarrheal type)

Explanation: ***Vomiting (emetic type)*** - The **emetic type** of *Bacillus cereus* food poisoning is characterized by prominent **nausea and vomiting** with a rapid onset (within 1-5 hours) after consuming food, particularly rice [1],[2]. - This is caused by the preformed **cereulide toxin**, a heat-stable cyclic depsipeptide [2]. *Abdominal cramps* - While *Bacillus cereus* food poisoning can include abdominal cramps, they are a more general symptom and not as specifically characteristic or defining as the emetic or diarrheal presentations [1],[2]. - Abdominal cramps are often present in both the emetic and diarrheal forms, but the distinctive feature lies in the primary gastrointestinal manifestation [3]. *Fever (uncommon)* - Fever is **rarely a prominent symptom** in *Bacillus cereus* food poisoning, distinguishing it from many other bacterial foodborne illnesses. - The disease is primarily mediated by toxins, leading to localized GI symptoms rather than systemic inflammatory responses that cause fever. *Diarrhea (diarrheal type)* - *Bacillus cereus* also causes a **diarrheal type** of food poisoning, characterized by diarrhea and abdominal pain, but typically with a longer incubation period (6-15 hours) and is caused by different toxins (**hemolysin BL and non-hemolytic enterotoxin**) [2]. - While diarrhea is a characteristic symptom of *Bacillus cereus* diarrheal type, the question lists vomiting as the emetic type, focusing on the specific emetic presentation which is distinct [3].

Practice by Chapter

Principles of Antimicrobial Therapy

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Fever of Unknown Origin

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HIV/AIDS and Related Infections

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Tuberculosis and Mycobacterial Diseases

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Tropical and Parasitic Infections

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Viral Infections (Hepatitis, Herpes, etc.)

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Healthcare-Associated Infections

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Fungal Infections

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Sepsis and Septic Shock

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Infection in Immunocompromised Hosts

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Emerging and Re-emerging Infections

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Antimicrobial Resistance

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Vaccination Principles

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