Infectious Diseases Practice Questions

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

Campylobacter infection. ***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.

Q: Risk of pneumococcal meningitis is seen in whom?

Post splenectomy patient. ***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.

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

Vomiting (emetic type). ***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].

Q: Which of the following is the treatment of choice for cryptococcal meningitis?

Amphotericin B. ***Amphotericin B*** - **Amphotericin B** is the **primary first-line antifungal agent** for severe fungal infections, including **cryptococcal meningitis**. - Current guidelines recommend **combination therapy with Amphotericin B plus Flucytosine** for induction therapy, with Amphotericin B being the **most critical component**. - Its broad spectrum of activity and ability to penetrate the **blood-brain barrier** make it highly effective against *Cryptococcus neoformans*. - **Liposomal Amphotericin B** is preferred due to reduced nephrotoxicity. *Fluconazole* - **Fluconazole** is an antifungal used for the **consolidation and maintenance phases** of cryptococcal meningitis treatment after initial induction therapy with Amphotericin B. - It is **not adequate as monotherapy** for the initial, acute management of severe cryptococcal meningitis due to slower fungicidal activity compared to Amphotericin B. *Itraconazole* - **Itraconazole** has **poor CNS penetration** and is generally **not recommended** for cryptococcal meningitis. - It is used for other fungal infections but is not part of standard treatment protocols for cryptococcal meningitis. *Flucytosine* - **Flucytosine** is an antifungal that is **always used in combination with Amphotericin B** (never alone) for cryptococcal meningitis to achieve a **synergistic effect** and improve outcomes. - It is **not used as monotherapy** because of rapid development of resistance when used alone. - While combination therapy is the gold standard, **Amphotericin B remains the primary agent**, making it the treatment of choice.

Q: Which of the following statements regarding giardiasis is false?

Bloody diarrhea. 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.

Q: Which of the following is NOT typically seen in cerebrospinal fluid (CSF) in tubercular meningitis?

Low opening pressure. ***Low opening pressure*** - While **elevated opening pressure** is common in tubercular meningitis due to inflammation and impaired CSF absorption, **low opening pressure** is not a typical finding. - Low opening pressure can occur with conditions like **CSF leak** or **spinal tap headache**, which are not directly characteristic of tubercular meningitis. *Low sugar* - **Low CSF glucose** (hypoglycorrhachia) is highly characteristic of bacterial and tubercular meningitis, as the bacteria or mycobacteria consume glucose. - The **CSF-to-blood glucose ratio** is typically less than 0.4 in tubercular meningitis. *High protein* - **Elevated CSF protein** is a consistent finding in tubercular meningitis, resulting from inflammation, increased vascular permeability, and breakdown of the blood-brain barrier. - Protein levels often range from **100-500 mg/dL** or even higher. *Lymphocytic Pleocytosis* - **Lymphocytic pleocytosis** (increased lymphocytes in CSF) is a hallmark of tubercular meningitis, although early stages might show a mixed cellular response. - The cell count typically ranges from **100-500 cells/µL**, predominantly lymphocytes.

Q: Maximum infection of CMV is seen after what duration post-transplantation?

1-4 months. ***1-4 months*** - The period of **1 to 4 months post-transplantation** is considered the peak risk period for **cytomegalovirus (CMV) infection** and disease due to a combination of intense immunosuppression and viral reactivation/transmission dynamics during this time [1]. - This window allows sufficient time for the transplanted organ to establish itself and for immunosuppressive regimens to reach their full effect, which then creates an environment highly susceptible to opportunistic viral infections like CMV [1]. *Immediate* - **Immediate post-transplant** (first few days) complications are usually related to surgery, organ function, or hyperacute rejection. - While viral exposure can occur, clinically significant CMV infection usually requires a longer incubation period. * 6 months* - After 6 months, while CMV infection can still occur (late-onset CMV disease), the **overall risk is generally lower** compared to the 1-4 month period. - This is because immunosuppression regimens are often tapered, and the recipient's immune system may have partially recovered or developed some anamnestic response by this time.

Q: Which of the following is not considered an opportunistic infection in AIDS?

Rubella. ***Rubella*** - Rubella, or **German measles**, is a relatively mild viral infection that typically affects children and is not considered an **opportunistic infection** in immunocompromised individuals like those with AIDS [1]. - While it can cause congenital rubella syndrome in infants whose mothers are infected during pregnancy, it does not disproportionately affect or cause severe disease in AIDS patients due to their compromised immunity [1]. *Candidiasis* - **Oropharyngeal** and **esophageal candidiasis** are common opportunistic infections in AIDS patients, often indicating significant immune suppression [2,3]. - The fungus *Candida albicans* can proliferate unchecked when the **CD4 count** is low [2]. *Kaposi's sarcoma* - This is a **cancer** caused by the **human herpesvirus 8 (HHV-8)**, which is a classic AIDS-defining illness [3]. - Its presence indicates severe immunodeficiency and was a hallmark of the early AIDS epidemic [3]. *Cytomegalovirus infection* - **Cytomegalovirus (CMV)** can cause severe and widespread disease in AIDS patients, including **retinitis**, **colitis**, and **encephalitis** [2]. - It becomes a significant risk when the **CD4 count** drops below 100 cells/mm³ [2].

Q: What is the therapy of choice for pseudomembranous enterocolitis?

Vancomycin. ***Vancomycin*** - **Oral vancomycin** is indicated for pseudomembranous enterocolitis, particularly for severe or recurrent cases, as it achieves high luminal concentrations in the colon to target *C. difficile* [1]. - Vancomycin works by inhibiting **bacterial cell wall synthesis**, effectively eradicating the toxigenic *C. difficile* strains responsible for the condition [1]. *Penicillin* - **Penicillin** is ineffective against *C. difficile* because *C. difficile* is a Gram-positive anaerobic bacterium producing toxins, and penicillin does not have the appropriate spectrum of activity. - In fact, many cases of pseudomembranous enterocolitis are triggered by prior **antibiotic use**, including penicillins, which disrupt the normal gut flora [2]. *Ampicillin* - Similar to penicillin, **ampicillin** is a broad-spectrum penicillin derivative and is not considered a treatment for *C. difficile* infection [3]. - Ampicillin can commonly be one of the **antibiotics that precipitates** the development of pseudomembranous enterocolitis by altering the normal gut microbiota [2]. *Erythromycin* - **Erythromycin**, a macrolide antibiotic, is not effective against *C. difficile* and is not used in the treatment of pseudomembranous enterocolitis. - Like other broad-spectrum antibiotics, erythromycin can **disrupt the normal gut flora**, potentially contributing to the overgrowth of *C. difficile* [2].

Question 1

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

Accepted Answer

Campylobacter infection

Answer

Cryptosporidiosis

Answer

Clostridium perfringes infection

Answer

Giardiasis

Question 2

Risk of pneumococcal meningitis is seen in whom?

Accepted Answer

Post splenectomy patient

Answer

Patient undergone neurosurgical intervention

Answer

Patient following cardiac surgery

Answer

Patient with hypoplasia of lung

Question 3

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

Accepted Answer

Vomiting (emetic type)

Answer

Abdominal cramps

Answer

Fever (uncommon)

Answer

Diarrhea (diarrheal type)

Question 4

Which of the following is the treatment of choice for cryptococcal meningitis?

Accepted Answer

Amphotericin B

Answer

Fluconazole

Answer

Itraconazole

Answer

Flucytosine

Question 5

Which of the following statements regarding giardiasis is false?

Accepted Answer

Bloody diarrhea

Answer

Metronidazole is the drug of choice

Answer

Absence of fever

Answer

Diarrhea with steatorrhea

Question 6

Which of the following is NOT typically seen in cerebrospinal fluid (CSF) in tubercular meningitis?

Accepted Answer

Low opening pressure

Answer

Low sugar

Answer

High protein

Answer

Lymphocytic Pleocytosis

Question 7

Maximum infection of CMV is seen after what duration post-transplantation?

Accepted Answer

1-4 months

Answer

Immediate

Answer

< 1 month

Answer

> 6 months

Question 8

Which of the following statements regarding the management of a nurse who got an accidental prick from an HIV-infected needle is true? Select the correct option.

Accepted Answer

Follow-up HIV testing is performed only at 6 months post-exposure.

Answer

Post-exposure prophylaxis should be started within 72 hours of exposure.

Answer

Viral markers are checked at the time of the prick.

Answer

Lamivudine is used as monotherapy in post-exposure prophylaxis.

Question 9

Which of the following is not considered an opportunistic infection in AIDS?

Accepted Answer

Rubella

Answer

Candidiasis

Answer

Kaposi's sarcoma

Answer

Cytomegalovirus infection

Question 10

What is the therapy of choice for pseudomembranous enterocolitis?

Accepted Answer

Vancomycin

Answer

Penicillin

Answer

Ampicillin

Answer

Erythromycin

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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