Infectious Diseases Practice Questions

Q: Asymptomatic HIV-positive patient has RPR 1:128, TPHA positive. No symptoms or signs. Previous syphilis treatment 2 years ago with documented 4-fold decline in titers. Most appropriate next step is:

CSF examination. ***CSF examination*** - In an HIV-positive patient with a **high RPR titer (1:128)** and a history of previous syphilis treatment, **neurosyphilis** must be ruled out, even without neurological symptoms. This is because **HIV can alter the natural history of syphilis**, increasing the risk of neurological involvement. - A **CSF examination** is crucial to look for signs of neurosyphilis, such as elevated white blood cell count, elevated protein, or a reactive VDRL, which would necessitate different and more aggressive treatment. *Repeat RPR in 3 months* - While monitoring RPR titers is important, a high titer of 1:128 in an HIV-positive patient is concerning enough to warrant immediate investigation rather than just observation [1]. Waiting 3 months could delay diagnosis and treatment of potential neurosyphilis. - This option is more appropriate if the patient had a **declining or stable low titer** and no prior history of high titers or if the clinical concern for active infection was lower. *Treat as reinfection* - While a high RPR titer *can* indicate reinfection, the most appropriate first step in an HIV-positive patient with a high titer and a history of prior treatment is to rule out **neurosyphilis** before automatically treating for uncomplicated reinfection. - Treating for reinfection without CSF evaluation could miss or delay the appropriate treatment for neurosyphilis, which requires a longer course of intravenous antibiotics. *Treat as late latent syphilis* - Late latent syphilis is typically characterized by **asymptomatic infection** of more than one year duration or unknown duration, with a reactive serology but no clinical signs [1]. However, the presence of **HIV** and a **very high RPR titer** changes the diagnostic approach significantly. - Treating for late latent syphilis without ruling out neurosyphilis would be inadequate if neurological involvement is present, as the treatment regimens differ.

Q: Assertion: HIV-positive patients with syphilis should receive the same treatment as HIV-negative patients. Reason: Serological response to treatment is similar in both groups.

A is true but R is false. **_A is true but R is false_** * **HIV-positive patients with syphilis** often have altered immune responses, leading to atypical presentations and a higher risk of **neurological complications** and treatment failure. Therefore, treatment regimens often need to be modified, such as extending the duration of therapy or using higher doses, especially for early syphilis in HIV-positive patients. * **Serological response** in HIV-positive individuals is often **less predictable** and may be slower or show less robust decline in antibody titers compared to HIV-negative individuals, making routine follow-up testing crucial. * The assertion that serological response is similar in both groups is **false** because HIV can affect the immune response to syphilis, potentially blunting the serological response to treatment and making interpretation more challenging.

Q: A 65-year-old woman with recurrent herpes labialis develops erosions on hand and foot after starting systemic chemotherapy. Most appropriate antiviral prophylaxis is:

Oral acyclovir 400mg twice daily. ***Oral acyclovir 400mg twice daily*** - **Standard prophylactic regimen** for HSV suppression in **immunocompromised patients** undergoing chemotherapy - **Acyclovir 400mg BID** is well-established, cost-effective, and provides adequate systemic coverage to prevent recurrent HSV outbreaks and complications like eczema herpeticum - This dosing is recommended by major guidelines (CDC, IDSA) for **long-term suppressive therapy** in immunosuppressed individuals - The patient's erosions on hands and feet after starting chemotherapy indicate reactivation requiring systemic prophylaxis *Oral valacyclovir 500mg daily* - Valacyclovir has **superior bioavailability** compared to acyclovir, but **500mg once daily is insufficient** for immunocompromised patients - For chemotherapy patients, valacyclovir prophylaxis requires **500mg TWICE daily**, not once daily - Once-daily dosing (500mg) is appropriate only for **immunocompetent** patients with recurrent HSV *Topical acyclovir only* - **Topical antivirals** are inadequate for preventing systemic or widespread HSV reactivation in immunocompromised patients - The presentation of **erosions on hands and feet** suggests disseminated or eczema herpeticum, requiring **systemic therapy** - Topical agents have poor penetration and are only suitable for limited, localized mucocutaneous lesions *Oral famciclovir 250mg daily* - **250mg once daily is subtherapeutic** for HSV prophylaxis in immunocompromised patients - Standard suppressive famciclovir dosing is **250mg TWICE daily** or 500mg once daily for immunocompetent patients - For chemotherapy patients, higher or more frequent dosing would be needed, making this option incorrect

Q: A patient comes to ED with fever and headache. On examination he has neck stiffness. CSF analysis was done: Glucose 55 mg/dl (normal 50-80), Protein 0.50 g/L (normal 0.18-0.45), ICT 35 cmH2O (normal 5-20), WBC 25 (predominantly lymphocytes). Most likely diagnosis is:

Coxsackie. ***Coxsackie*** - The CSF analysis shows **normal glucose**, **mildly elevated protein**, **moderately elevated opening pressure**, and a **淋巴细胞主导** pleocytosis, which are characteristic findings in **viral meningitis**, commonly caused by enteroviruses such as Coxsackie virus [1]. - The combination of **fever, headache, neck stiffness**, and the specific CSF profile strongly points towards a viral etiology [1]. *Cryptococcus* - While fungal meningitis can present with similar symptoms and lymphocyte-dominant pleocytosis, it typically causes **markedly low CSF glucose** and **higher protein levels** than observed here. - Diagnosis usually requires specific tests like **India ink stain** or **cryptococcal antigen detection**, which are not indicated by these CSF findings. *TB* - Tuberculous meningitis usually presents with **very low CSF glucose** (often 1 g/L), and predominantly **lymphocytic pleocytosis**, often with a very slow onset [2]. - The CSF profile in this case, particularly the normal glucose, makes TB less likely [2]. *N. Gonorrhea* - *Neisseria gonorrhoeae* can cause **meningitis**, but it is generally a rare presentation and usually results in **neutrophilic pleocytosis** in the CSF, similar to other bacterial meningitides. - The **lymphocytic predominance** in this patient's CSF makes *N. gonorrhoeae* an unlikely cause.

Q: Pulmonary manifestation for inhalational anthrax is:

Hemorrhagic mediastinitis. ***Hemorrhagic mediastinitis*** - Inhalational anthrax is characterized by the rapid development of **hemorrhagic mediastinitis** due to direct bacterial infection and subsequent toxin-induced vascular damage in the mediastinal lymph nodes. - This leads to a widened mediastinum on chest imaging, often with **pleural effusions** and surrounding edema. *Lobar consolidation* - **Lobar consolidation** is more typical of common bacterial pneumonias, such as those caused by *Streptococcus pneumoniae* or *Klebsiella pneumoniae* [1]. - While pulmonary symptoms occur in anthrax, it is not primarily a direct lobar parenchymal infection but rather an infection of the **mediastinal lymph nodes**. *Bronchopneumonia with type two respiratory failure* - **Bronchopneumonia** involves patchy inflammation centered around bronchioles, which is not the primary pattern of lung involvement in inhalational anthrax. - **Type 2 respiratory failure** (hypercapnic respiratory failure) results from ventilation-perfusion mismatch or hypoventilation, but its direct association with this specific anthrax manifestation is less characteristic compared to the hemorrhagic mediastinitis. *Can cause pneumonia* - While inhalational anthrax can lead to severe pulmonary symptoms and acute respiratory failure, describing it simply as "pneumonia" is insufficient as it fails to capture the unique and critical finding of **hemorrhagic mediastinitis**. - The disease's characteristic features, such as mediastinal widening and hemorrhage, differentiate it from typical bacterial pneumonias.

Q: Cerebrospinal fluid analysis shows lymphocytic pleocytosis, elevated protein, and low glucose. AFB stain positive. Likely diagnosis?

TB meningitis. ***TB meningitis*** - The combination of **lymphocytic pleocytosis**, **elevated protein**, and **low glucose** in CSF, along with a **positive AFB stain**, is highly indicative of **tuberculous meningitis** [1]. - **Mycobacterium tuberculosis** is an acid-fast bacillus (AFB) and causes a chronic inflammatory response in the meninges, leading to characteristic CSF changes [2]. *Bacterial meningitis* - Typically presents with **neutrophilic pleocytosis**, **markedly elevated protein**, and **very low glucose**, which differs from the lymphocytic predominance seen here [3]. - While bacteria can cause low glucose, the positive AFB stain rules out common bacterial causes. *Viral meningitis* - Characterized by **lymphocytic pleocytosis** and normal to mildly elevated protein, but usually has **normal glucose levels** [4]. - No specific staining like AFB would be positive in viral meningitis. *Fungal meningitis* - May show **lymphocytic pleocytosis**, elevated protein, and low glucose, similar to TB meningitis. - However, **AFB stain** would be **negative**, and diagnosis would rely on fungal stains or cultures.

Q: Which of the following markers persists in chronic hepatitis B and recurrent hepatitis B?

IgG Anti HbcAg. ### IgG Anti HbcAg - **IgG anti-HBc** (antibody to hepatitis B core antigen) persists throughout chronic hepatitis B infection and is also present during recurrent hepatitis B after liver transplantation, indicating past or ongoing infection [1]. - This antibody targets the **viral core antigen**, which is present in infected hepatocytes and is not circulating, thus the presence of IgM anti-HBc indicates an acute infection, while IgG anti-HBc indicates chronic or past infection [1]. ### Anti Hbs - **Anti-HBs** (antibody to hepatitis B surface antigen) indicates **immunity** to hepatitis B, either from vaccination or successful resolution of a past infection [1]. - It would typically be present in someone who has cleared the virus or been vaccinated, not in chronic or recurrent active infection. ### HBsAg - **HBsAg** (hepatitis B surface antigen) indicates an active hepatitis B infection, either acute or chronic [1]. While present in chronic hepatitis, its persistence alone doesn't specifically define recurrence, as it's the primary marker of chronic infection. - In recurrent hepatitis B after liver transplant, HBsAg would reappear, but **IgG anti-HBc** is also crucial for confirming the presence of the virus [1]. ### Anti-HBs - **Anti-HBs** (antibody to hepatitis B surface antigen) is a marker of **immunity** and indicates successful resolution of an infection or vaccination [1]. - Its presence signifies protection against the virus and would not be consistently high in the setting of persistent chronic or recurrent active infection.

Q: Dengue discharge protocol includes:

Return of normal appetite. ***Return of normal appetite*** - A **normal appetite** indicates that the patient's overall condition and gastrointestinal function are improving, suggesting recovery from the acute phase of dengue. - This is a key clinical sign that contributes to deciding whether a patient is stable enough for discharge. *Urine output > 0.5 ml/kg/hr* - While adequate **urine output** is important for assessing renal function and hydration status in dengue, a value of >0.5 ml/kg/hr is generally considered the *minimum adequate output* and is not, by itself, a specific discharge criterion. - Normal urine output is often cited as at least 1 mL/kg/hr, especially in children, and simply meeting the bare minimum does not guarantee full recovery. *24 hours after Recovery from shock* - Recovery from **shock** is a critical milestone, but discharge typically requires a longer period of observation and stability after the resolution of severe symptoms. - Patients are generally observed for at least **48 hours** after recovery from shock to ensure no relapse or complications before considering discharge. *24 hours after absence of fever without antipyretics* - The absence of **fever for 24 hours** without antipyretics is an important criterion for ruling out ongoing active infection, but for dengue, global guidelines often recommend a fever-free period of **48 hours** or more for discharge. - This longer observation period helps confirm that the patient has moved past the critical phase and is not at risk of re-developing complications.

Question 1

Asymptomatic HIV-positive patient has RPR 1:128, TPHA positive. No symptoms or signs. Previous syphilis treatment 2 years ago with documented 4-fold decline in titers. Most appropriate next step is:

Accepted Answer

CSF examination

Answer

Repeat RPR in 3 months

Answer

Treat as reinfection

Answer

Treat as late latent syphilis

Question 2

Assertion: HIV-positive patients with syphilis should receive the same treatment as HIV-negative patients.
Reason: Serological response to treatment is similar in both groups.

Accepted Answer

A is true but R is false

Answer

Both A and R are false

Answer

Both A and R are true, R explains A

Answer

Both A and R are true, R doesn't explain A

Question 3

A 65-year-old woman with recurrent herpes labialis develops erosions on hand and foot after starting systemic chemotherapy. Most appropriate antiviral prophylaxis is:

Accepted Answer

Oral acyclovir 400mg twice daily

Answer

Topical acyclovir only

Answer

Oral valacyclovir 500mg daily

Answer

Oral famciclovir 250mg daily

Question 4

A nurse got accidental prick from the HIV infected needle. Which of the following statements is false regarding the management of this nurse?

Accepted Answer

Zidovudine is used as monotherapy for post-exposure prophylaxis

Answer

Follow up viral markers of health care personnel should be measured at 6 weeks

Answer

Baseline viral markers of health care personnel should be done at the time of presentation

Answer

Washing hands with soap and water is advised

Question 5

A patient comes to ED with fever and headache. On examination he has neck stiffness. CSF analysis was done: Glucose 55 mg/dl (normal 50-80), Protein 0.50 g/L (normal 0.18-0.45), ICT 35 cmH2O (normal 5-20), WBC 25 (predominantly lymphocytes). Most likely diagnosis is:

Accepted Answer

Coxsackie

Answer

Cryptococcus

Answer

TB

Answer

N. Gonorrhea

Question 6

Pulmonary manifestation for inhalational anthrax is:

Accepted Answer

Hemorrhagic mediastinitis

Answer

Lobar consolidation

Answer

Bronchopneumonia with type two respiratory failure

Answer

Can cause pneumonia

Question 7

Cerebrospinal fluid analysis shows lymphocytic pleocytosis, elevated protein, and low glucose. AFB stain positive. Likely diagnosis?

Accepted Answer

TB meningitis

Answer

Bacterial meningitis

Answer

Viral meningitis

Answer

Fungal meningitis

Question 8

Which of the following markers persists in chronic hepatitis B and recurrent hepatitis B?

Accepted Answer

IgG Anti HbcAg

Answer

Anti Hbs

Answer

HBsAg

Answer

Anti-HBs

Question 9

Dengue discharge protocol includes:

Accepted Answer

Return of normal appetite

Answer

Urine output > 0.5 ml/kg/hr

Answer

24 hours after Recovery from shock

Answer

24 hours after absence of fever without antipyretics

Question 10

A patient with HIV develops CMV retinitis at CD4 count of 75/µL. When can prophylaxis be stopped?

Accepted Answer

CD4 >200/µL for 3 months

Answer

CD4 >100/µL

Answer

After 6 months of treatment

Answer

Viral load undetectable

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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