Infectious Diseases Practice Questions

Q: After 4 months of renal transplantation, which infection is most likely to develop?

Cytomegalovirus (CMV). ***Cytomegalovirus (CMV)*** - **CMV infection** or reactivation is most common in transplant recipients between 1 and 6 months post-transplantation, often peaking around 3-4 months when immunosuppression is high [1]. - It can cause a wide range of clinical syndromes, including **fever**, **leukopenia**, **gastroenteritis**, and organ-specific disease in immunocompromised individuals [1]. *EBV* - **Epstein-Barr virus (EBV)** is primarily associated with **post-transplant lymphoproliferative disorder (PTLD)**, which tends to occur later, typically more than 6 months after transplantation, especially in pediatric recipients [1]. - While EBV can reactivate, severe clinical disease or PTLD is less likely to peak at 4 months compared to CMV [1]. *Candida* - **Candida infections** are typically **early complications** after transplantation, usually occurring within the first month [1]. - They are often related to indwelling catheters, antibiotics, and surgical anastomoses, making them less likely to be the most common infection at 4 months. *Histoplasma* - **Histoplasma capsulatum** causes **histoplasmosis**, a fungal infection prevalent in endemic areas (e.g., Ohio and Mississippi River valleys). - While possible in immunocompromised patients, it's generally an **opportunistic infection** that can occur at any time, but is less specific to the 4-month post-transplant window compared to CMV.

Q: An incompletely immunized patient presents with hoarseness of voice, cervical lymphadenopathy, and a clinical condition as shown in the image. The membrane seen bleeds on attempted removal. Identify the lesion:

Diphtheria. ***Diphtheria*** - The image shows a **thick, grayish-white pseudomembrane** covering the tonsils, which is suggestive of diphtheria when supported by the clinical context. - The membrane bleeds on attempted removal, the patient is incompletely immunized, and there is cervical lymphadenopathy — findings that together support a diagnosis of diphtheria. - **Hoarseness** indicates laryngeal involvement, a severe complication of diphtheria due to pseudomembrane formation extending to the larynx, potentially causing airway obstruction. *Follicular tonsillitis* - This condition presents with **pus-filled follicles** or spots on the tonsils, which are typically yellow or white, rather than a confluent membrane. - While it causes throat pain and fever, it generally does not lead to the formation of a **firm, adherent pseudomembrane** or significant hoarseness from laryngeal obstruction as seen in diphtheria. *Aphthous ulcer* - An aphthous ulcer is a **small, painful, shallow sore** with a white or yellowish center and a red border, typically found on the non-keratinized oral mucosa. - It does not present as a widespread, thick membranous lesion covering the tonsils and causing hoarseness. *Infectious mononucleosis* - Infectious mononucleosis can cause a tonsillar membrane, but the membrane is typically less adherent and does not bleed on removal. - It is associated with systemic features such as posterior cervical lymphadenopathy, splenomegaly, and a positive monospot test, and lacks the severe airway compromise characteristic of diphtheria.

Q: What are the essential major blood culture criteria for diagnosing infective endocarditis?

Single positive culture of Coxiella burnetii. ***Single positive culture of Coxiella burnetii*** - A single positive blood culture for **Coxiella burnetii** or **anti-phase I IgG antibody titer > 1:800** is considered a major criterion for infective endocarditis due to its highly pathogenic nature in this context [1], [2]. - This organism is a known cause of **culture-negative endocarditis**, and specific serology or molecular tests are often required for diagnosis [1]. *Single positive culture of Corynebacterium species* - **Corynebacterium species** are often considered **contaminants** in blood cultures, especially *Corynebacterium jeikeium*, and typically require multiple positive cultures, often from different sites, to be considered significant pathogens for infective endocarditis [2]. - A single positive culture of these organisms alone is generally insufficient to meet major diagnostic criteria for endocarditis [2]. *Both HACEK and Coxiella cultures* - While both **HACEK organisms** and **Coxiella burnetii** can cause endocarditis, the combination of both is not a specific major criterion in itself. - The diagnostic criteria address each organism individually [2]. *Single positive culture of HACEK group* - **HACEK organisms** (**H**aemophilus, **A**ggregatibacter, **C**ardiobacterium, **E**ikenella, **K**ingella) are well-known causes of endocarditis, but usually require **two separate positive blood cultures** for infective endocarditis major criteria [2]. - A single positive culture of a HACEK organism is typically classified as a minor criterion unless other supporting evidence is present.

Q: Which of the following conditions is least associated with HIV infection?

Tertiary syphilis. ***Tertiary syphilis*** - While syphilis can be more aggressive in HIV-positive individuals, **tertiary syphilis** (e.g., gummas, neurosyphilis, cardiovascular syphilis) is not specifically or exclusively associated with HIV infection itself, but rather the untreated progression of syphilis within an immunocompromised host [1]. - The other conditions listed are **AIDS-defining illnesses** or strongly associated with the severe immunodeficiency caused by HIV [1]. *Oesophageal candidiasis* - This is an **AIDS-defining illness**, indicating severe immunosuppression in HIV-positive individuals [1]. - It results from an overgrowth of *Candida albicans* due to a compromised immune system [1]. *Kaposi sarcoma* - This is a cancer caused by **human herpesvirus 8 (HHV-8)**, and its incidence is significantly increased in HIV-infected individuals, leading to its classification as an **AIDS-defining illness** [1]. - It presents as vascular lesions on the skin, mucous membranes, lymph nodes, or internal organs [1]. *Primary CNS lymphoma* - This is another **AIDS-defining illness** that occurs with increased frequency in HIV-positive individuals, particularly those with advanced immunosuppression [1]. - It is often associated with the **Epstein-Barr virus (EBV)** in this population [1].

Q: Which is not included in AIDS related complex?

Ectopic pregnancy. ***Ectopic pregnancy*** - **Ectopic pregnancy** is a gynecological condition related to reproductive health and is **not a direct manifestation** of HIV infection or one of the opportunistic infections/conditions characteristic of AIDS-related complex. - While HIV can affect overall health during pregnancy, an ectopic pregnancy itself is a different medical issue. *Recurrent genital candidiasis* - **Recurrent genital candidiasis** can be a sign of **diminished immune function** in HIV-positive women [1]. - It is often considered an AIDS-defining condition or a common opportunistic infection seen in the progression of HIV to AIDS-related complex [1]. *Generalised lymphadenopathy* - **Generalized lymphadenopathy**, specifically **persistent generalized lymphadenopathy (PGL)**, is a common early manifestation of HIV infection [1]. - It reflects ongoing immune activation and is part of the spectrum of conditions included in AIDS-related complex [1]. *Chronic diarrhea* - **Chronic diarrhea** (lasting more than one month) is a frequent and significant symptom in individuals with HIV infection, particularly as the disease progresses [1]. - It can be caused by various opportunistic infections or directly by HIV, and is a component of AIDS-related complex or AIDS-defining illness [1].

Q: Which condition is most commonly associated with cryoglobulinemia?

Hepatitis C. **Hepatitis C** - **Hepatitis C virus (HCV) infection** is the most common cause of mixed cryoglobulinemia, with cryoglobulins being detected in a high percentage of infected individuals. - The chronic immune stimulation caused by HCV leads to the production of **monoclonal or polyclonal immunoglobulins** (cryoglobulins) that precipitate in the cold. *Ovarian cancer* - While certain malignancies can be associated with paraneoplastic syndromes, **ovarian cancer** is not typically linked to cryoglobulinemia. - Cryoglobulinemia is more commonly associated with **lymphoproliferative disorders** or chronic infections rather than solid tumors like ovarian cancer. *Diabetes* - **Diabetes mellitus** is not directly associated with cryoglobulinemia; it is a metabolic disorder affecting glucose regulation. - Complications of diabetes include microvascular and macrovascular disease, but not primary cryoglobulin formation. *Leukemia* - Certain hematological malignancies, particularly **lymphoproliferative disorders like Waldenström macroglobulinemia or multiple myeloma**, can be associated with cryoglobulinemia. - However, **leukemia** (especially acute forms) is less commonly linked to cryoglobulinemia than chronic infections like hepatitis C or certain B-cell lymphomas.

Q: Which of the following is a common neurological manifestation of neurosyphilis?

Tabes dorsalis. ***Tabes dorsalis*** - This is a late-stage manifestation of **neurosyphilis** characterized by the degeneration of the **dorsal columns** and dorsal roots of the spinal cord. - Clinical features include **shooting pains**, **ataxia**, **loss of proprioception**, and Argyll Robertson pupils. *Alzheimer's disease* - This is a progressive **neurodegenerative disease** causing **dementia**, primarily due to the accumulation of **amyloid plaques** and **neurofibrillary tangles** [1]. - Its pathology is distinct from neurosyphilis, which is caused by a bacterial infection (**_Treponema pallidum_**). *Parkinson's disease* - A **neurodegenerative disorder** characterized by the loss of **dopaminergic neurons** in the substantia nigra [1]. - Presents with motor symptoms like **tremor**, rigidity, **bradykinesia**, and postural instability, which are not typical of neurosyphilis [1]. *None of the above* - This option is incorrect because **tabes dorsalis** is a well-established and common neurological manifestation of neurosyphilis. - The other options represent distinct neurological conditions with different etiologies and pathologies.

Q: Most common organism associated with reactive arthritis is:

Chlamydia. ***Chlamydia*** - **Chlamydia trachomatis** is a commonly identified pathogen causing **genitourinary infections** that can trigger reactive arthritis [1]. - The organism itself is not present in the joint, but its antigens trigger an immune response leading to sterile arthritis [1]. *Staphylococcus* - **Staphylococcus aureus** is a common cause of septic arthritis, which involves direct bacterial invasion of the joint. - Reactive arthritis is a **sterile arthritis** triggered by an infection elsewhere, not directly caused by staphylococcal joint infection. *Shigella* - While **Shigella** is a known enteric pathogen that can trigger reactive arthritis, it is less commonly associated with the condition globally compared to Chlamydia [1]. - Reactive arthritis often follows episodes of **dysentery** caused by Shigella species [1]. *Yersinia* - **Yersinia enterocolitica** is another enteric bacterium that can induce reactive arthritis, typically after **gastrointestinal infections**. - Its prevalence as a trigger for reactive arthritis is generally lower than that of Chlamydia.

Question 1

After 4 months of renal transplantation, which infection is most likely to develop?

Accepted Answer

Cytomegalovirus (CMV)

Answer

EBV

Answer

Candida

Answer

Histoplasma

Question 2

An incompletely immunized patient presents with hoarseness of voice, cervical lymphadenopathy, and a clinical condition as shown in the image. The membrane seen bleeds on attempted removal. Identify the lesion:

Accepted Answer

Diphtheria

Answer

Follicular tonsillitis

Answer

Aphthous ulcer

Answer

Infectious mononucleosis

Question 3

What are the essential major blood culture criteria for diagnosing infective endocarditis?

Accepted Answer

Single positive culture of Coxiella burnetii

Answer

Single positive culture of Corynebacterium species

Answer

Both HACEK and Coxiella cultures

Answer

Single positive culture of HACEK group

Question 4

Which of the following conditions is least associated with HIV infection?

Accepted Answer

Tertiary syphilis

Answer

Kaposi sarcoma

Answer

Oesophageal candidiasis

Answer

Primary CNS lymphoma

Question 5

What is the most appropriate antibiotic choice for a bedridden patient with catheter-related urinary tract infection (UTI) and pneumonia?

Accepted Answer

Piperacillin-tazobactam

Answer

Amoxicillin

Answer

3rd gen cephalosporins

Answer

2nd gen cephalosporins

Question 6

What is the most commonly recommended COMPLETE antiretroviral regimen for a pregnant woman with HIV infection?

Accepted Answer

Tenofovir disoproxil fumarate/emtricitabine/dolutegravir

Answer

Abacavir/lamivudine

Answer

Didanosine/stavudine

Answer

Tenofovir disoproxil fumarate/emtricitabine (2-drug regimen)

Question 7

Which is not included in AIDS related complex?

Accepted Answer

Ectopic pregnancy

Answer

Recurrent genital candidiasis

Answer

Generalised lymphadenopathy

Answer

Chronic diarrhea

Question 8

Which condition is most commonly associated with cryoglobulinemia?

Accepted Answer

Hepatitis C

Answer

Ovarian cancer

Answer

Diabetes

Answer

Leukemia

Question 9

Which of the following is a common neurological manifestation of neurosyphilis?

Accepted Answer

Tabes dorsalis

Answer

Alzheimer's disease

Answer

Parkinson's disease

Answer

None of the above

Question 10

Most common organism associated with reactive arthritis is:

Accepted Answer

Chlamydia

Answer

Staphylococcus

Answer

Shigella

Answer

Yersinia

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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