Infectious Diseases Practice Questions

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: 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: An 11-year-old boy presented with a cough for 15 days. On examination, he was found to have cervical lymphadenopathy. Lymph node biopsy showed the following findings. What could be the diagnosis?

Tuberculosis. ***Tuberculosis*** - The image likely displays **granulomatous inflammation** with **caseous necrosis**, which is highly characteristic of **tuberculosis**, especially in someone presenting with a persistent cough and lymphadenopathy. - The presence of **cervical lymphadenopathy** along with a **cough** for 15 days in an 11-year-old boy points towards extrapulmonary tuberculosis or primary tuberculosis infection affecting the mediastinal lymph nodes with cervical involvement. *Leprosy* - While leprosy also causes granulomas, it typically manifests as skin lesions and nerve involvement, and lymphadenopathy is less common or specific as the primary initial presentation. - The granulomas in leprosy are often **epithelioid** with **foamy histiocytes** and numerous acid-fast bacilli, which are not explicitly described or obvious in the provided context for a definitive diagnosis without special stains. *Sarcoidosis* - Sarcoidosis involves **non-caseating granulomas**, meaning there is no central necrosis, which is a key differentiating feature from the caseating necrosis often seen in tuberculosis. - Although sarcoidosis can cause lymphadenopathy and cough, the microscopic features in the image, particularly if showing necrosis, would argue against sarcoidosis. *Syphilis* - Syphilis can cause lymphadenopathy (especially in secondary syphilis), but the characteristic histological finding is usually a **plasma cell-rich infiltrate** with **endarteritis obliterans**, not typically prominent granulomas with caseous necrosis. - Clinical presentation with cough and chronic lymphadenopathy in an 11-year-old would also make syphilis a less likely primary consideration without other suggestive signs.

Q: Punched out ulcers in the esophagus are most commonly associated with which of the following conditions?

CMV. ***Oesophagitis*** - Characterized by **punched-out ulcers** in the esophagus, often related to infectious causes. - Common in patients with **immunocompromised** states, where mucosal inflammation leads to these distinctive lesions [1]. *cmv* - Typically associated with **shallow ulcers** and **larger lesions**, not specifically "punched-out" ulcers. - CMV esophagitis usually presents with **linear ulcerations** and is less common in the absence of immune deficiency [1]. *candida* - Characterized by **white plaques** or pseudomembranes rather than **punched-out ulcers**. - Common in individuals with **oral thrush** and presents as **esophageal symptoms** such as dysphagia [1]. *herpes* - Often leads to **sharp, serpiginous ulcers** that are distinct from the punched-out variety. - Typically associated with **oral lesions** and presents with acute severe pain while swallowing [1]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Alimentary System Disease, pp. 347-348.

Q: A patient presents with hoarseness of voice and a clinical condition as shown in the image. Identify the lesion:

Diphtheria. ***Diphtheria*** - The image shows a **thick, grayish-white pseudomembrane** covering the tonsils and likely extending to other parts of the pharynx, which is a classic sign 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. *Membranous tonsillitis* - While "membranous tonsillitis" describes the presence of a membrane on the tonsils, this term is often used generally. However, the specific characteristics in the image (thick, grayish, adherent membrane with severe symptoms like hoarseness) are pathognomonic for **diphtheria**. - Other causes of membranous tonsillitis, such as infectious mononucleosis, typically present with a less adherent membrane and often lack the severe systemic toxicity and potential for rapid airway compromise seen in diphtheria.

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: 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].

Question 1

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 2

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 3

An 11-year-old boy presented with a cough for 15 days. On examination, he was found to have cervical lymphadenopathy. Lymph node biopsy showed the following findings. What could be the diagnosis?

Accepted Answer

Tuberculosis

Answer

Leprosy

Answer

Sarcoidosis

Answer

Syphilis

Question 4

Punched out ulcers in the esophagus are most commonly associated with which of the following conditions?

Accepted Answer

CMV

Answer

Reflux esophagitis

Answer

Herpes simplex virus (HSV)

Answer

Candida

Question 5

A patient presents with hoarseness of voice and a clinical condition as shown in the image. Identify the lesion:

Accepted Answer

Diphtheria

Answer

Follicular tonsillitis

Answer

Aphthous ulcer

Answer

Membranous tonsillitis

Question 6

Which condition is most commonly associated with cryoglobulinemia?

Accepted Answer

Hepatitis C

Answer

Ovarian cancer

Answer

Diabetes

Answer

Leukemia

Question 7

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 8

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 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

Which is not included in AIDS related complex?

Accepted Answer

Ectopic pregnancy

Answer

Recurrent genital candidiasis

Answer

Generalised lymphadenopathy

Answer

Chronic diarrhea

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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