Infections in Immunocompromised Host — MCQs
The combination of trimethoprim and sulfamethoxazole is effective against which of the following opportunistic infections in the AIDS patient?
AIDS, secondary infection will be all except
Which of the following is NOT seen in an HIV patient with a CD4 count less than 100 per microliter, who has a non-productive cough?
A 50-year-old woman is discovered to have metastatic breast cancer and develops bacterial pneumonia one week after receiving her first dose of chemotherapy. Which of the following best explains this patient's susceptibility to bacterial infection?
Most common infection post solid organ transplantation
A 25-year-old woman presents with a sudden onset of high fever, chills, and rigors. Blood cultures are pending. What is the next appropriate step in her management?
A 36 years male presented with complaint of productive cough and fever for last 2 months. He has undergone kidney transplantation 2 years back. His sputum examination revealed a gram positive filamentous bacteria that showed acid fastness with modified Ziehl-Neelsen staining (1% H2SO4). The most likely etiological agent is ?
In an HIV-infected individual, the Gram stain of lung aspirate shows yeast-like morphology. Which of the following is the least likely diagnosis?
What is the period called between the entry of an organism into the host and the point of maximum infectivity?
Which of the following can be prevented by transfusing irradiated RBCs?
Infections in Immunocompromised Host Indian Medical PG Practice Questions and MCQs
Question 1: The combination of trimethoprim and sulfamethoxazole is effective against which of the following opportunistic infections in the AIDS patient?
- A. Disseminated Herpes simplex infection
- B. Cryptococcal meningitis infection
- C. Tuberculosis infection
- D. Pneumocystis jirovecii (Correct Answer)
Explanation: ***Pneumocystis jiroveci*** - **Pneumocystis pneumonia (PCP)**, caused by *Pneumocystis jirovecii*, is a common and severe opportunistic infection in AIDS patients. - ** Trimethoprim-sulfamethoxazole (TMP-SMX)**, also known as Bactrim, is the **drug of choice** for both treatment and prophylaxis of PCP [1], [2]. *Disseminated Herpes simplex infection* - **Herpes simplex virus (HSV)** infections are typically treated with antiviral medications like **acyclovir, valacyclovir, or famciclovir**. - TMP-SMX has **no antiviral activity** and is ineffective against HSV. *Cryptococcal meningitis infection* - **Cryptococcal meningitis** is a fungal infection primarily treated with **amphotericin B** in combination with **flucytosine**, followed by fluconazole for maintenance. - TMP-SMX is **not active** against *Cryptococcus neoformans*. *Tuberculosis infection* - **Tuberculosis (TB)**, caused by *Mycobacterium tuberculosis*, requires a **multi-drug regimen** typically including isoniazid, rifampin, pyrazinamide, and ethambutol [3]. - While TMP-SMX has some activity against *Nocardia spp.* and some atypical mycobacteria, it is **not effective** for the treatment of *Mycobacterium tuberculosis*.
Question 2: AIDS, secondary infection will be all except
- A. Candida
- B. Kaposi's sarcoma (Correct Answer)
- C. HSV
- D. Rubella
Explanation: ***Kaposi's sarcoma*** - Kaposi's sarcoma is a **cancer** caused by human herpesvirus 8 (HHV-8) [2] that is common in patients with AIDS, but it is a **malignancy**, not a secondary infection [2],[3]. - While it arises due to immune suppression, it represents abnormal cell proliferation rather than direct microbial invasion. *Candida* - **Candidiasis** (e.g., oral thrush, esophageal candidiasis) is a common opportunistic fungal infection in AIDS patients due to their **impaired cellular immunity** [1]. - It often presents as **white plaques** on mucous membranes and is a clear example of a secondary infection. *HSV* - **Herpes Simplex Virus (HSV)** infections, including oral and genital herpes, are common and often severe in AIDS patients. - Due to immunocompromise, these infections can be **more widespread**, chronic, or recur frequently, qualifying as secondary infections. *Rubella* - **Rubella (German measles)** is a viral infection that is generally mild and self-limiting in immunocompetent individuals. - It is **not considered an opportunistic infection** or a common secondary infection specifically associated with AIDS; rather, it is listed as a differential diagnosis for the primary HIV infection rash [1].
Question 3: Which of the following is NOT seen in an HIV patient with a CD4 count less than 100 per microliter, who has a non-productive cough?
- A. Mycoplasma pneumoniae (Correct Answer)
- B. Pneumocystis jirovecii
- C. Cryptococcal infection
- D. Mycobacterium tuberculosis
Explanation: ***Mycoplasma pneumoniae*** - *Mycoplasma pneumoniae* is an atypical bacterium that causes **community-acquired pneumonia** in immunocompetent individuals. - While it can cause a non-productive cough, it is **not considered an opportunistic infection** in HIV patients with advanced immunosuppression (CD4 < 100), as its incidence is not significantly higher or more severe in this population compared to the general population. *Pneumocystis jirovecii* - **Pneumocystis pneumonia (PCP)** is a classic opportunistic infection in HIV patients, especially when the **CD4 count is below 200 cells/µL** [1]. - It commonly presents with a **non-productive cough**, fever, and dyspnea, and is a strong consideration in this clinical scenario [2]. *Cryptococcal infection* - **Pulmonary cryptococcosis**, caused by *Cryptococcus neoformans*, is an opportunistic infection in advanced HIV disease (CD4 < 100 cells/µL). - It often presents with **non-specific respiratory symptoms** including a non-productive cough, and can disseminate to the central nervous system. *Mycobacterium tuberculosis* - **Tuberculosis (TB)** is a common and serious opportunistic infection in HIV patients, particularly with **advanced immunosuppression** [1]. - Pulmonary TB can present with a **non-productive or productive cough**, fever, and weight loss, and is a significant cause of morbidity and mortality in this population [1].
Question 4: A 50-year-old woman is discovered to have metastatic breast cancer and develops bacterial pneumonia one week after receiving her first dose of chemotherapy. Which of the following best explains this patient's susceptibility to bacterial infection?
- A. Depletion of serum complement
- B. Impaired neutrophil respiratory burst
- C. Inhibition of clotting factor activation
- D. Neutropenia (Correct Answer)
Explanation: ***Neutropenia*** - **Chemotherapy** often causes **bone marrow suppression**, leading to a decrease in the absolute number of **neutrophils**, a condition known as neutropenia. - Neutrophils are crucial for the primary defense against **bacterial and fungal infections**, and their depletion significantly increases susceptibility, especially to **bacterial pneumonia**. *Depletion of serum complement* - While complement deficiency can increase susceptibility to certain infections, it is not a direct or common side effect of typical **chemotherapy regimens**. - Complement deficiencies are often **genetic** or related to specific **autoimmune diseases**, which are not indicated as the primary cause here. *Impaired neutrophil respiratory burst* - Impaired **neutrophil respiratory burst** (e.g., in **chronic granulomatous disease**) leads to a reduced ability to kill ingested bacteria, resulting in recurrent infections. - While chemotherapy can affect neutrophil function, severe impairment of the respiratory burst is not the primary mechanism of increased infection risk one week post-treatment; **neutropenia** is more immediate and profound. *Inhibition of clotting factor activation* - **Inhibition of clotting factor activation** would primarily manifest as **bleeding disorders**, not increased susceptibility to bacterial infections. - Chemotherapy can affect platelet count and function, but this mechanism does not directly explain increased risk of **bacterial pneumonia**.
Question 5: Most common infection post solid organ transplantation
- A. EBV
- B. CMV (Correct Answer)
- C. HSV
- D. HPV
Explanation: ***CMV*** - **Cytomegalovirus (CMV)** is the most common viral infection in solid organ transplant recipients, often reactivating in immunosuppressed patients [1]. - It can cause a wide range of clinical syndromes including **fever**, **leukopenia**, **hepatitis**, **pneumonitis**, and **gastroenteritis**, and is a significant cause of morbidity and mortality [1]. *EBV* - **Epstein-Barr virus (EBV)** is also common in transplant recipients but is most notably associated with **post-transplant lymphoproliferative disorder (PTLD)**, a serious complication [1]. - While present, it is not as frequently the cause of symptomatic infection as CMV in the immediate post-transplant period. *HSV* - **Herpes simplex virus (HSV)** infections can occur, manifesting as mucocutaneous lesions or, less commonly, severe systemic disease in transplant patients. - However, its incidence and severity are generally lower compared to CMV in the overall transplant population. *HPV* - **Human papillomavirus (HPV)** infections are typically associated with **warts** and increased risk of **malignancies** (e.g., anogenital cancers) in immunosuppressed individuals, including transplant recipients. - While important for long-term surveillance, HPV does not represent the most common acute infection post-transplant.
Question 6: A 25-year-old woman presents with a sudden onset of high fever, chills, and rigors. Blood cultures are pending. What is the next appropriate step in her management?
- A. Administer broad-spectrum antibiotics (Correct Answer)
- B. Wait for blood culture results
- C. Start antipyretic therapy only
- D. Order a CT scan
Explanation: ***Administer broad-spectrum antibiotics*** - The patient presents with classic signs of **sepsis** (high fever, chills, rigors), which is a medical emergency requiring prompt intervention [2]. - **Early administration of broad-spectrum antibiotics** is crucial to improve outcomes and reduce mortality in suspected sepsis, even before culture results are available [1]. *Wait for blood culture results* - Delaying antibiotic treatment in a patient with suspected sepsis can lead to rapid clinical deterioration and increased mortality [1]. - While blood cultures are essential to guide definitive therapy, initial empiric broad-spectrum antibiotics should not be withheld [3]. *Start antipyretic therapy only* - Antipyretics only address the symptom of fever and do not treat the underlying infection causing the fever and chills. - This approach would leave the potentially life-threatening infection untreated, leading to worsening patient condition. *Order a CT scan* - A CT scan is not the immediate priority in a patient presenting with acute signs of systemic infection and suspected sepsis. - While it may be useful later to identify a source of infection, controlling the infection with antibiotics is the most urgent step.
Question 7: A 36 years male presented with complaint of productive cough and fever for last 2 months. He has undergone kidney transplantation 2 years back. His sputum examination revealed a gram positive filamentous bacteria that showed acid fastness with modified Ziehl-Neelsen staining (1% H2SO4). The most likely etiological agent is ?
- A. Blastomyces dermatitidis
- B. Actinomyces israelii
- C. Nocardia asteroides (Correct Answer)
- D. Cryptosporidium parvum
Explanation: ***Nocardia asteroides*** - This patient, being an **immunocompromised kidney transplant recipient**, is highly susceptible to **opportunistic infections**. *Nocardia* species are **gram-positive, filamentous, branched bacteria** that are **weakly acid-fast** (positive with modified Ziehl-Neelsen staining, typically 1% H2SO4), commonly causing **pulmonary infections** with productive cough and fever. - Pulmonary nocardiosis can mimic tuberculosis or other fungal infections, and the acid-fast staining characteristic helps differentiate it from non-acid-fast filamentous bacteria like *Actinomyces*. *Blastomyces dermatitidis* - This is a **dimorphic fungus** that causes **blastomycosis**, an endemic infection in certain geographic regions, which is usually diagnosed by visualization of broad-based budding yeasts or culture. - It would not appear as a **gram-positive filamentous bacterium** with acid-fast properties in sputum. *Actinomyces israelii* - *Actinomyces israelii* is a **gram-positive, filamentous bacterium** that causes **actinomycosis**, often characterized by chronic abscesses, sinus tracts, and "sulfur granules." - Unlike *Nocardia*, *Actinomyces* species are **not acid-fast**, which rules it out given the staining results. *Cryptosporidium parvum* - This is a **protozoan parasite** that causes **cryptosporidiosis**, primarily manifesting as **gastroenteritis** (diarrhea), especially in immunocompromised individuals. - It would not present as a **filamentous bacterial form in sputum**, nor would it be diagnosed by Gram stain and acid-fast modified Ziehl-Neelsen staining in this context.
Question 8: In an HIV-infected individual, the Gram stain of lung aspirate shows yeast-like morphology. Which of the following is the least likely diagnosis?
- A. Candida tropicalis
- B. Cryptococcus neoformans
- C. Aspergillus fumigatus (Correct Answer)
- D. Penicillium marneffei
Explanation: ***Aspergillus fumigatus*** - While *Aspergillus* can cause pulmonary infections in immunosuppressed individuals, it typically presents as **hyphae**, not yeast-like morphology, on Gram stain. - Identification usually requires visualization of **septate hyphae with acute-angle branching**. *Candida tropicalis* - *Candida* species are common causes of opportunistic infections in HIV patients and present as **yeast and pseudohyphae** (though true hyphae can also be seen). - *Candida tropicalis* lung infection would appear as **yeast-like forms** on Gram stain, making it a plausible diagnosis. *Cryptococcus neoformans* - *Cryptococcus neoformans* is a significant pathogen in HIV-infected individuals, causing pulmonary and disseminated disease, and is characterized by its **yeast morphology** and prominent capsule. - Staining would reveal **budding yeast cells**, often with a clear halo due to the capsule, fitting the description. *Penicillium marneffei* - *Penicillium marneffei* is a dimorphic fungus endemic in Southeast Asia that causes disseminated infection in HIV patients, and it grows as **yeast-like cells** at body temperature. - In infected tissues, it appears as **intracellular and extracellular oval yeast-like cells** with transverse septation, consistent with the description.
Question 9: What is the period called between the entry of an organism into the host and the point of maximum infectivity?
- A. Generation Time
- B. Incubation Period
- C. Latent Period (Correct Answer)
- D. Prodromal Period
Explanation: ***Latent Period*** - The **latent period** is the time from entry of an organism into the host until the host becomes **infectious** (able to transmit the disease to others). - During this phase, the organism replicates within the host, but the host is not yet shedding sufficient pathogen to transmit infection. - This period ends when the host begins to shed the pathogen and can transmit it to susceptible individuals, which often coincides with peak infectivity in many diseases. - The latent period is crucial in epidemiology for understanding disease transmission dynamics and implementing control measures. *Generation Time* - **Generation time** (or serial interval) in epidemiology refers to the time interval between the onset of infection in a primary case and the onset of infection in a secondary case. - It reflects the average time between successive generations in a chain of transmission. - This is distinct from the latent period and does not specifically address the period until infectivity begins. *Incubation Period* - The **incubation period** is the time between exposure to an infectious agent and the **onset of clinical symptoms**. - It may overlap with or differ from the latent period; some diseases are infectious before symptoms appear (e.g., measles, chickenpox), while others become infectious only after symptoms develop. - The incubation period does not directly correlate with the timing of infectivity. *Prodromal Period* - The **prodromal period** occurs after the incubation period and is characterized by the appearance of **early, nonspecific symptoms** (e.g., malaise, fever, fatigue). - These symptoms precede the characteristic manifestations of the disease. - During the prodromal period, the person may already be infectious, but this period is defined by symptom characteristics, not infectivity timing.
Question 10: Which of the following can be prevented by transfusing irradiated RBCs?
- A. Graft versus host disease (Correct Answer)
- B. HLA Alloimmunization
- C. Transfusion Related Acute Lung Injury (TRALI)
- D. Immunomodulation
Explanation: Graft versus host disease - **Irradiation** of red blood cell (RBC) products inactivates proliferating donor **T-lymphocytes**, which are responsible for mediating transfusion-associated **graft-versus-host disease (TA-GVHD)**. - TA-GVHD is a severe and often fatal complication where donor immune cells attack recipient tissues. *HLA Alloimmunization* - **HLA alloimmunization** is prevented by **leukoreduction**, which removes donor leukocytes expressing HLA antigens, not by irradiation. - Irradiation targets the proliferative capacity of T-lymphocytes, but does not remove the cells themselves or prevent the presentation of HLA antigens. *Transfusion Related Acute Lung Injury (TRALI)* - **TRALI** is primarily associated with **donor antibodies** (anti-HLA or anti-HNA) in plasma that react with recipient neutrophils, leading to lung injury. - It is prevented by selecting plasma donors who have not been pregnant or by using male-only plasma, not by irradiating RBCs. *Immunomodulation* - **Transfusion-related immunomodulation (TRIM)** is a broad effect associated with multiple blood components, including cytokines and biological response modifiers in the transfused products. - While leukoreduction may reduce some aspects of TRIM, irradiation is not specifically used to prevent or reduce this phenomenon.
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