Infectious Diseases Practice Questions

Q: Which of the following infections is NOT transmitted through blood transfusion?

Cholera. **Explanation:** The correct answer is **Cholera**. The fundamental principle for transfusion-transmitted infections (TTIs) is that the pathogen must have a **viremic, bacteremic, or parasitemic phase** in the host's blood to be collected during donation. **Why Cholera is the correct answer:** * **Cholera** is caused by *Vibrio cholerae*, which is an **enterotoxin-mediated** non-invasive infection. The bacteria remain confined to the intestinal lumen and do not enter the bloodstream. Transmission occurs exclusively via the **fecal-oral route** (contaminated food/water). Therefore, it cannot be transmitted through blood. **Why the other options are incorrect:** * **West Nile Virus (WNV):** This is a known TTI. It causes a period of asymptomatic viremia in humans, allowing it to be transmitted via blood products and organ transplants. * **Toxoplasmosis:** *Toxoplasma gondii* can be transmitted via blood transfusion (specifically through infected leukocytes) or organ transplantation, particularly in immunocompromised recipients. * **Hepatitis B Virus (HBV):** This is one of the most common TTIs globally. It is a highly infectious blood-borne pathogen routinely screened for in all blood banks using HBsAg and Nucleic Acid Testing (NAT). **NEET-PG High-Yield Pearls:** * **Mandatory Screening in India:** Blood banks must screen for five infections: HIV, HBV, HCV, Syphilis (Treponema pallidum), and Malaria. * **Bacterial Contamination:** Platelets are the most common blood component associated with bacterial sepsis because they are stored at room temperature (20-24°C). * **Emerging TTIs:** Keep an eye on Zika virus, Babesiosis, and Leishmaniasis as potential transfusion risks often discussed in recent literature.

Q: A young man presents with skin lesions as shown in the image below. All of the following organisms can spread through dermal and subcutaneous lymphatics, except

Staphylococcus aureus. ***Staphylococcus aureus*** - While *Staphylococcus aureus* can cause various skin infections, it primarily spreads through **direct extension** or the **bloodstream**, not typically through the dermal and subcutaneous lymphatics in a pattern like the one shown. - Infections like cellulitis, abscesses, and impetigo caused by *Staphylococcus aureus* are usually localized or spread via contiguous tissue, rather than forming **linear nodular lesions** along lymphatic channels. *Sporothrix schenckii* - This fungus is a classic cause of **sporotrichosis**, which often presents with **lymphocutaneous spread** following traumatic inoculation. - The image shows **linearly arranged subcutaneous nodules** proximally along the arm, characteristic of lymphatic dissemination, often seen in sporotrichosis. *Nocardia asteroides* - **Nocardia infections** can also cause **lymphocutaneous disease** with a similar appearance to sporotrichosis, especially in immunocompromised individuals. - It can lead to a **chain of subcutaneous nodules and abscesses** tracking along lymphatic vessels from the initial site of infection. *Mycobacterium marinum* - **Mycobacterium marinum** causes **fish tank granuloma** or **swimming pool granuloma** following skin trauma in contaminated water. - It characteristically produces **ascending lymphocutaneous nodules** along lymphatic channels, similar to sporotrichosis, creating a **sporotrichoid pattern**. - The infection typically starts as a papule at the inoculation site and spreads proximally along lymphatics.

Q: All cause brain lesions except

Giardiasis. ***Giardiasis*** - **Giardiasis** is an intestinal infection caused by the parasite *Giardia lamblia* that primarily affects the **gastrointestinal tract**, leading to symptoms like diarrhea, abdominal cramps, and malabsorption. - It does not typically cause **brain lesions** or affect the central nervous system. *Cysticercosis* - **Neurocysticercosis**, caused by the larval stage of **_Taenia solium_** (pork tapeworm), is a common cause of **brain lesions**, cysts, and neurological symptoms like seizures [2]. - The larvae lodge in the brain parenchyma, leading to inflammation and damage [3]. *Bacteroides* - **_Bacteroides_ species** are anaerobic bacteria that are common commensals in the gut but can cause **brain abscesses** if they gain access to the central nervous system, often via sinusitis, otitis media, or trauma [1]. - These infections can lead to significant **intracranial lesions** and neurological deficits. *Tuberculosis* - **Tuberculosis** can cause various **brain lesions**, including **tuberculomas** (granulomas), **tuberculous meningitis**, and brain abscesses, particularly in immunocompromised individuals. - CNS involvement is a severe form of extrapulmonary TB and can result in significant neurological sequelae.

Q: Acute intravascular hemolysis can be caused by infection due to all of the following organisms except:

Clostridium tetani. ***Clostridium tetani*** - This organism causes **tetanus**, characterized by muscle spasms and lockjaw due to exotoxins, but it does **not directly cause intravascular hemolysis**. - Its pathology is primarily neurological, affecting neurotransmitter release at inhibitory synapses. *Bartonella bacilliformis* - This bacterium is the causative agent of **Carrion's disease**, which has two phases: an acute **hemolytic anemic phase** (Oroya fever) and a chronic eruptive phase (verruga peruana). - The acute phase is characterized by severe **intravascular hemolysis**, which can be life-threatening. *Plasmodium falciparum* - This parasite, responsible for the most severe form of malaria, infects **red blood cells**, leading to their lysis and causing **intravascular hemolysis**. - The destruction of red blood cells by the parasite directly contributes to **anemia** and other severe complications of malaria. *Babesia microti* - This is an intraerythrocytic parasite that causes **babesiosis**, a tick-borne disease. - Infections with *Babesia microti* are known to cause **hemolytic anemia** due to the parasite's replication within and subsequent destruction of red blood cells.

Q: All of the following are sexually transmitted, except?

Echinococcus granulosus. ***Echinococcus granulosus*** - ***Echinococcus granulosus*** is a **tapeworm** that causes hydatid cyst disease (echinococcosis) - Transmitted via the **fecal-oral route** through ingestion of eggs from infected canid (dog) feces - Humans are accidental intermediate hosts; **definitive hosts are dogs and other canids** - **NOT sexually transmitted** - this is the correct answer *Candida albicans* - While ***Candida albicans*** can occasionally be transmitted through sexual contact, it is **NOT classified as a sexually transmitted infection (STI)** - Most candidiasis cases arise from **overgrowth of endogenous commensal flora**, not from sexual transmission - Primary risk factors include antibiotic use, diabetes, immunosuppression, and hormonal changes - Sexual transmission is rare and not the primary mode of acquisition *Molluscum contagiosum* - **Molluscum contagiosum** is a **poxvirus infection** transmitted through direct skin-to-skin contact - In adults, it is **commonly sexually transmitted** and lesions appear in the genital, lower abdominal, and inner thigh regions - Classified as an STI when transmitted through sexual contact in adults - In children, transmission occurs through non-sexual contact *Group B streptococcus* - **Group B streptococcus (GBS)** is a **commensal organism** that colonizes the gastrointestinal and genitourinary tracts in 10-30% of healthy adults - While it can be found in the genital tract, it is **NOT classified as a sexually transmitted infection** - Colonization is typically endogenous, not acquired through sexual contact - Important as a cause of neonatal sepsis and meningitis through vertical transmission during delivery

Q: All the diseases caused by transfusion EXCEPT:

Plague. ***Plague*** - Plague is caused by the bacterium **Yersinia pestis** and is primarily transmitted through the bite of infected fleas or direct contact with infected animals, not via blood transfusion. - While extremely rare, it is **not a recognized transfusion-transmitted infection (TTI)** due to its epidemiology and the standard screening processes for blood products. *Hepatitis-C* - **Hepatitis C virus (HCV)** is a well-established transfusion-transmitted infection, as the virus can persist in donated blood and cause infection in recipients. - Prior to routine screening, **post-transfusion hepatitis** was a significant concern, with HCV being a major culprit. *HIV* - **Human Immunodeficiency Virus (HIV)** is highly transmissible through infected blood products and was a major concern for transfusions before robust screening methods were implemented. - All donated blood is now rigorously tested for **HIV antibodies and antigens** to prevent transmission. *Hepatitis-B* - **Hepatitis B virus (HBV)** is another well-known transfusion-transmitted infection, capable of causing acute and chronic liver disease in recipients. - Extensive **screening for HBV surface antigen (HBsAg)** and other markers is conducted on all donated blood to minimize transmission risk.

Q: Which of the following is not transmitted transplacentally –

Mumps. ***Mumps*** - **Mumps virus** is NOT considered a clinically significant cause of congenital infection via transplacental transmission. - While the virus may theoretically cross the placenta in rare cases, mumps is **not part of the TORCH infections** and does not cause the characteristic pattern of congenital abnormalities seen with other transplacental infections. - Maternal mumps during pregnancy is associated with an increased risk of **first-trimester abortion**, but not with a recognizable congenital syndrome. *Toxoplasma* - **Toxoplasma gondii** readily crosses the placenta, causing **congenital toxoplasmosis** (part of TORCH). - This results in the classic triad: **chorioretinitis, hydrocephalus, and intracranial calcifications**. - Risk and severity depend on the trimester of infection. *Rubella* - **Rubella virus** crosses the placenta, causing **congenital rubella syndrome (CRS)** (part of TORCH). - Classic manifestations include **cataracts, congenital heart disease (PDA), and sensorineural deafness**. - Maximum risk occurs with infection in the **first trimester**. *Syphilis* - **Treponema pallidum** crosses the placenta, causing **congenital syphilis** (part of TORCH - "Other"). - Manifestations include **stillbirth, hydrops fetalis, hepatosplenomegaly, rash, and bone abnormalities** (saddle nose, saber shins). - Can be prevented with **adequate maternal treatment before 16-18 weeks**.

Q: Which of the following is not a sexually transmitted disease -

Amoebiasis. ***Amoebiasis*** - Amoebiasis is caused by the parasite **Entamoeba histolytica** and is primarily transmitted through the **oral-fecal route**, often via contaminated food or water. - It is **not considered a sexually transmitted infection** in standard medical classifications, though rare transmission through oral-anal sexual contact has been documented. - This is the expected answer for diseases NOT primarily transmitted sexually. *Hepatitis B* - **Hepatitis B virus (HBV)** is readily transmitted through sexual contact, especially through the exchange of bodily fluids (blood, semen, vaginal fluids). - It is a **well-recognized sexually transmitted infection**, along with transmission through blood products and vertical transmission from mother to child. *Yaws* - Yaws is caused by the bacterium **Treponema pallidum pertenue** and is transmitted through **direct non-sexual skin-to-skin contact** with infectious lesions. - It is a **tropical disease primarily affecting children** through casual contact during play and is **NOT classified as a sexually transmitted disease**. - Note: While technically not an STD, amoebiasis is the conventional answer as yaws may appear in some older classifications of contact-transmitted diseases. *Bacterial vaginosis* - Bacterial vaginosis (BV) is an imbalance of naturally occurring vaginal bacteria, which can be influenced by sexual activity. - While **not strictly an STI** in the traditional sense (not caused by a single transmissible pathogen), it is more common in sexually active women and is often evaluated in STI clinics.

Q: Genital ulcers are seen in all except:

H. aegyptius. ***H. aegyptius*** - *Haemophilus aegyptius* is primarily known to cause **conjunctivitis (pinkeye)**, especially in children, and **Brazilian purpuric fever**, which is a severe systemic illness. - It does **not typically cause genital ulcers**, differentiating it from other listed pathogens. *H. ducreyi* - *Haemophilus ducreyi* is the causative agent of **chancroid**, which typically presents as painful **genital ulcers** with soft, friable bases. - These ulcers are often accompanied by **inguinal lymphadenopathy (buboes)**. *HSV* - **Herpes Simplex Virus (HSV)**, particularly HSV-2, is a common cause of **genital herpes**, characterized by painful, vesicular eruptions that progress to **ulcers** on the genitals. - These lesions often recur and are associated with **neuropathic pain and tenderness**. *Chlamydia* - While *Chlamydia trachomatis* is known for causing **genital infections** like urethritis and cervicitis, specific serovars (L1, L2, L3) are responsible for **lymphogranuloma venereum (LGV)**. - LGV typically begins with a **transient, often unnoticed, small genital ulcer** or papule, followed by marked **inguinal lymphadenopathy** and systemic symptoms.

Q: Which of the following organisms is least likely to cause urethritis?

H.ducreyi. ***Haemophilus ducreyi*** - *Haemophilus ducreyi* is the causative agent of **chancroid**, an STI characterized by **painful genital ulcers** and regional lymphadenopathy. - While it's an STI, its primary manifestation is **not urethritis** but rather ulcerative disease. - Therefore, it is the **least likely** among these options to cause urethritis. *Trichomonas vaginalis* - *Trichomonas vaginalis* is a common cause of **trichomoniasis**, which can manifest as urethritis in both men and women. - In men, it can cause **non-gonococcal urethritis (NGU)** with symptoms like dysuria and penile discharge. *Chlamydia trachomatis* - *Chlamydia trachomatis* is one of the most frequent causes of **non-gonococcal urethritis (NGU)**. - It is the **leading cause of NGU** and often leads to **asymptomatic urethritis**, but can also cause dysuria and discharge. *Neisseria gonorrhoeae* - *Neisseria gonorrhoeae* (gonococcus) is a classic cause of **gonococcal urethritis**. - It typically results in **purulent urethral discharge** and painful urination.

Question 1

Which of the following infections is NOT transmitted through blood transfusion?

Accepted Answer

Cholera

Answer

West Nile virus

Answer

Toxoplasmosis

Answer

Hepatitis B virus (HBV)

Question 2

A young man presents with skin lesions as shown in the image below. All of the following organisms can spread through dermal and subcutaneous lymphatics, except

Accepted Answer

Staphylococcus aureus

Answer

Sporothrix schenckii

Answer

Nocardia asteroides

Answer

Mycobacterium marinum

Question 3

All cause brain lesions except

Accepted Answer

Giardiasis

Answer

Cysticercosis

Answer

Bacteriodes

Answer

Tuberculosis

Question 4

Acute intravascular hemolysis can be caused by infection due to all of the following organisms except:

Accepted Answer

Clostridium tetani

Answer

Bartonella bacilliformis

Answer

Plasmodium falciparum

Answer

Babesia microti

Question 5

All of the following are sexually transmitted, except?

Accepted Answer

Echinococcus granulosus

Answer

Candida albicans

Answer

Molluscum contagiosum

Answer

Group B streptococcus

Question 6

All the diseases caused by transfusion EXCEPT:

Accepted Answer

Plague

Answer

Hepatitis-C

Answer

HIV

Answer

Hepatitis-B

Question 7

Which of the following is not transmitted transplacentally –

Accepted Answer

Mumps

Answer

Toxoplasma

Answer

Rubella

Answer

Syphilis

Question 8

Which of the following is not a sexually transmitted disease -

Accepted Answer

Amoebiasis

Answer

Hepatitis B

Answer

Yaws

Answer

Bacterial vaginosis

Question 9

Genital ulcers are seen in all except:

Accepted Answer

H. aegyptius

Answer

H. ducreyi

Answer

HSV

Answer

Chlamydia

Question 10

Which of the following organisms is least likely to cause urethritis?

Accepted Answer

H.ducreyi

Answer

Chlamydia

Answer

Gonococcus

Answer

Trichomonas

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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