Infectious Diseases Practice Questions

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.

Q: Intravascular hemolysis is not associated with:

Clostridium tetani. ***Clostridium tetani*** - *Clostridium tetani* causes **tetanus**, a neurological disorder characterized by muscle spasms and paralysis, primarily due to the **tetanospasmin neurotoxin**. - It does not produce toxins that directly lyse red blood cells, thus it is not associated with **intravascular hemolysis**. *Bartonella bacilliformis* - *Bartonella bacilliformis* causes **Carrion's disease (Bartonellosis)**, which includes an acute phase known as Oroya fever. - This bacterium invades and proliferates within **red blood cells**, leading to their destruction and severe **hemolytic anemia**. *Plasmodium falciparum* - *Plasmodium falciparum* is a parasite responsible for the most severe form of **malaria**. - It infects and replicates within **red blood cells**, causing them to rupture and leading to significant **intravascular hemolysis** and anemia. *Babesia microti* - *Babesia microti* is an intraerythrocytic parasite that causes **babesiosis**, transmitted by ticks. - It replicates within **red blood cells**, leading to their destruction and causing **hemolytic anemia**, similar to malaria.

Question 1

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 2

All of the following are sexually transmitted, except?

Accepted Answer

Echinococcus granulosus

Answer

Candida albicans

Answer

Molluscum contagiosum

Answer

Group B streptococcus

Question 3

All the diseases caused by transfusion EXCEPT:

Accepted Answer

Plague

Answer

Hepatitis-C

Answer

HIV

Answer

Hepatitis-B

Question 4

Which of the following is not transmitted transplacentally –

Accepted Answer

Mumps

Answer

Toxoplasma

Answer

Rubella

Answer

Syphilis

Question 5

Which of the following is not a sexually transmitted disease -

Accepted Answer

Amoebiasis

Answer

Hepatitis B

Answer

Yaws

Answer

Bacterial vaginosis

Question 6

Genital ulcers are seen in all except:

Accepted Answer

H. aegyptius

Answer

H. ducreyi

Answer

HSV

Answer

Chlamydia

Question 7

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

Accepted Answer

H.ducreyi

Answer

Chlamydia

Answer

Gonococcus

Answer

Trichomonas

Question 8

Intravascular hemolysis is not associated with:

Accepted Answer

Clostridium tetani

Answer

Plasmodium falciparum

Answer

Babesia microti

Answer

Bartonella bacilliformis

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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