Infectious Diseases Practice Questions

Q: Which of the following statements is true about erythema infectiosum?

It is caused by parvovirus B19.. ***It is caused by parvovirus B19.*** - **Parvovirus B19** is the definitive etiological agent of erythema infectiosum, also known as fifth disease. - This viral infection is common in **children** and presents with a characteristic rash. *The rash appears on the head and neck.* - The classic **slapped-cheek rash** does appear on the face (cheeks), but the more characteristic **lacy, reticular rash** typically appears on the **trunk and extremities**. - The neck is not a primary site of involvement, and this option is incomplete as it doesn't mention the distinctive truncal and extremity distribution. *The rash appears during the febrile phase.* - In erythema infectiosum, the **rash typically appears after the fever has subsided** (if fever was present at all). - The prodromal symptoms (mild fever, malaise) resolve before the characteristic slapped-cheek rash emerges. - By the time the rash appears, the patient is usually feeling better and is in the convalescent phase. *It primarily affects adults.* - Erythema infectiosum primarily affects **children**, particularly those of school age (5-15 years). - While adults can contract the infection, it is far more common in childhood.

Q: A 5-year-old boy presents with ear pain and fever. The left eardrum is inflamed with a small perforation, and pus is seen in the external canal. A swab of the area grows Streptococcus pneumoniae. Which of the following is the most likely mechanism for Streptococcus pneumoniae to cause otitis media?

direct extension from the nasopharynx. ***direct extension from the nasopharynx*** - *Streptococcus pneumoniae* commonly colonizes the **nasopharynx**, especially in children. - In children, the **Eustachian tube** is shorter, wider, and more horizontal, allowing bacteria to easily ascend from the nasopharynx into the middle ear. *hematogenous spread* - **Hematogenous spread** (spread through the bloodstream) is a rare mechanism for otitis media and is more characteristic of systemic infections or specific pathogens not typically associated with common acute otitis media. - The localized symptoms and presence of a perforation with pus are more consistent with a local infection spreading via a contiguous route. *direct inoculation on the ear* - **Direct inoculation** would imply an external injury or foreign body introducing bacteria directly into the middle ear, which is not suggested by the clinical presentation. - Otitis media typically originates from infections within the body, not external contamination of the ear itself. *spread through lymphatic tissue* - While lymphatic drainage occurs, **lymphatic spread** is not the primary mechanism for bacteria to reach the middle ear and cause otitis media. - The direct anatomical connection of the Eustachian tube offers a more direct and common pathway for infection.

Q: Nagayama spots are seen in

Roseola infantum. ***Roseola infantum*** - **Nagayama spots** are **erythematous papules** on the **uvula and soft palate** that are characteristic of **roseola infantum**, also known as **exanthem subitum**. - This viral illness, typically caused by **HHV-6** or **HHV-7**, primarily affects infants and young children, presenting with a high fever followed by a characteristic rash. *Measles* - Measles (rubeola) is characterized by **Koplik spots**, which are **bluish-white spots on the buccal mucosa** adjacent to the molars. - While measles also causes a rash, its specific enanthem is distinct from Nagayama spots. *Mumps* - Mumps is a viral infection primarily causing **parotitis** (swelling of the salivary glands)**. - It does not typically present with specific oral lesions like Nagayama spots or Koplik spots. *Rubella* - Rubella, or German measles, is characterized by a **maculopapular rash** that spreads rapidly but less intensely than measles. - While it may cause **Forchheimer spots** (petechiae on the soft palate), these are different from Nagayama spots and often less distinct.

Q: A child presents with perianal pruritus. Which of the following is the most likely cause of this symptom?

E. vermicularis. ***E. vermicularis*** - **Enterobius vermicularis**, or **pinworm**, is the most common cause of **perianal pruritus** in children, especially at night when the female worms migrate to the perianal region to lay eggs. - The itching can lead to **sleep disturbance, irritability**, and secondary bacterial infections due to scratching. *Ascaris* - **Ascaris lumbricoides** typically causes **gastrointestinal symptoms** such as abdominal pain, malnutrition, and, in severe cases, intestinal obstruction or biliary tract obstruction. - While it is a common intestinal nematode, **perianal pruritus is not a characteristic symptom** of ascariasis. *Ankylostoma duodenale* - **Ankylostoma duodenale**, or **hookworm**, is known for causing **iron-deficiency anemia** due to chronic blood loss from the intestinal attachment sites. - Its symptoms often include **abdominal pain**, diarrhea, and a characteristic **pruritic rash** (ground itch) at the site of larval penetration, typically on the feet, but not perianal pruritus. *S. stercoralis* - **Strongyloides stercoralis** can cause a range of symptoms, including abdominal pain, diarrhea, and a characteristic **larva currens rash** (migratory, serpiginous skin lesions) due to larval migration. - While it can cause skin manifestations, **perianal pruritus is not a primary or common symptom** of strongyloidiasis.

Q: What type of vaccine is recommended for prevention of rotavirus gastroenteritis in infants?

Live attenuated oral vaccine. ***Live attenuated oral vaccine*** - **Live attenuated oral vaccines** are the standard for rotavirus prevention, providing **strong mucosal immunity** in the gut where rotavirus replicates. - Two WHO-prequalified vaccines are available: **RotaTeq** (pentavalent) and **Rotarix** (monovalent), both with **comparable efficacy** (80-90% against severe disease). - The oral route mimics natural infection and induces **local IgA response** at the intestinal mucosa. *Inactivated vaccine* - **No inactivated rotavirus vaccine** is currently available or licensed for use. - Inactivated vaccines would provide systemic immunity but lack the **mucosal immune response** critical for preventing enteric infections. *Subunit vaccine* - **Subunit vaccines** for rotavirus are not currently used in clinical practice. - Live attenuated vaccines provide broader immunity by presenting **multiple viral antigens** naturally. *Conjugate vaccine* - **Conjugate vaccine technology** is used for bacterial polysaccharide antigens (e.g., Hib, pneumococcus), not for viral vaccines like rotavirus. - Rotavirus requires a vaccine that induces **mucosal immunity**, achieved through live oral vaccines.

Q: Which throat infection in a child requires systemic antibiotic therapy?

Group A beta-hemolytic streptococci. ***Group A beta-hemolytic streptococci*** - **Group A streptococcal (GAS) pharyngitis** (strep throat) is a common bacterial infection in children that requires antibiotic treatment to prevent **rheumatic fever** and **glomerulonephritis**. - Systemic antibiotics are crucial to eradicate the bacteria and reduce the risk of these serious **post-streptococcal complications**. *Pneumococci* - **Pneumococcal infections** typically manifest as otitis media, pneumonia, or sinusitis, not primarily as throat infections warranting oral antibiotics in otherwise healthy children. - While *Streptococcus pneumoniae* can colonize the nasopharynx, it rarely causes pharyngitis requiring specific treatment as a sole diagnosis. *Staph aureus* - *Staphylococcus aureus* is an uncommon cause of **pharyngitis** in children and does not typically lead to the severe systemic complications associated with GAS that necessitate routine antibiotic therapy. - Pharyngeal infections with *S. aureus* are often more problematic in specific populations (e.g., immunocompromised) and do not usually present as typical "strep throat." *All of the options* - This option is incorrect because only **Group A beta-hemolytic streptococci** consistently require systemic antibiotic therapy for uncomplicated pharyngitis in children due to the risk of significant post-infectious complications. - **Pneumococci** and **Staph aureus** do not typically cause pharyngitis that necessitates this specific management strategy in the same context.

Q: Which of the following is not a complication of Congenital Rubella Syndrome (CRS)?

Macrocephaly. ***Macrocephaly*** - While CRS can lead to various neurological complications, **macrocephaly** (abnormally large head circumference) is not a typical manifestation of the syndrome. Neurological issues in CRS more commonly involve **microcephaly** due to brain damage. - Other common neurological complications include **meningoencephalitis** and developmental delays, but not an enlarged head. *Retinopathy* - **Pigmentary retinopathy** (salt-and-pepper retinopathy) is a classic ocular manifestation of CRS, often present at birth. - This is a direct consequence of the rubella virus affecting the developing retinal structures. *Spontaneous abortion* - Maternal rubella infection, especially during the **first trimester**, carries a significant risk of **spontaneous abortion** due to severe fetal damage. - The virus's teratogenic effects can be so profound that the fetus is not viable. *Cardiac abnormalities* - **Congenital heart defects** are a hallmark of CRS, with **patent ductus arteriosus (PDA)** and **pulmonary artery stenosis** being the most common. - These abnormalities result from the rubella virus interfering with normal cardiac development during embryogenesis.

Q: Slapped cheek appearance is caused by:

Parvovirus. ***Parvovirus*** - **Parvovirus B19** causes Fifth disease, characterized by a distinctive bright red rash on the cheeks, which gives the appearance of "slapped cheeks." - This **erythematous rash** is a hallmark symptom, often followed by a lacy or reticular rash on the trunk and limbs. *Measles* - Measles, caused by the **measles virus**, presents with a **maculopapular rash** that starts on the face and spreads downwards, often preceded by **Koplik spots** in the mouth. - It does not typically cause a "slapped cheek" appearance. *Rubella* - Rubella, or **German measles**, is caused by the **rubella virus** and features a milder rash than measles, typically a fine, pink maculopapular rash that starts on the face and spreads to the rest of the body. - It is not associated with the "slapped cheek" rash. *HHV-6* - Human Herpesvirus 6 (HHV-6) is the cause of **roseola infantum**, or Sixth disease, which is characterized by a high fever followed by a sudden **rose-pink rash** on the trunk and neck as the fever breaks. - This rash does not produce the "slapped cheek" appearance.

Q: A 10-month-old child presents with a two-week history of fever, vomiting, and alteration of sensorium. A cranial CT scan reveals basal exudates and hydrocephalus. What is the most likely etiological agent?

Mycobacterium tuberculosis. ***Mycobacterium tuberculosis*** - The combination of **basal exudates** (inflammation at the base of the brain) and **hydrocephalus** on CT scan in a child with prolonged fever and altered sensorium is highly characteristic of **tuberculous meningitis**. - **Tuberculous meningitis** typically has a more insidious onset, and the thick exudates around the basal cisterns can obstruct CSF flow, leading to hydrocephalus. *Cryptococcus neoformans* - While it can cause chronic meningitis, **Cryptococcus neoformans** is more common in **immunocompromised individuals** (e.g., HIV/AIDS patients), which is not indicated here. - CT scans typically show **gelatinous pseudocysts** or dilation of Virchow-Robin spaces rather than prominent basal exudates in early stages. *Listeria monocytogenes* - Primarily affects **neonates**, **immunocompromised adults**, and the elderly. - Although it causes meningitis and encephalitis, **basal exudates** and significant **hydrocephalus** are less common than with tuberculosis. *Streptococcus pneumoniae* - This is a common cause of **acute bacterial meningitis** in children, often presenting with a rapid onset and severe symptoms. - While it can cause hydrocephalus, the presence of prominent **basal exudates** with a subacute course (two weeks) points away from typical pneumococcal meningitis.

Q: At what age is the MMR vaccination typically administered?

One year. ***One year*** - The **first dose** of the MMR (measles, mumps, and rubella) vaccine is typically given to children between **12 and 15 months of age**. - This timing is chosen because maternal antibodies, which might interfere with vaccine effectiveness, generally wane by this age. - The **second dose** is administered between 4 and 6 years of age. *Incorrect: 1.5 years* - While some vaccination schedules may show 18 months as acceptable, the **standard recommendation for the first dose is earlier**, between 12-15 months. - Delaying beyond 15 months leaves children vulnerable to measles during a high-risk period. *Incorrect: 6 months* - Administering the MMR vaccine at 6 months is generally **not recommended** for routine first dose. - At this age, **maternal antibodies** can still be present, which might neutralize the vaccine and reduce its effectiveness. - However, in outbreak situations or before international travel, a dose may be given as early as 6 months (but must be repeated after 12 months). *Incorrect: 2 months* - At 2 months, infants receive other routine vaccines (DTaP, IPV, Hib, PCV, Rotavirus), but **not MMR**. - MMR is a **live attenuated vaccine** requiring a more mature immune system to mount an effective response. - Maternal antibodies present at 2 months would interfere with MMR vaccine effectiveness.

Question 1

Which of the following statements is true about erythema infectiosum?

Accepted Answer

It is caused by parvovirus B19.

Answer

The rash appears on the head and neck.

Answer

The rash appears during the febrile phase.

Answer

It primarily affects adults.

Question 2

A 5-year-old boy presents with ear pain and fever. The left eardrum is inflamed with a small perforation, and pus is seen in the external canal. A swab of the area grows Streptococcus pneumoniae. Which of the following is the most likely mechanism for Streptococcus pneumoniae to cause otitis media?

Accepted Answer

direct extension from the nasopharynx

Answer

spread through lymphatic tissue

Answer

direct inoculation on the ear

Answer

hematogenous spread

Question 3

Nagayama spots are seen in

Accepted Answer

Roseola infantum

Answer

Measles

Answer

Mumps

Answer

Rubella

Question 4

A child presents with perianal pruritus. Which of the following is the most likely cause of this symptom?

Accepted Answer

E. vermicularis

Answer

Ascaris

Answer

Ankylostoma duodenale

Answer

S. stercoralis

Question 5

What type of vaccine is recommended for prevention of rotavirus gastroenteritis in infants?

Accepted Answer

Live attenuated oral vaccine

Answer

Subunit vaccine

Answer

Conjugate vaccine

Answer

Inactivated vaccine

Question 6

Which throat infection in a child requires systemic antibiotic therapy?

Accepted Answer

Group A beta-hemolytic streptococci

Answer

Pneumococci

Answer

Staph aureus

Answer

All of the options

Question 7

Which of the following is not a complication of Congenital Rubella Syndrome (CRS)?

Accepted Answer

Macrocephaly

Answer

Retinopathy

Answer

Cardiac abnormalities

Answer

Spontaneous abortion

Question 8

Slapped cheek appearance is caused by:

Accepted Answer

Parvovirus

Answer

Measles

Answer

Rubella

Answer

HHV-6

Question 9

A 10-month-old child presents with a two-week history of fever, vomiting, and alteration of sensorium. A cranial CT scan reveals basal exudates and hydrocephalus. What is the most likely etiological agent?

Accepted Answer

Mycobacterium tuberculosis

Answer

Cryptococcus neoformans

Answer

Streptococcus pneumoniae

Answer

Listeria monocytogenes

Question 10

At what age is the MMR vaccination typically administered?

Accepted Answer

One year

Answer

1.5 years

Answer

2 months

Answer

6 months

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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