MBBS Microbiology 3

Question 1

Which organism is the most common cause of neonatal meningitis and is acquired from the maternal vaginal flora during delivery?

Accepted Answer

Streptococcus agalactiae (Group B Strep)

Answer

Streptococcus agalactiae (Group B Streptococcus) is the most common cause of neonatal meningitis and sepsis, transmitted vertically from colonized mothers during delivery.

Question 2

A patient with AIDS develops ring-enhancing lesions on brain MRI. Which organism is most likely responsible?

Accepted Answer

Toxoplasma gondii

Answer

Toxoplasma gondii is the most common cause of ring-enhancing brain lesions in AIDS patients with CD4 counts below 100 cells/μL, caused by reactivation of latent infection.

Question 3

Which bacteria produce an exotoxin that causes food poisoning by pre-formed toxin ingestion, with symptoms beginning within 1-6 hours of eating?

Accepted Answer

Staphylococcus aureus

Answer

Staphylococcus aureus produces heat-stable enterotoxins in food; because the toxin is preformed, symptoms of nausea, vomiting, and cramping begin rapidly within 1-6 hours of ingestion.

Question 4

Which type of bacterial genetic transfer involves bacteriophages carrying bacterial DNA from one bacterium to another?

Accepted Answer

Transduction

Answer

Transduction is the process by which bacteriophages accidentally package and transfer bacterial DNA from a donor bacterium to a recipient bacterium.

Question 5

A Gram-negative organism causes urethritis and is the leading cause of bacterial STI in the United States. What is the causative agent?

Accepted Answer

Chlamydia trachomatis

Answer

Chlamydia trachomatis is the most common bacterial STI in the United States; it is an obligate intracellular organism that causes urethritis, cervicitis, and pelvic inflammatory disease.

MBBS - Bachelor of Medicine and Bachelor of Surgery Practice Test

MBBS - Bachelor of Medicine and Bachelor of Surgery Practice Test

MBBS Microbiology 3