MCQ on Obligate intracellular bacteria
1. Which term refers to bacteria that can only survive and reproduce within host cells?
a) Aerobic bacteria
b) Anaerobic bacteria
c) Facultative bacteria
d) Obligate intracellular bacteria
3. Which of the following intracellular bacteria is associated with 'Rocky Mountain spotted fever'?
b) Ehrlichia chaffeensis
a) Anaplasma phagocytophilum
c) Klebsiella granulomatis
d) Rickettsia typhi
5. Which bacterial structure is used by Chlamydiae to enter and infect host cells?
b) Elementary body
6. Coxiella burnetii, which causes Q fever, primarily infects which type of host cell?
d) Red blood cells
7. Which of the following intracellular bacteria belonging to the family Rickettsiaceae causes Scrub typhus?
b) Orientia tsutsugamushi
c) Rickettsia typhi
d) Rickettsia prowazekii
Answers with Explanation:
1. d) Obligate intracellular bacteria, they lack the necessary machinery to survive and replicate outside of host cells.
2. a) Trachoma, chronic inflammation of the conjunctiva (eye) transmitted to humans as a result of contact with infected secretions that contain Chlamydia trachomatis.
and Tuberculosis is caused by Mycobacterium tuberculosis, these bacteria are not obligate intracellular bacteria.
3. d) Rickettsia rickettsii, it is transmitted to humans through the bite of infected ticks. The disease is named after the Rocky Mountains, where it was first identified, but it can occur in various regions of North and South America. It is a gram-negative, obligate intracellular bacilli.
4. c) Klebsiella granulomatis, Donovanosis, also known as granuloma inguinale, is a rare bacterial infection caused by the bacterium Klebsiella granulomatis. It primarily affects the genital and perineal regions, leading to the formation of painless, progressive ulcers.
5. b) Elementary body (EB), it is the infective form of Chlamydia. It is the extracellular, environmentally resistant form that is released when an infected host cell bursts.
6. a) Alveolar macrophages, Humans are infected by the inhalation of contaminated aerosols from urine, feces or milk of farm animals. After infection, C. burnetii is phagocytized by host cells and multiplies within vacuoles and the organisms are picked up by macrophages and carried to the lymph nodes, from which they then reach the bloodstream.
7. b) Orientia tsutsugamushi, belongs to family rickettsiaceae, causes scrub typhus transmitted to humans through vector chiggers.
8. c) Reticulate bodies, Chlamydiae have two developmental cycle: elementary body and reticulate body. After entering a host cell, the elementary body transforms into the reticulate body.
9. d) White blood cells (WBC), the bacteria infection is acquired through a tick bite and disseminates to the bone marrow and spleen and primarily infects neutrophils of WBC, it is responsible for causing the disease anaplasmosis.
10. b) Their dormancy in harsh conditions. Obligate intracellular bacteria can enter a state known as "viable but non-culturable" (VBNC) when faced with unfavorable conditions due to reduced metabolic activity and inability to replicate, this allows them to survive under stress but remain undetectable using traditional culture methods.
11. a) Arthropod vectors, Rickettsia bacteria are often transmitted to humans through arthropod vectors, such as ticks, lice, and fleas.
12. d) Producing toxins. Producing toxins is a strategy more commonly associated with extracellular bacteria.
13. c) Lung epithelial cells. Legionella pneumophila is an obligate intracellular bacterium that primarily infects and replicates within alveolar macrophages in the lungs, causing a severe form of pneumonia known as Legionnaires' disease.
14. d) Tetanus, it is caused by the bacterium Clostridium tetani, which is not an obligate intracellular bacterium