Podcast
Questions and Answers
Which statement about Rickettsia is correct?
Which statement about Rickettsia is correct?
- They have a coccobacillary shape and are weakly Gram-negative (correct)
- They are obligate extracellular pathogens
- They can synthesize NAD+ and CoA
- They are Gram-positive bacteria
Which diagnostic test is commonly used for rickettsial infections?
Which diagnostic test is commonly used for rickettsial infections?
- Acid-fast staining
- Catalase test
- Weil-Felix agglutination test (correct)
- Gram staining
Which of the following is a characteristic clinical manifestation of rickettsial infections?
Which of the following is a characteristic clinical manifestation of rickettsial infections?
- Jaundice
- Vasculitis and rash (correct)
- Diarrhea
- Pneumonia
Which antibiotic is the preferred treatment for rickettsial infections?
Which antibiotic is the preferred treatment for rickettsial infections?
Which of the following statements about Rickettsia is incorrect?
Which of the following statements about Rickettsia is incorrect?
Which diagnostic method is commonly used for confirming rickettsial infections?
Which diagnostic method is commonly used for confirming rickettsial infections?
What is the key feature of the GENUS Rickettsia?
What is the key feature of the GENUS Rickettsia?
What type of bacteria are Rickettsiae?
What type of bacteria are Rickettsiae?
Which of the following is a characteristic symptom of diseases caused by Rickettsiae?
Which of the following is a characteristic symptom of diseases caused by Rickettsiae?
What is the purpose of the Weil-Felix test in the diagnosis of Rickettsia infections?
What is the purpose of the Weil-Felix test in the diagnosis of Rickettsia infections?
Which antibiotic is recommended for the treatment of Rickettsia infections?
Which antibiotic is recommended for the treatment of Rickettsia infections?
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Study Notes
Rickettsia Species Overview
- Rickettsia are gram-indeterminate, appearing gram-negative due to poor gram staining, and are pleomorphic in shape.
- They are obligate intracellular, requiring the host's ATP to survive.
- Rickettsia colonize endothelial cells, causing endothelial hyperplasia.
Characteristics
- Rickettsia have a coccobacillary shape and are weakly gram-negative.
- They are unable to produce NAD+ and CoA, making these essential for bacterial growth and replication.
Diagnosis
- Weil-Felix agglutination test is used for Rickettsia infections, causing cross-reaction with Proteus Vulgaris antigens.
- PCR and serology can also be used for diagnosis.
Disease Presentation
- Rickettsiosis presents with prodromal headache and fever, followed by vasculitis and rash.
- Vasculitis leads to inflammation and destruction of blood vessels.
- Rash may occur due to vasculitis.
Treatment
- Doxycycline is the primary treatment for Rickettsia infections.
- Chloramphenicol can be used in pregnant women.
- Supportive care with vascular collapse is essential.
Rickettsia Genus Features
- Rickettsia spp. are aerobic, gram-negative, coccobacilli.
- They are obligate intracellular bacteria, requiring host ATP.
- Rickettsia are unable to produce sufficient ATP, CoA, and NAD+.
Diseases Caused by Rickettsiae and Close Relatives
- Rocky Mountain Spotted Fever is caused by R. rickettsii, transmitted by ticks, and affecting ticks, dogs, rodents.
- Epidemic Typhus is caused by R. prowazekii, transmitted by human lice, and affecting humans.
- Endemic Typhus is caused by R. typhi, transmitted by fleas, and affecting rodents.
- Scrub Typhus is caused by Orientia tsutsugamushi, transmitted by mites, and affecting rodents.
- Ehrlichiosis is caused by E. chaffeensis and E. phagocytophila, transmitted by ticks, and affecting small mammals.
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