This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
Ehrlichia chaffeensis is causative agent of ? 
Select and explain. 
A. HME, B. HGE, C. Glandular fever, D. None
A: HME
Answer: A: HME 
Explanation: Ans. is 'a' i.e., HME Ehrlichiae These are gram negative, obligate intracellular bacteria which have affinity towards blood cells. They grow within phagosomes of phagocytes as mulberry-like clusters called morula. They are tick-borne. Three human infections caused by this group of organisms have been identified :? 1) Human monocytic ehrlichiosis (HME) - It is caused by E. chaffeensis, and transmitted by Amblyomma ticks. - Deer and rodents are believed to be reservoir hosts. - There is leucopenia, thrombocytopenia and elevated liver enzymes. 2) Human granulocytic ehrlichiosis (HGE) - It is caused by E. equi (E. phagocytophila), and transmitted by ixodes ticks. - Deer, cattle and sheep are suspected reservoirs. - There is leucopenia and thrombocytopenia. 3) Glandular like fever - It is caused by Ehrlichia sennetsu - No ahopod vector has been identified and infection is caused by ingestion of fish carrying infected flukes. - Theres is lymphoid hyperplasia with atypical lymphocytosis. Doxycycline is recommended for treatment of ehrlichiosis.