1. Chlamydia & Rickettsia MLAB 2434: Microbiology Keri Brophy-Martinez

2. General Characteristics Obligate intracellular organisms Can not be cultured on agar plates Dependant on a host for survival

3. Chlamydia Characteristics Unique growth cycle because they are deficient in independent energy metabolism Replication involves elementary body (EB) and reticulate body (RB) – EB’s are infectious and non-metabolically acitve – RB’s are noninfectious and metabolically active

4. Life Cycle of Chlamydia

5. Chlamydia pneumoniae Important respiratory pathogen (acute respiratory disease, pneumonia, and pharyngitis) Common (50% of adults have antibodies) College age students most susceptible Implicated in asthma Risk factor for Guillain-Barre’ syndrome

6. Chlamydia pneumoniae (cont’d) Reinfection common Biphasic clinical picture – Prolonged sore throat and hoarseness, followed by flu-like lower respiratory symptoms – Pneumonia and bronchitis

7. Chlamydia trachomatis Most commonly sexually transmitted bacterial pathogen in U.S. – Only HPV is a more commonly sexually transmitted disease – Major cause of sterility in U.S. – May be transmitted to newborns during delivery Results in conjunctivitis

8. Chlamydia trachomatis (cont’d) Other sites of infection – Trachoma – infection of the conjunctiva, resulting in scarring and blindness (Mostly in India and Egypt) – Lymphogranuloma venereum Infects lymph nodes STD found in immigrants from the tropics

9. Chlamydia psittaci Causes psittacosis (parrot fever) Identification based on history of close contact with birds and serologic evaluation

10. Laboratory Diagnosis If cultured, must be in cells Direct microscopic examination to find EB’s – visualized with fluorescein-conjugated antibodies Enzyme immunoassay Nucleic acid probes with and without amplification (PCR) Serologic tests are method of choice for detection (Four-fold rise in titer)

11. Rickettsia Intracellular, gram negative organism Requires host to replicate and survive Cause febrile illness through the bite of an arthropod Patient often presents with a rash Posses a cell wall

12. Rickettsia and Related Organisms DiseaseAgentArthropod Vector Rocky Mountain spotted fever Rickettsia rickettsiiWood tick Rickettsial poxRickettsia akariHouse mouse mites Murine typhusRickettsia typhiiRat flea Epidemic typhusRickettsia prowazekiiHuman body louse Scrub typhusOrientia tsutsugamushiChigger mites EhrlichiosisEhrlichia chaffeenisLone star tick Q feverCoxiella burnettiNone- spead by inhalation

13. Laboratory Diagnosis of Rickettsial Disease Immunohistochemical detection Serological tests PCR

14. References Kiser, K. M., Payne, W. C., & Taff, T. A. (2011). Clinical Laboratory Microbiology: A Practical Approach. Upper Saddle River, NJ: Pearson Education. Mahon, C. R., Lehman, D. C., & Manuselis, G. (2011). Textbook of Diagnostic Microbiology (4th ed.). Maryland Heights, MO: Saunders.