1. Rickettsia, Chlamydia and Mycoplasmas

2. Comparative study Rickettsiae, Chlamydiae, Mycoplasmas
Features
Rickettsiae
Clamydiae
Mycoplasmas
DNA + RNA in cell +
Size of cells
5OOnm
3OOnm
1OOnm
Intracellular parasite -
Growth in living cell
Inclusion body
Gorwth on media
Antibiotic sensivity
Transmission by vector

3. Rickettsia

4. General Characteristics
Small obligate intracellular coccobacilli
Gram negative (poorly), better stained with Giemsa (Blue)
Have cell wall, bigger than virus but smaller than bacteria
Have DNA and RNA
Have an ATP transport system that allows them to use host ATP
Arthropod reservoirs and vectors ( e.g., ticks, mites, lice or fleas).
Sensitive to antibiotics

5. Endothelial cells, micro blood vessels
Pathogenic Mechanism
Materials：
Endotoxin and Phospholipase A
Mechanism：
Bites or faeces of arthropod
Local lymph or micro blood vessels
(1st bacteremia)
Endothelial cells, micro blood vessels
in whole body
(2nd bacteremia)
Fever, rash, headache, etc
Targets:
Endothelial cells, micro blood vessels

6. Five genera in this class cause human diseases:
Rickettsia
Bartonella
Coxiella (does NOT cause skin rash)
Ehrlichia
Orientia

7. Diseases Caused by the Rickettsia
Organism
Vector
Reservoir
Rocky Mountain spotted fever
R. Rickettsii
Tick
Tick, wild rodents
Scrub typhus
R. Tsutsugamushi
Laval Mite (chiggers)
Mites, wild rodents
Epidemic typhus
R. Prowazekii
Louse
Humans, squirrel fleas, flying squirrels
Murine typhus
R. Thphi
Flea
Wild rodents
Q fever
Coxiella Burnetii
None
Cattle, sheep, goats, cats

8. Rickettsia rickettsii in endothelial cells of a blood vessel from a patient

9. Orientia tsutsugamushi growing in mouse abdominal macrophages (Giemsa)

10. R. Prowazekii
Louse
Human Human
Epidemic typhus

11. (much milder than epidemic typhus)
R. Typhi
Rodent
Flea Rat Tick Flea Human
Murine typhus
(much milder than epidemic typhus)

12. Coxiella Burnetii Q fever（query fever ）
Self-limiting flu-like syndrome with high fever (40℃)
Primary reservoirs are wild (cattle, sheep, goat etc.)
Non-cross reactive antigen with non-motile Proteus (Weil-Felix reaction negative)
Live in macrophages of vertebrate host

13. Diagnosis and Prevention
Microscopy
Serological Test (Weil-Felix reaction, ELISA, IF,
PCR)
Breaking the infection chain ( controlling and
killing the intermediate hosts and reservoir
hosts)
Inactivated vaccine has protective effect
Chloromycetin, tetracycline are helpful for
therapy, sulphonamides are not administered
(increasing the penetrating of the vessel).

14. Chlamydia

15. Characteristics Small obligate intracellular parasites
Contain DNA, RNA and ribosome and make their own proteins and nucleic acids, unable to make their own ATP
Have special growth cycle and replicate by binary fission
Possess a rigid cell wall similar to gram-negative bacteria
Sensitive to antibiotic

16. A. Elementary bodies (EB)
Special Growth Cycle
A. Elementary bodies (EB)
small (0.3～0.4 µm) infectious form
a rigid outer membrane
resistant to harsh environmental conditions outside of eukaryotic host cells
bind to receptors on host cells
initiate infection.

17. Chlamydia inclusion body

18. Chlamydia trachomatis
Only infects human epithelial cells (Except Biovar mouse)
Three biovars (biological variants):
Biovar Trachoma (14 Serologic types)
Biovar lymphogranuloma venereum, LGV (4 serologic types)
Biovar mouse

19. Genital tract infections
C. trachomatis (Biovar trachoma)
The most common sexually transmitted bacterial disease
C. trachomatis (Biovar: LGV)
Humans are the only natural host

20. Clinical Syndromes 1. Trachoma Chronic infection or repeated infection
inflammation and follicle formation involving the entire conjunctiva
Chlamydial
kerato-conjunctivitis

21. Clinical Syndromes 2. Inclusion conjunctivitis 3. Infant pneumonia
4. Urogenital infections
cervicitis, salpingitis
urethritis
5. Reiter's syndrome
6. Lymphogranuloma (LVG)

22. Laboratory diagnosis 1. Cytology 2. Culture 3. Serology
Examination of stained cell scrapings for the presence of inclusion bodies
2. Culture
the most specific method for diagnosis
cultures of susceptible cells
iodine-staining inclusion bodies
3. Serology
Detection of high titer IgM antibodies is indicative of a recent infection

23. Treatment and prevention
Tetracycline
Erythromycin
Sulfonamides
Vaccines are of little value and are not used.
Treatment coupled with improved sanitation to prevent reinfection is the best way to control infection.

24. Mycoplasmas

25. Morphology and Physiology
The smallest free-living organisms
Pass through some filters used to remove bacteria
Lack of a cell wall
Multiple shapes including round, pear shaped and even filamentous

26. Require complex media
Require sterols for growth and for membrane synthesis
Grow slowly (3 weeks) by binary fission and produce "fried egg" or “T strain” (tiny strain) colonies on agar plates

27. Pathogenesis Adherence factors
Adherence proteins are one of the major virulence factors
Adhesin localizes at tips of the cells and binds to sialic acid residues on host epithelial cells

28. Pathogenesis Toxic Metabolic Products
The intimate association provides an environment in which toxic metabolic products accumulate and damage host tissues
Products of metabolism : hydrogen peroxide and superoxide -- oxidize host lipids
Inhibit host cell catalase

29. Pathogenesis Immunopathogenesis M. pneumoniae is a superantigen
Activate macrophages and stimulate cytokine production and lymphocyte activation
Host factors contribute to pathogenesis

30. Organism
Disease
M. pneumoniae
Upper respiratory tract disease, Tracheobronchitis, atypical pneumonia
M. hominis
Pyelonephritis, pelvic inflammatory disease, postpartum fever
M. genitalium
Nongonococcl urethritis (NGU)
U. urealyticum
Nongonococcl urethritis (NGU)

31. M. Pneumoniae Need 10-20% Serum to culture in pH 7.8-8.0
Pathogenesis: P1 protein, capsule and saccharide
Spread  by close contact via aerosolized droplets
Cause tracheobronchitis
Cause “primary atypical pneumonia”
long duration
Antibodies play a role in controlling infection, particularly sIgA
Delayed type hypersensitivity
spread in confined populations

32. M. Pneumoniae Laboratory Diagnosis
Organisms can be cultured from sputum before symptoms occur and throughout the course of the disease.
Serology
Complement fixation test :A fourfold rise in titer is indicative of a recent infection.
Cold agglutinins are IgM antibodies that agglutinate human “O” erythrocytes at 4℃ but not at 37℃ not specific/a presumptive diagnosis
ELISA

33. M. pneumoniae Treatment and Prevention
The antibiotics of choice are tetracycline (adults only) and erythromycin.
Long duration of the disease, hard to isolate patients to avoid close contact for a long period of time.
No vaccines are currently available