1. Obligate Intracellular Pathogen
Rickettsia
Chlamydia

2. Family Rickettsiaceae: Genera
Zoonotic infection
Human microbial pathogens ~61% zoonotic
Rickettsia are arthropod-borne infections
Spotted Fever Group
Rickettsia rickettsii – Rocky Mountain spotted fever; rodent, tick
Typhus Group
Rickettsia typhi – Endemic typhus; rodent, flea
Rickettsia prowazekii – Epidemic typhus; mammal, louse

3. Rickettsia: Gram Stain and Culture
Gram (-) small, pleomorphic coccobacilli
Gram stain poorly, observed by Giemsa stain of infected cell
Grow in phagocytic, nonphagocytic cells
Lab culture in embryonated eggs or cell tissue culture (similar for virus)
Cultivation costly and hazardous; aerosol transmission occurs easily

4. Chlamydia, Rickettsia, Virus

5. Rickettsia: Lab ID
Giemsa, or Immunofluorescence assay (IFA) - direct detection MO in tissue
Weil-Felix reaction – Nonspecific test
Rickettsial antibody agglutinate Proteus vulgaris
Presumptive evidence of typhus group infection
Not very sensitive or specific, many false positives
Agglutination or Complement Fixation (CF) assay - use specific Rickettsial antigen, test for infection and antibody

6. Rickettsia: Virulence Factors
Induced phagocytosis, intracelluular growth – protected from host immune clearance
Replicates in endothelial cells – cell damage, vasculitis
Recruitment of actin - intracellular spread

7. Rickettsia: Infection and Disease
Disease worldwide, USA
Arthropod reservoir/vector (tick, mite, louse, flea)
Diseases characterized by fever, headache, myalgias, usually rash

8. R. rickettsii: Rocky Mountain Spotted Fever (RMSF)
USA ~ cases/year
Ticks must remain attach for hours
Incubation 7 days - headache, chills, fever, aching, nausea
Followed by maculopapular rash on extremities (including palms and soles), spread chest, abdomen
If untreated
Petechial rash, hemorrhages skin and mucous membranes
Vascular damage, MO invades blood vessels
Death up to 20%, due to kidney or heart failure

9. Rocky Mountain Spotted Fever

10. Rickettsia: Typhus Group
Incubation 5-18 days
Symptoms - severe headache, chills, fever, maculopapular rash (subcutaneous hemorrhaging as MOs invade blood vessel)
Rash begins on upper trunk; spread to whole body except face, palms of hands, soles of feet
Lasts ~2 weeks
Patient may have prolonged convalescence

11. R. typhi : Endemic Typhus Fever
Disease worldwide in warm, humid areas (Gulf states, So Cal.; S. America, Africa, Asia, Australia, Europe)
Murine typhus - rat primary reservoir, transmitted to human by rat flea
Disease occurs sporadically
Clinically same, but less severe than epidemic typhus
Restricted to chest, abdomen; generally uncomplicated, lasts <3 weeks
Low fatality

12. R. prowazekii : Epidemic Typhus Fever
Disease C & S Americas, Africa; less common USA
Human, squirrel primary reservoir
Transmitted by louse; bites, defecates in wound
At risk - people living in crowded, unsanitary conditions; often war, famine, natural disaster
Complications - myocarditis, CNS dysfunction
Mortality high untreated cases, up to 20%
Brill-Zinsser disease - individual may harbor MO, latent infection with occasional relapses

13. Rickettsia: Treatment and Prevention
RMSF
Doxycycline drug of choice
Avoid ticks, wear protective clothing, use insect repellents, insecticides
In infested areas, check and remove ticks immediately
Typhus Fever
Doxycycline effective
Improve personal hygiene and living conditions, reduce lice by insecticides, control rodent population
Inactivated vaccine for epidemic typhus

14. Family Chlamydiaceae: Genera
Chlamydia trachomatis – STD, eye infection
Chlamydophila pneumoniae – pneumonia
Chlamydophilia psittaci – pneunomia (psittacosis); birds, humans
Obligate intracellular parasite
Cell wall similar G(-) bacilli, lack peptidoglycan
Energy parasites, use ATP of host cell
Giemsa stain - Chlamydia inclusions in tissue

15. Chlamydia: Life Cycle – Elementary Body (EB)
Circular, infectious form; nm
Metabolically inactive
Resistant to harsh environments
0 hour - EB binds to host cell, induced phagocytosis
Outer membrane of EB prevents lysosome fusion, survives in phagosome
8 hours - EB reorganizes into Reticulate Body (RB)

16. Chlamydia: Life Cycle – Reticulate Body (RB)
Noninfectious form, larger, less dense, nm
Metabolically active
8-30 hours
Synthesize new materials
Multiply by binary division
Form inclusion body
Reorganize, condense into EB
35-40 hours - cell lyses, releases EB, begins cycle again

17. Chlamydia: Lab ID Stain tissue Cell culture DNA amplification test
Giemsa stain
Direct fluorescent antibody (DFA)
ELISA
Less sensitive
Cell culture
More sensitive method
Grow MO in tissue culture, stain infected cells
DNA amplification test
Recently developed
Specific, sensitive
Now routine test of choice

18. Chlamydia: Virulence Factors
Intracellular replication – protected from host immune defense
Prevent fusion of phagolysome – evades phagocytic killing
Repeated infections by C. trachoma result in cell pathology
Serotypes A-K and L1, L2, L3 - serotype identifies strain’s clinical manifestation

19. Chlamydia trachomatis: Trachoma
“rough” “trachoma” granulations on conjunctiva
Serotypes A-C
Single, greatest cause blindness developing countries
Infections mainly children (reservoir), infected first three months life
Transmission eye-to-eye, direct contact (droplet, hand, clothing, fly)
Chronic infection, reinfection common
Conjunctival scarring, corneal vascularization
Scars contract, upper lid turn in so eyelashes cause corneal abrasions
Leads to secondary bacterial infections, blindness

20. C. trachomatis: Lymphogranuloma Venereum
Serotypes L1, L2, L3
Venereal disease, occurs developing, tropical areas
Primary stage - painless lesion (vesicle or an ulcer) occurs site of entry in few days, heals with no scarring; but widespread dissemination
Secondary stage - occurs 2-6 weeks later, symptoms of regional suppurative lymphadenopathy (buboes), may drain for long time, accompanied by fever and chills. Arthritis, conjunctival, CNS symptoms
Tertiary stage - urethrogenital perineal syndrome; structural changes, such as non-destructive elephantiasis of the genitals, rectal stenosis

21. C. trachomatis: STD Urogenital tract infection - serotypes D-K
Major cause of nongonococcal urethritis; frequently found concomitantly with N. gonorrhoeae
In males - urethritis, dysuria, sometimes progresses to epididymitis
In females - mucopurulent cervical inflammation, can progress to salpingitis and PID
USA - #1 STD

22. C. trachomatis: Inclusion Conjunctivitis
Newborns and adults
Genital tract infection source of eye infection (serotypes D-K)
Benign, self-limited conjunctivitis, heals with no scarring
Newborns infected during birth process:
1-2 weeks, mucopurulent discharge
Lasts 2 weeks, subsides
Some develop afebrile, chronic pneumonia
In adults – causes an acute follicular conjunctivitis with little discharge

23. Chlamydia: Treatment and Prevention
Genital tract infection and conjunctivitis:
Adult - azithromycin or doxycycline, prompt treatment of patients and partners
Newborn – erythromycin
Public Health education
Trachoma:
Need prompt treatment, prevent reinfection
Systemic tetracycline, erythromycin; long term therapy necessary
Improve living, sanitary conditions
Difficult to prevent endemic disease in developing countries due to lack of resources, medical care

24. Chlamydophilia pneumoniae: RT Infection
Human pathogen; common infection, especially 6-25 yr. old
Most infections asymptomatic or mildly symptomatic
Sore throat, hoarseness, flulike symptoms
May cause sinusitis, pharyngitis, bronchitis, pneumonia
Accounts for ~10% hospitalized pneumonia

25. Chlamydophila psittaci: Psittacosis
“parrot” “parrot fever”
Naturally infects avian species
Mild to severe respiratory infections
Human infection by contact infected bird
Infection - subclinical to fatal pneumonia
Commonly causes atypical pneumonia with fever, chills, dry cough, headache, sore throat, nausea, and vomiting

26. Case Study 9 - Chlamydia
A 22-year-old man came to the emergency department with a history of urethral pain and purulent discharge that developed after he had sexual contact with a prostitute. Gram stain of the discharge revealed abundant gram-negative diplococci resembling Neisseria gonorrhoeae. The patient was treated with penicillin and sent home. Two days later, the patient returned to the emergency room with a complaint of persistent, watery urethral discharge. Abundant white blood cells but no organisms were observed in Gram stain of the discharge. Culture of the discharge was negative for N. gonorrhoeae but positive for C. trachomatis.

27. Case Study 9 - Questions
1. Why is penicillin ineffective against Chlamydia? What antibiotic can be used to treat this patient?
2. Describe the growth cycle of Chlamydia. What structural features make the EBs and RBs well suited for their environment?
3. Describe the differences among the three species in the family Chlamydiaceae that cause human disease.

28. Class Assignment Textbook Reading
Chapter 40 Zoonotic and Rickettsial Disease
The Rickettsiaceae
Omit: Remaining last two Sections of reading
Omit: Key Terms, Learning Assessment Questions
Chapter 24 Chlamydia, Mycoplasma, and Ureaplasma
Chlamydia
Key Terms
Learning Assessment Questions

29. Final Exam Tue., March 20, 2012 8:30 – 10:30 am
Mycobacterium thru Ureaplasma
Lecture, Reading, Key Terms, Learning Assessment Questions
Case Study 7, 8, 9, 10 (Mycobacterium, Clostridium, Chlamydia, Legionella)
Exam Format:
Multiple Choice
Terms
True/False Statements
Short Essay
Review, Review, Review!
Repetition is the key to retention