1. Obligate Intracellular Pathogen
Rickettsia
Chlamydia

2. D. Rickettsia - Virus-like bacteria Infect cells lining the capillaries (intracellular). Transmitted by insects (arthropods). Defective bacteria - leaky plasma membranes, very small micrometers. Ex. Rocky Mountain Spotted Fever, typhus, Q fever.
E. Chlamydia - “virus-like” (intracellular) Spread from one human to the next. Very small: micrometers. Defective bacteria - can’t make their own ATP. Complicated reproductive cycle. Diseases: blindness, urethritis, and pneumonia.

3. Rickettsia

4. Chlamydia

5. F. Mycoplasma -
Sometimes form long strands that resemble fungi in microscopic appearance.
No cell walls - instead contains sterols.
Ameboid locomotion - disease: “walking” pneumonia
The smallest bacteria micrometers

6. Mycoplasma “fungus-form”

7. Chlamydia & Rickettsia

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

9. 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

10. Rickettsia and Related Organisms
Disease
Agent
Arthropod Vector
Rocky Mountain spotted fever
Rickettsia rickettsii
Wood tick
Rickettsial pox
Rickettsia akari
House mouse mites
Murine typhus
Rickettsia typhii
Rat flea
Epidemic typhus
Rickettsia prowazekii
Human body louse
Scrub typhus
Orientia tsutsugamushi
Chigger mites
Ehrlichiosis
Ehrlichia chaffeenis
Lone star tick
Q fever
Coxiella burnetti
None- spead by inhalation

11. 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

12. 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

13. Chlamydia, Rickettsia, Virus

14. 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

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

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

18. 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

19. Rocky Mountain Spotted Fever

20. 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

21. 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

22. 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

23. 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

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

26. 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

27. 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

29. 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)

30. 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

32. Chlamydia: Lab ID Stain tissue Cell culture 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

33. 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

34. 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

35. Reinfection common
Biphasic clinical picture
Prolonged sore throat and hoarseness, followed by flu-like lower respiratory symptoms
Pneumonia and bronchitis

36. 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

37. Other sites of infection
Trachoma – infection of the conjunctiva, resulting in scarring and blindness (Mostly in India and Egypt)
Lymphogranuloma venereum
Infects lymph nodes

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

39. 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

40. C. trachomatis: Lymphogranuloma Venereum
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
C. trachomatis: Lymphogranuloma Venereum

41. C. trachomatis: 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

42. 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

43. 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

44. 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)

45. 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.

46. Normal Flora:
Commensals are regularly found in certain human microbiotopes. The normal human microflora is thus the totality of these commensals. Table 1.7 lists the most important microorganisms of the normal flora with their localizations.
Bacteria are the predominant component of the normal flora. They proliferate in varied profusion on the mucosa and most particularly in the gastrointestinal tract, where over 400 different species have been counted to date.

47. The count of bacteria per gram of intestinal content is 101–105 in the duodenum, 103–107 in the small intestine, and 1010–1012 in the colon. Over 99% of the normal mucosal flora are obligate anaerobes, dominated by the Gram-neg. anaerobes. Although life is possible without normal flora(e.g., pathogen-free experimental animals), commensals certainly benefit their hosts. One way they do so is when organisms of the normal flora manage to penetrate into the host through microtraumas, resulting in a continuous stimulation of the immune system. Commensals also compete for living space with overtly pathogenic species, a function known as colonization resistance .On the other hand, a potentially harmful effect of the normal flora is that they can also cause infections in immunocompromised individual.