OBLIGATE INTRACELLULAR PARASITES

Share common characteristics of being
obligate intracellular parasites –
reproduce only within a mammalian cell.
• Do not grow on artificial media.
• Only reproduce in a living host cell, just like
viruses.

i. Rickettsia spp.
ii. Chlamydia spp.
iii. Coxiella spp.

Gram (-)
● Rod-shaped (Coccobacilli)
● MOT: Insect bites; Ticks
● Enter the host cell thru
phagocytosis
● Arthropod-borne disease

“Epidemic Typhus”

Lice

“Endemic Murine Typhus”

Mites, rat fleas

“Rocky Mountain Spotted Fever”

Ticks

(+) Rashes start on distal extremities

Weil-Felix Test

headache, fever, rashes, & eschar

Gram (-)
(-) peptidoglycan layer
Elemental body: Infective form
(extracellular)
Reticulate body: Metabolically
active; can replicate
(intracellular)

Atypical Pneumonia

(+) TWAR strain
(+) Resembles Mycoplasmal Pneumonia

Fever and headache

Psittacosis

Inhalation of dust from feathers
of birds or dried particles from
droppings

: Headache, fever, chills

Trachoma or “Chronic Conjunctivitis”
Eyes: May cause blindness

Direct contact with eye secretions

: Inclusion Conjunctivitis
- Eyes: Common in neonates

Passage from birth canal

Genital tract: Usually sexually-transmitted

S/sx are similar with gonorrhea, may lead to pelvic inflammatory disease in
women

(+) Lymphadenopathy
• (+) Characterized by small lesions in the groin/pelvic region

“Silent disease”
Usually asymptomatic; chronic

Azithromycin, Doxycycline

Lymphogranuloma Venereum

Gram (-)
Endospore former
Manifestation: Q Fever
Can multiply intracellularly
60% cases – asymptomatic

Acute Q Fever s/sx:
 Fever
 Headaches
 Muscle ache
 Cough

Chronic Q Fever: Endocarditis

Ehrlichia canis & Ehrlichia chaffeensis

Ehrlichiosis

Common in canine species

Human Monocytic Ehrlichiosis

Lone Star Ticks

Flu-like symptoms;
rashes – common in children