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Veterinary Bacteriology & Mycology > Obligate Intracellular Pathogen Intro & Chlamydia > Flashcards

Obligate Intracellular Pathogen Intro & Chlamydia Flashcards

1
Q

What are the 3 smallest groups of bacteria? How do they compare in size?

A
  1. Chlamydiales
  2. Rickettsiales (Anaplasma, Ehrlichia, Rickettsia, Coxiella)
  3. Mycoplasma

Chlamydiales > Rickettsiales > Coxiella > Mycoplasma

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2
Q

What kind of pathogens are Chlamydiales, Rickettsiales, and Mycoplasma?

A

obligate pathogens of animals and arthropods
- Rickettsiales = arthropods
- Mycoplasma = lives both extracellular and intracellular

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3
Q

What are the 3 major reasons that Chlamydiales, Rickettsiales, and Mycoplasma seek out an intracellular lifestyle in their host?

A
  1. have highly permeable cell membranes that are unable to hold in electrolytes and water (host cell maintains osmotic pressure)
  2. unable to make enough of their own ATP
  3. cholesterol demand
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4
Q

What culture media is necessary for Chlamydiales and Rickettsiales growth?

A

living cell cultures (obligate intracellular pathogens)

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5
Q

How does Mycoplasma characteristically grow on media?

A

fried egg colony growth with gliding motility
- fastidious = grows slowly, causes chronic disease (cancer?)

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6
Q

What are the 2 life forms of Chlamydiales and Coxiella?

A
  1. spore-like particle: infective form taken during extracellular life that allows it to persist in the environment for decades
  2. actively replicating: host cell destructive form taken during intracellular life
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7
Q

What are the forms of Chlamydia, Coxiella, and Anaplasma/Ehrlichia called while in the cytoplasm of host cells and outside of host cells?

A

INTRACELLULAR
- Chlamydia = reticulate/inclusion bodies (RB)
- Coxiella = large cell variant (LCV)
- Anaplasma & Ehrlichia = reticulate cells (morula)

EXTRACELLULAR
- Chlamydia = elementary body
- Coxiella = small cell variant (SCV)
- Anaplasma & Ehrlichia = dense-cored cells (DC)

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8
Q

How do Chlamydia, Coxiella, Anaplasma, Ehrlichia, and Rickettsia behave within host cells?

A
  • Chlamydia, Coxiella, Anaplasma, Ehrlichia = vegetative cell forms hide within vacuoles to avoid lysosomes
  • Rickettsia = vegetative forms move freely in the cytoplasm to allow it to consume cholesterol
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9
Q

What are the most common transmission route of Chlamydiales, Rickettsiales, and Mycoplasma?

A
  • Chlamydiales: airborne, sex, contagious
  • Rickettsiales: Anaplasma, Ehrlichia = ticks; Ricketssia = ticks, lice, mites, fleas; Coxiella = ticks, airborne, contagious
  • Mycoplasma: airborne, contagious
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10
Q

What is the predilection site of Chlamydiales and Mycoplasma? What does this cause?

A
  • mucous membrane epithelium (tubular organs) tropism
  • MAKePSR syndrome: mastitis, arthritis, keratoconjunctivitis, pneumonia, septicemia, reproductive disorders
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11
Q

What are the predilection sites of the members of Rickettsiales? What does this cause?

A

RBC, WBC, blood vessels

  • Anaplasma: RBC, WBC, and platelet lysis
  • Ehrlichia: RBC and WBC lysis, endothelial damage
  • Rickettsia: endothelial damage, bleeding (rash)
  • Coxiella: endothelial damage, phagocyte lysis
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12
Q

How does the iceberg concept apply to clinical cases of Chlamydiales, Rickettsiales, and Mycoplasma infection?

A

the presence of clinical signs is an indicator of a huge amount of the population being subclinical carriers and the possible involvement of multiple animal species in the geographical area

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13
Q

What type of bacteria is Chlamydia? What aspect of its structure is unique?

A

Gram-negative cocci

cell wall has very little to no peptidoglycan (still has an outer membrane with LPS)

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14
Q

How does the lack of peptidoglycan in Chlamydia’s cell wall affect staining and treatment?

A
  • best stained by Giemsa stain than Gram stain
  • best treated by tetracycline and chloramphenicol than β-lactams
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15
Q

What are the 3 possible forms of Chlamydia?

A
  1. EXTRACELLULAR - airborne and infectious, elementary body (EB) —> able to survive in the environment
  2. INTRACELLULAR - replicative form, reticular body (RB) —> destructive form
  3. INTRACELLULAR - non-replicating aberrant form, abnormal reticular body
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16
Q

When does Chlamydia transform into the intracellular abnormal reticular body form? What is its purpose?

A
  • antimicrobial treatment
  • attack by host defense system

formed for survival and persistence in harsh conditions

17
Q

Chlamydia, abnormal (aberrant) reticular bodies:

A
18
Q

What 3 environmental stresses are the elementary bodies of Chlamydia resistant to? What does this form do?

A
  1. high temperatures
  2. osmotic pressure
  3. ultraviolet light

infected vertebrates, typically transmitted by air

19
Q

How do the 2 forms of Chlamydia compare?

A

ELEMENTARY BODY: extracellular, infectious, metabolically inactive, rigid cell wall, small, electron-dense nucleoid, DNA and RNA content is the same

RETICULAR BODY: intracellular, replicating, metabolically active, fragile cell wall, large, diffuse nucleoid, RNA > DNA

20
Q

What are the 4 possible ways of transmission for Chlamydia?

A
  1. airborne —> inhaling aerosols of dried sputum, feces, or feather dust
  2. sexual intercourse
  3. contact
  4. ingestion

animal to animal, animal to human, animal to animal

21
Q

What are the host ranges of the 10 common Chlamydia species?

A
  1. C. abortus - ruminants, pigs, humans
  2. C. avium - pigeons, psittacines
  3. C. caviae - guinea pig
  4. C. felis - cat, humans
  5. C. muridarum - rodents, mice
  6. C. pecorum - domestic and wild ruminants, pigs
  7. C. psittaci - birds, pigs, ruminants, pets, equine, humans
  8. C. suis - swine
  9. C. pneumoniae - humans, horses, reptiles, amphibians
  10. C. trachomatis - humans ONLY
22
Q

What is the tropism of Chlamydia? What does it cause?

A

columnar epithelium and mucosal membranes

  • Mastitis (chronic)
  • Arthritis
  • Keratoconjunctivitis (pinkeye, trachoma)
  • Pneumonia (rhinitis, bronchitis)
  • Septicemia
  • Reproductive disorders (abortion, infertility, orchitis)
23
Q

What are the 3 common clinical signs of chlamydiosis from C. abortus?

A
  1. ovine enzootic abortion storms (sheep)
  2. purulent placentitis (sheep)
  3. follicular vaginitis (cow)
24
Q

What 4 species of Chlamydia cause chronic conjunctivitis, keratitis, and blindness (trachoma)?

A
  1. C. felis - dogs, cats
  2. C. trachomatis - humans
  3. C. suis - pigs
  4. C. pecorum - koala
25
Q

Clinical signs in Chlamydia-infected host animals:

A
26
Q

What 3 enzymes and 2 surface structures do Chlamydia use as virulence factors?

A

ENZYMES:
1. neuraminidase - digests cilia and mucus
2. catalase
3. protease

SURFACE STRUCTURES
1. LPS - escape phagocytosis
2. outer membrane proteins - adhesion

27
Q

What virulence factor is necessary for Chlamydia survival inside host cells?

A

Type 3 secretion system (invasin)

28
Q

What samples can be collected for Chlamydia infection diagnosis?

A
  • vaginal or penile discharge
  • nasal discharge
  • conjunctiva swabs (tears)
  • whole blood or serum
  • milk
  • synovial fluid
29
Q

What is necessary for Chlamydia culturing? What are 2 possible media?

A

cell lines (obligate intracellular)

  1. yolk sacs of chicken embryos
  2. Buffalo Green Monkey Kidney cells
30
Q

What genes for Chlamydia diagnosis using PCR?

A
  • ompA
  • 23S
  • 16S

(quick, convenient)

31
Q

What is the gold standard for serology testing for Chlamydia? What are other options?

A

indirect immunofluorescent IgG antibody assays

  • species-specific ELISA
  • direct fluorescent antibody
  • histopathological staining of biopsy with Ziehl Neelsen of Giemsa stains to observe intracellular incluson bodies
32
Q

What are the 2 best treatments for Chlamydia infection?

A
  1. tetracycline - Doxycycline***
  2. fluoroquinolone - Azithromycin
    (good at penetrating cytoplasm)
  • treatment must start as early as possinle and continue for at least 7 days
33
Q

Why should antibiotic treatment for Chlamydia infection be done carefully?

A

treatment may not kill Chlamydia, which induces persistent chlamydial infections due to the formation of aberrant bodies

34
Q

What are the 2 vaccines available for Chlamydia?

A
  1. C. abortus live vaccines prevent enzootic abortion in small ruminants
  2. C. felis vaccine prevents conjunctivitis and keratitis in pets

(efficacy controversal —> induce aberrant form?)

35
Q

How are Chlamydia infections controlled?

A
  • avoid close contact or mating of infected animals with a healthy herd/flock
  • separate infected animals quickly, quarantine, and treat them

Veterinary Bacteriology & Mycology (47 decks)

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