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61 Cards in this Set

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  • Back
What is the shape of Rickettsiae?

Gram + or -?

How do they reproduce?

What type of parasites are they?

Where are they usually found?
rods OR cocci

gram negative

reproduce by binary fission

obligate intracellular parasites

usually found in arthropods, usually non-pathogenic (just parasitic)
Once the complete genome sequence of Rickettsia prowazekii was determined similarities to what were noted?
mitochondrial DNA
How do Rickettsia persist even after immune response?
protected intracellular location
What are the 3 major pathogenic caused by Rickettsia?
R. rickettsii, R. typhi, C. burnetii
How does rickettsia infect?
1. introduced by arthropod bite (tick or mite), or the host scratching arthropod feces into the broken skin (insects, such as fleas and lice).

2. . Organisms proliferate in endothelial cells and cause leakiness of blood vessels. They are widely disseminated in the blood.
What are the symptoms of rickettsia disease?
Headache, chills and fever, followed by petechiae and often a hemorrhagic rash.
What is the fatality rate? What is it dependent upon?
Fatality rate varies widely, depending on species and strain of organism, from 1% to 90%.

The average is probably around 20% if untreated.

Those who recover are usually immune.
Which bacteria causes rocky mountain spotted fever?

What is the vector?

What is the reservoir?
Rocky mountain spotted fever

R. rickettsii

vector: tick

reservoir: wild rodents and dogs
What bacteria causes marine typhus? Vector? Reservoir?
R. typhi

vector: rat flea

reservoir: small rodents
What bacteria causes Q fever? Vector? Reservoir?
C. burnetii

Vector: tick (inhalation of organism)

Reservoir: cattle, sheep, goats
How can diagnosis of rickettsia be made?
serology with convalescent serum

A four-fold rise in titer is diagnostic.
What are 3 types of serologic tests that can be employed in detecting Rickettsiae?
1. Weil-Felix agglutination

2. Serologic tests using rickettsial Ags

3. Direct immunofluorescence or PCR of skin biopsy (may become more commonly used to ID the organism)
How does the Weil-Felix agglutination test work?
certain strains of Proteus vulgaris used as antigens--known as X strains, which CROSS-REACT with some rickettsiae, is only of HISTORICAL INTERST.

It lacks sensitivity and specificity and should not be used any more.

basically, who'll be question # 85 on the exam though :)
What are you looking for in a serologic test using rickettsial Ags?
looking for a fourfold rise in titer OR

a single high titer of IgM, IgA, or IgG.

These tests may not identify the species of Rickettsia.
Does Coxiella burnetii require an arthropod vector?

How is it able to survive for a long time in the environment?

How does the disease most commonly manifest itself?
Does not require an arthropod vector for transmission; most common route of transmission is respiratory.

Much more resistant to drying than other rickettsiae. It may form a resistant structure resembling a cyst or spore.

The disease is an acute febrile systemic illness, which most commonly manifests itself as an atypical pneumonia, but may cause hepatitis or endocarditis.
Is Q fever usually fatal?
No, but might become chronic. ex. endocarditis, hepatomegaly, thrombocytopenia may all be late manifestations
What serves as the host for Coiella burnetii?

Does human-human transmission occur?
ticks, insects, birds, wild and domestic animals, cattle, sheep, goats

often latent in birds and mammals--shed into environment

Ordinarily, no human-to-human transmission.
Where is Coxiella burnetii common?

Because of this what was changed?
common in dairy herds, and dairy cattle can pass the organism in their milk.

The temperature required for pasteurization of milk was slightly increased to eliminate Coxiella burnetii.
How can Coxiella burnetii be diagnosed?
Which genus is known as an emerging disease?

What are the symptoms of disease?

fever, myalgia, headache, leucopenia, and thrombocytopenia.
What does Ehrlichia chaffeenis disease often mistaken for?

Where is this disease often found?
Rocky mountain spotted fever.

BUT there's NO RASH!!

seen mainly in the southeast and midwest.
How is Ehrilichia chaffeensis transmitted?

What is the reservoir?
by humans and ticks

deer are the reservoir
Where does Ehrlichia chaffeensis replicate?

What does it form?
in monocytes and macrophages

forms inclusion bodies called morulae which are aggregates of bacteria
How is Ehrlichia diagnosed?
indirect immunofluorescence using acute and convalescent serum




What does Ehrlichia granulocytophila resemble in symptoms?

Where is it found?
Rocky Mountain Spotted Fever

found especially in the upper Midwest and the Northeast
What is the vector for Ehrlichia granulocytophila?

What can it be transmitted with?

What is the reservoir?
tick of genus Ixodes--might be transmitted with Lyme disease!

reservoir: rodents and deer
Where does Ehrilichia granulocytophila replicate?

How can this occur?
In granulocytes (neutrophils) with inclusion bodies = morulae.


Can invade neutrophils by producing proteins that BLOCK APOPTOSIS of the neutrophil, prolonging its survival, and thus ensuring that the Ehrlichia has adequate time to multiply.

The lifespan of the neutrophil is extended from a few hours to perhaps 2 FULL DAYS!
How can Ehrlichia diagnosed?
4-fold increase in Ab titer to E. Equi or by PCR

Note: closely related to E equi of horses
What disease does Ehrlichia granulocytophila cause?
Human Granulocytic Ehrlichiosis (HGE)
What type of problems might arise in an individual with Ehrlichia granulocytophila?
heart problems
What disease does Ehrlichia chaffeensis cause?
Human Monocytic Ehrlichiosis
What does Ehrlichia canis resemble and who does it affect?
resembles Ehrlichia chaffeensis

endemic in dogs--occasionally infect humans
What does Ehrlichia ewingii resemble and who does it affect? Where does it grow?
Also resembles Ehrlichia chaffeensis

also a pathogen of dogs

grows in granulocytes
What is an elementary body and which type of bacteria have it?
no active metabolism--dormant protective feature of chlamydiae
What is the elementary body made of ?

What does it look like?

Does it produce peptidoglycan?

What allows for rigidity of the cell wall?
Dense, spherical body 0.2 to 0.4 μm in diameter

surrounded by a rigid cell wall which looks like that of Gram-negative bacteria.

***the wall does NOT contain normal peptidoglycan, even though chlamydial genome sequences show that they have the genes for peptidoglycan biosynthesis.

Rigidity of the cell envelope is due to extensive disulfide cross-linking in the major outer membrane protein (MOMP), a porin.
In comparison to E. Coli how much DNA does the Chlamydiae genome contain?

How many genes does Chlamydiae have?
only 1/4 as much as E. Coli

Chalamydiae has about 1000-1100 genes

b/c cuts out all unnecessary genes, which it will get from its host. Ex. C. pneumoniae and trachomatis
What do you use to stain chlamydiae?
use Giemsa stain
Describe the development cycle of Chlamydiae. How long does the cycle take?
1. Attachment to host cell, usually an epithelial cell.

2. Elementary body enters host cell via receptor-mediated endocytosis

3. Within the protective membrane-bounded vesicle, there is loss of rigidity of the EB cell wall by reduction of disulfide linkages.

The cell enlarges to form a structure called the RETICULATE BODY, which is about 1 μm in diameter.

The reticulate body looks like a normal Gram-negative bacterial cell.

The vacuole is prevented from undergoing fusion with the lysosome.

4. Reticulate bodies replicate by binary fission and are non-infectious.

5. At the completion of the chlamydial life cycle, the reticulate bodies differentiate back into elementary bodies.

The late inclusion body (vacuole) contains 100 or more elementary bodies.

6. Rupture of the vacuole and of the cell releases the elementary bodies to repeat the cycle.

The total cycle takes 48-72 hours.
What type of parasite is chlamydiae?

Does it produce its own ATP?
obligate intracellular parasites

doesn't synthesize its own ATP--energy parasites!!

Also don't produce otehr biosynthetic capabilities--remember--cutting down on # of genes
What are characteristics of the diseases caused by Chlamydiae?

inapparent infection

carrier state


ex. pelvic inflammatory disease (scarring can lead to obstruction of the fallopian tubes)
What effect do Abs have on chlamydiae?
Antibodies are produced but do not appear to have protective effect
What is the most common infectious cause of blindness in the world?

Which antigenic types?

What is the reservoir?


How is it transmitted?
Chlamydiae trachomatis

trachoma--antigenic types A-C

Reservoir: infected humans

Host: humans

Transmission: fingers, fomites, flies (have to have it for months or years)
How can trachoma Ag types A-C be identified?
examine conjunctival scrapings for inclusion bodies by staining
When does the WHO plan to have blinding trachoma eradicated?
2020 by using oral antibiotics and public health measures
What do Chlamydia trachomatis antigenic types D-K cause?

What is the mode of transmission?
sexually transmitted diseases

transmission by secretions from infected genitourinary tracts (often asymptomatic)
Which is more common STD in women Nisseria gonorrhoeae or Chlamydia trachomatis?
chlamydia trachomatis is 8x more likely to be found in asymptomatic females
When was chlamydia trachomatis made nationally reportable?

also common notifiable diseases
What diseases can be caused by Chlamydia trachomatis (7)?
1. Non-gonococcal urethritis in males (probably about 50% of all cases)

2. Cervicitis in females (often asymptomatic)

3. pelvic inflammatory disease (PID), ectopic pregnancy, and infertility among women.

4. conjunctivitis in the newborn, and neonatal pneumonia in children under eight weeks of age. (Contracted from the mother at birth.)

5. Swimming pool conjunctivitis in adults. Transmitted in inadequately chlorinated swimming pools, or by contamination of the eye with genitourinary exudates on towel or fingers.

6. Reiter’s Syndrome. Arthritis, urethritis, conjunctivitis. Complication following chlamydial infection. Immunologically mediated in some genetically predisposed individuals.

7. Inflammation caused by this organism increases the transmission of HIV by three- to five-fold.
How is Chlamydia diagnosed?
inoculation of cell cultures and looking for characteristic inclusion bodies by staining or fluorescent antibody.

Non-culture direct tests on clinical specimens may be used, but may yield false negatives.

The Food and Drug Administration has approved a PCR test for detection of C. trachomatis.
How often does the CDC recommend screening for sexually active women <20?

<20 at least annually

>20 with one or more risk factors (lack of barrier contraception, and new or multiple sex partners during the preceding three months.)
What causes lymphogranuloma venereum?

What are the antigenic types of Lymphogranuloma venereum (LGV)?
third disease caused by Chlamydia trachomatis

L1, L2, L3 antigenic types
How is Lymphogranuloma vernerum transmitted?

Where is it found?

What does it infect?

What does it cause?
Lymphogranuloma vernerum

A VD transmitted via sexual contact thru minute abrasions

NOT found in the US

infects RETICULOENDOTHELIAL CELLS causes lesions in the local LYMPH NODES

can lead to RUPTURE of infected lymph node = formation of abscesses, fissures, sinus tracts, and fistulas

can lead to elephantitis= lymphedema
What is the pneumonic for reiter's syndrome?
can't see, can't pee, can't climb a tree

conjunctivitis, urethritis, arthritis
Which type of chlamydia is transmitted thru birds?

How are people infected?
Chlamydia psittaci

Transmission via respiratory route by exposure to infected birds who excrete the organism through feces and nasal discharge
How does Chlamydia psittaci infect the host?

What does it sometimes manifest itself as?
Organisms travel through the blood to the reticuloendothelial cells of the liver and spleen, multiply there, and then invade the lungs by hematogenous seeding.

A systemic influenza-like disease which may also manifest itself as a severe pneumonia.
What does the laboratory diagnosis look like?
a four-fold rise in specific antibody titer between acute and convalescent serum.
Why is it easy to get this from birds?
Latency in the reservoir is a problem.

An asymptomatic bird may transmit the disease.

During stress, clinical disease may ensue in an animal with a latent infection.
How is Chlamydia pneumoniae transmitted?
human to human thru respiratory route
What infections does Chlamydia pneumoniae cause?
Causes both upper and lower respiratory tract infections, including bronchitis, pneumonia, and sinusitis.
How is Chlamydia pneumoniae diagnosed?
by serology.
What types of diseases is Chlamydia pneumoniae thought to be involved with?
adult onset asthma, wheezing, asthmatic bronchitis--all controversial

atherosclerotic plaques in 50% studied (coronary and carotid aa)