Chlamydia, Rickettsia, Mycoplasma, and Similar Organisms Chapter 20

What causes Rocky Mountain Spotted Fever

Rickettsia rickettsii

How is Rocky Mountain Spotted fever transmitted

Through bites from an infected hard tick

Which ticks are responsible for spreading Rickets

Dog tick (Dermacen-tor variabilis)

Wood Tick (Dermacentor andersoni)

Where is the dog tick found

In the southeast US

Where is the wood tick found

Rocky Mountain region and Southwestern Canada

When do most Rocky Mountain Spotted fever infections happen

Between April and September

How long is the incubation period after a tick bite for Rickettsia rickettsii

About one week

What are the main symptoms of Rocky Mountain spotted fever

1. High fever

2. Severe Headache

3. Muscle Pain

4. Nausea

5. Vomiting

6. Abdominal pain

What is a key sign of severe infection for Rickettsia rickettsii

A spotted or Erythematous rash

Where does the rash first appear in Rickettsia rickettsii

On the ankles and wrists, then spread to the palms and the soles it enlarges in size and developing ecchymoses

What complications can happen in severe rocky mountain spotted fever

1. Myocardial

2. Neurological

3. Pulmonary

4. Hepatic

5. DIC

6. Hypotension

7. Low blood volume

What happens to R. rickettsii once it it taken up by endothelial cells

It escapes the phagosome, replicates in the cytoplasm, and spreads to adjacent cells

What does the spread of R. rickettsii cause

Vasculitis

What are some complications that can arise from R. rickettsii

1. Myocardial

2. Neurological

3. Pulmonary

4. Hepatic

5. DIC

6. Hypotension

7. Low blood volume

How is Rocky Mountain spotted fever treated?

Doxycycline or chloramphenicol

What is an important preventive measure for Rocky Mountain spotted fever?

Controlling the tick population

What causes rickettsialpox

Rickettesia akari

How is rickettsialpox transmitted

Through the bite of a mouse mite

What is the major animal reservoir for rickettsia akari

The house mouse

How do humans relate to Rickettsia akari

They are accidental hosts

What is the first phase of the Rickettsia akari infection like

A papule develops at the site of the bite, and a eschar forms after 1-3 weeks

What symptoms occur in the second phase of rickettsialpox

1. Fever

2. Severe headache

3. Chills

4. Sweating

5. Photophobia

What kind of rash develops in the second phase of Rickettsia akari

A papulovesicular rash that crusts over after 2-3 days

How serious is rickettsialpox

It is mild

What is the treatment for rickettsialpox?

Doxycycline RP

Where is rickettsialpox commonly found?

In crowded urban areas with rodents or mice in korea, ukraine, or east US

What causes EPIDEMIC typhus

Rickettsia prowazekii.

Where is EPIDEMIC typhus most common?

In central and south America, Africa and less frequent in the US in crowded unsanitary places

What is the vector for Rickettsia prowazekii

The human body louse

How do fleas contribute to the spread of R. prowazekii

Infected fleas can transmit the bacteria from flying squirrels to humans in the southeastern United States

How does the louse become infected with R. prowazekii?

By feeding on a infected human, the bacteria invade the cells on the louse gut

How is the R. prowazekii infection transmitted from the louse to human

The infected louse poops on a human while feeding, and the poop is scratched into the skin

Can R. prowazekii remain in the body

It can remain dormant in the lymph tissue of the hose

What is Brill-Zinsser disease?

A reactivation disease caused by R. prowazekii that occurs after a primary infection.

What are symptoms of epidemic typhus

1. Fever

2. Headache

3. Muscle pain

4. Joint pain

5. Neurological symptoms

6. Rash on palms, soles, or face

How is epidemic typhus treated

Tetracycline

What are important preventive measures for EPIDEMIC typhus?

Controlling the rodent and lice populations.

What causes ENDEMIC typhus

Rickettsia typhi.

Where is ENDEMIC typhus commonly found?

In warm, humid climates worldwide, including Africa, Asia, Australia, Europe, and the Americas.

What is the primary animal reservoir for R. typhi?

Rats.

What are the main vectors for Rickettsia typhi?

The rat flea and the cat flea

How do fleas transmit R. typhi to humans?

Infected fleas either defecate on the skin while feeding or bite the host directly.

What are the common symptoms of ENDEMIC typhus?

1. Fever

2. Chills

3. Headache

4. Muscle Pain

5. Nasuea

Where does the rash typically appear in ENDEMIC typhus?

Chest and Abdomen

How severe is ENDEMIC typhus compared to Rocky Mountain Spotted Fever?

It is generally less severe.

What is the treatment for endemic typhus?

Tetracycline.

What causes scrub typhus

Orientia tsutsugamushi.

What are the vectors for scrub typhus

Infected chiggers and mites

What is the primary animal reservoir for Orientia tsutsugamushi.

It is Rats

Where is scrub typhus found

Eastern Asia, Australia, and Japan

What are the common symptoms of scrub typhus?

1. Headache

2. Fever

3. Muscle pain

4. Maculopapular rash

Where does the rash usually appear in scrub typhus?

On the trunk, then it spreads to the arms and legs

What forms at the site of the initial bite?

A black eschar

What complications can occur with scrub typhus?

enlarged spleen or lymph nodes

How can Rickettsia be detected in skin tissue?

Using immunohistochemistry staining and fluorescein or enzyme-labeled polyclonal antibodies

What are some other methods to detect Rickettsia?

PCR

How can tissue samples be cultured for detecting Rickettsia?

In embryo eggs or tissue culture, or by staining directly with an immunofluorescence stain

Can serology diagnose an acute Rickettsia infection?

No, most often confirms a diagnosis in a convalescent specimen

What historic test was used to identify Rickettsia?

The Weil-Felix reaction, where patient serum agglutinates specific strains of Proteus Vulgaris (OX-19,OX-2,OX-K)

Which strains agglutinate for Rocky Mountain spotted fever in the Weil-Felix test?

OX-19 and OX-2

Is the Weil-Felix test still used in the U.S.?

No, because it lacks specificity and produces variable results.

What containment level is required for Rickettsia testing?

Level 3

What are the two genera in the Anaplasmataceae family?

Ehrlichia and Anaplasma.

Where can these Ehrlichia and Anaplasma survive and grow

1. Cytoplasmic vacuoles

2. Within neutrophils

3. Monocytes

4. Platelets

5. Erythrocytes

What are the two forms of Ehrlichia and Anaplasma

The dense elementary body and the reticulate body

Where does the Anaplasmataceae organism replicate?

In the phagosome of the host cells

What does the Anaplasmataceae prevent from forming in the host cell?

The formation of the phagolysosome

How do Ehrlichia and Anaplasma organisms multiply inside the host cell?

Binary Fission

What do the bacteria clusters within the host cell form?

Morulae, which are round to oval bacterial clusters

What happens when the host cell ruptures?

The morulae break into individual EBs, and the cycle continues.

Where do Ehrlichia organisms multiply in the host?

In the phagosomes of host leukocytes

What is Ehrlichia chaffeensis the agent of?

Human monocytic ehrlichiosis

What is the primary vector for E. chaffeensis?

The lone star tick

What are the primary animal reservoirs for E. chaffeensis?

Deer

Dogs

Humans

What are the common symptoms of human monocytic ehrlichiosis (HME)?

1. Influenza-like symptoms

2. High fever

3. Headache

4. Malaise

5. Muscle pain (myalgia)

What blood-related issues can occur in E. chaffeensis infection?

Leukopenia

Neutropenia

Thrombocytopenia

Elevated ALT/AST

What does Ehrlichia ewingii cause?

Granulocytic ehrlichiosis.

How does E. ewingii infection compare to human monocytic ehrlichiosis (HME)?

It closely resembles HME but specifically invades granulocytes, especially neutrophils.

What is the vector for E. ewingii?

Also the lone star tick

What is the primary animal reservoir for E. ewingii?

It is dogs

What does Anaplasma phagocytophilum cause?

Human granulocytic anaplasmosis (HGA).

How does Human granulocytic anaplasmosis (HGA) compare to human monocytic ehrlichiosis (HME)?

HGA resembles HME in symptoms but involves different reservoirs and vectors.

What are the animal reservoirs for A. phagocytophilum?

Chipmunks

White-footed Mice

Cattle

Horse

Dogs

What ticks are vectors for A. phagocytophilum?

Ixodes scapularis and Ixodes pacificus

How is A. phagocytophilum transmitted to humans?

Through the larva and nymph stages of ticks ingest blood from an infected host during a blood meal.

Are humans accidental hosts for A. phagocytophilum?

YES

Which blood cells does A. phagocytophilum invade?

Neutrophils

Eosinophils

Basophils

What are the common symptoms of Human granulocytic anaplasmosis or HGA

1. Influenza like symptoms

2. Headache

3. Muscle pain

4. Rash in small %

What blood-related issues can occur in Human granulocytic anaplasmosis

1. Leukopenia

2. Thrombocytopenia

3. Elevated Liver enzymes

Is infection with A. phagocytophilum more severe than with E. ewingii?

YES

How are Ehrlichia and Anaplasma infections diagnosed?

Through patient history, clinical symptoms, and demonstration of the morulae within host cells.

What are morulae?

Cytoplasmic vacuoles found within host cells.

Where can morulae be found

In the buffy coat of peripheral blood during febrile episodes

What stain can be used to detect morulae in the blood?

Giemsa stain.

What direct antigen testing methods can help diagnose Ehrlichia and Anaplasma infections?

Nucleic Acid Amplification Testing on bone marrow, liver, or spleen tissue.

When are most Ehrlichia and Anaplasma infections diagnosed?

retrospectively.

What is the treatment for Ehrlichia and Anaplasma infections?

Doxycycline EA

What is Chlamydiaceae

A family of obligate intracellular organism

Why was Chlamydiaceae orginally thought to be a virus

Because they cannot survive outside of animal host cells and cannot produce their own ATP

What are the key characteristics of Chlamydiaceae?

1. Have a gram negative like cell wall

2. Contain both DNA and RNA

3. Posses a prokaryotic ribosome

4. Can make proteins, lipids, and nucleic acids

5. Depend on the host for ATP

6. Replicate through binary fission