Microbiology Quiz: Chlamydia & Rickettsia

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Questions and Answers

What is the primary complicating factor associated with trench fever caused by Bartonella Quintana?

Roseolar rash

Exhaustion

Peliosis of the liver

Endocarditis (correct)

What characteristic distinguishes Chlamydia from other bacteria?

Filamentous structure

Presence of muramic acid in cell walls

Obligate intracellular parasitism (correct)

Lack of ATP

During the cycle of Chlamydia, what does the elementary body (EB) induce upon infection?

Phagocytosis by the host cell (correct)

Lysis of host cell

Formation of inclusion bodies

Binary fission in the cytoplasm

Which of the following features is NOT true about Bartonella species?

They multiply rapidly within 24 hours Signup and view all the answers

What are the replicative forms of Chlamydia called during its developmental cycle?

Reticulate bodies Signup and view all the answers

What is one of the key complications associated with Rickettsia prowazekii infection?

Mental confusion Signup and view all the answers

Which laboratory method is considered the most useful for detecting antigens in biopsy tissues?

Direct Immunofluorescence Signup and view all the answers

What characteristic rash is associated with Rocky Mountain spotted fever?

Petechiae and hemorrhages in skin and mucous membranes Signup and view all the answers

Which cytokines are activated by Cytotoxic T-cell lymphocytes to target intracellular Rickettsiae?

Interferon-gamma and Tumor necrosis factor alpha Signup and view all the answers

In Rickettsial pox caused by R. akari, what is a notable physical finding at the entry site?

A black painless eschar Signup and view all the answers

Which statement correctly describes the distribution of the maculopapular rash in Rickettsia prowazekii infection?

Starts at the upper trunk and spreads to the whole body except the face Signup and view all the answers

What is the primary vector for the transmission of Rickettsial pox?

Mouse mite Signup and view all the answers

Which serological method helps to differentiate between IgM and IgG antibodies for early diagnosis?

Indirect Immunofluorescence Signup and view all the answers

What is the primary method of laboratory diagnosis for Human Ehrlichiosis?

PCR Signup and view all the answers

Which vector is responsible for transmitting E.chaffeensis?

Amblyomma ticks Signup and view all the answers

What is the typical duration of disease onset before a diagnosis can be made for Human Ehrlichiosis?

3-4 days Signup and view all the answers

Which of the following organisms is characterized by cytoplasmic inclusions in monocytes?

Ehrlichia Signup and view all the answers

Which symptom is NOT commonly associated with Human Ehrlichiosis?

Rash Signup and view all the answers

What laboratory method can be used to diagnose Q fever?

Isolation in cell lines Signup and view all the answers

How does Anaplasma phagocytophilum evade the host immune system?

By antigenic variation Signup and view all the answers

What is a common zoonotic reservoir for Bartonella quintana?

Rats Signup and view all the answers

Which treatment is recommended for Brucella infections?

Streptomycin Signup and view all the answers

What type of environment does Brucella require for growth?

Aerobic, capnophilic conditions Signup and view all the answers

What is a common clinical manifestation of Brucella infection?

Musculoskeletal pain Signup and view all the answers

How does Brucella evade the immune system?

Inhibiting phagosome-lysosome fusion Signup and view all the answers

What diagnostic method can identify Brucella antibodies?

Rose Bengal card test Signup and view all the answers

Which serotypes are associated with non-gonococcal urethritis?

Serotypes D-K Signup and view all the answers

What is a key virulence factor of Legionella pneumophila?

Inhibition of phagosome-lysosome fusion Signup and view all the answers

What type of stain is NOT commonly used for observing microorganisms like Chlamydia and Legionella?

Gram stain Signup and view all the answers

Which disease is caused by Legionella pneumophila?

Legionnaires' disease Signup and view all the answers

Which method is used for the culture of Legionella pneumophila?

Buffered charcoal yeast extract agar with CO2 Signup and view all the answers

What is the fatality rate of Legionnaires' disease in healthy individuals?

15% Signup and view all the answers

What characteristics describe Brucella species?

Small, motile, Gram-negative coccobacilli Signup and view all the answers

Which of the following is NOT a serious concern regarding Legionella pneumophila infections?

Subclinical infections in healthy individuals Signup and view all the answers

Study Notes

Rickettsia

Cytotoxic T-cell lymphocytes and CD8 cells play a role in host defense against rickettsial infections.
Interferon-gamma and tumor necrosis factor alpha activate endothelial cells to kill intracellular Rickettsiae.
Rickettsia prowazekii causes Epidemic typhus.
- Symptoms include severe headache, chills, fever, maculopapular rash (due to subcutaneous hemorrhages from blood vessel invasion).
- The rash starts on the upper trunk and spreads to the whole body except the face, palms, and soles.
- Complications can include mental confusion, myocarditis, and latent infection (Brill Zinsser Disease).
Rocky Mountain spotted fever is caused by R. rickettsii and is potentially fatal.
- Characterized by fever, headache, chills, myalgia, nausea, and a maculopapular rash.
- The rash starts on the extremities including palms and soles and spreads to the chest and abdomen.
- Rash progresses into petechiae with hemorrhages due to vascular damage.
- Complications can involve the lungs, CNS, heart, kidneys, and lead to Disseminated Intravascular Coagulation (DIC).
- Death may occur during the second week due to kidney or heart failure.
Rickettsial pox is caused by R. akari and is typically mild and not fatal.
- Spread through the bite of a mouse mite from a mouse reservoir.
- A black painless eschar with a red halo forms at the bite site.
- Followed by fever, malaise, headache, a vesicular rash, regional lymphadenopathy, and resembles chicken pox.

Laboratory Diagnosis of Rickettsia

Direct Microscopy
Serology
- Indirect Immunofluorescence (detects antibodies)
  - Differentiates between IgM and IgG antibodies, useful for early diagnoses.
- Direct Immunofluorescence (detects antigen in tissue)
  - Most effective diagnostic tool, provides results 3-4 days into illness.
  - 100% specific and 70% sensitive.
Molecular tools
- PCR
Culture
- Tissue culture systems
- Hens' eggs
Animal models
- Guinea pigs
- Mice

Ehrlichia

Small, Gram-negative, obligate, intracellular bacteria.
Anaplasma phagocytophilum causes human granulocytic Ehrlichiosis.
- Spread by Ixodes ticks.
- Animals like deer, cattle, and sheep serve as reservoirs.
E. chaffeensis causes human monocytic Ehrlichiosis.
- Spread by Amblyomma ticks
- Deer are the primary reservoir
Both species multiply in cells to form mulberry-shaped aggregates called morulae.
Characterized by
- Lymphadenopathy
- Hepatosplenomegaly
- Leucopenia
- Thrombocytopenia
- DIC

Ehrlichia Pathogenesis

Cytokine-mediated immunopathogenesis
A. phagocytophilum evades the host immune system through antigenic variation.
E. chaffeensis
- Modulates host defense mechanisms
- Blocks phagosome-lysosome fusion, allowing for survival inside macrophages.
- Inhibits apoptosis, prolonging the lifespan of host cells to accommodate its slow generation time.

Q Fever

Caused by Coxiella burnetii
Zoonosis (found in cattle, sheep, and goats)
Transmission through inhalation of infectious material or ingestion of contaminated milk.
An intracellular parasite that infects macrophages and is resistant to lysosomal enzymes.
Characterized by sudden onset of fever, chills, headache, but no rash.
Disease can manifest as atypical pneumonia, CNS involvement, and endocarditis.

Bartonella quintana

First isolated by Vinson in 1960.
Used to self inoculate with the bacteria to prove Koch's postulates using human volunteers.
Causes
- Trench Fever: transmitted by body lice
- Bacillary angiomatosis: involves neovascularization, often occluding blood flow
  - Also caused by Bartonella henselae involving spleen and liver (peliosis)
- Endocarditis
Bartonella is fastidious, slow-growing (12-45 days), facultative, intracellular, Gram-negative bacilli
Invades red blood cells and other cells
Causes bacteremia
Symptoms include headache, exhaustion, leg pains, high, relapsing fever, and a roseolar rash.
Complication: endocarditis

Chlamydia

Obligate intracellular parasites.
Energy parasites - they lack the ability to produce ATP on their own.
Cell walls share some similarities with Gram-negative bacteria but lack muramic acid.
Have a complex developmental cycle.
- Elementary body (EB) is the infective form. It induces phagocytosis.
- Reticulate body (RB) is the replicative form. It multiplies inside the phagocytic vesicle.

Chlamydia Developmental Cycle

EB reorganizes into the noninfectious, metabolically active RB after approximately 6-8 hours.
RB divides by binary division to form inclusion bodies that condense into EBs.
The cell lyses and releases EBs, starting the cycle again.

Chlamydia Serotypes and Diseases

Serotypes A-K and L1,2,3.
Sexually transmitted infections
- Non-gonococcal urethritis: D-K
- Lymphogranuloma venereum: L1,2,3
Eye infections
- Trachoma (causes blindness): A-C
Neonatal infections
- Neonatal inclusion conjunctivitis: D-K
- Neonatal pneumonia
Adults: Atypical pneumonia
Chlamydia pneumoniae and C. psitacci can also cause pneumonia.

Laboratory Diagnosis of Chlamydia

Direct Microscopy
- Iodine stain
- Giemsa stain
Direct Immunofluorescence
- Fluorescence antibody

Culture of Chlamydia

Yolk sac of a 6-8 day old chick embryo
Tissue culture
- Irradiated McCoy and HeLa cell lines

Legionella pneumophila

Discovered in 1976 during an outbreak of atypical pneumonia at the American Legion convention in Philadelphia, leading to the name "Legionnaires’ disease."
Prefers slow moving or stagnant water at temperatures between 20-50°C.
An intracellular pathogen that infects macrophages and alveolar epithelial cells.
Inhibits phagosome-lysosome fusion, allowing for intracellular growth.
Causes Legionnaires’ disease (atypical pneumonia) and Pontiac fever.
Fatality rates are higher in immunocompromised individuals (75%) compared to healthy individuals (15%).
Can cause multi-organ involvement, affecting the gastrointestinal system, CNS, liver, and kidneys.

Epidemiology of Legionella pneumophila

Opportunistic disease
- Primarily affects people with underlying illnesses or weak immune systems.
- Common in middle-aged and elderly individuals, those with COPD and smokers.
Reservoir of infection:
- Cooling towers of air conditioning systems
- Hot water lines
- Soil and water
Nosocomial infections are a major concern, particularly in healthcare settings.

Legionella Virulence Factors

Inhibits phagosome-lysosome fusion, allowing for intracellular growth.
Endotoxin inhibits the generation of peroxide in phagocytic cells.

Morphology and Culture Characteristics of Legionella pneumophila

Small, motile, Gram-negative, pleomorphic rods that stain poorly.
Direct fluorescent antibody
Urinary antigen testing: rapid, easy, and inexpensive.
Media: buffered charcoal yeast extract (BCYE) agar in CO2.
Selective agent: antibiotics
Molecular tools

Brucella

Small, Gram-negative coccobacilli
Non-motile, aerobic, capnophilic
Zoonosis - spreads from animals to humans.
Facultative intracellular pathogen, infecting the reticuloendothelial system (RES).
Survives within macrophages by inhibiting phagosome-lysosome fusion.
Causes brucellosis, a systemic disease.
Symptoms are often non-specific and include fatigue, weight loss, weakness, fever, chills, abdominal pain, diarrhea, vomiting, undulant fever (recurrent fevers), and typhoid-like fevers.
Can also cause musculoskeletal symptoms and affect the CNS (depression) and cardiovascular system (endocarditis).

Laboratory Diagnosis of Brucella

Blood culture
Serology
- Standard agglutination test: detects IgM antibodies.
- IgG: detected through ELISA.
Molecular tools
Animals:
- Antibody detection: Rose Bengal card test

Treatment of Rickettsial, Chlamydial, Legionella, and Brucella Infections

Rickettsia: Doxycycline, chloramphenicol
Chlamydia: Doxycycline, erythromycin
Legionella: Erythromycin, tetracycline
Brucella: Streptomycin, doxycycline

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Description

Test your knowledge on diseases caused by Chlamydia and Rickettsia, including complications and distinguishing characteristics. This quiz covers key topics like trench fever and specific features related to Bartonella species. Perfect for microbiology students looking to reinforce their understanding.