Microbiology Lecture 3.5: Anaerobic Gram-Negative Bacteria

What type of bacteria are incapable of using oxygen as a final electron acceptor?

Obligate Anaerobes

Where are anaerobes the predominant bacterial microbiota?

Mucous membranes (Respiratory, gastrointestinal, genitourinary)

What causes anaerobe infections?

1. Impaired blood supply

2. Tissue Necrosis

What allows anaerobic microbiota to gain access to newly desirable environments?

Breaks in mucosal epithelium

What are the end results of anaerobe infections?

1. Localized tissue destruction

2. Inflammation

What conditions are susceptible to anaerobe infections?

1. Open wounds

2. Diabetes

3. Cancers

4. Infected teeth

What are the common causes of anaerobe infections?

1. Antibiotics poor against anaerobes

2. Human/animal bites

Gram negative anaerobic bacteria are ________ members of host microflora

Endogenous

What are Koch's Postulates?

1. Microorganism found in abundance in all organisms suffering from the disease and NOT found in healthy organisms

2. Microorganism is isolated and grown in pure culture

3. Cultured microorganism causes disease when introduced to healthy organism

4. Microorganism is reisolated from the experimental host and is identical to original microorganism

What are the species in Socransky's Red Complex most associated with?

Periodontal disease

What are the species in Socransky's Red Complex?

1. P. gingivalis

2. T. forsynthensis

3. T. denticola

What are Socransky's modified postulates?

1. Associated with disease

2. Treatment results in elimination

3. Evidence of host response

4. Cause disease in animal model

5. Produce virulence factors

Are gram negative anaerobes opportunistic or non oppotunistic?

Opportunistic

What is the ability of gram negative anaerobes to become opportunistic dependent on?

Virulence Factors

What are the tissues that are damaged that causes serious infections by gram negative anaerobes?

1. Subcutaneous

2. Pleuropulmonary

3. Intraabdominal

4. Genital

What is virulence that becomes intensified when co-infections by certain species exist?

Synergistic Enhanced Virulence

What are Bacteroides species a major inhabitant of?

Human colon

If Bacteroides species are in the human colon, what relationship does it have with the human body?

Mutualism

When do gram negative anaerobic bacteria cause disease?

When they are in areas of the body where they don't belong

What do Bacteroides species invade body tissue through?

Wounds in intestinal mucosa

What do Bacteroides species form when they are in body tissues?

Abscess

What are the traits of the interior of abscess?

1. Anaerobic

2. Impenetrable to antibiotics

What are the virulence factors of Bacteroides species?

1. Capsule

2. Fimbriae

3. Lipases/Proteases/Collagenases

4. Beta-lactamase

What are the virulence factors of Bacteroides species that allow for tissue destruction and abscess formation?

1. Lipases

2. Proteases

3. Collagenases

What are the diseases caused by Bacteroides species?

1. Abscesses

2. Pressure ulcers

3. Appendicitis

4. Bacteremia

What do Prevotella species colonize in humans?

1. Mouth

2. Vagina

3. Gastrointestinal Tract

What are the virulence factors of Prevotella?

1. Capsule

2. IgA, IgM, IgG proteases

3. Collagenases

4. Beta-lactamase

What are the diseases caused by Prevotella species?

1. Abscesses

2. Pneumonia

3. Bacteremia

4. UTIs

5. Periodontitis

What do Fusobacterium species colonize in humans?

1. Mouth

2. Vagina

3. Gastrointestinal Tract

What are the virulence factors of Fusobacterium species?

1. Capsule

2. Leukotoxin

3. Hemolysins

4. Hemagglutinin

5. Phospholipase C

6. Beta-Lactamase

What is the function of Hemagglutinin?

Facilitate attachment to host cells

What is the function of Phospholipase C?

Mediate host tissue destruction

What are the diseases caused by Fusobacterium species

1. Lemierre syndrome

2. Abscess

3. Bacteremia

4. Abdominal infections

5. Pulmonary infections

What is the complication of throat infections that lead to inflammation of internal jugular veins?

Lemierre Syndrome

What kind of anaerobe are Porphyromonas species?

Obligate Anaerobes

What is the most common species to cause disease in humans?

Porphyromonas species

What do Porphyromonas species colonize in humans?

1. Mouth

2. Respiratory Tract

3. Gastrointestinal Tract

Where does P. gingivalis form a biofilm?

Below gingival surface

What is the result of inflammatory responses to P. gingivalis?

Detachment of gums from teeth

What are the virulence factors of P. gingivalis?

1. Capsule

2. Fimbriae

3. Beta-Lactamase

4. Proteases

What are the proteases in P. gingivalis?

1. Collagenases

2. Gingipains

What kind of proteases are gingipains?

Cysteine Proteases

What is the disease caused by P. gingivalis?

Chronic adult periodontitis

Why do anaerobic infections generally require surgery?

Antibiotics cannot penetrate abscesses