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Veterinary Bacteriology & Mycology > Bacteroides, Prevotella, & Porphyromonas > Flashcards

Bacteroides, Prevotella, & Porphyromonas Flashcards

1
Q

What are the 3 major characteristics of Bacteroides, Prevotella, and Porphyromonas?

A
  1. non-spore-forming
  2. Gram-negative
  3. anaerobic
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2
Q

What are the most common spore-forming and non-spore-forming anaerobes?

A

SPORE-FORMING:
- Gram +: Clostridium

NON-SPORE-FORMIN:
- Gram +: Actinomyces
- Gram -: Bacteroides, Prevotella, Porphyromonas, Fusobacterium

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3
Q

Why is oxygen toxic to obligate anaerobic bacteria?

A

these bacteria lack….
- superoxide dismutase: turns superoxide into less reactive hydrogen peroxide
- catalase: turns hydrogen peroxide into oxygen and water

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4
Q

Where are anaerobic bacteria typically part of the normal flora in animals and humans? What is their function?

A

mucous membranes - GI tract, oral cavity, urogenital tract

protect against pathogens at mucosal surfaces

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5
Q

What happens at each mucosal membrane when the anaerobic bacteria are able to act as opportunistic pathogens? When are they able to cause disease?

A
  • GI tract: IBD
  • oral cavity: periodontal disease
  • urogenital tract: pelvic inflammatory disease, UTI

trauma/perforation of the mucous membrane

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6
Q

What is characteristic of anaerobic bacterial disease? How does this affect treatment?

A

polymicrobial nature —> synergism with facultative anaerobic bacteria

broad spectrum antibiotics required

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7
Q

How do obligate and facultative bacteria work together to cause polymicrobial disease?

A

OBLIGATE anaerobes provide protection against antimicrobials and phagocytosis by forming abscesses

FACULTATIVE anaerobes scavenge molecular oxygen, which reduces redox potential

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8
Q

What are 4 common virulence factors of anaerobic bacteria?

A
  1. capsule*** - antiphagocytic, abscess formation
  2. LPS
  3. fimbriae - attachment
  4. toxins/exoenzymes - tissue damage
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9
Q

What is an abscess? How do they aid in anaerobic bacterial infection?

A

collection of pus that includes the buildup of fluid, living/dead WBCs, dead tissue, and bacteria

  • protection from antibiotics
  • protection from phagocytosis
  • bacteria are able to break free upon rupture, migrate into blood vessels, and cause systemic infection
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10
Q

What should be sampled in anaerobic infections? What are 2 important aspects to isolated these bacteria?

A

pus, discharges, tissues —> rapid transport in anaerobic transport media

  1. enriched media with vitamin K and hemin
  2. anaerobic cultures in a chamber jar, container, or bag
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11
Q

What are the 2 treatments for anaerobic infections?

A
  1. antibiotic therapy - tend to be resistant to β-lactams
  2. surgical intervention
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12
Q

What is Bacteroides?

A

non-spore-forming, Gram-negative, pleomorphic, bile-resistant, anaerobic rods that tend to be aerotolerant

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13
Q

What are 2 characteristic substances that Bacteroides produce?

A
  1. capsular polysaccharides
  2. short-chain fatty acids (SCFA) - strong odor characteristic of anaerobic infection
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14
Q

Where is Bacteroides typically found? What species is the most clinically significant pathogen?

A

normal flora of GI tract, oral cavity, and urogenital tract
(makes up 30% of the total colonic bacteria)

Bacteroides fragilis

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15
Q

How do the capsular polysaccharides and short-chain fatty acids produced by Bacteroides act as virulence factors?

A

CAPSULAR POLYSACCHARIDES: help with adherence to peritoneal surface, inhibit phagocytosis, and cause abscess formation

SCFA: inhibit phagocytosis and intracellular killing

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16
Q

What 3 enzymes are produced by Bacteroides and act as virulence factors?

A
  1. zinc metalloprotease
  2. protease
  3. hemolysin
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17
Q

What short-chain fatty acids are produced by Bacteroides? What is used to produce them?

A
  • propionate
  • butyrate
  • acetate

dietary fiber

18
Q

What are 3 beneficial effects of Bacteroides production of short-chain fatty acids?

A
  1. acts as an energy source
  2. inhibits the growth of other pathogens (Salmonella) by interrupting pH homeostasis (propionate)
  3. anti-inflammatory effects (butyrate)
19
Q

What 2 media are typically used to isolate Bacteroides? What do they usually look like?

A
  1. TSA with 5% sheep blood - fastidious!
  2. Bacteroides bile esculin agar - bile tolerant
    + anaerobic incubation >48 hours

circular, white/gray, 2-3 mm colonies that are shiny and smooth

20
Q

What antibiotics do Bacteroides tend to be resistant to?

A

penicillin, kanamycin, vancomycin, colistin
(can grow on media containing these)

21
Q

How does the site of infection affect diseases caused by Bacteroides?

A
  • NATURAL HABITATS (mucous membranes): intra-abdominal infection, pelvic infections
  • BITE WOUND/TRAUMA: skin and soft tissue infections
  • HEMATOGENOUS: bacteremia, septic arthritis, meningitis, upper respiratory infection, endocarditis, pericarditis
22
Q

What characteristic anaerobic lesions can result from Bacteroides infection?

A
  • abscess formation
  • inflammatory disease caused by polymicrobial infections
23
Q

What are common clinical symptoms of bacteremia caused by Bacteroides from a cat bite? What is seen on cytological analysis? Microbiological analysis? How can infection be confirmed?

A
  • inflammation and wound filled with pus
  • neutrophilic leukocytosis
  • Gram-negative tods resistant to kanamycin, vancomycin, bile, and colistin
  • PCR, sequencing
24
Q

Why is surgical drainage of abscesses necessary for treatment of Bacteroides infection (+ other anaerobic bacteria)?

A
  • there is no blood supply to abscesses so antibiotics cannot be delivered hematogenously
  • abscesses tend to have a low pH and antibiotics tend to work at a neutral pH
25
Q

What is Prevotella?

A

short, Gram-negative, obligate anaerobic rod (coccobacilli)

26
Q

Where is Prevotella typically found? What antibiotics do they tend to be resistant to?

A

flora of oral cavity and gut

  • kanamycin
  • vancomycin
27
Q

What are the 2 clinically significant species of Prevotella? What do they cause?

A
  1. P. melaninogenica - interdigital necrobacillosis in cattle
  2. P. heparinolytica - lesions in the buccal cavity in horses and cats
28
Q

What 3 virulence factors play an important role in Prevotella infection?

A
  1. capsule
  2. protease
  3. T9SS - specific to Bacteriodetes
29
Q

What characteristic substance is produced by Prevotella? What are 3 effects it has?

A

succinate

  1. inhibit phagocytosis of polymorphonuclear leukocytes
  2. pro-inflammatory mediator (IBD = increased succinate in lumen)
  3. improves glucose homeostasis
30
Q

What are 4 common post-mortem findings in septicemia caused by Prevotella in a cow? 3 findings on histopathological examination?

A
  1. hydroperitoneum
  2. hydropericardium
  3. petechial hemorrhage
  4. multiple abscesses in the liver
  • hepatocellular necrosis
  • neutrophilic infiltrates
  • abscess formation
31
Q

Where can specimens be taken from septicemia caused by Prevotella in a cow? What would be expected to grow?

A

liver lesions + blood

Gram-negative anaerobic bacteria —> P. melaninogenica

32
Q

What is Porphyromonas? What fermentation does it undergo?

A

non-spore-forming, Gram-negative, non-motile obligate anaerobic rods/coccobacilli

ASACCHAROLYTIC, but proteolytic —> flourishes in deep periodontal pockets, which lack sugar

33
Q

How does Porphyromonas grow on blood agar? Where is it commonly found?

A

small, black colonies (porphyrin pigment)

members of the oral microbiota in humans and animals —> etiological agent of periodontitis (P. gingivalis in humans and P. gulae in animals)

34
Q

How does Porphyromonas respond to antibiotics?

A
  • sensitive to vancomycin
  • resistant to kanamycin
35
Q

What unique protease is produced by Porphyromonas? What 4 functions does it have?

A

gingipains

  1. nutrient acquisition
  2. adhesion and tissue invasion
  3. destruction of host tissue
  4. dysregulation of host immune responses
36
Q

How is periodontal disease caused by Porphyromonas infection commonly treated?

A

clindamycin and interferon-α (suppresses inflammatory response) —> inhibits Porphyromonas gulae

37
Q

Bacteroides, Prevotella, Porphyromonas, summary:

A
38
Q

Are Bacteroides, Prevotella, and Porphyromonas zoonotic?

A

YES - animal bites

39
Q

Animal bites are common. 60-80% are caused by _____ and 20-30% by _______.

A

dogs
cats

(humans bite, too! —> Bacteroides in oral cavity)

40
Q

Susie was bitten by her neighbor. She developed a fever and bacteremia was suspected. The etiological diagnosis was confirmed by…..

a. aerobic culture
b. anaerobic culture
c. both

A

C

41
Q

Meningitis case report from a 78 year old man: CSF examination showed multiple neutrophils with bacteria within them. CSF cultures of CSF has no growth in aerobic conditions and black-pigmented colonies on blood agar in anaerobic conditions. Gram stain showed short Gram-negative rods that didn’t grow on blood agar with vancomycin. What is likely responsible?

A

Porphyromonas

(Prevotella and Bacteroides would grow well in agar with vancomycin)

Veterinary Bacteriology & Mycology (47 decks)

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