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Multisystems > Micro-Anaerobic Bacterial Infections > Flashcards

Micro-Anaerobic Bacterial Infections Flashcards

1
Q

What is the difference between anaerobe, facultative anaerobe, microaerophilic and aerotolerant?

A

Anaerobe- cannot grow at 10% CO2
Facultative- grows aerobically and anaerobically
Microaerophilic - grows poorly aerobically, grows well anaerobically
Aerotolerant- grows at 2-8% oxygen

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2
Q

What enzyme is produced by certain anaerobic organisms that allows them to be aerotolerant?

A

superoxide dismutase

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3
Q

What area of the body has the highest colony count of anaerobic bacteria?

A

Colon has 1000:1 anaerobes to aerobes

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4
Q

What 5 things can change the enteric flora?

A
  1. antibiotics
  2. antacids
  3. pregnancy
  4. age
  5. loss of teeth
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5
Q

What are the 6 main benefits of indiginous normal flora of the skin and mucousal surfaces?

A
  1. colonization resistance- interferes with the growth of pathogenic bacteria [bacteriocins, interferes w/nutrients, interferes with adhesion]
  2. vitamin K production [bacteriodes fragilis]
  3. metabolize bile acids and sterols
  4. modify drugs [sulfasalazine, digoxin]
  5. metabolize lipids, proteins, urea, carbs
  6. mucousal immunity
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6
Q

Why do stool and anaerobic abscesses smell bad?

A

Anaerobes produce SCFA and methylmercaptan that impede phagocytic killling by neutrophils

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7
Q

What 4 host factors allow anaerobic infection to occur?

A
  1. break in anatomic barriers to normal flora
  2. host immune mechanisms [LESS important]
  3. decreased redox potential of tissue
  4. specific clinical presdispositions
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8
Q

What anaerobic infections are you more likely to see with diabetes?

A

Osteomyelitis, cholescystitis

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9
Q

Which anaerobes are likely to be involved with the following cancers:

  1. colon
  2. uterus
  3. lung
  4. leukemia
A
  1. Clostridium perfringens bacteremia, C. septicum
  2. Clostridium and/or bacteriodes
  3. mixed aerobe/anaerobe oral flora aspirate
  4. clostridium perfringens, septicum, tertium[cecitis], capnocytophaga
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10
Q

What anaerobic infection is associated with acatalsemia, Down syndrome and AIDS?

A

necrotizing gingivitis

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11
Q

What 3 bacterial factors play a role in anaerobic infection?

A
  1. size of inoculum
  2. synergy with aerobic/facultative anaerobes
  3. virulence factors
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12
Q

What are the adherence virulence factors of anaerobes?

A

Pili/fimbrae
adhesin
capsule

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13
Q

What are the enzyme/toxins produced by anaerobes?

A
  1. superoxide dismutase

2. exotoxins [esp. clostridium alpha toxin -phospholipaseC which hydrolyzes cell membranes]

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14
Q

What surface structure on B. fragillis allows it to inhibit opsonophagocytosis and induce abscess formation?

A

Capsule

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15
Q

What is the function of SCFA produced by anaerobic bacteria?

A

Inhibits phagocytic killing by neutrophils

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16
Q

What six anaerobes are most commonly involved in invasive clinical infection?

A
  1. bacteriodes fragilis
  2. prevotella, porphyromonas [pigmented, fluoresce]
  3. fusobacterium nucleatum
  4. peptostreptococcus
  5. clostridium perfringens, ramosum, septicum
  6. Actinomyces
17
Q

What are the 3 presentations of anaerobic infection in the CNS?
What are the 2 ways the anaerobes get to the CNS?
What is treatment?

A
  1. brain abscesses
  2. epidural abscesses
  3. subdural empyemas [abscess in preformed cavity]
    They are often multiple and polymicrobial.

How did the infections get there?

  1. contiguous spread from chronic otitis, mastoiditis, sinusitis
  2. hematogenous spread from lung abscess with R-L shunt

May be curable WITHOUT surgical drainage

18
Q

What is the presentation of Lemmiere’s syndrome?

What bacteria causes it?

A

peritonsillar abscess caused by fusobaterium necrophorum which infects the lateral pharyngeal space with septic jugular vein thrombosis.
Metastatic abscesses go to the lungs and other organs.

19
Q

What is Ludwig’s angina?
What bacteria causes it?
What is the presentation?

A

submandibular space infection caused by mixed aerobes/anaerobes.

Presents with: swelling of the floor of mouth and neck, drooling, trismus, dyspnea.

20
Q

What is Vincent’s angina?

A

“trench mouth” which is necrotizing gingivitis caused by Fusobacterium and anaerobic spirochetes

21
Q

What is the most common cause of pleuropulmonary infection by anaerobes?
What are the 3 ways these pleuropulmonary infections present?
What are the 3 most common organisms?

A

Most common cause is aspiration of oral/gastric contents especially with severe peridontal disease resulting in:
1. aspiration pneumonia
2. lung abscess
3. pleural empyema
[usually affects posterior segments of the lung]

The 3 most common organisms are:

  1. prevotella
  2. fusobacterium
  3. peptostreptococcus
22
Q

What aerobic organisms can accompany prevotella, fusobacterium and peptostreptococcus in pleuropulmonary infections?
Which aerobes are common in the hospital setting?

A

Viridians strep

Hospital setting:

  1. gram neg aerobes
  2. staphylococci
23
Q

What organisms cause intraabdominal infections like appendicitis, diverticulitis, ischemic bowel, liver abscesses, pylephlebitis [septal portal vein thrombosis] secondary peritonitis and biliary tract infections?

A

Polymicrobial including coliforms and anaerobes

24
Q

Which 5 anaerobic bacteria are associated with female genital tract infections?

A 
Prevotella
Peptostreptococcus
porphyromonas
Clostridium 
Bacteriodes
25
Q

What 2 anaerobic bacteria are associated with IUDs?

A
  1. actinomycosis

2. eubaterium nodatum

26
Q

A patient presents with necrotizing fasciitis and gas in the tissue. What organism is most likely responsible?

A

clostridium

27
Q

What organisms are responsible for Fournier’s gangrene?

A

Fournier’s gangrene is mixed anaerobic/aerobic necrotizing cellulitis of the scrotum.

Anaerobes= prevotella, porphyromonas, peptostreptococcus, bateriodes, fusobacterium
Aerobes= GABHS, other strep, staph, G- aerobes, facultative rods
28
Q

What organisms are associated with a human bite?

A
  1. Oral anaerobes [fusobacterium] PLUS

2. eikenella corrodens [facultative]

29
Q

What bacteria is associated with animal bites?

A

Pasteurella multocida [facultative]

30
Q

Bacteremia of anaerobes is infrequent and often polymicrobial. If it is gram negative anaerobe bacteremia [ex. bacteriodes] what is there a high likelihood of?

A

Underlying abdominal or female pelvic pathology

31
Q

What does C. septicum bacteremia suggest?

A

colon cancer or leukemic cecitis

32
Q

A patient presents with C. perfringens and C. novyi bacteremia and soft tissue inflammation. How did this person most likely get it?

A

IVDU [skin popping]

33
Q

What are signs that help diagnose anaerobic infection?

A
  1. clinical situations where infections are at skin or mucousa
  2. foul odor [due to SCFA production]
  3. gas or black discoloration
  4. gangrene, necrosis, abscess
  5. polymicrobial on gram stain
  6. sterile pus [doesn’t grow on routine culture]
  7. classic toxin features of histotoxic clostridia
34
Q

Do not submit __________ for anaerobic culture because they will be positive, but misleading.
What are 3 ways you can collect appropriate samples for anaerobes?

A

Do not submit mucousal samples. Instead:

  1. fine needle aspirate of pus
  2. bronchial secretion collection with a protected brush
  3. tissue biopsies

Submit to lab immediately in an anaerobic transport medium

35
Q

What 3 procedures will the lab do on anaerobic samples?

A
  1. direct microscopy
  2. inoculate selective and nonselective media
    - growth takes 4-72 hours except some clostridium
36
Q

What are the ONLY 3 situations where you would run antibiotic susceptibility tests on anaerobes?

A
  1. isolate was from a normally sterile site [blood, CSF]
  2. known virulent organisms
  3. infection requires prolonged therapy with the correct drugs [endocarditis, osteomyelitis, brain abscess]
37
Q

What drug do you NOT use to treat anaerobic infections?

A

Fluoroquinolones [ciprofloxacin, ofloxacin, levofloxacin]

38
Q

What drug was previously recommended for anaerobic infections “above the diaphragm” but is no longer used due to high resistance?

A

Penicillin

  • increasing resistance due to b-lactamases
  • prevotella, porphyromonas, bacteriodes, fusobacterium

Multisystems (29 decks)

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