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Flashcards in Anaerobes Deck (19)
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0
Q

Anaerobic infection species

A

Can predict species based on location!
- almost all anaerobic from patient’s endogenous flora

Above diaphragm (ex oral): penicillin sensitive, mixed Gram + cocci, Gram (-) bacilli
Below diaphragm (ex intra-abdominal): penicillin resistant (B fragilis), mixed Gram (-) bacilli (colonic)

Skin/cellulitis: Clostridia

1
Q

Overview of anaerobes

A

True anaerobes - cannot tolerate high ox-red potential, superoxide, H2O2
- lack superoxide dismutase, usually lack catalase

Major part of normal flora (GI, female, oral) -> abcesses

  • normally mixed (anaerobe or microaerophile) vs single species (aerobic or facultative aerobes) - look if there are multiple aerobes!
  • foul discharge, gas

Normal tissue - high O2 (ox-red potential) -> suppress growth
Susceptible tissue - low O2, ox-red due to wound, impaired perfusion or necrosis

Predispositions
- aspiration, GI surgery, abortion, bite, trauma, malignancy, poor dental hygiene

2
Q

Anaerobic methodology

A

Do NOT expose to air!
-> direct into special vial (ex thioglycollate = reducing agent)
- do not submit oral or fecal samples
Anticipate mixed reactions - may not detect all pathogens
Gram stain -> spores, morphology (ex Fusobacterium)
Culture -> colony morphology (ex Prevotella)
- sensitivity assays not as reliable
Metabolism - ex fatty acid production

3
Q

Bacterium fragilis

A

Most abundant anaerobic Gram (-) bacillus
- tolerates traces of O2
- pleiomorphic
Feces (10>11 CFU/g) -> extraintestinal ->
- intra-abdominal (bowel rupture)
- female (abcess post abortion, IUD, delivery)
- septicemia (+ Clostridium perfringans = 80% of anaerobic sepsis, this is still only 8% of total though due to aerobic..)

RESISTANT TO PENICILLIN
resistant to bile

Virulence = capsule
Mixed with E coli = increased virulence

4
Q

Prevotella melaninogenicus

A
Anaerobic Gram (-) rod
Oral -> periodontal, occassional genital

Sensitive to penicillin
More sensitive to O2 than B fragilis (difficult to culture)

Name = black hemin (-> cytochrome synthesis, necessary for growth)
- aka Bacteroides melaninogenicus

5
Q

Fusobacterium

A
Anaerobic Gram (-) rod
 - tapered ends, very skinny (-> "spindle" shaped)

Oral -> lung, pleuropulmonary
(second species intestinal -> abdominal)

Sensitive to penicillin
Sensitive to O2 (difficult to culture)

6
Q

Corynebacterium

A

non-diptheriae = diptheroids

Pleiomorphic anaerobic Gram + rod
- some strains aerotolerant
Normal skin flora -> contaminates cultures
- occassional endocarditis

7
Q

Lactobacillus

A

Normal flora of intestine, vagina

  • > low pH, prevent pathogen growth
  • non-pathogen!
  • used for yogurt, saurkraut, etc…
8
Q

Actinomyces

A

Anaerobic Gram (+) rods

  • branching
  • sulfur granules = characteristic microcolonies + debris -> yellow
  • colonies = “molar tooth” appearance

Usually after trauma, surgery
Normal oral -> dental, oral, lung infections
Normal GI -> abdominal
- sinus tract

9
Q

Anaerobic cocci

A

Pseudostreptococcus - chains of Gram + cocci but obligate anaerobe

  • widely involved in infections
  • oral (-> pulmonary, brain abcess), UG -> gyn, GI

Pseudostaphylococcus - clumps of Gram + cocci but obligate anaerobe
- oral, URI -> lung, GI -> abdominal

Veillonella - anaerobic Gram (-) cocci
- not pathogenic, commensal

10
Q

Anaerobic treatment

A

Drain the abcess (no antibiotics work!)

Penicillin (unless B fragilis, abdominal)
B fragilis -> Clindamycin, Cephalosporins (ex cefoxitin)
Chloramphenicol = static
Metronidazole/Flagyl

Add aminoglycoside if mixed aerobic/anaerobic
- gentamycin + cefoxitin or clindamycin

11
Q

Propionibacterium

A

Anaerobic Gram + bacilli

Skin -> acne

12
Q

Prophyromonas

A

Anaerobic Gram - rod

Oral, periodontal

13
Q

Overview of anaerobes

A

Spores -> Clostridium

Gram + rods - Propionibacterium, Actinomyces, (bifido, lacto)
Gram (-) rods - spirochetes if motile
- nonmotile - Bacteroides, Fusobacterium, Prevotella, Porphyromonas
Gram + cocci - Peptostreptococcus
Gram (-) cocci - Viellonella

Narrow within category via gas chromotography of fatty acid products

14
Q

Oral pathogens

A
  • > brain abcess, sub or epidual empyema
  • > otitis media -> meningitis
  • > dental, periodontal

Prevotella
Peptostreptococcus
Actinomyces
Fusobacterium

Streptococcus viridans (aerobe)

Human bite: oral anaerobes, Eikenella corrodens

15
Q

Respiratory pathogens

A

URI -> facial abscess, CNS, sinusitis
-> aspiration pneumonia, abscess, bronchiectasis

Prevotella
Peptostreptococcus
Fusobacterium
Actinomyces (trauma, URI only)

Aerobes:
Streptococcus
Staphylococcus (URI or nosocomial pulm)
Enterobacteriae (nosocomial pulm only)

16
Q

Bacteremia pathogens

A

90% are aerobic

Anaerobes - 80% are Clostridium perfringans + B fragilis
also Fusobacterium, Peptostreptococcus

17
Q

Abdominal pathogens

A
  • > peritonitis, abscess (rupture)
  • > liver, subphrenic abscess
  • > appendicitis

Bacteroides fragilis (penicillin resistant!)
Fusobacterium
Peptostreptococcus
Clostridium

Aerobes:
E coli
Klebsiella
Proteus
Pseudomonas
Group D Strep
Enterobacter
Staphylococcus (liver rectal)
18
Q

Gyn pathogens

A
  • > abscess post procedures, delivery, IUD, abortion
  • > endometritis

B fragilis
Prevotella
Fusobacterium
Peptostreptococcus

Aerobes:
E coli
Proteus
Staphylococcus
Group B streptococcus