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Microbiology > Anaerobes > Flashcards

Anaerobes Flashcards

1
Q

require atmosphere of 15-21% oxygen as found in air or CO2 incubator
i.e., Mycobacteria

A

Obligate aerobe

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2
Q

require oxygen content lower than ambient air (<5%)

i.e., Campylobacter, Neisseria, Helicobacter

A

Microaerophilic

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3
Q

organisms that multiply equally in the presence or absence of air
i.e., Enterobacteriaceae

A

Facultative anaerobe

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4
Q

require increased CO2 (5-10%)

i.e., Haemophilus, Neisseria

A

Capnophile

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5
Q

can survive some oxygen exposure, but will not be able to preform metabolic processes unless in an anaerobic environment
i.e., Bacteroides

A

Aerotolerant anaerobe

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6
Q

requires strict anaerobic environment and are killed almost immediately in the presence of oxygen
i.e., Clostridium

A

Obligate anaerobe

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7
Q

Exogenous anaerobes

A
  • exist outside of the body
  • infection develops at site of entry
  • i.e., Clostridium, Fusobacterium
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8
Q

Endogenous anaerobes

A
  • exist inside the body
  • source of infection in/throughout body
  • usually polymicrobial infections
  • i.e., Bacteroides, Peptostreptococcus, Actinomyces
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9
Q

Skin anaerobes

A

Propionibacterium, Peptostreptococcus

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10
Q

Respiratory tract anaerobes

A

Prevotella, Porphyromonas, Fusobacterium

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11
Q

Gastrointestinal tract anaerobes

A

Bacteroides, Bifidobacterium, Clostridium, Eubacterium

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12
Q

Genitourinary tract anaerobes

A

Fusobacterium, Prevotella, Bacteroides, Lactobacillus

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13
Q

Predisposition to Anaerobic infections

A
  • trauma to protective barriers (bowel, genital tract)
  • vascular stasis (no oxygen to site)
  • bite wounds, oral surgery, oral flora into deep lungs, burns with soil contamination
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14
Q

Anaerobic bacteria (characteristics)

A
  • close proximity to mucosal surface
  • produces a foul odor
  • large quantity of gas
  • black color or brick-red fluorescence
  • distinct morphological characteristics (pleomorphic, fusiform)
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15
Q

Gram-positive, spore-forming, anaerobic, bacilli

A

Clostridium

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16
Q
  • boxcar-shaped gram-positive bacilli
  • double zone of hemolysis on Brucella blood agar or blood agar
  • lecithinase +
A

C. perfringens

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17
Q
  • heavily swarming

- terminal spores

A

C. tetani

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18
Q
  • heavily swarming

- subterminal spores

A

C. septicum

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19
Q

Clostridium Clinical Infections

A
  • mostly exogenous (wounds, ingest toxin)
  • endogenous is C. difficile
  • tetanus, gas gangrene, botulism, food poisoning
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20
Q

C. perfringens food poisoning

A
  • 3rd most common after Salmonella and Shigella

- Type A and Type C

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21
Q

C. perfringens Type A food poisoning

A
  • ingestion of enterotoxin
  • causes diarrhea and cramps
  • usually self-resolving
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22
Q

C. perfringens Type C food poisoning

A
  • causes Enteritis necroticans
  • acute onset of severe abdominal pain and bloody diarrhea, vomiting
  • necrotic inflammation of small intestines
  • fatal without treatment
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23
Q
  • causes Botulism
  • Botulism toxins A-G
  • Toxins A, B, E associated with human disease
  • causes flaccid paralysis
  • caused by ingestion of toxin, ingestion of spores (infants), or wound botulism
  • 2 hours to 8 days
A

C. botulinum

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24
Q

infant botulism

A
  • ingestion of spores in contaminated honey

- colonize colon and produce toxins

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25
Q

Tetanus

A
  • caused by C. tetani
  • tetanospasmin neurotoxin (inhibits neurotransmitters)
  • symptoms begin after 7 days (long incubation)
  • muscular rigidity of jaw, neck and lumbar
  • vaccine available (DPT)
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26
Q

Myonecrosis (gas gangrene)

A
  • most commonly caused by C. perfringens
  • contaminated wounds from trauma or surgery
  • alpha toxin causes tissue necrosis and deeper invasion
  • tissue death that leads to amputation
  • treat with antibiotics, surgical debridement and hyperbaric oxygen (to kill anaerobes)
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27
Q

Bacteremia

A
  • C. perfringens is most common
  • C. septicum is marker for GI malignancy
  • C. bifermentans and C. tertium are secondary
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28
Q

Antibiotic-associated diarrhea

A
  • C. difficile
  • causes pseudomembranous colitis (bloody diarrhea, necrosis)
  • antibiotics destroy flora, but not Clostridium so increased toxin production (Toxin A and B)
  • nosocomial infection
  • test for toxin, not culture
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29
Q

Gram-positive non-spore-forming anaerobic bacilli

A
  • Actinomyces, Bifidobacterium and Propionibacterium
  • Mobiluncus
  • Lactobacillus
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30
Q

Actinomyces, Bifidobacterium and Propionibacterium

A
  • cause Actinomycosis (sulfur granules)
  • P. acnes is frequent blood culture contaminant
  • normal skin flora
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31
Q

Actinomycosis

A

chronic granulomatous disease characterized by sinus tracts and fistulae that erupt to the surface and drain pus that contains “sulfur granules”

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32
Q
  • bacterial vaginosis

- overgrowth when Lactobacillus decreases

A

Mobiluncus

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33
Q
  • highly pleomorphic bacilli
  • contaminant
  • bacteremia and endocarditis in ICP
A

Lactobacillus

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34
Q

Anaerobic gram-negative bacilli

A
  • Bacteroides fragilis
  • Prevotella
  • Porphyromonas
  • Fusobacterium
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35
Q
  • # 1 normal flora in colon
  • most commonly isolated anaerobe from blood cultures
  • # 1 agent in peritonitis and intra-abdominal abscess
  • grows on KVLB and BBE
  • resistant to vanco, kanamycin and colistin disks
A

Bacteroides fragilis

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36
Q
  • P. melaninogneica is #1 normal flora of gingiva
  • also found in vagina
  • peridontal disease, sinusitis, pneumonia, brain abscesses
A

Prevotella

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37
Q
  • slow grower
  • normal flora of oropharynx and urogenital tract
  • head and neck infections
A

Porphyromonas

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38
Q
  • commensal bacteria in gingiva
  • normal in GI, GU and URT
  • mixed infections (abscesses, peritoneal infections, diabetic foot ulcers)
  • Lemierre disease (F. necrophorum)
A

Fusobacterium (necrophorum and nucleatum)

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39
Q
  • long, thin rods with pointed ends
  • breadcrumb, speckled or smooth colonies
  • greening of agar with air exposure
  • fluoresces chartreuse
  • nonhemolytic, indole +, lipase -
A

F. nucleatum

40
Q
  • slightly pleomorophic with rounded ends
  • circulate colonies
  • greening with air exposure
  • beta-hemolytic, indole +, lipase +
  • fluoresces chartreuse
A

F. necrophorum

41
Q

Anaerobic cocci

A
  • Peptostreptococcus, Anaerococcus, Finegoldia, Parvimonas, Peptoniphilus (gram-positive)
  • Veillonella (gram-negative)
42
Q

Anaerobic cocci clinical infections

A
  • brain abscesses, meningitis, aspiration pneumonia, lung abscess, gingivitis
  • polymicrobial infections
43
Q

Specimen collection

A
  • acceptable specimens must be collected
  • tissue biopsy or needle aspiration is best
  • must be actual site of infection (not surface)
  • rapid processing (because of oxygen toxicity)
44
Q

Aspirates

A
  • needle and syringe
  • inject specimen into prereduced anaerobically sterilized media (PRAS)
  • vortex and plate to isolation media
45
Q

Anaerobic infections

A

MOST ARE POLYMICROBIAL

46
Q

Swabs

A

not recommended for specimen collection

47
Q

Blood

A

must collect anaerobic and aerobic blood culture bottles

48
Q

Anaerobic chambers

A
  • glove boxes, anaerobic jars, biobags

- oxygen-free environment

49
Q

Direct examination of anaerobic specimen

A
  • rules in or out pathogens
  • establishes polymicrobial or monomicrobial
  • presumptive identification
  • aids in selection of culture media
  • determines specimen quality
50
Q

Gram-staining anaerobes

A

use methanol instead of heat as a fixative

51
Q

Anaerobic chambers

A
  • 5-10% Hydrogen gas
  • 5-10% CO2 gas
  • 80-90% Nitrogen gas
  • Palladium-coated alumina pellets to remove all oxygen
  • desiccant to absorb excess water
  • indicator (turns when O2 present)
52
Q

Anaerobic cultures

A
  • foul odor
  • characteristic morphology on anaerobic agars
  • unique morphology on gram stain
  • good growth on Bacteroides bile-esculin agar (BBE)
  • double zone of hemolysis
  • brick-red fluorescence on KVLB
53
Q

Kanamycin vancomycin laked blood (KVLB)

A
  • anaerobes have brick-red fluorescence on agar

- Porphyromonas and Prevotella turn it black

54
Q

Processing suspected anaerobes

A
  • Observe growth and morphology on selective media
  • Observe gram-stain and cell morphology
  • aerotolerance test
  • inoculate pure culture plate and add disks
55
Q

determines whether an organism is a strict anaerobe or a facultative anaerobe

A

Aerotolerance test

56
Q

Aerotolerance test (plates)

A
  • chocolate agar plate incubated in CO2 incubator

- anaerobic blood agar plate incubated anaerobically

57
Q

Brick-red fluorescent anaerobes

A

Prophyromonas and Prevotella

58
Q

Chartreuse fluorescent anaerobes

A

Fusobacterium nucleatum, Fusobacterium necrophorum and Clostridium difficile

59
Q

red fluorescent anaerobe

A

Veillonella

60
Q

Catalase test

A

separates Bacillus (+) and Clostridium (-)

61
Q

Anaerobe tests

A

catalase test
spot indole test
rapid urease test
rapid motility test

62
Q

Spot indole test

A
  • dilated cardiomyopathy with ataxia (DCMA) reagent
  • blue/green is positive
  • different from regular indole test
63
Q

Anaerobe special potency disks

A

Vancomycin disk, Kanamycin disk, Colistin disk

64
Q

Vancomycin disk

A
  • gram-positive bacillus and Porphyromonas are susceptible

- Fusobacterium are resistant

65
Q

Kanamycin disk

A
  • Bacteroides (not fragilis), Bilophila, Fusobacterium and Veillonella are susceptible
  • Porphyromonas, B. fragilis are resistant
66
Q

Colistin disk

A
  • Bacteroides (not fragilis), Bilophila, Fusobacterium, Veillonella and Prevotella are susceptible
  • Porphyromonas, B. fragilis are resistant
67
Q

Anaerobic antimicrobial disks

A

Bacteroides fragilis is resistant to all 3 (Vanco, Kanamycin and Colistin)

68
Q

Nitrate disk

A

organisms that have ability to reduce nitrate

69
Q

Sodium polyanethol sulfonate (SPS) disk

A
  • Peptostreptococcus anaerobius is susceptible

- Peptoniphilus asaccharolyticus is resistant

70
Q

Bile disk

A
  • for organisms that can grow in 20% bile

- B. fragilis

71
Q

Egg Yolk Agar (EYA)

A
  • Lecithinase cleaves lecithin found in egg yolk and releases insoluble fat
  • forms opaque zone around colony
  • C. perfringens (lecithinase +)
72
Q

Lipase

A
  • hydrolyzes triglycerides and diglycerides to fatty acids and glycerol
  • iridescent, multicolored sheen
  • F. necrophorum (+)
73
Q

Clostridium (identification)

A
  • double zone of hemolysis
  • Cycloserine-cefoxitin-fructose agar (CCFA)
  • lecithinase and lipase reactions
  • spot indole, rapid urease, gelatin hydrolysis
74
Q
  • selective and differential for C. difficile

- has yellow “ground glass” colonies

A

Cycloserine-cefoxitin-fructose agar (CCFA)

75
Q

Bile-tolerant gram-negative bacilli

A

Bacteroides fragilis

76
Q

Bile-sensitive pigmented gram-negative bacilli

A

Porphyromonas and Prevotella

77
Q

Bile-sensitive nonpigmented gram-negative bacilli

A

Bacteroides ureolyticus, Campylobacter, Bilophila wadsworthia

78
Q

B. fragilis (special media)

A

KVLB and BBE biplate

79
Q

Pigmented Gram-negative bacilli

A

Bacteroides, Prevotella, Porphyromonas

80
Q
  • produces protoporphyrin
  • brown-black color shift of macroscopic colonies over 2-3 weeks
  • brick-red fluorescence
A

Prevotella

81
Q
  • brick-red fluorescence

- no growth on media containing vancomycin

A

Porphyromonas

82
Q
  • isolated following tooth extraction
  • nonpigmented
  • pits the agar
  • urease +
A

B. ureolyticus

83
Q

Prevotella (body sites)

A

vagina and oral cavities

84
Q
  • gram-negative
  • long, thin, tapered rods
  • may be pleomorphic
A

Fusobacterium

85
Q
  • classic fusiform shape
  • indole +, lipase -
  • butyric acid from PYG media
A

F. nucleatum

86
Q

Other Fusobacterium

A

F. mortiferum, F. russi

87
Q
  • many clinical specimens contain these
  • vagina and abscesses
  • tetrads, chains or clusters
  • P. anaerobius, P. asaccharolyticus
A

Anaerobic gram-positive cocci

88
Q
  • gram-positive cocci
  • SPS sensitive
  • indole -
  • acid production in PYG
A

Peptostreptococcus anaerobius

89
Q
  • gram-positive cocci
  • SPS resistant
  • indole +
A

Peptostreptococcus asaccharolyticus

90
Q

Antimicrobial susceptibility testing is performed in

A 
brain abscesses
endocarditis
prosthetic device infection
vascular graft infection
joint infections
osteomyelitis
bacteremia
91
Q

Highly virulent/commonly resistant anaerobes

A 
B. fragilis
Prevotella
Clostridium
Fusobacterium
B. wadsworthia
Sutterella wadsworthensis
92
Q

Treatment of anaerobic diseases

A
  • destroy reduced environment (debridement, draining)
  • hyperbaric oxygen environment
  • antimicrobials, antitoxins
93
Q

Definitive ID tests

A
  • biochemical systems
  • gas-liquid chromatography
  • ribosomal sequencing
94
Q

Presumptive ID tests

A
  • disks
  • media
  • morphology
95
Q
  • pitting of agar

- urease +

A

Bacteroides ureolyticus

96
Q

Actinomyces

A
  • cause Actinomycosis (sulfur granules)

- molar tooth colonies

Microbiology (26 decks)

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