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MICRO 442 > Anaerobes!!! MICROM442 Deck 21 > Flashcards

Anaerobes!!! MICROM442 Deck 21 Flashcards

1
Q

ambient air=

A

About 21% O2, 0.03% CO2

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2
Q

Obligate anaerobes can only handle up to 0.5% O2, what is an example?

A

clostridium species

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3
Q

Facultative anaerobes: use fermentation to grow in places without oxygen,
but use aerobic respiration in places with oxygen, what is an example?

A

ecoli and staph. aureus

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4
Q

Aerotolerant anaerobes: do not use oxygen to live, but can exist in its
presence for a period of time, what is an example?

A

cutibacterium acnes

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5
Q

Microaerophiles: Prefer lower oxygen (5%), increased CO2 (8-10%), what is an example?

A

camphylobacter

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6
Q

Capnophiles (=carbon dioxide “loving”): Require increased CO2 (5-10%), what is an example?

A

Neissseria gonorrhoea

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7
Q

obligate anaerobe growth in thioglycate media

A

very bottom of the tube only

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8
Q

obligate aerobe growth in thioglycate media

A

only at the top of the tube

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9
Q

facultative anaerobe growth in thioglycate media

A

half and half mix, but microbes growing in the top half

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10
Q

aerotolerant anaerobe

A

grows throughout the tube

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11
Q

aerotolerant + facultative anerobes grow in larger amounts of the media beccause

A

aerobic respiration produces more ATP

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12
Q

aerobic respiraton

A
  • O2 = final electron acceptor
  • Yields lots of ATP
  • Oxygen can grab electrons and
    form reactive oxygen species
    (ROS) that damage cells
  • Bacterial antioxidant enzymes
    help detoxify these products
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13
Q

Bacterial antioxidant enzymes
help detoxify these products

A
  • Catalase
  • Peroxidase
  • Superoxide dismutase
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14
Q

Anaerobes

A
  • Can use inorganic compounds as
    alternative electron acceptors:
    NO3- NO2− SO₄²-
  • Some use fermentation
  • Overall yield less ATP
  • Some are prone to forming ROS
  • Some lack antioxidant enzymes
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15
Q

oxygen tolerance is a?

A

SPECTRUM

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16
Q

what factors typically influence a bacterias sensitivity to oxygen?

A
  • Protective antioxidant enzymes
    -How active?
    -How abundant?
    -Where in the cell they’re located
  • How quickly the bacteria take up oxygen
  • If they possess enzymes that promote internal formation of ROS
  • How sensitive their overall systems are to ROS
    -Enzymes with iron cofactors are particularly sensitive
    -DNA damage
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17
Q

what percentage of oral bacteria are anaerobes?

A

90

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18
Q

what percentage of colon bacteria are anaerobes

A

99%

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19
Q

where do anaerobes live on the body?

A

-upper respiratory tract
-colon
-oral cavity
-skin
-vagina

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20
Q

upper respiratory tract infx

A

-oral/neck anscesses
-pnemonia

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21
Q

colon infx

A

-intra-abdominal infx
-abscesses
-appendicitis

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22
Q

more infx :’(

A

-bloodstream
-endocarditis

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23
Q

oral cavity infx

A

-dental infx
-sinusitis
-brain abscess
-pneumonia

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24
Q

skin infx

A

-acne
-would infx
-surgical site infx

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25
Q

vagina infx

A

-bacterial vaginosis
-adverse pregnancy outcomes
-pelvic inflammatory disease

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26
Q

internal displacement cause of infx

A

-trauma, burns, wounds
-surgery
-aspiration pneumonia
-bowel or intestinal perforation
-appendicitis
-bloodstream infx
-endocarditis

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27
Q

host factors

A

-abx therapy
-chemotherapy injures mucosa
-immunosuppression
-diabetes

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28
Q

external sources

A

-environmental contamination
-food-borne illness
-water exposure
-injection drug use
-animal bites

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29
Q

toxin treatments

A

-antitoxin
-immune globulin
-vax

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30
Q

source control treatment

A

drain abscess, deride/remove necrotic tissue

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31
Q

antibiotics

A

-anaerobic infx often mixed, often need multiple
-metronidazole, clindamycin
-Piperacilllin/tazobactam, Ampicillin/sulbactam
-carbapenems

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32
Q

blood culture enrihment

A

-patient with possible bloodstream infx
-always use BOTH aerobic and anaerobic bottles
-put into fancy machine
-nutrient broth + pH colorimetric indicator

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33
Q

anaerobic bottle contains both?

A

CO2 and NO2

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34
Q

what signifies growth in the blood culture instrument?

A

CO2 production and pH change

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35
Q

Anaerobic blood agar plates

A

Hemolysis patterns with sheep’s blood

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36
Q

Enrichment broths

A
  • Chopped meat/Cooked meat broth
  • Thioglycolate broth
    -Differential: where the organisms grow
  • Reducing agents deplete oxygen
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37
Q

Selective media

A

Inhibitors like antibiotics or bile

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38
Q

Differential media

A
  • Pigment production
  • Esculin hydrolysis = dark brown colonies
  • pH indicators
  • Egg yolk to visualize toxin activity
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39
Q

anaerobic indicator

A

white= anaerobic
pink=oxygen present

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40
Q

palladium catalyst

A

2H2 + O2 -> 2H2O

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41
Q

For other specimens

A

Tissue, abscesses, normally sterile body fluids (joint, pleural, CSF, etc.)

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42
Q

Incubation conditions without oxygen

A
  • Specialized airtight containers
  • A way to remove oxygen
  • A way to generate an anaerobic gas
    mixture
  • An indicator to show if it’s working
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43
Q

Example: Vacuum system

A
  • Evacuates air with vacuum pump
  • Replaces with anaerobic gas mixture
  • Add anaerobic indicator to jars
  • Add PALLADIUM catalyst to jars to take care of remaining oxygen
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44
Q

Example: Anaerobic chamber

A
  • Passbox/vacuum airlock to transfer materials
  • Armholes to reach plates on the inside
  • Palladium catalyst box
  • 5% CO2, 5% H2, 90% N2 mixture pumped in
  • Temperature control to incubate
45
Q

ID with gram stain

A

-Fusobacterium nucleatum
pointy Gram-negative rods
-Clostridium spp.
Boxy Gram-positive rods
Can chain, can have spores

46
Q

ID with biochemical tests

A

OLD NEWS: Indole, catalase, urease, susceptibility to special antibiotic
MORE COMMON: Long-wave UV fluorescence

47
Q

Long-wave UV fluorescence

A
  • C. difficile, Fusobacterium: chartreuse, yellow-green
  • Some Prevotella, Porphyromonas: red
48
Q

ID with MALDI-TOF MS (Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry)

A
  • Mix bacteria with an organic matrix, hit with a laser to generate protonated ions
  • Accelerate through a vacuum to get a peptide profile based on time to flight
  • Compare pattern to a database to match with known organisms
  • Instrument $$$, but consumables cheaper and hands-on time is minimal
  • Becoming the standard in larger laboratories
49
Q

ID with sequencing

A
  • After isolation on plates or directly from patient specimen
  • PCR + Sanger sequencing
  • Next generation sequencing
    -Can resolve templates if multiple species are present
    -Many anaerobic infections are polymicrobial
50
Q

Sanger cannot anwser the

A

cause of infx

51
Q

NGS better if there is a

A

polymicrobial infx

52
Q

NGS can be used for either

A

growth on plates or directly from patient ssample

53
Q

Gm+ rods we are concerned with (CCCA)

A
  • Clostridium
  • Clostridioides
  • Cutibacterium
  • Actinomyces
54
Q

GM- rods we are concerned with (BF)

A
  • Bacteroides
  • Fusobacterium
55
Q

Gram-negative rods with pleomorphic morphology, gut
commensals

A

bacteroides

56
Q

what are bacteroides often isolated from?

A

blood, intra-abdominal
abscesses, appendicitis

57
Q
  • B. fragilis
  • B. thetaiotaomicron
  • Others
A

Bacteroides fragilis group

58
Q

Baceroides abx resistance B. fragilis

A

beta-lactamase
production → treatment with BL/BLIs metronidazole

59
Q

Baceroides abx resistance nimA-H genes

A

nitroimidazole reductase decreases efficacy of metronidazole, a common antibiotic for
anaerobic coverage

60
Q

Bacteroides Bile Esculin Agar

A

-esculin hydrolysis = dark colonies (black)
-abx + bile inhibit most bacteria other than fragilies group

61
Q

what type of rods are fusobacterium

A

gram neagtive rods

62
Q
  • Often found in polymicrobial brain
    abscesses, especially with preceding
    sinusitis or dental treatment
  • Long and tapered appearance
A

Fusobacterium nucleatum

63
Q

fusobacterium necophorum

A
  • Associated with Lemierre’s syndrome
  • Rare complication in post-antibiotic era
  • Oropharyngeal infection first
  • Infected blood clots in jugular vein
  • Septic emboli spread to other organs
  • Gram stain morphology variable
64
Q

“spidery” on gram stain

A

cutibacterium acnes

65
Q

Cutibacterium acnes

A
  • Aerotolerant anaerobe
  • Often found on skin, causes acne
  • Can form biofilm, concern with implant
    infection after orthopedic surgeries
66
Q
  • Gram-positive, filamentous, beaded
    looking, grow very slowly
  • Facultative anaerobes
  • Part of oral & GI flora
  • Slow and chronic infections
  • “Lumpy jaw”
  • Yellow “sulfur granules” containing
    organism in abscesses
A

Actinomyces species

67
Q
  • Gram-positive rods
  • Some form spores
  • Some make toxins
  • Most are obligate anaerobes
A

Clostridium and Clostridioides

68
Q

Gas gangrene, botulism, tetanus, food poisoning can be caused by different

A

Clostridium species

69
Q

causes diarrhea/colitis in association with abx use and transferred from genus clostridium to clostridioles

A

C. dif

70
Q

what triggers sporulation

A

starvation/stress

71
Q

what triggers germination

A

nutrients

72
Q

why can clostridium be mistaken as GM- rods if they should stain GM+?

A

overdecolorize easily (often taken from blood culture)

73
Q

source of inx for clostridium gas gangrene

A

trauma-associated injury or spontaneous

74
Q

trauma-associated injury for gas gangrene

A

war, natural disasters, post-operative

75
Q

spontaneous (GI tract commonly) gas gangrene

A
  • Most often C. septicum
  • Underlying malignancy, diabetes, immunosuppression
76
Q

gas gangrene mechanism and clinical picture

A
  • Spreads via blood to invade muscles
  • Vegetative cells or spores enter deep tissue, quickly
    spread and destroy several inches per hour
  • Shock, organ failure, high mortality rate
  • Best treatment: amputation :’(
77
Q

what two toxins are in gas gangrenee promoted by C.perfringens?

A

alpha and theta

78
Q

Alpha toxin (phospholipase C)

A
  • Damages cell membranes
  • Promotes blood clots = anaerobic tissue environment
79
Q

theta toxin (perfringolysin O)

A
  • Pore-forming toxin
  • Synergy with alpha toxin
80
Q

X-ray shows gas in tissue

A

Case of gas gangrene after
intramuscular saline injection
associated with IV drug use

81
Q

C. perfringens on Egg Yolk Agar

A
  • Made with egg yolk suspension
  • Phospholipase C/alpha toxin forms opaque
    precipitate
82
Q

C. perfringens on brucella blood agar

A
  • Double zone of hemolysis
  • Narrow zone: theta toxin
  • Wider zone: alpha toxin
83
Q
  • Caused by C. botulinum, also C. butyricum, C. baratii
  • Neuroparalytic illness caused by toxin
A

BOTULISM

84
Q

infant botulism

A

baby consumes spores, they germinate in
intestine and vegetative bacteria produce toxin

85
Q

Wound botulism

A

bacteria enter a wound through injury, surgery,
or illicit drug injection

86
Q

Foodborne botulism

A

homemade, improperly
canned/preserved/fermented food with toxin in it

87
Q

Iatrogenic botulism

A

too much is injected during a medical or
cosmetic procedure (iatrogenic botox poisoning)

88
Q

toxin that binds at nerve ending synapses, prevents release of neurotransmitters at neuromuscular junctions and results in LACK OF STIMULUS TO MUSCLE FIBERS

A

botulinum toxin

89
Q

what are the symptoms of botulism?

A

slurred speech, trouble breathing, weak muscles, droopy eyelids, blurry vision, trouble swallowing

90
Q

Dx of botulism

A

DO NOT WAIT FOR LAB CONFIRMATION TREAT IMMEDIATELY, PCR, Mouse bioassay, culture

91
Q

treatment botulism

A

*Heptavalent antitoxin targets 7 serotypes
* Arrests progression of illness, but does not reverse it
* Long term recovery requires regeneration of new neuromuscular
connections

92
Q

Tetnaus caused by clostridium tetani leads to spastic paralysis caused by toxin. How is it transmitted?

A
  • Spores in the environment contaminate
    wounds
  • Crush injury, puncture wounds
  • Injection drug use
  • Spores germinate into vegetative cells
    which then produce toxin
93
Q
  • Blocks inhibitory signals to motor neurons at
    CNS system
  • Similar mechanism, but different binding site
    from botulinum toxin which is at
    neuromuscular junctions
  • Painful, spastic muscle contractions
A

tetani toxin

94
Q

symptoms/treatment of tetanus

A
  • Jaw cramping/lockjaw, muscle spasms, jerking and
    stiffness, seizures
  • Can progress to respiratory paralysis and death
  • Human tetanus immune globulin (TIG) – antibodies
    to toxin
  • CDC recommends routine tetanus vaccination with
    boosters throughout life
95
Q

DTaP vax for

A

young children

96
Q

Tdap for

A

young teens

97
Q

Td/Tdap for

A

adults

98
Q
  • Spores survive in improperly cooked/heated meat and then germinate
  • Humans ingest vegetative cells in the food
  • Form spores and enterotoxins (damage intestinal epithelia) in the small intestine
  • Diarrhea
  • Self-limiting but can be severe in young, elderly, immunocompromised
A

C. perfringens

99
Q

The most frequently reported nosocomial

A

clostridioides difficile

100
Q

C. diff transmission

A
  • Spores are found in the environment and are difficult to clean from hospital surfaces
  • Fecal-oral transmission, spores germinate in the intestine
101
Q

C. diff risk factors

A

Healthcare-associated infection
* Previous C. diff infection
* Older age (65+)
* Recent stay at hospital or nursing home
* Immunocompromised patients
* Antibiotic exposure wipes out competing intestinal bacteria and allows C. diff to take over
Community-acquired infection
* Usually younger and healthier patients, less severe infection

102
Q

what organ do c.diff toxins act on

A

large intestine (colon)

103
Q

internalized by epithelial cells and disrupts tight junctions

A

Toxin A (TcdA)

104
Q

promote collapse of the actin cytoskeleton = cell rounding and death
* Strong host inflammatory response
* Pseudomembranous colitis: plaques on mucosal surface with inflammatory exudate
* Hypervirulent strain (ribotype 027): hyperexpression of toxins

A

Toxin A and Toxin B (TcdB)

105
Q
  • Watery diarrhea
  • Fever
  • Abdominal pain
  • Loss of appetite
A

C. diff infx

106
Q

C. diff diagnosis

A
  • Complicated and controversial to diagnose
  • False positives: asymptomatic colonization, particularly in infants and children
  • People get diarrhea for other reasons: laxatives, antibiotics, other infections
  • PCR to detect genes that encode toxin
  • Toxin testing (tissue culture cytotoxicity, enzyme immunoassay) – less sensitive
107
Q

C. diff treatment/prevention

A
  • C. diff can be treated with 10 days vancomycin or fidaxomicin
  • Use isolation and contact precautions to prevent spread
  • Wear gloves and a gown
  • Wash hands between seeing patients (soap and water is best)
  • Keep infected patients in separate rooms
  • Prescribing more targeted, appropriate antibiotics in general (vs broad-spectrum)
108
Q

C. diff fecal transplant

A
  • Goal: reestablish a healthy gut microbiota in patients with recurrent C. diff infection
  • Method:
  • Screen for healthy donors (clinical history, test stool for pathogens)
  • Oral capsules (poop pills), colonoscopy to inject stool, nasoenteric tubes
  • Concerns:
  • Long-term risks, unknown health issues with donors
  • One case in 2019: drug resistant E. coli from stool donor cause bloodstream infection and
    death in an immunocompromised patient and clinical trial was halted

MICRO 442 (25 decks)

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