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Micro Test 3 > Anaerobic Organisms > Flashcards

Anaerobic Organisms Flashcards

1
Q

What is an obligate anaerobe?

A

growth occurs only in an anaerobic environment, absent of oxygen

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2
Q

Describe a STRICT obligate anaerobe

A

usually not diagnosed with human infections, oxygen is toxic. Diagnosis usually not via culture as difficult for organisms to survive outside in vivo environment

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3
Q

Describe MODERATE obligate anaerobe

A

These are the cause of human infections. They are able to survive in reduced oxygen environments. These can routinely be cultured in the the labs. They require appropriate transport.

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4
Q

How do anaerobes obtain energy?

A

fermentation because it does not require oxygen. some can carry out anaerobic respiration where the final electron receptor is something other than oxygen.

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5
Q

What are exogenous anaerobes?

A

exist outside the body, live in soil, freshwater, and saltwater sediments.

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6
Q

What are endogenous anaerobes?

A

exist inside the body and live on skin and mucosal surfaces.

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7
Q

what do anaerobic infections generally contain?

A

a mixture of anaerobic and facultative anaerobic organsims.

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8
Q

What are some examples of exogenous infections

A

foodborne illnesses, such as botulism and gastroenteritis. Wound infection: tetanus, gas gangrene, crepitant cellulite, benign superficial infections, human and animal bites.

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9
Q

What are some examples of endogenous infections?

A

bacteremia, meningitis, endocarditis, abscess of an organ, dental infections, intrabdominal abcess, osteomyelitis.

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10
Q

What are some predisposing conditions?

A

trauma of mucous membranes or skin that decrease blood flow so that there is decreased 02. Conditions that cause vascular stasis: surgery, shock, edema, tissue necrosis

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11
Q

what are macroscopic indications that anaerobes are involved in the infection?

A

purulent specimen, large quanities of gas or foul odors, black exudate, sulfur granules, necrosis and gangrene.

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12
Q

if an infection continues despite aminoglycoside treatment, then it is an indication for what?

A

anaerobic culture

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13
Q

What is critical for specimen collection?

A

selection of the appropriate medium and transport

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14
Q

What are examples of sites that may be contaminated by indigenous flora? are these acceptable?

A

cervix, decubitis ulcers, stool, vagina, urine, sputum, bronchial washing. not acceptable

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15
Q

What are some examples of acceptable specimens?

A

synovial fluid, CSF, blood and bone marrow, aspirated exudates, direct lung aspirates, lung tissue, tissue biopsies, suprapubic aspirate.

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16
Q

The best specimen collection…

A

sterile body sites, aspirates, and tissues. the worst is swabs.

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17
Q

What is an anaerobic chamber?

A

allows for oxygen free environment, media used for culture stored in this oxygen free environment.

18
Q

What are the steps involved in specimen processing?

A

grinding the tissues, centrifuge to concentrate specimens and plate the sediment.

19
Q

What are the exceptions to antibiotic susceptibility testing (because its not normally performed)

A

for research purposes, to assist in life-threatening disease, known resistance, persistence of infections, severity of infection.

20
Q

What antibiotics should be tested/

A

PCN G, broad-spectrum antipseudomonal PCN, clindamycin, cefotoxin and possibly other cephalopsorins.

21
Q

How do we create an environment where anaerobes can not grow?

A

debridement, draining, stop spread, use of antitoxins, hyperbaric oxygen.

22
Q

Describe the clostridium species?

A

normal flora of lower GI tract, found in soil, most infections are exogenous sources. Its virulence factors are toxins.

23
Q

What is clostridium species clinical significance?

A

botulsim, gas gangrene, tetanus, psuedomenbranous colitis, wounds, abcesses, bactermia, food poisoning and gastroenteritis.

24
Q

What is clostridium’s gram stain?

A

gram-positive bacilli (some may stain gram negative). most can produce spores when they are stressed.

25
Q

Describe clostridium botulinum

A

widely distributed in soil and water. associated with home canning. its virulence factor is a neurotoxin.

26
Q

What is clostridium botulinum’s clinical significance?

A

foodborne: symptoms 1 to 3 days after ingestion. symptoms include blurred vision, dry mouth, constipation, abdominal pain, progressing bilateral weaknes. treatment is an antitoxin. usually seen in infants up to 6 months. they eat honey. “floppy baby syndrome”

27
Q

Can clostridium botulim cause a problem with wounds?

A

yes. symptoms usually develop within 4 days. treatment is supportive, antitoxin, and antibiotics.

28
Q

Where is clostridium botulinum normally identified?

A

a public health lab

29
Q

Describe clostridium perfringens

A

It is the MOST FREQUENTLY isolated clostridium species. it is frequently found in soil which suggest surfaces contaminated with the organism. virulence factor is an ALPHA EXOTOXIN.

30
Q

What does the alpha exotoxin do?

A

it lyses things.

31
Q

What food products can clostridium perfringens be found in?

A

meat products. incubation is usually 8-24 hours. abdominal cramps, watery diarrhea with no fever, vomitting, self-limiting. NO TREATMENT NECESSARY.

32
Q

What type of skin infection can clostridium perfringens?

A

gas gangrene, pain an swelling on infected area within a week. gas formation in the tissue. gram stain will show large rectangular rods with lack of inflammatory cells.

33
Q

What is the treatment for clostridium perfringens?

A

debride, excise, or amputation of dead tissue. antibiotic therapy: pcn and clindamycin. hyperbaric chamber.

34
Q

What is the causative agent of tetanus?

A

clostridium tetani

35
Q

What can prevent clostridium tetani?

A

dtap or td or tdap

36
Q

What is the antibiotic associated clostridium?

A

clostridium difficile.

37
Q

describe clostridium difficile

A

endogenous or nosocomial (spores in hospital environment)

38
Q

What is the bactericides fragilis group?

A

normal flora of the mouth, upper respiratory tract, GI TRACT, urogenital

39
Q

What is the most common anaerobe isolated in the lab?

A

bacteroides fragilis

40
Q

Describe bacteroides fragilis

A

growth occurs at 48-72 hours, produces beta-lactamases causing PCN and some cephalosporin resistance.

Micro Test 3 (4 decks)

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