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Quiz 3 Microbiology > Anaerobic infections and normal flora > Flashcards

Anaerobic infections and normal flora Flashcards

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1
Q

What are common symptoms of anaerobic infections?

A

foul-smelling discharge from short-chain fatty acids and gas in the necrotic tissue

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2
Q

Where will you most commonly find anaerobic infections?

A

deep or necrotic tissue, where oxygen tension is low

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3
Q

Are most anaerobic infections mixed or does a single organism infect a tissue?

A

Usually anaerobic/microaerophilic infections=mixed or polymicrobial
Aerobic organisms = single species

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4
Q

Most anaerobic infections are caused by bugs found where?

A

In the patient’s endogenous flora

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5
Q

Bacteroides fragilis can be found in infections located in what general area of the body?

A

Infections below the diaphragm.

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6
Q

How long does it take to culture anaerobic organisms?

A

> 48 hrs

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7
Q

What is the typical morphology of species infecting the mouth? Are they sensitive or resistant to penicillin?

A

gram-positive cocci, gram-negative rods, mixed anaerobic infections.
These are sensitive to penicillin

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8
Q

What is the typical morphology of species infecting the abdominal area? Are they sensitive or resistant to penicillin?

A

gram-negative rods, mixed anaerobes

Penicillin resistant

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9
Q

How would you identify clinically important anaerobic bacteria?

A

Gram stain and morphology, production of unusual fatty acids

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10
Q

What are the anaerobic gram negative rods?

A

Bacteroides fragilis
Prevotella melaninogenicus
Fusobacterium species

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11
Q

Is B fragilis penicillin resistant or sensitive?

A

RESISTANT

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12
Q

If a patient has gram negative septicemia, the causative organism is most likely to be:

A

clostridium perfringens OR B. Fragilis

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13
Q

What is the most ommon anaerobic gram negative rod?

A

B fragilis

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14
Q

What is a major virulence factor of B fragilis?

A

The capsule

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15
Q

What is a common cause of B fragilis infection?

A

intraabdominal bowel rupture and female genital infections following procedures

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16
Q

Prevotella melaninogenicus is a common cause of:

A

oral infections–causing periodontal disease

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17
Q

What is prevotella melaninogenicus sensitive to?

A

Penicillin and also more sensitive to traces of oxygen

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18
Q

What color colonies does prevotella form when grown on blood agar plates?

A

black pigment

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19
Q

How would you distinguish fusobacterium morphologically?

A

needle shaped and very thin rods

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20
Q

What is fusobacterium sensitive to?

A

penicillin and trace oxygen

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21
Q

What are the nonspore forming anaerobic gram positive rods?

A 
Bifidobacterium
Corynebacterium
Lactobacillus
actinomyces
Clostridia
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22
Q

What does bifidobacterium look like on a gram stain?

A

Gram + rods with a tendency to branch with pleomorphic structure. Found in the colon. Not pathogenic.

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23
Q

What infection does corynebacterium cause?

A

Usually just contaminates blood samples as a normal inhabitant of the skin.

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24
Q

What morphology does corynebacterium take on?

A

Pleomorphic gram positive rods

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25
Q

Where do you normally find lactobacillus? What is its relevance clinically?

A

Found in intestine and vagina. Non pathogenic, important in maintaining low pH to prevent growth of pathogens

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26
Q

Where do you normally find actinomyces?

A

oral pharynx and GI tract

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27
Q

What is the morphology of actinomyces?

A

gram positive branching rods

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28
Q

Where does actinomyces cause infection?

A

oral/dental/abdominal infections with sinus tract

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29
Q

What are the diagnostic features of actinomyces?

A

sulfur granules
“molar tooth” appearance
branching rods

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30
Q

What is an anaerobic gram positive cocci?

A

peptostreptococcus

31
Q

What does peptostreptococcus infect?

A

pulmonary infections
brian abscesses
OB-GYN

32
Q

What is an anaerobic gram negative cocci? What is its importance?

A

veillonella. Not an important pathogen

33
Q

would you ever submit oral or fecal cultures for anaerobes?

A

No

34
Q

What kind of media would you use for culturing anaerobic bacteria?

A

thioglycollate broth

35
Q

How would you treat an anaerobic infection?

A 
Penicillin (except below the diaphragm)
Clindamycin
3rd generation cephalosporins
Chloramphenicol
Metronidazole
Surgical drainage for abscess
Metronidazole
36
Q

What vitamins do the normal intestinal flora produce?

A

Vitamin B12 and Vitamin K

37
Q

What is a problem with bacterial overgrowth in the small bowel?

A

fat malabsorption and vitamin B12 deficiency

38
Q

What are the normal aerobes of the mouth flora?

A 
viridans streptococci 
Neisseria species
Diphtheroids
S. epidermidis
Eikenella corrodens
39
Q

What is the morphology of viridans strep?

A

gram positive cocci, sometimes in chains

40
Q

What is the predominant normal microorganism found in the mouth?

A

Viridans strep

41
Q

What pathology can V strep cause?

A

bacterial endocarditis, dental plaque

42
Q

What is the morphology of diptherioids?

A

pleomorphic gram positive rods.

43
Q

What is the significance of diptheroids?

A

Most common contaminant of blood culture. Rare infection causing endocarditis

44
Q

What is the morphology of S epidermidis?

A

gram positive cocci, round, and grape like clusters

45
Q

What pathology can S epidermidis cause?

A

Common contaminant of blood cultures. Can infect catheters, intravascular devices

46
Q

Upon hospitalization, patients may have their normal oral flora replaced with:

A

gram negative rods like E coli or klebsiella

47
Q

What pathology does Eikenella corrodens cause?

A

human bites and clenched fist injuries

48
Q

What are common oral anaerobes?

A 
fusobacterium
prevotella
anaerobic streptococci
actinomyces
anaerobic spirochetes
49
Q

Which oral anaerobes are penicillin sensitive?

A

fusobacterium
prevotella
anaerobic streptococci

50
Q

Where would you stop finding oral flora?

A

lower trachea in healthy individuals

51
Q

How would you treat an infection above the diaphragm?

A

With penicillin

52
Q

When would you have stomach flora?

A

In cases of gastric achlorhydria or gastric obstruction

53
Q

What bacteria would you find in upper small intestine?

A

Usuallly pretty sterile.

May find some gram positive aerobes. Sterile because of rapid movement and also unconjugated bile acids

54
Q

What species do you find in terminal ileum?

A

E coli, enterobacter, gram negative organism. Anaerobes such as B fragilis predominate

55
Q

What species do you find in the large intestine?

A

Mostly anaerobes

56
Q

How is ammonia formed in the colon?

A

splitting urea

57
Q

What do you use to treat infections below the diaphragm for anaerobic apecies?

A

clindamycin, cefoxitin, metronidazole

58
Q

What are the predominant aerobic flora in the gut?

A

Coliforms (enteric gram negative rods) and enterococcus

59
Q

What happens to bile with abnormal bacterial growth in the small intestine?

A

More conversion of conjugated bile acid to free bile acid, causing fat malabsorption

60
Q

What is the major source of ammonia in the blood?

A

Bacterial degradation biproduct

61
Q

What does intestinal bacteria do to bile pigments?

A

Converts bilirubin to stercobilin

62
Q

What is the predominant organism of the skin?

A

Staphylococcus epidermidis

63
Q

What other pathogens are found in the skin?

A

S aureus
Diphtheroids
proprionibacterium and peptococcus

64
Q

What are the species in the upper respiratory tract?

A

S aureus
viridans strep
Neisseria
Anaerobes: bacteroides, fusobacterium, clostridium, peptostreptococcus

65
Q

What is the normal flora of the Gu tract?

A

lactobacillus in women
E coli and enterobacter, which can cause UTI
Group B streptococci. Can cause newborn sepsis

66
Q

How would you tell the difference between B fragilis and Clostridium?

A

Clostridium is a spore forming obligate aerobe. In contrast, B. Fragilis does not form spores

67
Q

What do anaerobes use as electron acceptors?

A

nitrogen or other inorganics

68
Q

What enzyme do anaerobes lack?

A

Some lack superoxide dismutase and all lack catalase

69
Q

Where would you find regions of low redox potential and therefore anaerobic infections?

A

Oral cavities, ileum and colon, female genital tract

70
Q

What organisms would you suspect in gingivitis?

A 
fusobacterium
prevotella
peptostreptococcus
viridans strep (aerobe)
actinomyces
71
Q

What gram negative rod would you see in a human bite infection?

A

eikenella corrodens

72
Q

What organisms would you suspect in upper respiratory infections spreading to the brain?

A

ACTINOMYCES

but also prevotella, fusobacterium, peptostreptococcus, strep viridans

73
Q

What kind of infection would you expect with actinomyces?

A

An oral, pulmonary, or abdominal abscess or sinus tract infection

Quiz 3 Microbiology (4 decks)

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