21a: anaerobic infections - jonathan

Question 1

page Q-3 has a chart of common anaerobic infection sites and their corresponding bacteria. It is not to be memorized.

Answer 1

page Q-3 has a chart of common anaerobic infection sites and their corresponding bacteria. It is not to be memorized.

Question 2

Knowledge of local flora aids in Dx and Tx. For example:
Compare oral infections vs intraabdominal infections in their gram stain, shape, and penicillin senstitivity vs resistance

Answer 2

Oral infections: Gram + cocci and Gram - rods, penicillin senstitive
Intraabdominal infections: Gram - rods, penicillin resistant

Question 3

With regard to Bacertoides fragilis, Dx of infection, is this bacteria found below or above the diaphragm?

Answer 3

Bacteroides fragilis is penicillin resistant and found in infections below the diaphragm.
This can be used to distinguish between upper GI tract vs lower GI tract and genital area infections.

Question 4

What are the Dx tools for anaerobic bacteria?

Answer 4

Gram stain, morphology, spores, and production of unusual fatty acids (analyzed by gas chromatography)

Question 5

What is the most common anaerobic gram - rod?

Answer 5

Bacteroides fragilis

Question 6

Note: only 10% of bacteremias are caused by anaerobes. Which two anaerobes cause the most bacteremias?

Answer 6

Bacteroides fragilis

Clostridium perfringens

Question 7

Describe Bacteriodes fragilis with regard to…
Relationship to bile?
Tolerance of Oxygen?
Penicilin (Important!)?
Under what circumstances it is a common infection?

Answer 7

Resists bile
May tolerate some oxygen during growth
PENICILLIN RESISTANT
intraabdominal rupture and female genital infections

Question 8

Is Bacteriodes fragilis resistant or sensitive to penicillin?

Answer 8

Penicillin RESISTANT

Question 9

What are the virulence factors of Bacteroides fragilis?

With what co-infection is Bacteroides fragilis more severe?

Answer 9

Capsule

More severe with E. coli co-infection

Question 10

What is the gram stain and shape of Prevotella melaninogenicus?

Answer 10

Anaerobic gram - rod

Question 11

Describe Prevotella melaninogenicus with regard to…
Where is common site of infection (1)?
What is a specific disease called at the common site of infection?
Penicilin sensitive or resistant?
What is its distinctive feature when grown on blood agar?

Answer 11

Oral infections
Periodontal disease
Penicillin SENSITIVE
Black pigment from hemin precursor necessary for growth

Question 12

What is the gram stain and shape of Fusobacterium species?

Answer 12

Gram - rod

Question 13

Describe Fusobacterium species with regard to...
Microscopic shape as a rod?
Penicillin sensitive or resistant?
Oxygen sensitive or resistant?
Common sites of infections?

Answer 13

has tapered ends and are thinner than normal Gram - rods
Penicillin SENSITIVE
Oxygen SENSITIVE
Oral infections, lung abscesses, pleuropulminary infections
Note: some species are in GI infections, but says we don’t need to know these

Question 14

Recap:
What are the names of the anaerobic gram negative rods?
Which is RESISTANT to penicillin?

Answer 14

Bacteroides fragilis
Prevotella melaninogenicus
Fusobacterium species

B. fragilis is RESISTANT

Question 15

What are the names of the non-spore forming anaerobic gram + rods?

Answer 15

Bifidobacterium
Corynebacterium
Lactobacillus
Actinomyces
Clostridia (some form spores) are covered in a prior lecture

Note: Bifidobacterium is not needed for exam.
Corynebacterium and Lactobacillus are also deemphasized.

Question 16

Corynebacterium… (this seemed deemphasized in the notes)
What tissue does it normally inhabit?
What test does it normally contaminate?
What is it commonly called?
Not a common infection, but there is one exception, which is?

Answer 16

Skin
Contaminates blood samples
Anaerobic diphtheroid
Endocarditis in compromised patients

Question 17

Lactobacillus… (this seemed deemphasized in the notes)
What tissues does it normaly inhabit?
What is the symbiotic function in our bodies?
What common fermented food products use this bacteria?

Answer 17

GI flora and vagina
Keeps the pH low
Used in yogurt and sauerkraut

Question 18

Actinomyces… this one is highlighted.
Gram stain and shape?
Oxygen sensitive or resistant?
What tissue does it normally inhabit?
What infections does it cause?
What is the characteristic growth feature?

Answer 18

nonspore forming anaerobic gram + rod
Oxygen TOLERANT
Oral pharynx and GI tract
Infections: cervical-facial (oral and dental) and abdominal with sinus tract
Sulfur granules (yellow granules of microcolonies plus cellular debris) are characteristic along with a molar tooth appearance

Question 19

Recap and Preview:
What are the names of the anaerobic gram negative rods (3)?
What are the names of the anaerobic gram positive rods (4)?
What are the names of the anaerobic gram negative cocci (1)?
What are the names of the anaerobic gram positive cocci (1)?

Answer 19

Anaerobic Gram - Rods: Bacteroides fragilis, Prevotella melaninogenicus, Fusobacterium species

Anaerobic Gram + Rods: Corynebacterium, Lactobacillus, Actinomyces, Clostridia

Anaerobic Gram - Cocci: Veillonella (quick note: commensal, not a pathogen)

Anaerobic Gram + Cocci: Peptostreptococcus

Question 20

Peptostreptococcus…
What is the gram stain and morphology?
What tissues does it normally inhabit?
Most anaerobes are in mixed cultures, in what tissues can peptostreptococcus found in pure cultures?

Answer 20

Gram + Cocci IN CHAINS.
Resembles streptococci in morphology, but is an anaerobe
Normal flora of mouth, urogenital, and GI tract
Common infection
Can be found in pure culture in pleuro-pulmonary infections, brain abscesses, and OB-GYN infections

Question 21

What are the proper steps to culture an anaerobe?
What is the medium for culturing anaerobes?
Which cultures should not be submitted for anaerobes?

Answer 21

Collect specimen with little exposure to air and inject into an anaerobic culture
Look for gram staining (fusobacterium) or morphology (Prevotella) may be helpful
Thioglycollate broth
Oral or fecal should not be submitted for anaerobes

Question 22

What is the medium for culturing anaerobes?

Answer 22

Thioglycollate broth

Question 23

What cultures should not be submitted for anaerobes?

Answer 23

Oral or fecal

Question 24

What are Tx for anaerobes (7)?

This is total answer.

Answer 24

1) Penicillin, except for B. fragilis, thus for infections below the diaphragm, penicillin must be used in combination with other antibiotics
2) Clindamycin
3) Newer cephalosporins (cefoxitin) are effective against B. fragilis
4) Chloramphenicol (static)
5) Metronidazole
6) Aminoglycosides (aerobes) + Gentomycin + Cefoxitin or Clindamycin are used for mided aerobe-anaerobe
7) Surgical drainage (antibiotics cannot get to inside an abscess)