Anaerobic Infections and Normal Flora

Question 1

Common Features of Anaerobic Infections

Answer 1

Abscesses originate from native flora.
Characterized by foul-smelling, gas in necrotic tissue
Look for predisposing conditions.
Mixed infections with at least one anaerobe

Question 2

Depending on whether the infection is located above or below the diaphragm what distinction can be made?

Answer 2

B. fragilis is located below the diaphragm and is penicillin resistant.

Question 3

Why does knowledge of local flora aid in empirical therapy?

Answer 3

Because anaerobic cultures more than 48 hours

Question 4

What is used for identification and characterization of clinically important anaerobic bacteria?

Answer 4

Gram stain, morphology and production of unusual fatty acids

Question 5

Bacteroides fragilis

Answer 5

Most common Gram - rod, pleiomorphic. Large numbers in intestine, results in septicemia, Penicillin Resistant. C. perfringens and B fragilis cause almost all anaerobic septicemias.

Question 6

Prevotella melaniongenicus

Answer 6

Gram - rod, oral infections, peridontal disease, black pigment grown on bld agar

Question 7

Fusobacterium

Answer 7

Gram - rod, tapered ends and very thin, penicillin and O2 sensitive. Oral infections, lung abcesses

Question 8

What are the anaerobic gram negative rods that cause infection?

Answer 8

Bacteroides fragilis, prevotella melaniogenicus, Fusobacterium

Question 9

What are the non-spore forming anaerobic gram positive rods that cause infection?

Answer 9

Bifidobacterium, Corynebacterium, Lactobacillus, Actinomyces, Clostridia

Question 10

Bifidobacterium

Answer 10

Gram + rod, branching, large numbers in large intestine, rarely cause infection

Question 11

Corynebacterium

Answer 11

Pleomorphic rod, normal inhabitant of skin not usually cause infection

Question 12

Lactobacillus

Answer 12

Gram + rod, normal intestinal flora, important in maintaining low pH coverts sugar to lactic acid

Question 13

Actinomyces

Answer 13

Gram + branching rod, dental abscesses, sinus tracts, sulfur granules!

Question 14

Peptostreptococcus

Answer 14

Gram + cocci chains, anaerobic. normal flora of mouth, widely involved in infections

Question 15

Anaerobic Methodology

Answer 15

Use very little air exposure, gram stain important, anticipate mixed infections. Do not submit oral or fecal cultures for anaerobes.
Media include: thioglycollate broth, which removes oxygen from liquid media

Question 16

Treatment for Anaerobic infections

Answer 16

Penicillin, except b. fragilis, clindamycin, surgical drainage in abscesses

Question 17

What is the importance of normal flora?

Answer 17

Protection from pathogens.
Nutritional function - produce B and K vit
Bacterial overgrowth in small bowel can cause fat malabsorption and B12 deficiency

Question 18

Bacterial overgrowth in small bowel can cause…

Answer 18

fat malabsorption and B12 deficiency

Question 19

Four Aerobes in Normal Mouth flora

Answer 19

Viridans streptococci - Gram + rod
Neisseria - Gram - diplococci
Diphtheroids - Gram + pleomorphic rod
S. epidermidis - Gram + cocci grape clusters

Question 20

Virdians streptococci

Answer 20

Gram + rod, may be in chains. predominant in mouth, most common cause of subacute bacterial endocarditis

Question 21

Neisseria

Answer 21

Gram - diplococci, some species are non-pathogens

Question 22

Diptheriods

Answer 22

pleomorphic Gram + rods, most common contaminants of blood cultures since also colonize skin. Rare cases of infection

Question 23

Staphylococcus Epidermidis

Answer 23

Gram + cocci, grape-like clusters, coagulase negative

Question 24

Anaerobes in Oral Cavity

Answer 24

DO NOT extend below trachea, aspiration pneumonia
Fusobacterium - Gram - cigar rod, penicillin sensitive
Prevotella - Gram - rod penicillin sensitive
Anaerobic streptococci - Gram + chain, penicillin sensitive
Actinomyces - Gram + branching rod

Question 25

Why can’t organisms be cultured from stomach? Exceptions?

Answer 25

Due to the high acidity, gastric achlorhydria and gastric obstruction allow bacteria to proliferate

Question 26

Are there bacteria in the upper small intestine?

Answer 26

No, usually sterile due to peristalsis

Question 27

Bacteroides in the large intestine

Answer 27

Gram - anaerobic rods, non-spore forming. Metabolic activity generate ammonia, acid and gas. Fragilis: resistant to penicillin, intraabdomial infections

Question 28

Large Intestine Flora

Answer 28

Bacteroides, Bifidobacterium, Lactobacilli, Clostridia, coliform

Question 29

Bile Acid deconjugation

Answer 29

Large bowel flora convert conjugated bile to free bile acids, conjugated is necessary for normal fat absorption