45 Anaerobes I

Question 1

anaerobes fail to grow on the surface of what?

Answer 1

solid media in air (18% O2) supplemented w/5-10% CO2

moderate anaerobe: 2-8% O2 (eg propionibacterium, clostridium)

strict anaerobe:

Question 2

probiotics containing anaerobes (eg _____ & _______) are ingested by many people to maintain indigenous anaerobe flora.

Answer 2

lactobacilli, bifidobacteria

Question 3

majority of anaerobic infections are endogenous or exogenous?

Answer 3

endogenous, but most exogenous infections are caused by clostridia

Question 4

what is the disease assoc w/each?:
C.tetani
C.botulinum
C.perfringens
C.difficile

Answer 4

C.tetani - tetanus

C.botulinum - botulism

C.perfringens - food poisoning, cellulitis, myositis, myonecrosis

C.difficile - diarrhea, pseudomembraneous colitis

Question 5

body parts w/highest [Anaerobes]?

Answer 5

teeth, gingiba, colon, vagina (not stomach because of acidic pH)

Question 6

which anaerobic bacteria is the outlier that colonizes the skin?

Answer 6

propironibacterium

Question 7

infection w/a facultative anaerobe does what to anaerobes?

Answer 7

uses up the already diminished O2 supply and thus encouraces growth of obligate anaerobes

Question 8

clinical and lab clues for anaerobic infections?

Answer 8

• foul odor from lesion or discharge
• infection near mucosal surface
• tissue necrosis, gangrene, abscess formation w/gas
• assoc w/malignancy
• diarrhea assoc w/Abx tx
• massive hemolysis
• sulfur granules in discharge
• unique gram stain morphology
• fail to grow aerobically

Question 9

problems w/identification of anaerobic infections?

Answer 9

• derived from normal flora - is it a pathogen or contaminant? Tell by clinical sxs
• death by air
• slow growth of orgs (due to inefficiency of fermentation)

Question 10

appropriate specimens for anaerobic cx?

Answer 10

• collected in a sterile manner
• tissue biopsies, surgical specimens, needle aspirates, blood

NOT: contaminated w/orgs colonizing the skin and mucosal surfaces like swabs, sputum, or urines

Question 11

anaerobic, non-spore forming GP rods?

Answer 11

actinomyces, lactobacillus, mobiluncus, propionibacterium

Question 12

anaerobic GP cocci?

Answer 12

peptostreptococcus

Question 13

peptostreptococcus disease?

Answer 13

Polymicrobial infections:

• Sinusitis, pleuropulm infecteions, brain abscesses
• intraabd. Infections
• endometritis, pelvic abscesses
• cellulitis, necrotizing fasciitis
• osteomyelitis

Question 14

peptostreptococcus treatment?

Answer 14

• usu susceptible to penicillin but tx should cover all orgs of infection – generally combination therapy: beta-lactam-beta-lactamase inhibitor, can include metronidazole combined w/extended spectrum cephalosporin, aminoglycoside, or FQ
• empiric therapy adjusted when results of susceptibility tests available

Question 15

actinomyces general characteristics?

Answer 15

• delicate filamentous structure

- sulfur granules colony

Question 16

actinomyces pathogenesis?

Answer 16

• chronic lesions that become suppurative and form abscesses connected by sinus tracts
• involves disruption of mucosal barrier (surgery like dental procedures/GI surgery, trauma, aspiration, foreign body like IUD, diverticulitis, appendicitis)

Question 17

actinomyces disease?

Answer 17

Actinomycosis

• cerebral
• cervicofacial
• thoracic
• abdominal
• pelvic

Chronic infection w/relapsing/remitting course assoc w/abscess, draining sinuses, fibrosis

• often mistaken for malignancy

Question 18

actinomyces treatment?

Answer 18

Abx: penicicllin; erythromycin or clindamycin

Surgical debridement (liver is highly vascular, thus [Abx] is high enough and don’t need debridement)

Question 19

lactobacillus general characteristics?

Answer 19

long, thin GP rods (non-spore-forming)

mostly clinically insignificant (found in probiotics)

Question 20

lactobacillus disease?

Answer 20

may cause septicemia in immunocompromised or endocarditis in ppl w/underlying valve abnormalities

• bloodstream infection of lactobacillus causing endocarditis

Question 21

lactobacillus treatment?

Answer 21

Abx: high [penicillin] and gentamicin (pcn or a combo of Abx) – bacteria resistant to vancomycin

Question 22

mobiluncus general characteristics?

Answer 22

curved rod, GN or G-variable

colonizes genital tract

Question 23

mobiluncus disease? dx? tx?

Answer 23

• multiplies to high numbers in women w/ bacterial vaginosis (may be impt cause or marker of disease)
• clue cells suggest Dx of BV
• tx of BV w/metronidazole (even though Mobiluncus itself is resistant)

Question 24

propionibacterium general characteristics?

Answer 24

clumps of short rods

- most commonly isolated anaerobe in microbiology lab

Question 25

propionibacterium disease and treatment?

Answer 25

- acne - invasive infections in pts w/indwelling foreign bodies: prosthetic heart valves, prosthetic joints, indwelling catheters - topical benzoyl peroxide - penicillin, tetracyclines, erythromycin, clindamycin

Question 26

bacteroides fragillis general characteristics?

Answer 26

anaerobic GN rod w/LPS but lacks endotoxin activity most common clinically significant anaerobe grows easily in culture (pleimorphic GNRs w/inflammatory cells)

Question 27

B.fragilis virulence?

Answer 27

polysaccharide capsule prevents phagocytosis and stimulates abscess formation other factors too

Question 28

B.fragilis disease? dx? treatment?

Answer 28

abscess formation: - intraabdominal infections - PID and endometritis - surgical wound infections - S/ST infections after surgery or trauma dx: grows well in culture, always consider post-op (tends to be necrotic and thus crepitus present) tx: - resistant to penicillins - metronidazole plus active vs other organisms in infection (polymicrobial) - surgical debridement

Question 29

fusobacterium general characteristics?

Answer 29

anaerobic GNR - normal flora of oropharynx, GI and GU, long, filamentous

Question 30

fusobacterium pathogenesis?

Answer 30

- untreated dental caries extend to dental alveoli and result in osteomyelitis or may spread into mandible - spreads to thorax via parapharyngeal spaces

Question 31

fusobacterium disease?

Answer 31

- acute necrotizing ulcerative gingivitis (“trench mouth”) - pharyngitis, tonsillitis (Vincent’s angina) - Jugular venous thrombophlebitis (Lemierre’s syndrome) = pharyngitis complicated by peritonsillar abscess w/subsequent spread through pharyngeal spaces inferiorly  into internal jugular  localized thrombophlebitis  clots embolize to other organs (**lung) and form abscesses at those sites

Question 32

fusobacterium treatment?

Answer 32

- penicillin and clindamycin For Lemierre’s: B-lactam-B-lactamase inhibitor and debridement of abscess