Anaerobic infections

Question 1

Bacteroides fragilis

Answer 1

intra-abdominal infections (peritonitis or local abscesses)
anaerobic
non-sporeforming
G- rod
most common cause of serious anaerobic infections
-50% resist to PCN and all are resist to aminoglyco

Question 2

B. fragilis virulence factors

Answer 2

-Polysaccharide capsule –> antiphago and abscess promoting
-lipid A endotoxin
enzymes

Question 3

Actinomyces israelii

Answer 3

G+ rods
non sporeforming
branching filamentous pattern like fungi
facultative intracellular
facultative or obligate anaerobes
form SULFUR GRANULES --> visualization for Dx
Tx with PCN

Question 4

Acitnomyces israelii pathogenesis

Answer 4

• destructive disease of connective tissue (opportunistic)
• formation of granulomas, pyogenic lesions, and abscesses
• cervicofacial –> most common; dental surgery or disease
• abdominal –> rupture of appendix or cecum
• thoracic –> extension of cervicofacial dz or aspiration
• pelvic –> intrauterine devices

Question 5

Clostridium perfringens

Answer 5

gas gangrene
G+ rod; anaerobe; sporeforming
grow in traumatized tissue, esp muscle
pain, edema, cellulitis, and CREPITATION

Question 6

C. perfringens patho and virulence

Answer 6

Alpha toxin –> hydrolyzes lecithin and sphingomyelin
enzymes
localized cellulitis –> amputations
abdominal
gas gangrene/myonecrosis –> contaminated deep wounds
Tx with tissue debridement, PCN, and hyperbaric O2

Question 7

Clostridium tetani

Answer 7

-tetanus
G+ spore-forming rod; anaerobic
DRUMSTICK SHAPE
-tetanospasmin –> causes spastic paralysis –> retrograde axonal xsport to CNS –> inhib GABA or glycine
-CP: trismus / opistothonos (generalied spasms)
-neonate form –> contam umbilicus

Question 8

C. tetani Dx and Tx

Answer 8

• add rabies and strychnine poisoning to diff Dx
• culture may or may not yield growth –> strictly a toxemia
• no immunity to natural infection
• Tx with tetanus immune globulin and debridement of necrotic tissue
• Tx with metronidazole and immunize with tetanus toxoid

Question 9

Newborn meningitis

Answer 9

Group B strep
E. coli
Listeria monocytogenes