Gram - Rods/Bacilli

Question 1

Escherichia coli

aerobic & facultative

Answer 1

disease from endogenous or contaminated water/food
Lactose fermentor, Encapsulated (K antigen), catalase +, fimbrae for adhesion - most common bug to become antibiotic resistant from plasmid uptake
#1 cause of UTIs, LPS endotoxin --> sepsis, K antigen --> neonatal meningitis

Question 2

EHEC (Enterohemorrhagic E. coli)

Answer 2

common from consuming undercooking meats
Characterized by bloody diarrhea - does not ferment sorbitol - shiga-like toxin can lead to hemolytic urea syndrome in kids, glomerular damage, platelet aggregation/reduced count –> RBC shearing and hemolysis
0157:H7 serotype

Question 3

ETEC (Enterotoxigenic E. coli)

Answer 3

“travelers diarrhea” - usually from water sources –> watery diarrhea
Heat labile toxin - Increases cAMP (similar to cholera toxin)
Heat stabile toxin - increases c GMP

Question 4

Psuedamonas auruginosa

aerobic & facultative

Answer 4

oxidase +, catalase +, encapsulated, Exotoxin A –> inactivated EF-2 by ribosylation (same as diptheria)
Infections due to surgery, trauma, BURNS, immunocompromised, nocosomial in Cystic Fibrosis (chronic lung infections, pneumonia, death), osteomyelitis, hot tub folliculitis, echthyma gangrenosum, otitis externa
tx- piperacillin/Tazo, aminoglycosides and fluoroquinolones

Question 5

Bacteroides fragilis

aerotolerant anaerobe

Answer 5

Produces destructive tissue enzymes, an antiphagocytic capsule, and superoxide dismutase
common in peritoneal abscesses

Question 6

Rickettsia
(gram - bacillococcus)
(Obligate intracellular)

Answer 6

Poor gram staining, unable to produce CoA and NAD+, spread by ticks and lyse
Causes Rocky Mountain Spotted Fever - spreads centrally FROM the extremities
Presents early with headache and fever –> vasculitis and rash
Tx- Doxycycline