Gram Negative Rods Flashcards
McConkeys agar**
- good for enteric organisms***
- also for nonenterics like Yersinia and Pseudomonas
lactose fermenters vs. nonfermenters**
Fermenters
- turn purple on McConkeys
1. Fast –> klebsiella, enterobacter, E. coli
2. slow –> citrobacter, serratia
Non-fermenters
- turn clear on McConkeys
1. oxidase + –> pseudomonas*
2. oxidase - –> salmonella, proteus, shigella, yersinia
gram negative rods
- thin peptidoglycan wall surrounded by LPS –> Lipid A endotoxin
- enterobacteriacea family
Klebsiella pneumoniae
-pneumonia in alcoholics and diabetics*
- red “jelly” sputum in lungs
- HEMORRHAGIC lungs***
E. coli
- fibrimbiae attach to mucosa and can climb mucociliary tract
- most don’t have a capsule
- capsule (K antigen) seen in meningeal strains*** (ex. meningitis in newborns)
types of E. coli***
- enterohemorrhagic (EHEC) –> hemorrhagic/bloody diarrhea
- enterinvasive (EIEC) –> shigella like dysentery
- enteropathogenic (EPEC) –> childrens diarrhea
- enterotoxigenic (ETEC) –> travelers diarrhea (clear)
- due to inc cAMP/GMP –> inc water secretion
- EHEC and EIEC more invasive –> bloody diarrhea***
- EPEC and ETEC less invasive –> clear diarrhea***
EHEC
-E. coli 0157:H7**
- only the toxin causes the illness***
- no invasion of host
-HUS in children***** (hemolytic anemia, thrombocytopenia, renal failure)
EIEC
-only the organism kills it with invasion, not the toxin***
enterobacter
- nosocomial UTIs
- resistant to antibiotics
citrobacter and serratia
citrobacter
-normal gut flora
serratia**
- red colonies (red pigment)**
- nosocomial
- cause osteomyelittis in IV drug users
MacConkey lactose fermenters***
- citrobacter (slow)
- serratia (slow)
- klebsiella (rapid)
- enterobacter (rapid)
- E. coli (rapid)
Pseudomonas aeruginosa
-resistant attitude –> use antipseudomonal drugs
- BE PSEUDO**
- external otitis “swimmers eare”**
-loves water*
- blue-green pigment (pyocyanin)
- flourescent green colonies on culture**
- grape-like odor**
salmonella
- flagellated (motile)
- spread bloodstream
- 2 types: typhoid fever and diarrhea
- bloody diarrhea + fecal leukocyte (monocytic response)
- osteomyelitis in sickle cell patients***
salmonella typhi (typhoid fever)
-fever, constipation, diarrhea
- Rose spots** (macules on trunk/abdomen)
- Pulse-temp dissociation** (high fever, slow pulse)
Shigella
- no flagella (non-motile)
- spread cell to cell
- invades mucosal cells (Peyer’s patch M cells) inducing apoptosis
- very few bacteria can cause disease*
- PMN (neutrophil) response