Listeria, Pseudomonas, & Various Anaerobes Flashcards
Listeria organism
hemolysis?
metabolic profile?
motility?
- Gram positive rod
- Slight hemolysis
- Acid but no gas from CHO fermentation…facultative psychrophile (facultative intracellular parasite)
- Weird tumbling motility
Food sources of listeria
unpasteurized milk, cheese, processed meats
or long term storage of meats and cheese in the refrigerator
- Adult presentation of listeria
- Perinatal listeria from infected _____ during ____
- What are the types?
Diarrhea & dysentery
*Followed by meningitis or bacteremia (occasionally myocarditis) in IC patients
From infected _placenta _during Third trimester
- Early onset = stillbirth & granulomas
- Late onset = Type 4b
Listeria pathogenic factors (5)
- Siderophores (bind iron)
- Intracellular growth
- Internalin = binds cadherin receptor (uptake into cell)
- Listeriolysin O = activated by low pH of phagolysosome
- ActA = causes actin polymerization (moves to new cell)
Listeria preferred antibiotic
ampicillin
(or amp + aminoglycoside)
*erythromycin can also be used
Pseudomonas aeruginosa organism
respiration
other characteristics
- gram negative rod (single polar flagellum)
- respiratory metabolism but can use NO3- as electron acceptor. Can use many Carbon sources
- Fruity aroma, blue-green fluorescent pigment
Major pseudomonas pathogenic factor?
How does this occur?
Biofilms
via homoserine lactones and Quorum-sensing signal
(Pseudomonas Quinolone Signal = PQS)
Pseudomonas are almost always _______ infections
opportunistic, nosocomial
Who are susceptible to skin biofilm pseudomonas infections?
burn patients and diabetics
Cystic fibrosis presentation for pseudomonas
lung biofilms with high amts of persister cells
Pseudomonas causes what other localized infections? (5)
- otitis externa
- eye infections (#1 lasik complication…you’ll get green eyes!)
- UTI (catheters)
- Ecthyma gangrenosum in diabetics
- Folliculitis (from contaminated water)
What do ecthyma gangrenosum lesions look like?
erythematous, non-pyrogenic ulcerations
Does Pseudomonas cause bacteremia?
Yep.
Especially in Leukemia & burn patients, and diabetics
Is pseudomonas resident flora?
Yes, on moist areas of skin
NON-invasive in people with normal immunity
**CF patients have it as normal URT flora!
Pathogenic factors of pseudomonas (6)
- Adhesion pili
- Hypermutable strains in biofilm
- Persister cells
- Biofilm + Alginate capsule
- **LPS ** (typical of G-)
- Type 3 Secretion System
- Toxins = exotoxins A and S, Elastase, Pyocyanin/Polychelin
Function of toxins A and S from pseudomonas
A = ADP ribosylates EF-2 (diptheria toxin analog)
S = ADP ribosylates H-ras p21; signals apoptosis
Pyocyanin and Pyochelin create ________
oxygen radicals
3 Control measures for pseudomonas
- sterile environment (blue light?)
- topical ABX
- Prevention of biofilm (DNAase)
ABX for pseudomonas
Severe infection Tx?
Cipro is most frequently used (but resistance is problem)
Cipro + aztreonam
Severe = Gentamycin + ticarcillin or carbenicillin
**Meropenem + levofloxacin can prevent
Why shouldn’t we treat pseudomonas with quinolones?
Activates biofilm formation
(PQS)
Other pseudomonads
Acinetobacter baumanii - ventilator associated
burkholderia cepacia - catheter associated
General anaerobes:
Infections are almost always _____
Prefer to live at ______. How is this made possible?
Mixed infections
Low redox potential (less O2) - which is generated by facultative organisms like E. coli
None of the anaerobes has ______. Thus…
cytochromes
…no ETC or respiration
Six common anaerobes
- Bacteroides fragilis
- Prevotella melaninogenica
- Porphyromonas gingivalis
- Fusobacterium
- Peptostreptococcus
- Propionibacterium acnes
