Listeria, Pseudomonas, & Various Anaerobes

Question 1

Listeria organism

hemolysis?

metabolic profile?

motility?

Answer 1

• Gram positive rod
• Slight hemolysis
• Acid but no gas from CHO fermentation…facultative psychrophile (facultative intracellular parasite)
• Weird tumbling motility

Question 2

Food sources of listeria

Answer 2

unpasteurized milk, cheese, processed meats

or long term storage of meats and cheese in the refrigerator

Question 3

• Adult presentation of listeria
• Perinatal listeria from infected _____ during ____
  • What are the types?

Answer 3

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

Question 4

Listeria pathogenic factors (5)

Answer 4

1. Siderophores (bind iron)
2. Intracellular growth
3. Internalin = binds cadherin receptor (uptake into cell)
4. Listeriolysin O = activated by low pH of phagolysosome
5. ActA = causes actin polymerization (moves to new cell)

Question 5

Listeria preferred antibiotic

Answer 5

ampicillin

(or amp + aminoglycoside)

*erythromycin can also be used

Question 6

Pseudomonas aeruginosa organism

respiration

other characteristics

Answer 6

• 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

Question 7

Major pseudomonas pathogenic factor?

How does this occur?

Answer 7

Biofilms

via homoserine lactones and Quorum-sensing signal

(Pseudomonas Quinolone Signal = PQS)

Question 8

Pseudomonas are almost always _______ infections

Answer 8

opportunistic, nosocomial

Question 9

Who are susceptible to skin biofilm pseudomonas infections?

Answer 9

burn patients and diabetics

Question 10

Cystic fibrosis presentation for pseudomonas

Answer 10

lung biofilms with high amts of persister cells

Question 11

Pseudomonas causes what other localized infections? (5)

Answer 11

• otitis externa
• eye infections (#1 lasik complication…you’ll get green eyes!)
• UTI (catheters)
• Ecthyma gangrenosum in diabetics
• Folliculitis (from contaminated water)

Question 12

What do ecthyma gangrenosum lesions look like?

Answer 12

erythematous, non-pyrogenic ulcerations

Question 13

Does Pseudomonas cause bacteremia?

Answer 13

Yep.

Especially in Leukemia & burn patients, and diabetics

Question 14

Is pseudomonas resident flora?

Answer 14

Yes, on moist areas of skin

NON-invasive in people with normal immunity

**CF patients have it as normal URT flora!

Question 15

Pathogenic factors of pseudomonas (6)

Answer 15

1. Adhesion pili
2. Hypermutable strains in biofilm
3. Persister cells
4. Biofilm + Alginate capsule
5. **LPS ** (typical of G-)
6. Type 3 Secretion System
7. Toxins = exotoxins A and S, Elastase, Pyocyanin/Polychelin

Question 16

Function of toxins A and S from pseudomonas

Answer 16

A = ADP ribosylates EF-2 (diptheria toxin analog)

S = ADP ribosylates H-ras p21; signals apoptosis

Question 17

Pyocyanin and Pyochelin create ________

Answer 17

oxygen radicals

Question 18

3 Control measures for pseudomonas

Answer 18

• sterile environment (blue light?)
• topical ABX
• Prevention of biofilm (DNAase)

Question 19

ABX for pseudomonas

Severe infection Tx?

Answer 19

Cipro is most frequently used (but resistance is problem)

Cipro + aztreonam

Severe = Gentamycin + ticarcillin or carbenicillin

**Meropenem + levofloxacin can prevent

Question 20

Why shouldn’t we treat pseudomonas with quinolones?

Answer 20

Activates biofilm formation

(PQS)

Question 21

Other pseudomonads

Answer 21

Acinetobacter baumanii - ventilator associated

burkholderia cepacia - catheter associated

Question 22

General anaerobes:

Infections are almost always _____

Prefer to live at ______. How is this made possible?

Answer 22

Mixed infections

Low redox potential (less O₂) - which is generated by facultative organisms like E. coli

Question 23

None of the anaerobes has ______. Thus…

Answer 23

cytochromes

…no ETC or respiration

Question 24

Six common anaerobes

Answer 24

• Bacteroides fragilis
• Prevotella melaninogenica
• Porphyromonas gingivalis
• Fusobacterium
• Peptostreptococcus
• Propionibacterium acnes

Question 25

Bacteroides: organism and location

virulence factors?

Answer 25

Gram negative rod that hangs out in colon

• Antiphagocytic capsule
• Can produce some SuperOxide Dismutase and CAT (so a little O2 resistant)
• Extracellular enzymes- Neuraminidase and Heparinase

Question 26

Prevotella organism, virulence factor, and infection location

Answer 26

Oral gram negative coccobacillus

Collagenase

Brain and Lung abcesses

Question 27

Porphyromonas gingivalis organism, locations

Answer 27

Gram negative rod (oral)

implicated in gingivitis, oral abcesses, and infections of warm moist areas

Question 28

Fusobacterium organism and location

Answer 28

gram neg fusiform

**oral **and **colonic **

Question 29

Peptostreptococcus organism and location

Answer 29

Gram positive coccus

Colonic

Question 30

Propionibacterium acnes organism and location

Answer 30

Gram positive pleomorphic

Epidermal (acne, possibly brain abcesses)

Question 31

What antibiotic is particularly good at treating anaerobes?

Answer 31

Metronidazole

Question 32

What causes the abcesses in anaerobe infections?

Answer 32

production of tissue-destroying enzymes

Question 33

General control of anaerobes

Answer 33

Drainage (also allows O2)

PenG (NOT for bacteroides or prevotella… use Metronidazole and clindamycin)

**Ceph³ **for brain abcess

2nd line drugs = Ceph², Ceph³, and carbapenems