3.6.4. Legionelle and Pseudomonas

Question 1

Where does legionella typically come from? Describe it’s bacteriological features.

Answer 1

It lives in water, and iron rich soil. It is a gram negative rod.

Question 2

What makes legionella so environmentally hardy?

Answer 2

• Can endure extreme temperatures up to 65C - Resists chlorination - Can survive in amebas which is cool because it can use the ameba as protective measure

Question 3

legionella - common symptoms?

Answer 3

Nasea, vomiting, GI symptoms, which is weird. If you see this with someone who has PNA, start thinking about legionella

Question 4

legionella - risk factors for infection?

Answer 4

1- Hematologic malignancies, lung cancer, AIDS, Renal Failure 2- Immune suppression, cigarette smoking, 50+ y.o. 3- Alcohol possible factor 4- Males more affected than females 5- You need cell mediated immunity to fight this, so if you don’t, trouble

Question 5

what type of pathogen is legionella?

Answer 5

it is a facultative intracellular pathogen that survives in macrophages

Question 6

what is the best way to identify legionella?

Answer 6

To get the bacteria out of the macrophages, you need to do a Bronchoalveolar Lavage to recover them from patients. The bacteria also requires a special medium (amino acids and iron) and made a buffered charcoal yeast extract agar. In 4 days to a week, there was growth. BUT, this is painful for the patient and takes a long time. UA is also acceptable to detect the LPS antigen via ELISA

Question 7

what strain of legionella most commonly affects humans?

Answer 7

L. pneumophila

Question 8

what other illness presents similarly to legionella that you should consider ruling out?

Answer 8

Pontiac Fever - Influenza like. Fever, chills, myalgia, headache (HA), no evidence of PNA, self limiting

Question 9

legionella treatment?

Answer 9

Most strains make B-lactamase, so DON’T USE penicillin. Macrolides - Erythromycin and Azithromycin. Fluoroquinilones - Ciprofloxacin, Levofloxacin.

Question 10

Describe the bacteriological features of Psudomonas Aeruginosa

Answer 10

it is a Gram negative rod, flagellated. It is a strict aerobe that uses oxidative metabolism, meaning that it is a nonfermenter

Question 11

Where is Psudomonas Aeruginosa commonly found?

Answer 11

Abundant on fruits, vegetables, whirlpools, respiratory therapy equipment. It is especially prevalent in hospital setting due to patient susceptibility and antibiotic resistance

Question 12

What are the two most important virulence factors of Psudomonas Aeruginosa?

Answer 12

• LPS. - Alginate capsule (resists clearance by the host and promotes surface adhesion)

Question 13

in normally HEALTHY individuals, name TWO conditions that P. aeruginosa can cause

Answer 13

• Foliculitis - Swimmer’s ear - outer ear infection

Question 14

in COMPROMISED patients, name FIVE conditions that P. aeruginosa can cause

Answer 14

• PNA in cystic fibrosis patients - Burn infections - Hospital acquired infections - Cellulitis - Like when someone wears wet saturated boots - UTI - especially with catheters in the hospital

Question 15

how do you identify P aeruginosa in the lab?

Answer 15

use MacConkey agar (Lac-) to see if it grows

Question 16

is P aeruginosa oxidase (+) or (-)?

Answer 16

oxidase (+)

Question 17

when P aeruginosa grows on pyocyanin, what color will result? Why is this? How can you tell it’s P aeruginosa?

Answer 17

it will grow GREEN. this is because it can only metabolize glucose and leaves the other CHOs behind. If you waft the plate, you’ll smell an artificial grape-like odor

Question 18

Automatic 5/5 - flip to see the lab algorithm for identifying gram negative orgaisms (pink = need to know)

Answer 18