Where does legionella typically come from? Describe it's bacteriological features.
It lives in water, and iron rich soil. It is a gram negative rod.
What makes legionella so environmentally hardy?
- 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
legionella - common symptoms?
Nasea, vomiting, GI symptoms, which is weird. If you see this with someone who has PNA, start thinking about legionella
legionella - risk factors for infection?
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
what type of pathogen is legionella?
it is a facultative intracellular pathogen that survives in macrophages
what is the best way to identify legionella?
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
what strain of legionella most commonly affects humans?
what other illness presents similarly to legionella that you should consider ruling out?
Pontiac Fever - Influenza like. Fever, chills, myalgia, headache (HA), no evidence of PNA, self limiting
Most strains make B-lactamase, so DON'T USE penicillin. Macrolides - Erythromycin and Azithromycin. Fluoroquinilones - Ciprofloxacin, Levofloxacin.
Describe the bacteriological features of Psudomonas Aeruginosa
it is a Gram negative rod, flagellated. It is a strict aerobe that uses oxidative metabolism, meaning that it is a nonfermenter
Where is Psudomonas Aeruginosa commonly found?
Abundant on fruits, vegetables, whirlpools, respiratory therapy equipment. It is especially prevalent in hospital setting due to patient susceptibility and antibiotic resistance
What are the two most important virulence factors of Psudomonas Aeruginosa?
- LPS. - Alginate capsule (resists clearance by the host and promotes surface adhesion)
in normally HEALTHY individuals, name TWO conditions that P. aeruginosa can cause
- Foliculitis - Swimmer’s ear - outer ear infection
in COMPROMISED patients, name FIVE conditions that P. aeruginosa can cause
- 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
how do you identify P aeruginosa in the lab?
use MacConkey agar (Lac-) to see if it grows
is P aeruginosa oxidase (+) or (-)?
when P aeruginosa grows on pyocyanin, what color will result? Why is this? How can you tell it's P aeruginosa?
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
Automatic 5/5 - flip to see the lab algorithm for identifying gram negative orgaisms (pink = need to know)