Streptomyces, Corynebacteria Flashcards
are Streptomyces high or low GC?
high (actinobacteria)
where are Streptomyces found?
ub in SOIL
describe Streptomyces
- mycelial (grow as a network of filaments)
- prod spores at end of terminal hyphae
- strict anaerobes
- nutrtionally versatile
describe Corynebacteria
what are they pathogens of?
- G+ve
- aerobic
- non-motile
- club shaped rods
- pathogens of animals, plants and saprophytes
what key disease does Corynebacterium cause?
Diphtheria
what area does Diphtheria affect?
upper resp tract
also WOUND inf (less common)
what does Diphtheria cause (symptoms)?
- sore throat
- low grade fever
how is Diphtheria transmitted?
contact or droplets
what does the toxin produced in Diphtheria cause?
- causes destruction of epithelium
- causes local inflammation
- necrotic epithelium becomes embedded in exuded FIBRIN & immune cells forming PSEUDOMEMBRANE
describe the pathology of Diphtheria?
- severe symptoms caused by TOXIN –> travels to all parts of body via blood
- LESIONS in heart, kidney, NS—> acute nephritis and heart weakness
- 5-10% mortality even w/ treatment
describe the Diphtheria toxin
what is it encoded by
what is the structure
-encoded by LYSOGENIC phage
- two domains:
A (catalytic)
B (receptor binding)
mechanism of Diphtheria toxin
Mechanism: 1) ‘B’ binds to receptor on host cell surface
2) ‘A’ domain cleaved off, enters cell
3) ‘A’ adds ADP RIBOSE onto Elongation Factor EF2 of aa assembly
4) prevents EF2 interacting w/ tRNA
5) no longer brings aa attached to tRNA O toxin INHIBITS PROTEIN SYNTHESIS
what is used in the Diphtheria vaccine?
-inactivated Diphtheria toxin inn DPT vaccine
what is used for Diphtheria treatment?
antitoxin
how is Diphtheria diagnosed?
DEFINITIVE test= ELEK test for toxigenicity
- antitoxin soaked filter paper placed on media growing streaks
- look for IMMUNOPRECIPITATION (opaque streaks)
OTHER TESTS: - G stain
- methylene blue—>shows beaded bugs from swab
