Coynebacterium!! MICROM 442 Deck 12 Flashcards
kornyne = club, shape?
pleomorphic rods with clubbed ends
GM?
+
non-motile and non?
sporulating
only resevoir
human
spread by>
- spread by respiratory droplets, cutaneous lesions
and fomites; - pharyngeal/nasal carriage in some convalescent
cases
Principal virulence factor is diphtheria toxin [DT]
- classic A-B subunit toxin: B unit accomplishes cell
binding [R] and translocation [T]; A subunit is catalytic [C]
toxin taken up by?
- toxin uptake by endocytosis; acidification of endosome
releases active A into cytosol
ADP-ribosylation of elongation factor 2 irreversibly
halts protein synthesis; cell dies
DT encoded on lysogenic
bacteriophage
DtxR [chromosomal gene, not phage encoded]
- represses expression in high-iron conditions
- host iron mostly heme-bound and intracellular
- DT co-regulated with:
- endogenous genes encoding
bacterial iron transport system - hmuO [heme oxygenase] for utilizing heme and
hemoglobin as an iron source
local toxin effects
- pharyngitis; epithelial cell necrosis & inflammation
- debris, fibrin, formation of pseudomembrane
- gray/yellow/white membrane with surrounding
inflammation - mechanical obstruction of airway
this organism causes a psuedo what to form?
psuedo membrane
systemic toxin effects
- myocarditis; significant cardiomyopathy [~25% cases]:
enlargement, arrhythmia, pump dysfunction,
shortness of breath - paralysis of soft palate and select muscle groups,
most seriously the diaphragm
Superficial skin infections, tropical, hot, and arid
regions; usually without systemic complications
Sx’s contrasted with systemic illnesses as a result of
differential toxin distribution and action
Dx: isolate from lesions by culture on selective media
[Tinsdale agar] for 48hrs containing
- potassium tellurite: [inhibits Gram negative bacteria
and oropharyngeal microbiota] - dark brown/black colony; H2S production from L-
cystine produces dark brown halo
Prevented, and disease almost completely eliminated,
by vaccination [DTaP]
- toxoid for vaccination: formalin treated DT
- functionally inactivates B
- maintains A structure/antigenicity
- Ab blocks toxin activity/uptake
- Ab does not eliminate infection
- mild disease boosts immunity
Corynebacterium jeikeium; skin microbiota
- bacteremia, endocarditis, pneumonia, osteomyelitis,
meningitis; - immunocompromised patients or those with indwelling
devices, e.g., catheters, are particularly susceptible; - nosocomial infections;
- multi-drug resistant
