Corynebacterium and Other Gram Positive Rods Flashcards
Genus Corynebacteria characteristics
- found in nature (soil, water plants) and mucosa and skin flora of humans and animals
- catalase positive
- pleomorphism results in palisades, picket fences, or Chinese letters
- non acid fast
- non branching gram positive rods
- non spore forming
Cornyeform (diphtheroids) bacteria
An opportunistic pathogen that affects immunocompromised patients (Rhodoccus equi)
Metachromatic granules (characteristic of Corynebacterium)
Contain polymerized inorganic phosphate, an energy rich compound that acts as a reserve store of energy and phosphate
MALDI-TOF MS
Reliably identifies toxigenic strains of Cornyebacterium. But it is still limited right now
Media for Corynebacterium Diphtheria
Cystine tellurite:
- Cystine: selective, enhances growth of fastidious organisms
- potassium tellurite:
-selective:
Inhibits gram positive and gram neg bacteria
- differential:
Reduction of potassium tellurite, colonies are gray-black
-Modified tinsdale agar: organisms are differentiated based on the conversion of the tellurite to tellurium
- results in black colonies
- Loeffler medium: contains serum and egg and stimulates growth of organism and production of metachromatic granules in the cells.
- gray, white translucent colonies
-Pai agar
4 diphtheriae bio types differentiated by colony morphology
- Intermedius
- Mitis
- Gravis
- Belfanti
Vaccines for Diptheriae
Dtap and Tdap are the vaccines
ID of Diptheria toxin
Elek test: immunodiffusion test, definitive ID by detection of diptheriae toxin
Corynebacterium diptheriae significance
-releases an exotoxin that causes damage to heart and neural cells and can be lethal
- causes respiratory and cutaneous diphtheria
- causes pharyngitis and forms a pseudo membrane made up of cellular debris
Toxin production for Diptheriae
Exotoxin released into bloodstream and has 2 subunits
- A subunit: blocks protein synthesis by inactivating elongation factor
- B subunit: binds to heart and neural tissue
This is for Respiratory Diptheriae
Presumptive Diagnosis of Diptheriae
- Determined by cystine-tellurite blood agar and modified tinsdale agar
- growth on sheep blood agar (observation of hemolytic reactions)
- loeffler and pai media: serum and egg and stimulate production of monochromatic granules
- Loeffler methylene blue stain: detects monochromatic granules
Definitive idenitification for Diptheriae
- Gueinea pig lethality test- lethal effect is neutralized by Diptheria antitoxi
- immunodiffusion test: Elek plate, Diptheria antitoxin filter paper strip
- tissue culture cell test: cytopathic effect is neutralized by Diptheria antitoxin
- EIA
- PCR
Corynebacterium jeikeium (JK)
- opportunistic infections of blood, wounds, dialysis exit site, bone marrow transplant
- causes meningitis, bacteremia, endocarditis, septicemia, pneumonia
- opportunistic pathogen (immunocompromised)
- normal skin flora
- rule out if found in blood culture or in pure culture from normally sterile site
- gram + coccobacilli that resemble strep
- urease -, no nitrate reduction, ferments glucose
- non-hemolytic, enhanced growth on Tween 80
- identified by MALDI Tof
- susceptible to vancomycin
-multi drug resistant
C. Urealyticum
- normal skin flora
- causes UTIs, kidney stones, alkaline encrusted cystitis and pyelitis
C. Ulcerans
-normal skin flora
- causes diphtheria like infections, zoonotic and cutaneous infections