1. Lecture # 8 Basmah Almaarik
Corynebacterium
Lecture # 8
Basmah Almaarik

2. Gram positive non spore forming earobic bacilli
Catalase +ve
Catalase -ve
Motile
(at room temp.)
Non Motile
Sugar fermentor
Non sugar fermentor
Listeria
Coryebacterium
Lactobacilli
Erysipleothrix

4. Eryspleothrix Gram stain: -G+ve fine bacilli Culture:
-Grow on Blood Agar
-Non motile
Biochemical reaction:
-Catalase –ve
-Produce H2S from triple sugar iron (TSI)- Blackening of the media

5. Genus: Corynebacterium
Mostly normal flora skin & mucous membranes.
Considered contaminants, largely ignored and called “Diphtheroids”
Major pathogen is:
C.diphteria  cause diphteria
Most common skin contaminant seen in labs.

6. Gram Stain: Gram positive Non motile Pleomorphic rods arranged in:
Palisades
Chinese letter formation
Easley decolorized
Use decolorizer fast

7. Special Stains
are used to demonstrate Volutin granules which are intracytoplasmic storage form of complexe inorganic polyphosphate. They are called metachromatic granules due to their displaying the metachromatic effect; they appear red when stained with methylene blue.
Neisser’s technique
Albert stain

8. Convex, white to gray tiny colonies
Culture:
Aerobic or facultatively anaerobic:
can grow with or without O2
Slow grower ( 48 hours ).
Need nutritionally rich media
such as blood media (non hemolytic colonies).
Catalase positive.
Convex, white to gray tiny colonies

9. Media
Tinsdale ( or Tellurite-cystine blood agar ) (selective and diffrential)
Blood tellurite Agar (selective)
Loeffeler’s medium. (non selective)

10. Tinsdale Media (differential and selective)
Serum (or blood)  enrichment.
Tellurite, sodium thiosulfate: inhibit other normal flora.
Cystine: interact with tellurite to produce hydrogen sulphide witch gives the brown halo.
C.diphtheriae  black colonies, surrounded by a dark brown halo

11. Tinsdale Media (differential and selective)
the differentiation is due to the brown hallow that is formed around the colonies in the pathogenic strains only.
C.diphtheriae

12. Organisms other than corynebacteria sp. are generally inhibited
Blood Tellurite Agar
Potassium tellurite  selective
Organisms other than corynebacteria sp. are generally inhibited
Corynebacteria diphtheriae reduces tellurite and produces grey or grey-black colonies, can be hemolytic or non-hemolytic.
Commensal diphtheroid colonies are grey and non-hemolytic.

13. Loeffler’s Media
Used mainly for the induction of granules produced by C.diphteria.
It is not used as primary isolating media because commensal diphtheroids may overgrow the diphtheria.
C.diphteriae :
appear as yellowish growth on slant.
It grows rapidly on this media producing significant growth in 4-6 hours.

14. It is buried just beneath the surface of the agar plate before
Elek Test
used to determine whether the organism is able to produce the diphtheria toxin or not
Filter paper strip impregnated with diphteria antitoxin
It is buried just beneath the surface of the agar plate before
The agar hardens.
Enriched media with serum
Streak bacteria at right angle to antitoxin strip
Presence of precipitation lines indicates toxin production

15. Always do +ve & -ve controls
(known nontoxigenic strain)
Test strain
+ve control
(toxigenic strain)

16. YOUR WORK FOR TODAY  You have 2 organisms C. diphtheriae Diphthoroids
Sub to tinsdale
See the black colonies in 24 hours
Do gram stain
See demonstration plates

17. Corynebacterium jeikeium (JK group)
Opportunistic, immuno-compromised
Resistant to many antibiotics
Sensitive to vancomycin

18. Corynebacterium urealyticum:
Rare cause of UTI

19. Diphtheriae  very rare because of vaccination
DPT
D = Diphtheria
P = Pertussis
T = Tetanus

20. THANK YOU