Lecture # 8 Basmah Almaarik Corynebacterium Lecture # 8 Basmah Almaarik

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

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

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.

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

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

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

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

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

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

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.

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.

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

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

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

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

Corynebacterium urealyticum: Rare cause of UTI

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

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