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Genus: Corynebacterium

Species: C.diphtheriae

Gram positive rod

clubbing at both ends

metachromatic granules or volutin are composed ofpolyphosphates and act as energy storage sites

nonsporting, noncapsulated and nonmotile

appear in pairs, palisades, or small group (Chinese letters).12/13/15Dr Ellabib MS1

Non spore forming gram positivebacilli

D i p h t h e r i a

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General characteristics

Found as free-living saprophytes

embers of the usual flora of humans and animals

Corynebacterium diphtheriae is the most significant pathogen

Biotypes Varities

based on colony shape, biochemical propertiesand virlence

!ravis, Mitis, "ntermedis and #lfanti !ther species may cause infections in the immunocompromised hosts

12/13/15Dr EllabibMS

2

Corynebacterium Species

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C. pseudotuberculosis

C. jekeium

C. ulcerans

12/13/15Dr Ellabib MS3

$ther Corynebacteria

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"o#igenic Corynebacterium diphtheriae

$orld%ide distribution

rare in places %here vaccination programs e#ist

&#oto#in as the virulence factor 

'iphtheria to#in% "o#in is produced by certain strains

% ysogenied by bacteriophage %ith to#in gene (to#*)

% "o#in is antigenic12/13/15Dr Ellabib MS&

C. diphtheriae: Agent of Diphtheria 

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"o#in consists of t%o fragments  +: +ctive fragment

nhibits protein synthesis

Catalyes transfer of +' to lin/ %ith &F0 +'.&F 

(inactive)

eads to cell1tissue death

2 fragment

2inds to specific cell membrane receptors

ediates entry of fragment + 

12/13/15Dr Ellabib MS5

 'o(igenic Corynebacteriumdiphtheriae

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12/13/15Dr Ellabib MS)

heparin*binding epidermal gro+th

factor speci-c membranereceptor.

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espiratory +c3uired by droplet spray

4nimmunied individuals are susceptible

5onrespiratory Systemic

S/in and cutaneous forms

12/13/15Dr Ellabib MS

Clinical Forms of Diphtheria 

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ncubation period60 to 7 days

Symptoms: sore throat, fever, malaise

"o#in is produced locally, usually in the pharyn# or tonsils

"o#in causes tissue necrosis

Forms a tough grey to %hite pseudomembrane

12/13/15Dr Ellabib MS0

espiratory diseasediphtheria

#lls nec4

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Systemic infections "o#in is absorbed in the blood stream and carried systemically

 +ffects the /idneys, heart, and nervous system

'eath occurs due to cardiac failure

Cutaneous formore prevalent in the tropics

nfections occur at the site of minor abrasions

aybe superinfected %ith Streptococcus pyogenes and1or Streptococcus aureus12/13/15Dr EllabibMS

Clinical Infections:

Non-Respiratory Disease

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Clinical observation

solation of the organism

"ested for virulence

 +nimals or immunological precipitin reaction (&&8 "est)

2lood agar and "ellurite agar (blac/ colonies)

12/13/15Dr Ellabib MS16

Diagnosis

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1. Clinical

2. Laboratory Diagnosis 

a. Cltral Characteristics.  oeffler9s slant or ai9s slant4sed to demonstrate pleomorphism and

metachromatic granules; <2abes= &rnst bodies

. Serum "ellurite or modified "insdale- bro%n or grayish to blac/ halos

around the colonies

12/13/15Dr Ellabib MS11

Diagnosis

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. In vivo toxin test using guinea pigs

. Subcutaneous

. Intracutaneous

. In vitro tests

. Elek’s gel precipitation test 

. Tissue culture test  12/13/15Dr EllabibMS

12

DETECTION OF TOXIGENICITY 

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Life-threatening infection

Prompt neutralization of toxin

Eradication of the organism

A single dose of horse antiserum Inactivates any circulating toxinDoes not affect toxin already bound to a cell-surface receptor

Penicillin or erythromycin

12/13/15Dr Ellabib MS13

"reatment

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Immunization with toxoid

sually administered in the D!P triple vaccine together with

tetanus toxoid and pertussis antigens

"hould be started in infancy #ooster dose at $% years interval

12/13/15Dr Ellabib MS1&

7revention

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Corynebacterium species 8ommon 9ora of the nose, throat, nasopharyn(,

s4in, rinary tract and con:nctiva

 'hey do not prodce e(oto(in 8ommon blood cltre commensal May case infective endocarditis of prosthetic

valves, lng abscess, rinary tract infection;

12/13/15Dr Ellabib MS15

D"7<'<E$"DS

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12/13/15Dr Ellabib MS1)