Corynebacterium Corynebacterium diphtheriaediphtheriae

General CharacteristicsGeneral Characteristics

Gram PositiveGram Positive Club shaped rodClub shaped rod Forms clusters of “Chinese-Forms clusters of “Chinese-

characters”characters” Aerobic Aerobic Non-spore formingNon-spore forming Exterior fimbriae Exterior fimbriae Contains no plasmids Contains no plasmids Toxigenic and Non-toxigenic formsToxigenic and Non-toxigenic forms

Compound Light Compound Light MicroscopeMicroscope

The club or bar appearance of the cells is The club or bar appearance of the cells is due to pockets of inorganic phosphate due to pockets of inorganic phosphate which form metachromatic granules when which form metachromatic granules when stained stained

Electron MicroscopeElectron Microscope

ReservoirReservoir

Human BodyHuman Body Normal flora of skin and Normal flora of skin and

nasopharynx nasopharynx Enters upper respiratory tract and Enters upper respiratory tract and

cutaneouscutaneous

TransmissionTransmission

Spread by inhalation of airborne Spread by inhalation of airborne bacteria bacteria

Direct contacted with an infected Direct contacted with an infected person person

Open woundsOpen wounds

Virulence FactorsVirulence Factors Diphtheria toxin Diphtheria toxin

Diphtheria toxin gene is encoded by a Diphtheria toxin gene is encoded by a bacteriophagebacteriophage

Phage Beta Phage Beta DT inhibits of protein synthesis (elongation DT inhibits of protein synthesis (elongation

factor 2)factor 2) C. Diphtheria without this gene is not as C. Diphtheria without this gene is not as

harmfulharmful Repressor (DtxR) gene, is activated by iron Repressor (DtxR) gene, is activated by iron

and prevents transcription of the tox geneand prevents transcription of the tox gene High iron levels = no toxin releaseHigh iron levels = no toxin release Low iron levels = toxins releasedLow iron levels = toxins released

Clinical DiseasesClinical Diseases

Respiratory diphtheria is caused by Respiratory diphtheria is caused by C. C. diphtheriaediphtheriae bacteria adhering to and bacteria adhering to and colonizing the tonsils, nasal cavity, and colonizing the tonsils, nasal cavity, and throat throat

Cutaneous diphtheria can be caused by Cutaneous diphtheria can be caused by both the toxigenic and the nontoxigenic both the toxigenic and the nontoxigenic strains of strains of C. diphtheriaeC. diphtheriae Creates deep, erosive ulcers Creates deep, erosive ulcers

If left untreated could damage the heart If left untreated could damage the heart and nerves and eventually lead to death.and nerves and eventually lead to death.

Identification/DiagnosisIdentification/Diagnosis

Upper-respiratory tract illness characterized Upper-respiratory tract illness characterized by sore throat, low-grade fever, and an by sore throat, low-grade fever, and an adherent membrane of the tonsils, pharynx, adherent membrane of the tonsils, pharynx, and/or nose and/or nose Creates a pseudomembrane, a greenish-gray film that hardens Creates a pseudomembrane, a greenish-gray film that hardens

in the pharynx from inflammation and can cause asphyxiation. in the pharynx from inflammation and can cause asphyxiation.

Sample of the bacteria is isolated from the Sample of the bacteria is isolated from the patient’s throat/mouth and cultured patient’s throat/mouth and cultured

““Bull Neck” appearanceBull Neck” appearance To test for toxigenicity, the Elek test is To test for toxigenicity, the Elek test is

performed performed

SymptomsSymptoms

Cystine-Tellurite blood agar, Cystine-Tellurite blood agar, incubated at 35 degrees C in A incubated at 35 degrees C in A CO(2)-enriched atmosphere. CO(2)-enriched atmosphere. Colonies of Colonies of Corynebacterium Corynebacterium diphtheriaediphtheriae on tellurite containing on tellurite containing agar are gray-black, while most of agar are gray-black, while most of the usual oral flora are inhibited.the usual oral flora are inhibited.

TreatmentTreatment

Diphtheria infection is treated with Diphtheria infection is treated with diphtheria antitoxindiphtheria antitoxin

Formalin eliminated the toxicity of Formalin eliminated the toxicity of DT without destroying its DT without destroying its immunogenicity. Formalin-treated immunogenicity. Formalin-treated DT, now called diphtheria toxoid DT, now called diphtheria toxoid

14-day course of antibiotics, 14-day course of antibiotics, preferably Erythromycin or preferably Erythromycin or Penicillin Penicillin

PreventionPrevention Tdap (Adults) or DTaP (Under 7 yrs old) Tdap (Adults) or DTaP (Under 7 yrs old)

VaccinesVaccines combined vaccine against diphtheria, tetanus combined vaccine against diphtheria, tetanus

(Lockjaw), and pertussis (whooping cough) (Lockjaw), and pertussis (whooping cough)

Children should get 5 doses of DTaP vaccine, one dose at each of the following ages: 2 months 4 months 6 months 15-18 months 4-6 years

Prevention (cont.)Prevention (cont.)

Tdap A single dose of Tdap is recommended

for people 11 through 64 years of age. TdTd

Td, protects only against tetanus and diphtheria

recommended every 10 years.

QuestionsQuestions What is a common symptom of a toxigenic C. diphtheriae What is a common symptom of a toxigenic C. diphtheriae

infection?infection? a) Chickens Necka) Chickens Neck b) Bulls Neckb) Bulls Neck c) Giraffe’s neckc) Giraffe’s neck d) None of the Aboved) None of the Above

C. diphtheriae infection is treated with:C. diphtheriae infection is treated with: a) antibioticsa) antibiotics b) antitoxinsb) antitoxins c) no treatment except replenish waterc) no treatment except replenish water d) both a and bd) both a and b

ReferencesReferences Mandlik, A., Swierczynski, A., Das, A. and Ton-That, H. (2007), Mandlik, A., Swierczynski, A., Das, A. and Ton-That, H. (2007),

Corynebacterium diphtheriaeCorynebacterium diphtheriae employs specific minor pilins to employs specific minor pilins to target human pharyngeal epithelial cells. Molecular target human pharyngeal epithelial cells. Molecular Microbiology, 64: 111–124. doi: 10.1111/j.1365-Microbiology, 64: 111–124. doi: 10.1111/j.1365-2958.2007.05630.x 2958.2007.05630.x

Holmes, R.K. (2000) Biology and molecular epidemiology of Holmes, R.K. (2000) Biology and molecular epidemiology of diphtheria toxin and the tox gene. J Infect Dis 181 (Suppl. 1): diphtheria toxin and the tox gene. J Infect Dis 181 (Suppl. 1): S156–S167.S156–S167.

Coordinating Center for Infections Diseases/Division of Bacterial and Coordinating Center for Infections Diseases/Division of Bacterial and Mycotic Diseases "Diphtheria" 6 October 2005Mycotic Diseases "Diphtheria" 6 October 2005

Todar, Kenneth, University of Wisconsin-Madison Department of Todar, Kenneth, University of Wisconsin-Madison Department of Bacteriology, "Diphtheria" 2002Bacteriology, "Diphtheria" 2002

National Center for Immunization and Respiratory Diseases: Division of Bacterial National Center for Immunization and Respiratory Diseases: Division of Bacterial

Diseases, “Diphtheria”Diseases, “Diphtheria” February 7, February 7, 2011 2011 http://www.cdc.gov/ncidod/dbmd/diseaseinfo/diptheria_t.htmhttp://www.cdc.gov/ncidod/dbmd/diseaseinfo/diptheria_t.htm