1. Corynaebacterium Diphtheriae
Dr. Qurat-Ul-Ain Senior Demonstrator Microbiology, KEMU, Lahore

2. Corynebacterium diphtheriae

4. Introduction Klebs--1883 discovered Loefflers--1884 cultured
Also known as KLB
Emil von Behring- 1890
produced antitoxin
Awarded nobel prize
Emil Von Behring

6. Morphology Gram positive bacilli. 3-6 μ x 0.5-0.8 μ.
v or k or L shape.
Chinese letter pattern, angular arrangement, palisade arrangement
Metachromatic granules. volutin granules, polymetaphosphate energy storage depots
Alberts stain – green and bluish black
Nonmotile noncapsulated, nonsporing
pleomorphic

8. Corynebacterium Biotypes
C diphtheriae gravis
C diphtheriae intermedius
C diphtheriae mitis
Helpful for epidemiological tracing
Culture identified by biochemical tests.

9. Transmission and Risk factors
solely among humans
spread by droplets
secretions
direct contact
Poor nutrition
Crowded or unsanitary living conditions
Low vaccine coverage among infants and children
Immunity gaps in adults

10. Virulence Factors 1. Diphtheria toxin !!! 2. Dermonecrotic toxin
blocks protein synthesis
2. Dermonecrotic toxin
sphingomyelinase
increases vascular permeability
3. Hemolysin
4. Cord factor -Toxic trehalose
corynemycolic acid, corynemyolenic acid

11. Pathogenesis Part A Part B Bound receptor internalized Endosome
Active site
N terminal
Enzyme
Part B
Binding site
Binds to membrane receptor
Bound receptor internalized
Endosome
Hydrolysed by protease
Disulfide broken
Part A released

13. Clinical Features/ Types of Diphtheria
Incubation period 2-5 days (range, 1-10 days)
May involve any mucous membrane
Classified based on site of infection

14. Pharyngeal and Tonsillar Diphtheria
Insidious onset
Exudate spreads within 2-3 days and may form adherent membrane
Membrane may cause respiratory obstruction
Pseudomembrane: fibrin, bacteria, and inflammatory cells, no lipid
Fever usually not high but patient appears toxic

17. Clinical classification
i) Malignant (hypertoxic) diphtheria Signs: severe toxemia and adenitis, lymph glands swelling in the neck Complications: death-circulatory failure, paralytic sequelae ii) Septic diphtheria: Signs: ulceration with pseudomembrane formation and cellulites (gangrene around pm) iii) Hemorrhagic diphtheria Signs: local and general bleeding from edge of psudomembrane, conjunctival, epistaxis and purpura

18. Pseudomembrane COVERS CONTAINS tonsils, bacteria uvula, lymphocytes
palate
nasopharynx
larynx.
CONTAINS
bacteria
lymphocytes
plasma cells
fibrin
dead cells

19. Cutaneous Diphtheria

20. Systemic complications
Nerves
toxic peripheral neuropathy
paralysis of short nerves
mouth, eye, facial extremities
Cardiac
Congestive heart failure
high amount of toxin hours
Low amount of toxin 2-6 weeks

22. Diphtheria Antitoxin Produced in horses First used in the U.S. in 1891
Used only for treatment of diphtheria
Neutralizes only unbound toxin
Lifetime of Ab: 15 days – 3 weeks, wait 3-4 weeks before giving toxoid. Only given once.

23. Diphtheria Toxoid Formalin-inactivated diphtheria toxin
Schedule Three or four doses + booster Booster every 10 years
Efficacy Approximately 95%
Duration Approximately 10 years
Should be administered with tetanus toxoid as DTaP, DT, Td, or Tdap

24. i) primary immunization –
Schedule
i) primary immunization –
- infants and children doses, 4-6 weeks th dose after a year booster at school entry
ii) Booster immunization
- adults Td toxoids used (traveling adults may need more)
Shick test-to test sensitivity (allergic reaction)

25. Diphtheria and Tetanus Toxoids Adverse Reactions
Local reactions (erythema, induration)
Exaggerated local reactions (Arthus-type)
Fever and systemic symptoms not common
Severe systemic reactions rare

26. Schick test Be used to ascertain population risk
This test involves the injection of a minute amount of the
diphtheria toxin under the skin. The absence of a reaction
indicates immunity.

27. Control Immunization diphtheria toxoid Schick test Passive immunity
check for antibodies
Passive immunity
Antibodies
Antibiotics
Penicillin & erythromcyin

28. DIAGNOSIS
Clinical: Muscle weakness, edema and a pseudomembranous material in the upper respiratory tract characterizes diphtheria.
Laboratory: Tellurite media is the agar of choice for isolation of Corynebacteria, which produce jet black colonies

29. Diphtheria Laboratory diagnosis
Rapid diagnosis required
Differentiate from commensals
“diphteroids”
nose & throat
Throat swabs (confirmatory)
Blood Tellurite

30. Specialized media
Loeffler serum: best colonial morphology Dextrose horse serum (1887) now Dextrose beef serum
Tellurite: black colonies Not diagnosticallly significant .tellurite inhibits many organisms but not C. diphtheriae

31. Blood tellurite Selective & differential medium
Corynebacteria are resistant to tellurite
Reduced to tellurium
Forms deposit in colonies
Colonies appear dark