Transcript Corynebacterium diphtheriae file

Introduction
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Klebs--1883 discovered
Loefflers--1884 cultured
Also known as KLB
Emil von Behring- 1890
produced antitoxin
• Awarded nobel prize
Emil Von Behring
Morphology
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Gram positive bacilli. 3-6 μ x 0.5-0.8 μ.
v or k or L shape.
Chinese letter pattern, angular arrangement
Metachromatic granules. volutin granules,
polymetaphosphate energy storage depots
• Alberts stain – green and bluish black
• Nonmotile noncapsulated, nonsporing
• pleomorphic
Cultivation
• Loefflers serum slope– creamy white
colonies in 6-8 hrs
• Potassium tellurite medium—black
colonies
• Blood agar
Biochemical reactions
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Hiss serum
Ferments glucose ,maltose with acid only
Lactose, sucrose, mannitol not fermented
Urease negative
Starch –only gravis type, not intermedius
or mitis
Pathogenicity
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Produces exotoxin
Lysogenic conversion with beta phage
Toxin – heat labile protein
A and B fraction
Toxicity- disease
Antigenicity- immunity
Toxoid – toxin without toxicity
Toxin
Mechanism of action
-B subunit binds to receptor
-toxin molecule cleaved at protease sensitive site
between
A-B portion (remain bonded by disulfide link)
-receptor-toxin complex englufed into vesicle of
host cell
-reduction of disulfide bond, A subunit released
into cytoplasm
-Necrosis/neuotoxic effects on organism by
exotoxin
Biotypes
1)gravis(13 types)-most serious disease
Colonies: large, irregular, gray
2)mitis(40 types)-mild illness
colonies: small, round, convex, black
3)intermedius(4 types)-intermediate
severity
Colonies: small, flat and gray
Diphtheria
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Children, fatal if not treated in time
Exclusively human disease
Droplet infection- fomites
Fever, cervical lymphadenopathy,
pseudomembrane
• Myocarditis arrhythmia fatal
• Polyneuropathy, paltine paralysis
• Rare in adults.
Pseudomembrane formation
Thick membrane lining throat
that interferes with eating,
drinking and breathing
Contents: WBC, RBC,
bacteria, disintegrating
epithelial cells
Cause: fibrinous exudate
from local necrosis by
exotoxin (removal of PF may
cause bleeding)
Localization: faucial,
laryngeal, nasal, otitic,
conjunctival, genital,
cutaneous
Faucial:
Signs: sore throat, fever
complications: prostration, dyspnea, asphyxia, arhythmia,
difficulties of speech, vision, swallowing, movement
Septic:
Ulceretic:
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
Complications
1)Asphyxia-obstruction of resp tract
2)Acute circulatory failure
3)kidney failure
4)paralysis-soft palate, eye muscles,
extremities (3rd-4th week)
5)septic sequelae-pnemonia, otitis media
Laboratory diagnosis
• Sample collection: Throat swab or swab
from membrane
• Microscopy: Gram stain and Alberts stain
• Culture: Loefflers and PT
• Biochemicals
• Virulence test in vivo and in vitro
Virulence test contd
In vivo
Guinea pig– subcutaneous
intradermal
Test and control animals to be used
In vitro
Eleks gel precipitation test
Toxigenicity test (virulence test)
i) Animal inocculation
-bacteria culture emulsified in water and 0.8 ml injected into 2 guinea pigs
GP A-has dipht antitoxin (injected 2 hours before)
GP B-Doesn't have antitoxin
Result: Guinea pig B dies.
ii) Elek's gel precipitation test
-filter paper saturated with antitoxin is placed on agar plate with 20% horse
serum
-bacterial culture streaked at right angles to filter paper
iii) tissue culture test
-incorporation of bacteria into agar overlay of eukaryotic cell culture
monolayers.
Result: toxin diffuses into cells and kills them
iv) PCR assays
-test presence of specific bacteriophate gene (tox)
Elek's gel precipitation test
EPIDEMIOLOGY
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Formally important pediatric disease
Developed countries - Eradicated
Developing countries serious problem
Rare in 1st year – maternal antibodies
Peak 1-5 years, 5-10 years- decreases there after
Immunity – sub clinical infections
Carriers outnumber cases – throat & nasal
Rarely spread through milk
Prevention
• Active immunity- DPT dosage
– Antitoxin level – 0.01/ ml protective
• Passive immunity- ADS
– When susceptibles are exposed
– 500 – 1000 units sc of Anti Diphtheritic Serum ( ADS)
• Combined immunisation
– First dose of adsorbed toxoid on one arm
– ADS on another arm
– To be continued with full course of active
immunization
Prevention
a) DTP (DPT)• Formal toxoid - Incubation of Toxin at pH 7.4 -7.6 for 3 –
4 weeks at 37 °C
• Adsorbed toxoid – purified toxoid adsorbed on to
aluminum phosphate or hydroxide
• triple vaccine given to children.
trivalent preparation
• Diphtheria toxoid, Tetanus toxoid and Pertussis vaccine
Td- contains absorbed tetanus and ten-fold smaller dose of
diphtheria toxoid.
b) Schedule
i) primary immunization –
- infants and children
- 3 doses, 4-6 weeks
- 4th 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)
Treatment
• Antitoxin – 20,000 to 1 lakh units
• Antibiotic therapy – Penicillin
• Carriers - Erythromycin
Patch in the throat
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Diphtheria
Streptococcal tonsillitis
Oral thrush– Candida albicans
Spirochete- Borrelia vincenti
Other Corynebacteria
1. C. ulcerans:
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Diphtheria like lesions
Spread thru milk
Antitoxin protective, erythromycin
2. C.minutissimum–
Erythrasma
3. C. tenuis:
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Trichomycosis axillaris
4. C.pseudotuberculosis:
– Veterinary importance
5. C.parvum:
– Immunomodulator
6. A. haemolyticum:
– pharyngitis, skin ulcers
7. C.jakieum:
– Skin inf/ BSI in IC. Rx- Vancomycin.
Diphtheroids
• Morphologically resembling diphtheria but
do not cause any disease.
• Present as commensals in throat, skin
• Do not contain metachromatic granules.
• Do not produce any toxin ie virulence test
is negative.
• C.hofmani, C.xerosis, C.pseudodiphtheriticum