corynebacteria
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Presentation regarding corynebacteriumTRANSCRIPT
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QUIAMBAO, JERIKA C.
MD2
AUGUST 7, 2015
CORYNEBACTERIA
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Describe th morphology of Corynebacterium
Enumerate the important members of the genus CorynebacteriaC. diphtheriaeC. xerosisC. hofmanii
LEARNING OBJECTIVES
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Discuss the characteristics/virulence factors of Corynebacterium diphtheriae by relating it to the following:Diseases producedHost responseLaboratory identificationTreatmentPreventive and controlEpidemiological features
LEARNING OBJECTIVES
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Morphology:From the Greek word karyne which means “club”0.5-1.0 um in diameter and several micrometers longGram-positive pleomorphic rodsPalisade form (“picket fence” appearance)Irregularly distributed within the rods, usually near
the poles that give them “club-shaped” appearanceWith metachromatic granules as storage
granulesOnce stained with methylene blue, staining does not
appear uniformMost metachromatic granules made of phosphates
Beaded appearanceResembles Chinese letters
Corynebacterium
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Other Characteristics:Aerobic or facultativeNon-motile; Non-sporeformingNon-acid fastPositive reaction for catalasePositive reaction for cytochrome oxidase
Widely distibuted in nature, commonly found in soil and water
Reside on the skin and mucous membranes of humans
Corynebacterium
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Corynebacterium diphtheriaeCausative agent of Respiratory or
Cutaneous DiphtheriaIncubation period: 2-4 daysSpread by droplets or contact with a
susceptible carrierGrow on mucous membranes or in skin
abrasionsPrimary target cells are upper
respiratory tracts, heart, and nervesIn vitro production depends on the iron
concentration
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Heat labile polypeptide (MW 62,000)Fragment B- required for:
Binding to the receptor of the toxin (receptor domain)
Transfer of A into the cell (translocation domain)
Fragment A – active siteInhibits polypeptide elongation by
inactivating EF-2 (Elongation Factor-2) by NAD-riboxylation
Diphtheria Toxin
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Diphtheria toxin is absorbed into the mucous membranes and causes destruction of epithelium and a superficial inflammatory response
Results in a firmly adherent, dirty, gray, spreading pseudomembrane composed of inflammatory necrosis, fibrin, epithelial cells, neutrophils, monocytes, and bacteria
Diphtheria
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Wound or skin diphtheriaoccurs chiefly in the tropics, among
alcoholics, homeless individuals and other impoverished groups
A membrane may form on an infected wound
Absorption of toxin is usually slight and the systemic effect is negligible
Diphtheria
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VirulenceAttributable to their capacity for
establishing infection, growing rapidly, and then quickly elaborating toxin that is effectively absorbed
C. diphtheriae does not actively invade deep tissues
Diphtheria
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ClinicalNO rapid laboratory tests
Direct smearsAlkaline methylene blue
Gram stainBeaded rods in typical arrangement
DIAGNOSTIC LABORATORY TESTS
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SpecimenSwab
Pseudomembrane nasal swabsTonsillar fossae, posterior pharynxRetriuvular areas, naresOther involved sites, cutaneous lesions
Transport Medium: Semi-solid transport mediaSwab specimen – easily dehydrated
Less than 24 hours – Amies or Stuart
More than k24 hours – add tellurite
DIAGNOSTIC LABORATORY TESTS
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MediaBlood Agar Plate (BAP)
Used to rule out hemolytic streptococciColonies appear small, granular, and
gray with a small zone of hemolysis
DIAGNOSTIC LABORATORY TESTS
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MediaTellurite Agar Platee.g. Cystine-tellurite blood agar
(CTBA); modified Tinsdale’s mediumReduces tellurite to telluriumInhibits most normal floraBlack or brownish coloniesBiotypes: gravis, intrmedius, and mitis
DIAGNOSTIC LABORATORY TESTS
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Elek TestCommercially prepared strips of filter
paper containing diphtheria antitoxin are in the agar medium perpendicular to the streaks of the patient’s strain, a known toxin-producing strain and a non-producing strain
Where diffused toxin (if produced y the growth) and antitoxin meet at optimal concentrations, a precipitin line is seen in the agar
DIAGNOSTIC LABORATORY TESTS
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AntitoxinFrom horses, sheep, goat, and rabbits
Antitoxin should be given intravenously on the day of clinical diagnosis of diphtheria is made and need not to be repeated
Intramuscular antitoxin: mild casesErythromycin or Penicillin
Inhibit growth of organismsEliminate coexistent streptococci and C. diphtheriae in carriers
TREATMENT
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Diptheria toxoid immunizationDPT - Diphtheria, Pertussis, TetanusDT – Diphtheria and Tetanus (for children younger than 7 years old
Td – Diphtheria and Tetanus (for adolescents and adults)
PRIMARY PREVENTION: limit the distribution of toxigenic diphtheria bacilli and maintain high level of active immunization
PREVENTION
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Strict isolation for pharyngeal diphtheria
Contact isolation for cutaneous diphtheria
Until 2 negative cultures or after 14 days of antibiotic therapy
CONTROL
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Classification
Nonlipophilic Corynebacteria
Lipophilic Corynebacteria
Other Coryneform bacteria
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Nonlipophilic CorynebacteriaC. ulceransC. pseudotuberculosisC.xerosisC. striatumC. minutissimumC. aycolatumC. auris – ear infection in childrenC. pseudodiphtheriticum - respiratory
tract infectionC. uronalyticum – urinary tract pathogen
Other Coryneform bacteria
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Lipophiilic CorynebacteriaC. jikeium – nosocomial infectionsC. Urealyticum – urinary tract infection
Other Coryneform bacteria
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Corynebacterium xerosisCommonly encountered in conjucntival sacs
Recovered from patients with prosthetic-valve endocarditis
Corynebacterium hofmaniiNormal inhabitant of pharynxRecovered from the blood of patients with subacute bacterial endocarditis
Other Coryneform bacteria
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Jawetz, Melnick & Adelberg’s Medical Microbiology, 26th Edition Burrows Textbook of Microbiology, 22nd Edition https://www.google.com.ph/search?q=diphtheria&espv=2&biw=1275&bih=
637&source=lnms&tbm=isch&sa=X&ved=0CAYQ_AUoAWoVChMImdrVscqPxwIVQyWUCh10JgNx#imgrc=9PH-AtCm12UMMM%3A
https://www.google.com.ph/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=diphtheria
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References:
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