QUIAMBAO, JERIKA C.

MD2

AUGUST 7, 2015

CORYNEBACTERIA

Describe th morphology of Corynebacterium

Enumerate the important members of the genus CorynebacteriaC. diphtheriaeC. xerosisC. hofmanii

LEARNING OBJECTIVES

Discuss the characteristics/virulence factors of Corynebacterium diphtheriae by relating it to the following:Diseases producedHost responseLaboratory identificationTreatmentPreventive and controlEpidemiological features

LEARNING OBJECTIVES

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

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

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

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

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

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

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

ClinicalNO rapid laboratory tests

Direct smearsAlkaline methylene blue

Gram stainBeaded rods in typical arrangement

DIAGNOSTIC LABORATORY TESTS

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

MediaBlood Agar Plate (BAP)

Used to rule out hemolytic streptococciColonies appear small, granular, and

gray with a small zone of hemolysis

DIAGNOSTIC LABORATORY TESTS

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

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

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

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

Strict isolation for pharyngeal diphtheria

Contact isolation for cutaneous diphtheria

Until 2 negative cultures or after 14 days of antibiotic therapy

CONTROL

Classification

Nonlipophilic Corynebacteria

Lipophilic Corynebacteria

Other Coryneform bacteria

Nonlipophilic CorynebacteriaC. ulceransC. pseudotuberculosisC.xerosisC. striatumC. minutissimumC. aycolatumC. auris – ear infection in childrenC. pseudodiphtheriticum - respiratory

tract infectionC. uronalyticum – urinary tract pathogen

Other Coryneform bacteria

Lipophiilic CorynebacteriaC. jikeium – nosocomial infectionsC. Urealyticum – urinary tract infection

Other Coryneform bacteria

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

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

https://www.google.com.ph/search?q=diphtheria&espv=2&biw=1275&bih=637&source=lnms&tbm=isch&sa=X&ved=0CAYQ_AUoAWoVChMIz_3M28qPxwIVBLqUCh2_hgxs#imgrc=_

https://www.google.com.ph/search?q=corynebacterium&espv=2&biw=1275&bih=593&source=lnms&tbm=isch&sa=X&ved=0CAYQ_AUoAWoVChMImpTZ7ayJxwIVgbGUCh14FAqP&dpr=1#tbm=isch&q=corynebacterium+chinese+letters&imgdii=d4IuPJQ50W8d6M%3A%3Bd4IuPJQ50W8d6M%3A%3B6qnoWyG1Hgs8TM%3A&imgrc=d4IuPJQ50W8d6M%3A

https://www.google.com.ph/search?q=corynebacterium&espv=2&biw=1275&bih=593&source=lnms&tbm=isch&sa=X&ved=0CAYQ_AUoAWoVChMImpTZ7ayJxwIVgbGUCh14FAqP&dpr=1#imgrc=_

References:

Thank you for listening!