Gram Positive Bacilli Corynebacterium PDF

Gram Positive Bacilli Corynebacterium General characteristics • • • • • Corynebacteria are Gram-positive, catalase positive, non-spore-forming, non-motile, rod-shaped bacteria that are straight or slightly curved • Metachromatic granules are usually present representing stored phosphate regions...

Gram Positive Bacilli Corynebacterium General characteristics • • • • • Corynebacteria are Gram-positive, catalase positive, non-spore-forming, non-motile, rod-shaped bacteria that are straight or slightly curved • Metachromatic granules are usually present representing stored phosphate regions General characteristics • It is also known as the Klebs-Löffler bacillus General characteristics • Genus has many species • Most commensals called: Diptheroids • Human pathogens : 1.C.diphtheriae- Diphtheria (3 biotypes) gravis, mitis, and intermedius 2.C.hemolyticum- sore throat, ulcers 3.C.jeikium or Corynebacteria JK) :systemic infections in immunosuppressed, heart valve infections (endocarditis) commensal 4.C.ulcerans-pharyngitis like diphtheria Diphtheria • Respiratory diphtheria- more serious • Cutaneous diphtheria –skin infection, wound contaminated with C.diphtheria, rarely systemic • http://www.youtube.com/watch?v=ukgqInfKFzg&feature= BFa&list=LPoLBcpijWpfA Respiratory Diphtheria • • • • Serious and fatal, if untreated Begins upper resp. tract Organism inhaled Exotoxin( neurotoxin) spreads via blood to other organs (heart, muscle, kidney, liver) • Throat acute inflammation – white membrane over the throat , can spread down and cause death from asphyxia (Laryngeal diphtheria) • Clinical diagnosis : presence of membrane • Major infection in the past prior to anti-toxin and vaccination White pseudomembrane of Diphtheria Bullous neck Cutaneous diphtheria Lab diagnosis • Specimen: nasophyrangeal swab , wound swab Lab diagnosis Microscopy: • Gram stain: pleomorphic gram pos bacilli,gram variable, coryneform (Chinese letter arrangement) Special stain: Albert’s stain(KLB stain): • Stains volutin (metchromatic polyphosphate granules found in cytoplasm). - Malachite Green: Bacilli green, - Toludine blue :granules (dark red spot) Culture • Selective media- used to differentiate commensal species from C.diphtheriae 1) Hoyle’s Tellurite blood agar (Hoyle's Agar is a selective media that uses tellurite to differentially select Corynebacterium diphtheriae from other upper respiratory tract flora) 2) Tindsdale medium (production of H2S) The dark halo is due to the production of H2S from cystine, interacting with the tellurite salt icture of C.diphtheriae gravis showing typical black colonies on blood tellurite agar Gray colonies of the commensal corynebacteria on Tellurite agar. Hoyle’s Tellurite agar. Illustrating severa black colonies. C.diphtheriae are the colonies with the diffuse halo in the surrounding agar. Lab Diagnosis Identification by: • Biochemical tests: Hiss’s Serum sugars. • Glucose & maltose +, Sucrose – • Urease + : C. ulcerans. • Gelatin liquefied.(C.ulcerans+ C.diphtheriae) Virulence testing of C.diphtheriae 1. ELEK’s test ( Ag-Ab test) Method of test• • • • • Horse serum agar used Filter paper with antitoxin Test organism Known positive and negative control Check for precipitation • 2.Guinea pig inoculation. ELEK test 500-1000 i.u/ml of antitoxin Test org 1 Pos control 2 Neg control 3 Pos control 4 Test org 5 ELEK’s Gel precipitation test Treatment of Diphtheria • Mainstay of treatment is Antidiphtheritic serum (antitoxin). • Antibiotics used for: 1. Treatment of carriers 2. Synergistic with antitoxin for patients. • Sensitive to Erythromycin, Penicillin & Clindamycin. Areas and countries of risk for Diphtheria ? Vaccine