Aerobic Gram Positive Bacilli

Subdecks (4)

Cards (64)

  • Corynebacterium also known as Kleb Loeffler's bacillus
    • slightly curved
    • slightly wider ends
    • club shaped
    • diptheroid
    • lipophilic and no lipophilic
  • Lipophilic Corynebacterium is fastidious that grow slowly on standard culture media
  • When we talk about lipophilic organism, the growth is enhanced if lipids are included in the culture media
    • major virulence factor of Corynebacterium diphtheria
    • heat labile
    • this toxin is produced by the strains of Corynebacterium diphtheriae infected with a lysogenic B-phage which carries the gene tox
    • has a protein of 62,000 daltons
    Diphtheria Toxin
  • responsible for the cytotoxicity
    Fragment A
  • responsible for binding to receptors on human cells; mediated the entry of fragment A into the cytoplasm
    Fragment B
  • Respiratory diphtheria: sudden onset with exudative pharyngitis, sore throat, low grade fever and malaise.
    • MOT: aerosol through nasopharyngeal route or nasal oral discharges
    • Exotoxin can lead to pseudomembrane formation
    • Patients that has respiratory diphtheria are characterized as having bulls neck appearance
  • Cutaneous diphtheria: a papule can develop on the skin, which progresses to a non healing ulcer (lesions on skin)
  • Corynebacterium diphtheria laboratory diagnosis
    • highly pleomorphic
    • palisades or as individual cells lying at sharp angles to another in V or L formations
    • club shape swellings or beaded forms are common
    • stain irregulary especially with methylene blue
    • metachromatic areas: Babes Ernst granules
  • Babes Ernst granules represents the accumulations of polymerized polyphosphates
  • Culture characteristics of C. diphtheriae
    • facultative anaerobic
    • optimal growth temp: 37C
    • multiply at: 15 - 40C
    • Grows on nutrient agar
    • Loefflers serum or Pai agars - morphology of he organism is demonstrated
  • Cystine Tellurite Blood agar (CTBA)
    • selective and differential media
    • presence of potassium tellurite which inhibits many non coryneform bacteria
    • modification of tindsdale medium
    • black or brownish due to the reduction of tellurite
  • Organisms that produces brown halo on CTBA
    • C. diphtheriae
    • C. ulcerans
    • C. pseudotuberculosis
  • C. diphtheriae
    • lacks urease production
    • ferment: glucose & maltose
    • producing acid but no gas
    • reduces nitrate to nitrite
  • The in vitro diphtheria toxin detection procedure is an immunodiffusion test described first by Elek
  • Elek test : organisms are streaked on medium of low iron content 10mm apart
  • Laboratory Diagnosis:  Treatment
    • Diphtheria is treated by prompt administration of anti toxin
    • DOC : penicillin
    • Erythromycin : used for penicillin sensitive people
  • Corynebacterium amycolatum
    • the most frequently recovered corynebacterium species from human
    • part of normal skin biota
    • flat, dry, matte, waxy appearance and non lipophilic
    • resistant to wide range of anti microbials including B lactams, fluoroquinolones, macrolides, and aminoglycosides
  • Corynebacterium jeikeium
    • named after Johnson and Kaye
    • limited to patients who are IMCP
    • most common cause of corynebacterium associated prosthetic valve endocarditis in adults.
    • lipophilic
    • non hemolytic
    • urease and nitrate reduction negative
    • TOC : Vancomycin
  • Corynebacterium pseudodiphtheriticum
    • often appear palisades
    • grows well on standard laboratory media
    • reduces nitrate
    • produces urease
    • their respiratory tract infection can mimicmimic the respiratory diphtheria
    • does not show characteristic of pleomorphic morphology
  • Corynebacterium pseudotuberculosis
    • veterinary pathogen
    • causes granulomatous lymphadenitis in human
    • dermonecrotic toxin: causes death in various cell types
    • produces diphtheria toxin
    • produces brown halo on CTBA
    • produces urease
    • SBA: small, yellowish-white colonies
  • Corynebacterium striatum
    • considered commensal or skin contaminant
    • non lipophilic and pleomorphic
    • produces small, shiny, convex colonies in about 24 hours
    • resistant to penicillin, other B lactams, macrolides, and fluoroquinolones
    • Susceptible to vancomycin
  • Corynebacterium ulcerans
    • veterinary pathogen
    • causing mastitis in cattle
    • humans usually acquire thru contact with animals and ingestion of unpasteurized dairy
    • Grows well on SBA
    • does not reduce nitrate to nitrite
    • urease positive
  • Corynebacterium urealyticum
    • most commonly associated with UTI
    • lipophilic and strict aerobe
    • pinpoint, non hemolytic, white colonies
    • DOC : Vancomycin