Aerobic Gram Positive Bacilli

• 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