NSF, NB, Catalase NEGATIVE bacilli

• 3 species of Non spore forming, Non branching, catalase (-) bacilli

  • Gardnerella vaginalis
  • Arcanobacterium and Trueperella
  • Erysipelothrix rhusiopathiae
• Three species in the genus Erysipelothrix:

  • Erysipelothrix rhusiopathiae

  Erysipelothrix tonsillarum

  Erysipelothrix inopinata
• Erysipelothrix rhusiopathiae

  • Gram positive, catalase negative
  • Non-spore-forming
  • Pleomorphic rod that has a tendency to form long filaments
  • Usual route of infection is through cuts or scratches on skin
  • Can be found worldwide; commensal pathogen on vertebrates and even invertebrates
  • Only species in this genus that can cause disease in humans
• Clinical Infections

  1. Erysipeloid - localized skin disease; occur on fingers by direct inoculation [seal or whale finger]
  2. Septicemia - associated with endocarditis
• Laboratory diagnosis (Microscopy)

  • Thin, rod-shaped, gram-positive organism that can form filaments
  • Arranged singly, in short chains, or in a “V” shape
  • Decolorized easily, so it may appear gram variable
• Laboratory diagnosis (culture characteristics)

  • Grows on SBA and chocolate agar
  • Nonhemolytic and pinpoint
  • After 48 hours of incubation
  • A smaller, smooth form is transparent, glistening, and convex with entire edges
  • Larger, rough colonies are flatter with a matte surface, curled structure, and irregular edges
  • often appear a-hemolytic
• Laboratory diagnosis (identification)

  • Catalase negative
  • Nonmotile
  • Pleomorphic
  • Aerobic or facultatively anaerobic
  • Hydrogen sulfide positive
  • Voges-Proskauer test negative
  • Gelatin stab culture: “test tube brush-like” pattern at 22°C
• Arcanobacterium and Trueperella

  The two organisms above are associated to cause infections in human;

  1. Trueperella (Arcanobacterium) pyogenes
  2. Trueperella (Arcanobacterium) bernardiae

  This organism is an animal pathogen and best known for causing infections in cattle

  1. Trueperella pyogenes
• Arcanobacterium and Trueperella Laboratory Diagnosis

  • Catalase negative
  • Small colonies on SBA: narrow zone of -hemolysis after 24 to 48 hours of incubation
  • A black opaque dot is observe on the agar when the colony is scraped away.
  • Pitting of the agar
  • Lipase and lecithinase positive
  • Exhibits a reverse CAMP reaction (CAMP inhibition reaction)
• Gardnerella vaginalis

  • Short, pleomorphic gram-positive rod or coccobacillus
  • Stains gram variable or gram negative
  • Found to be a normal biota of the human genital tract, but can cause infection such as Bacterial Vaginosis
• Gardnerella vaginalis Laboratory Diagnosis

  MICROSCOPY: “clue cells” aids the diagnosis of BV

  • Large, squamous, epithelial cells with gram positive or gram variable bacilli and coccobacilli clustered on edges
• Gardnerella vaginalis - Amsel’s Clinical Criteria: 3 of 4

  1. Homogenous, thin, white discharge that smoothly coats the vaginal walls
  2. Clue cells
  3. pH of the vaginal fluid is greater than 4.5, if decreased, the gardnerella vaginalis will cause infection
  4. fishy odor of vaginal discharge before or after the addition of 10% potassium hydroxide, the whiff test
• Gardnerella vaginalis - Culture Characteristics

  • Grows best in 5% to 7% CO2 at a temperature of 35°C to 37°C
  • Grows on SBA as pinpoint, nonhemolytic colonies
  • Medium of choice: human blood bilayer tween (HBT) agar