Aerobic Gram positive rods

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Basics

  • If something is aerobic and spore forming, it is a Bacillus

Bugs

Bacillus anthracis (Anthrax)

  • X-ray Findings: a mediastinal widening near C6-C7 can be observed, but this is not the most common form of anthrax.
    • Usually PA (Posterior->Anterior) films are produced (patient standing, X-ray emitter behind, plate in front).
    • If the patient is too sick, an AP (Anterior->Posterior) film can be used instead
    • This is a very important point since not just any mediastinal widening is caused by anthrax.
  • Black eschars can be caused by either anthrax or a virus from sheep exposure (OrF virus)
  • If you open and debride the eschar and it is anthrax, systemic spread could kill the patient.
  • Therefore, it is important to obtain a detailed history before proceeding with any surgery.

Bacillus cereus

  • should refrigerate cooked rice promptly if leftover and reheat later
  • if left at inadequate cooling (~10°C), Bacillus cereus spores can form.
  • these spores not only survive cooking but are activated into vegetative organisms on cooking
  • These organisms infect food and produce elaborate toxins.

Corneybacterium diptheria

  • asphyxia: diptheria cytotoxin kills cells and causes sloughing on oropharynx, leading to mechanical aspiration of the membrane
  • pseudomembrane sloughing occurs with mononucleosis as well, but the cell is less likely to be asphyxiated than in the case of diptheria.
  • Corneybacterium diptheria is club shaped (bigger at one end than the other), which results in bizarre combinations and weird angles (somewhat like Chinese words) in their colonies under a microscope.

Listeria monocytogenes

  • incredibly sophisticated tactic: actin manufacturing
  • creates a micromuscle to infect adjacent cells - unique and very adaptive.
  • at 2.5°C, Listeria monocytogenes is the only thing that can grow
  • named after Lord Lister, who applied Pasteur's Principles in medical settings.
  • the bug was discovered by Dr. Robert Murray Sr at McGill University in the 30's and 40's, who named the bug to commemorate Lord Lister (much the same way as Listerine, the mouthwash)
  • His son, Dr. Robert Murray Jr. researched at Western in the 50's, 60's and 70's and was president of the American Microbiology Association.
  • The bug works by increasing monocytogenesis in blood (random note - no idea where it came from.)
  • Murray Sr. at a conference once disagreed when the sitting president described a presentation as "interesting."
  • Causes meningitis, especially in neonate (vertical transmission)

Resources

  • Aerobic Gram Positive Rods Presentation (PPT) and Handout (DOC | PDF)