Bacillus and Clostridium Species

Study Notes

Bacillus and Clostridium species are ubiquitous and can survive in the environment for many years due to their ability to form spores.

Causes fatal sepsis in grazing mammals, such as cattle and sheep.
Characterized by Medusa-head (curled hair) colonies.
Poly-D-glutamic capsule, unusual because it's composed of amino acid residues, not polysaccharide.
Capsule can be detected by the McFadyean reaction.
Produces protective antigen (PA) that combines with edema factor (EF) and lethal factor (LF) to form toxins.
Enters humans through injured skin, mucous membranes, and inhalation of spores into the lungs.

Cutaneous anthrax: results from contact with material containing anthrax endospores, over 90% of anthrax cases.
Characterized by a pruritic papule with a central black eschar.
Gastrointestinal anthrax: rare form of anthrax, caused by ingestion of undercooked food containing anthrax endospores.
Symptoms: abdominal pain, vomiting, and bloody diarrhea.
Inhalation anthrax (Woolsorter’s disease): most dangerous form of anthrax.
Causes hemorrhagic necrosis, edema of mediastinum, substernal pain, pronounced mediastinal widening, hemorrhagic pleural effusions, and sepsis.

AVA BioThrax vaccine: 0.5 mL I.M. at 0 and 4 weeks, then at 6th, 12th, 18th months, then annual booster.
Treatment: Ciprofloxacin, Pen G with Gentamicin or Streptomycin.
Prophylaxis: Ciprofloxacin/Doxycycline with vaccine for 4 weeks, without vaccine for 8 weeks.

Part of the normal flora of the human intestine.
Usually found in grains like rice.
Characterized by “swarming movement” in semisolid culture media.
Produces an enterotoxin that causes food poisoning.
Heating food does not always kill the spores, which germinate as the food cools.
Causes:
- Emetic type: nausea, vomiting, abdominal cramps, and diarrhea.
- Diarrheal type: profuse diarrhea with abdominal pain and cramps.
- Eye infections: severe keratitis, endophthalmitis, and panophthalmitis.
- Endocarditis, meningitis, osteomyelitis, and pneumonia.
Treatment: usually self-limiting, but in severe cases, oral rehydrating salt (ORS) can be used to prevent dehydration.
For penicillin-resistant strains, use Vancomycin or Clindamycin with or without an aminoglycoside.