Gram Positive Bacilli

Question 1

Bacillus cereus

Answer 1

• Β hemolytic colonies with irregular edges, motile
• Cause of food poisoning
• Resistant to 10ug Penicillin

Question 2

Bacillus anthracis

Answer 2

• Boxcar shaped
• Aerobic, nonhemolytic (γ), “Medusa Head” colonies, nonmotile

1. Cutaneous Antrax: most common, necrotic skin lesions “black eschars”
2. Pulmonary Anthrax: “Woolsorter’s Disease” inhalation of spores from sheep wool
3. Gastrointestinal Anthrax: rare, following ingestion of spores

Question 3

Corynebacterium diptheriae

Answer 3

Nonhemolytic (γ), non-spore forming, nonmotile, “Chinese Letter” pattern

Pathogenic strains are infected with bacteriophage that carries gene for diptheria toxin - causes cell death and pseudomembrane in throat

Question 4

Erysipelothrix rhusiopathiae

Answer 4

Non-spore forming, in filaments/chains or “V”s, pinpoint γ or α hemolytic colonies, nonmotile

Erysipeloid: localized infection on hands from handling fish

Question 5

Lactobacillus

Answer 5

Pinpoint α hemolytic colonies

Predominant flora in vagina during reproductive years

Question 6

Listeria monocytogenes

Answer 6

• Microaerophillic, small indistinct zone of Β hemolysis, Non-spore forming, usually in pairs, tumbling motility
• Septicemia and meningitis in newborns and immunocompromised
• Grows in wide temperature range (0.5-45C)