Aerobic Gram Positive Bacilli

Question 1

What is Gram stain of Bacillus species?

Answer 1

• Regular
• Large
• Gram Positive rods
• Endospores

Older cultures are easily decolourised and can appear gram variable or negative

Question 2

What are the general characteristics of Bacillus spp.

Environment, catalase, motility

Answer 2

• Aerobic
• Mesophilic (1)
• Catalase Positive
• Motile - peritrichous flagella (2)

NB. Diverse genus - some species lack spores, some anaerobes

1. Mesophilic: Grows best in moderate temperatures (20 - 45 deg)
2. Peritrichous: flagella over entire surface of bacterium

Question 3

What are the aerobic endospore forming gram positive bacilli?

Answer 3

• Bacillus
• Geobacillus
• Lysinibacillus
• Paenibacillus
• Brevibacillus

Question 4

Where can aerobic endopsore forming GPB be found and why?

Answer 4

Ubiquitous in nature, particularly exotic and extreme environments.
Why- endospores are resistant to heat, dessication, radiation, disinfectants.

Question 5

How are aerobic endospore forming GPB transmitted and can it be transmitted person to person?

Answer 5

• Ingestion
• Injection
• Injury
• Inhalation
• Contact with spore contaminated material (e.g. anthrax infected carcasses)
• Person to person transmission is rare

Question 6

In general, what is the clinical significance of aerobic endospore forming GPB other than Bacillus cereus and Bacillus anthracis

Answer 6

• Little to no pathogenic potential
• Environmental organisms which may act as opportunistic pathogens
• Likely contaminants of unknown significance in non-sterile sites and wounds
• May cause systemic disease in immunocompromised or immunosuppressed individuals