Bacillus

Bacillus General Characteristics of Bacillus  ~ 60 species; Gram-positive or Gram-variable bacilli • Large (0.5 x 1.2 to 2.5 x 10 um) • Most are saprophytic contaminants or normal flora • Bacillus anthracis is most important member  Produce endospores  Aerobic or facultatively anaerobic  Catalase positive (most) • Rapidly differentiates from Clostridium Bacillus spp. are ubiquitous • Soil, water, and airborne dust • Thermophilic ( 75°C) and psychrophilic ( 5-8°C) • Can flourish at extremes of acidity & alkalinity (pH 2 to 10) Diseases Associated with Bacillus Laboratory Characteristics of Bacillus On blood agar • Large, spreading, gray-white colonies, with irregular margins • Many are beta-hemolytic (helpful in differentiating various Bacillus species from B. anthracis) Spores seen after several days of incubation, but not typically in fresh clinical specimens