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Gram-Positive BacilliGram-Positive BacilliPart OnePart One
MLAB 2434: MicrobiologyKeri Brophy-Martinez
General Characteristics: General Characteristics: BacillusBacillus
Habitat◦Thermal springs, fresh and salt water,
soil, on plantsAerobicSpore-formers
◦Resistant to radiation, heat, disinfections, and desiccation
Mostly contaminants in clinical specimens◦EXCEPTION: Bacillus anthracis
More on SporesMore on SporesProduced when the bacteria gets stressed
◦ Drying◦ Temperature extremes
Aid in organism’s survival
Heat shock induces spores◦ Temperature raised to 56o
Gram stain◦ Appear as clear areas within the bacterial cell
SignificantSignificant Bacillus Bacillus Species SpeciesBacillus anthracis
◦ Agent of anthrax, a disease in livestock◦ Humans acquire infection by contamination of
wound or ingestion or inhalation of sporesBacillus cereus
◦ Causes food poisoning◦ An opportunist
Bacillus subtilis◦ Common laboratory contaminant◦ Used in sterility testing
Bacillus anthracisBacillus anthracisCutaneous anthrax
◦ “Malignant pustule” (also called “black escher”)◦ Woolsorter’s disease/ Rag-pickers disease◦ Organisms gain access through cuts; localized
infection◦ Majority of cases in the world are cutaneous
Inhalation anthrax◦ Acquired through inhalation of spores◦ May result in respiratory distress and death
Gastrointestinal◦ Acquired by ingestion of contaminated raw meat◦ Usually fatal
Bacillus anthracisBacillus anthracis: : Clinical Infections in Humans Clinical Infections in HumansCutaneous anthrax
Laboratory DiagnosisLaboratory DiagnosisMedia
◦Most species grow well on SBA Most species beta-hemolytic, except B.
anthracis
◦No growth on MacConkey◦Fast growers◦Colony characteristics vary
Catalase positive
Laboratory DiagnosisLaboratory Diagnosis
Goal in identification is to RULE OUT B. anthracis
If B. anthracis is suspect, MUST work under safety hood
Other Bacillus, identified to genus level ONLY
Identification Identification of Bacillus of Bacillus anthracisanthracis
Microscopic morphology◦ Large, square-
ended gram-positive rods
◦ Bamboo appearance
◦ Spores may be absent in patient smears
Identification Identification of Bacillus of Bacillus anthracisanthracis
Colony Morphology◦ Nonhemolytic on blood
agar; raised, large, grayish white, irregular, fingerlike edges
◦ “Medusa head” or “beaten egg whites”
Bacillus cereusBacillus cereusFood poisoning
◦ Diarrheal syndrome Associated with meat, poultry, and soups Incubation period of 8 to16 hours Fever uncommon Resolves within 24 hours
◦ Emetic form Associated with fried rice Abdominal cramps and vomiting Incubation period of 1 to 5 hours Resolves in 9 hours
Bacillus cereusBacillus cereusLocal infections
◦ Postsurgical/traumatic wounds◦ Burns◦ Eye infections
Rare conditions◦ Meningitis◦ Bacteremia◦ Endocarditis◦ Osteomyelitis
Bacillus subtilisBacillus subtilis
Found in the environmentCommon laboratory and hospital contaminantUsed as a QC agent for sterilization procedures
Key Characteristics of Key Characteristics of Bacillus SpeciesBacillus Species
Characteristic B. Anthracis B. Cereus Other Bacillus
Beta-hemolysis Negative Positive, Large zones
variable
Motility Negative Positive Positive
Pencillin Sensitive Resistant Variable
ReferencesReferences http://www.atsu.edu/faculty/chamberlain/golden2000/
case5.htm http://chesschumpion.blogspot.com/2007/03/time-to-put-on-
your-thinking-caps.html http://en.wikipedia.org/wiki/File:Bacillus_subtilis_Gram.jpg https://labs.uhstx.com/clinical_int/dols/appb.htmlhttp://
www.iccb.state.il.us/pt3/mod/science/mod_bio111/mod10/p4.html
http://www.flickr.com/photos/microbeworld/sets/72157625392265538/detail/http://www.uaz.edu.mx/histo/pathology/ed/ch_9b/c9b_clue.htm
Kiser, K. M., Payne, W. C., & Taff, T. A. (2011). Clinical Laboratory Microbiology: A Practical Approach . Upper Saddle River, NJ: Pearson Education.
Mahon, C. R., Lehman, D. C., & Manuselis, G. (2011). Textbook of Diagnostic Microbiology (4th ed.). Maryland Heights, MO: Saunders.