Gram-Positive Bacilli Part One MLAB 2434: Microbiology Keri Brophy-Martinez

General Characteristics: Bacillus Habitat Thermal springs, fresh and salt water, soil, on plants Aerobic Spore-formers Resistant to radiation, heat, disinfections, and desiccation Mostly contaminants in clinical specimens EXCEPTION: Bacillus anthracis

More on Spores Produced 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

Significant Bacillus Species Bacillus anthracis Agent of anthrax, a disease in livestock Humans acquire infection by contamination of wound or ingestion or inhalation of spores Bacillus cereus Causes food poisoning An opportunist Bacillus subtilis Common laboratory contaminant Used in sterility testing

Bacillus anthracis Cutaneous anthrax Inhalation 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 anthracis: Clinical Infections in Humans Cutaneous anthrax

Laboratory Diagnosis Media Catalase positive 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 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 of Bacillus anthracis Microscopic morphology Large, square-ended gram-positive rods Bamboo appearance Spores may be absent in patient smears

Identification of Bacillus anthracis Colony Morphology Nonhemolytic on blood agar; raised, large, grayish white, irregular, fingerlike edges “Medusa head” or “beaten egg whites”

Bacillus cereus Food poisoning Diarrheal syndrome Emetic form 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 cereus Local infections Postsurgical/traumatic wounds Burns Eye infections Rare conditions Meningitis Bacteremia Endocarditis Osteomyelitis

Bacillus subtilis Found in the environment Common laboratory and hospital contaminant Used as a QC agent for sterilization procedures

Key Characteristics of Bacillus Species B. Anthracis B. Cereus Other Bacillus Beta-hemolysis Negative Positive, Large zones variable Motility Positive Pencillin Sensitive Resistant Variable

References 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.sta te.il.us/pt3/mod/science/mod_bio111/mod10/p4.html http://www.flickr.com/photos/microbeworld/sets/721576253922655 38/detail/http://www.uaz.edu.mx/histo/pathology/ed/ch_9b/c9b_clu e.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.