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Lecture 5

BIOL 1122 Lecture 5: Strep Bacillus Clostridium

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BIOL 1122
Evan Hunter

Strep, Bacillus, Clostridium Streptococci General Characteristics ● Gram-positive cocci ● Short chains 2-8 cells ● Required enriched media under reduced oxygen tension (microaerophilic and facultatively anaerobic) ● Sheep blood agar - environment for differentiation based on hemolytic properties ● 3 types of hemolysis produced on BAP due to production or lack of hemolysins (streptolysins) ○ Alpha (𝛂)- partial hemolysis - greening - viridans group ○ Beta (𝛂) - complete hemolysis - clear - The Beta strep group ○ Gamma (𝛂) - nonhemolytic streptococci ● Catalase negative ● Oxidase negative ● Significant human pathogens - S. pyogenes, S. pneumoniae, Enterococcus faecalis Streptococci Divisions ● Streptococcus divided into 3 groups ○ The Beta-streptococci ○ The Pneumococci ○ The viridans streptococci The Beta Streptococci ● Separated based on cell wall carbohydrate or lipotechoic acid antigens ● A-V (Lancefield grouping system named after Rebecca Lancefield who discovered some B streps and named them A-E) ● Most pathogenic to man - belong to A serological grouping (GABHS - Group A Beta Hemolytic Streptococci) ● Some part of natural flora of many individuals ● Streptoccocis pyogenes = 𝛂-strep Group A = GABHS ● Most GABHS produce 2 types of hemolysins ○ Streptolysin O (oxygen liable) ○ Streptolysin S (oxygen stable) ■ When microbiologist streaks suspected GABHS, blood agar is stabbed at 2 parallel locations to detect streptolysin O activities 𝛂-strep Grp. A = Streptococcus pyogenes ● Causes airborne infections 𝛂-strep Grp. B (S. agalactiae): found in flora in vagina, causes neonatal meningitis, sepsis, pneumonia, omphalitis and vaginitis 𝛂- strep Grb. C (S. equi): causes wound infections, peurperal sepsis and endocarditis Bacillus General characteristics: ● Gram positive ● King size rods, singly or in chains ● Endospore-forming ● Frequently in soil, water, dust, plants and animals ● Some strictly aerobic, others facultatively anaerobic ● Identification factors ○ Anaerobic growth ○ Starch hydrolysis ○ Carbohydrate fermentation ○ Nitrate reduction ○ Citrate utilization ○ Hemolysis on BAP ● Some may form large colonies on BAP (white pigment) ● Some cultivated on BAP may spread all over the surface of the plate ○ Rhizoid or circular fan-like ● Clinical isolates often hemolytic ● Most catalase + Diseases ● Bacillus anthracis: ○ Anthrax is most common in agricultural regions ■ Occurs in animals - transmitted to man by direct contact ■ Man to man transmission not probable ○ Can occur in 3 forms ■ Cutaneous ■ Pulmonary ■ Gastrointestinal ○ Spores can live in soil for years ○ Infection ■ Handling animal products ■ Inhaling anthrax spores ■ Eating undercooked meat ○ Treatment ■ Penicillin ■ Eruythromycin ■ Tetracycline ■ chloramphenicol ○ Non-hemolytic on BAP ○ Vaccine ■ Cell-free filtrate (dead bacteria) ■ Indicated for individuals whose occupation requires close contact w animals and their byproducts and for those engaged in investigational activities ■ 93% effective in protecting against cutaneous anthrax ● Bacillus cereus: ○ Causes food poisoning w gastroenteritis ■ Associated frequently w consumption of boiled rice stored at room temp ○ Hemolytic on BAP Identification ● Malachite green endospore stain ○ Relies on applying heat to drive the dye into the spore ○ Smear is rinsed and counterstained with safranin ○ Spores appear green w
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