ESSENTIAL MICROBIOLOGY PORTAGE
LEARNING MODULE 6 FINAL SCRIPT 2026
SOLVED QUESTIONS WITH FULL SOLUTIONS
◉ Bacillus anthracis. Answer: Primary pathogen, Rarely
encountered in US
-Large GPB with central or terminal spores, usually not swollen
-Grows well on SBA - large white colonies with irregular curled
margin- "Medusa Head" colonies under dissecting microscope
-Non hemolytic, non motile, lecithinase positive, starch hydrolysis
positive
-Tenacity test, String of Pearls test
◉ B. anthracis disease states: Anthrax. Answer: -Cutaneous -
"malignant pustule"
-Pulmonary - "wool sorter's disease"
-GI - rare; ingestion of spores from improperly cooked infected meat
-Cutaneous and pulmonary anthrax seen during 9/11 terrorist
attacks
◉ Other Bacillus species. Answer: -Bacillus subtilis - major lab
contaminant
-Bacillus stearothermophilus - spores used to check autoclave
,◉ Other Bacillus species: Bacillus cereus. Answer: -Found in the
environment and food
-Causes food poisoning - emetic toxin heat stable - causes vomiting
(Oriental fried rice kept warm); heat labile toxin causes diarrhea
-Wide zone of beta hemolysis; motile
◉ Non spore forming GPB. Answer: -Corynebacterium
-Club shaped rods
-Resemble "Chinese letters"; some are normal URT flora
(diptheroids or Corynebacterium species)
◉ non spore forming GPB: Primary pathogen Corynebacterium
diptheriae. Answer: -causes diphtheria: respiratory disease or
wound infection
-Produces powerful neurotoxin that may cause suffocation
-Pseudomembrane formation on tonsils, larynx, trachea
-Epidemic before DPT vaccine
◉ C. diptheriae con't. Answer: -Narrow zone of beta hemolysis on
SBA
-Use Loeffler medium to enhance metachromatic granules (Babes-
Ernst bodies) - irregular staining granules that appear as beads
, (accumulation of nutrient reserves); may be picked up using
methylene blue stain
-Gray to black colonies on Potassium Tellurite agar - inhibits most
normal URT flora
-Tinsdales media - black colony/brown halo
-Modified Elek test - looking for exotoxin specific to C. diptheriae
◉ listeria (species: monocytogenes). Answer: -Small gram positive
bacilli
-Resembles Group B strep on SBA
-Beta hemolytic
-Catalase positive
-Bile esculin positive
-CAMP test positive
-Umbrella motility at 25 degrees C
-Tumbling "end over end" motility on wet prep
◉ Listeria diseases. Answer: -Highly fatal form of meningitis in
newborns
-Causes still birth, miscarriage
-Major pathogen of animals
-Found on cabbage, raw fruit, dairy products (Polar bars, Mexican
cheese, raw hot dogs)
LEARNING MODULE 6 FINAL SCRIPT 2026
SOLVED QUESTIONS WITH FULL SOLUTIONS
◉ Bacillus anthracis. Answer: Primary pathogen, Rarely
encountered in US
-Large GPB with central or terminal spores, usually not swollen
-Grows well on SBA - large white colonies with irregular curled
margin- "Medusa Head" colonies under dissecting microscope
-Non hemolytic, non motile, lecithinase positive, starch hydrolysis
positive
-Tenacity test, String of Pearls test
◉ B. anthracis disease states: Anthrax. Answer: -Cutaneous -
"malignant pustule"
-Pulmonary - "wool sorter's disease"
-GI - rare; ingestion of spores from improperly cooked infected meat
-Cutaneous and pulmonary anthrax seen during 9/11 terrorist
attacks
◉ Other Bacillus species. Answer: -Bacillus subtilis - major lab
contaminant
-Bacillus stearothermophilus - spores used to check autoclave
,◉ Other Bacillus species: Bacillus cereus. Answer: -Found in the
environment and food
-Causes food poisoning - emetic toxin heat stable - causes vomiting
(Oriental fried rice kept warm); heat labile toxin causes diarrhea
-Wide zone of beta hemolysis; motile
◉ Non spore forming GPB. Answer: -Corynebacterium
-Club shaped rods
-Resemble "Chinese letters"; some are normal URT flora
(diptheroids or Corynebacterium species)
◉ non spore forming GPB: Primary pathogen Corynebacterium
diptheriae. Answer: -causes diphtheria: respiratory disease or
wound infection
-Produces powerful neurotoxin that may cause suffocation
-Pseudomembrane formation on tonsils, larynx, trachea
-Epidemic before DPT vaccine
◉ C. diptheriae con't. Answer: -Narrow zone of beta hemolysis on
SBA
-Use Loeffler medium to enhance metachromatic granules (Babes-
Ernst bodies) - irregular staining granules that appear as beads
, (accumulation of nutrient reserves); may be picked up using
methylene blue stain
-Gray to black colonies on Potassium Tellurite agar - inhibits most
normal URT flora
-Tinsdales media - black colony/brown halo
-Modified Elek test - looking for exotoxin specific to C. diptheriae
◉ listeria (species: monocytogenes). Answer: -Small gram positive
bacilli
-Resembles Group B strep on SBA
-Beta hemolytic
-Catalase positive
-Bile esculin positive
-CAMP test positive
-Umbrella motility at 25 degrees C
-Tumbling "end over end" motility on wet prep
◉ Listeria diseases. Answer: -Highly fatal form of meningitis in
newborns
-Causes still birth, miscarriage
-Major pathogen of animals
-Found on cabbage, raw fruit, dairy products (Polar bars, Mexican
cheese, raw hot dogs)
