Gram Positive Bacteria

Question 1

Staphylococcus aureus

Answer 1

gram-positive cocci in clusters

catalase positive, coagulase postive

Protein A (binds Fc-IgG inhibiting complement fixation and phagocytosis)

Question 2

Staphylococcus epidermidis

Answer 2

gram-positive, cocci

catalase positive, coagulase negative, novobiocin sensitive

Question 3

Streptococcus pneumoniae

Answer 3

lancet-shaped, gram-positive diplococci; encapsulated, IgA protease;

catalase negative, alpha hemolytic (partial green); optochin sensitive

Question 4

Viridans group strep

Answer 4

gram-positive cocci, no capsule

catalase negative, alpha hemolytic, optochin resistant

Question 5

Strep pyogenes (group A)

Answer 5

gram-positive cocci

catalase negative, beta hemolytic (complete clear), bacitracin sensitive

Question 6

Strep agalactiae

Answer 6

group B strep

gram-positive cocci

catalase negative, beta hemolytic, bacitracin resistant

Question 7

Enterocooci

Answer 7

group D strep

gram-positive cocci

catalase negative, non hemolysis, growth in bile and 6.5% NaCl

Question 8

Strep bovis

Answer 8

group D strep

colonizes the gut

bacteremia, subacute endocaritis in colon cancer patients

Question 9

C. tetani

Answer 9

gram-positive, spore-forming, obligate anaerobic bacilli

found in soil

produces tetanospasmin, exotoxin causing tenanus

Question 10

C. botulinum

Answer 10

gram-positive, spore-forming, obligate anaerobic bacilli

produces a preformed, heat-labile toxin that inhibits Ach release

Question 11

C. perfringens

Answer 11

gram-positive, spore-forming, obligate anaerobic bacilli

produces alpha toxin (lecithinase - phospholipase)

Question 12

C. difficile

Answer 12

gram-positive, spore-forming, obligate anaerobic bacilli

produces 2 toxins:
Toxin A - enterotoxin - binds to brush border of gut
Toxin B - cytotoxin - destroys the cytoskeletal structure of enterocytes –> pseudomembanous colitis (white/yellow membrane-like plaques on colonoscopy)

often secondary to antibiotic use (clindamycin or ampicillin)

Question 13

Listeria monocytogenes

Answer 13

gram-positive facultative intracellular rod

cause by ingestion of unpasteurized milk/cheese and deli meats or vaginal transmission during birth

Question 14

Acitinomyces

Answer 14

gram-positive anaerobe, long, branching filaments

Question 15

Mycobacterium leprae

Answer 15

gram-positive, acid-fast bacillus