Micro - Clinical Bacteriology (Gram + Basics)

Question 1

What are the Gram-positive branching filaments bacteria? What are the characteristics that distinguish them from one another?

Answer 1

(1) ACTINOMYCES - anaerobe, not acid fast (2) NOCARDIA - aerobe, acid fast

Question 2

Which of the Gram-positive branching filaments bacteria are aerobic versus anaerobic? Which is acid fast versus not acid fast?

Answer 2

AEROBIC, ACID FAST - Nocardia; Anaerobic, not acid fast - Actinomyces

Question 3

What are the Gram-positive rods (bacilli)?

Answer 3

(1) CLOSTRIDIUM (2) CORYNEBACTERIUM (3) LISTERIA (4) BACILLUS (5) MYCOBACTERIUM

Question 4

Which of the Gram-positive rods are actually acid fast?

Answer 4

Mycobacterium

Question 5

Which of the Gram-positive rods is an aerobe, and which is an anaerobe?

Answer 5

AEROBE - Bacillus; ANAEROBE - Clostridium

Question 6

What are the groups of Gram-positive cocci? How can they be distinguished?

Answer 6

(1) Staphylococcus - clusters, catalase positive (2) Streptococcus - chains, catalase negative

Question 7

What characterizes all Staphylococcus? What are the names of the main species in Staphylococcus, and how can they be distinguished?

Answer 7

Gram + bacteria, cocci in clusters; (1) S. aureus - Coagulase positive (2) S. epidermidis - Coagulase negative, novobiocin sensitive (3) S. saprophyticus - Coagulase negative, novobiocin resistant

Question 8

Of the Staphylococcus bacteria, which are coagulase positive? Which are novobiocin sensitive?

Answer 8

S. aureus = coagulase positive; S. epidermidis = novobiocin sensitive

Question 9

What characterizes all Streptococcus? What are the names of the main species in Staphylococcus, and what is the main way to distinguish/categorize them?

Answer 9

Gram + bacteria, cocci in chains; differentiate species via Hemolysis: (1) ALPHA HEMOLYTIC - S. pneumoniae, Viridans streptococci (2) BETA HEMOLYTIC - S. pyogenes (Group A Strep), S. agalactiae (Group B Strep) (3) GAMMA HEMOLYTIC - Group D Enterococcus, Group D Nonenterococcus

Question 10

What does alpha-hemolytic mean, and how do these kind of bacteria appear on blood agar plates? What are the alpha-hemolytic Streptococci? How can they be distinguished from one another?

Answer 10

Partial hemolysis, green; (1) S. PNEUMONIAE - capsule (+ quellung), optochin sensitive (2) VIRIDANS STREPTOCOCCI - no capusle, optochin resistant (Note: Enterococci may also be alpha-hemolytic or gamma-hemolytic)

Question 11

What does beta-hemolytic mean, and how do these kind of bacteria appear on blood agar plates? What are the beta-hemolytic Streptococci? How can they be distinguished from one another?

Answer 11

Complete hemolysis, clear; (1) S. PYOGENES (GROUP A) - Bacitracin sensitive (2) S. AGALACTIAE (GROUP B) - Bacitracin resistant

Question 12

What does gamma-hemolytic mean, and how do these kind of bacteria appear on blood agar plates? What are the gamma-hemolytic Streptococci? How can they be distinguished from one another?

Answer 12

No hemolysis, normal or no plate change; (1) GROUP D ENTEROCOCCUS - growth in bile AND 6.5% NaCl (2) GROUP D NONENTEROCOCCUS - growth only in bile NOT 6.5% NaCl

Question 13

Give prominent examples of Group D Enterococcus versus Nonenterococcus.

Answer 13

ENTEROCOCCUS - E. faecalis; NONENTEROCOCCUS - S. bovis

Question 14

What kind(s) of hemolysis do Enterococcus display?

Answer 14

Either alpha OR gamma hemolytic

Question 15

What are the most important Gram-positive pathogens?

Answer 15

(1) Staphylococcus - particularly S. aureus (2) Streptococcus - particularly, S. pneumoniae, S. pyogenes, and S. agalactiae (3) Clostridium (4) Listeria (5) Bacillus (6) Mycobacterium

Question 16

Which bacteria does novobiocin help us distinguish, and what are their different responses to it?

Answer 16

Coagulase negative Staphylococcus: (1) S. epidermidis - Novobiocin sensitive (2) S. saprophyticus - Novobiocin resistant

Question 17

Which bacteria does optochin help us distinguish, and what are their different responses to it?

Answer 17

Alpha-hemolytic streptococci: (1) Viridans streptococci - Optochin resistant (2) S. pneumoniae - Optochin sensitive

Question 18

Which bacteria does bacitracin help us distinguish, and what are their different responses to it?

Answer 18

Beta-hemolytic streptococci: (1) Group B Strep (S. agalactiae) - Bacitracin resistant (2) Group A Strep (S. pyogenes) - Bacitracin sensitive

Question 19

How do alpha-hemolytic bacteria appear on blood agar? What are examples? What are characteristics that define/distinguish these bacteria?

Answer 19

Form green ring around colonies on blood agar; (1) Streptococcus pneumoniae - catalase negative & optochin sensitive (2) Viridans streptococci - catalase negative & optochin resistant

Question 20

How do beta-hemolytic bacteria appear on blood agar? What are examples? What are characteristics that define/distinguish these bacteria?

Answer 20

Form clear area of hemolysis on blood agar; (1) Staphylococcus aureus - catalase and coagulase positive (2) Streptococcus pyogenes (Group A strep) - catalase negative & bacitracin sensitive (3) Streptococcus agalactiae (Group B strep) - catalase negative & bacitracin resistant (4) Listeria monocytogenes - tumbling motility, meningitis in newborns, unpasteurized milk

Question 21

What kind of hemolysis does Listeria monocytogenes display? With what major things should you associate Listeria monocytogenes?

Answer 21

Beta-hemolytic; (1) Tumbling motility (of the bacteria itself) (2) Meningitis in newborns (3) Unpasteurized milk