Pre-lec 1: staph and strep

The two species of coagulase-negative staphylococci most often isolated in clinical laboratories are:

a. S. captitus and S. lugdunensis

b. S. saccharolyticus and S. epidermidis

c. S. epidermidis and S. saprophyticus

d. Staphylococcus aureus and S. epidermidis

c. S. epidermidis and S. saprophyticus

Why do staphylococci spread so easily when infecting the skin?

a. They produce hyaluronidase, which hydrolyzes hyaluronic acid present in the intracellular ground substance that makes up connective tissue.

b. they produce lipase, which melts the fat under the skin, making it easier to spread.

c. all of the above

d. The hemolysins kill the white and red blood cells; then the protease liquefies the skin protein, allowing easy penetration for the bacteria.

a. They produce hyaluronidase, which hydrolyzes hyaluronic acid present in the intracellular ground substance that makes up connective tissue.

A 20-year old woman goes to her physician complaining of burning upon urination, frequency, and general malaise. Her physician orders a urine culture, which grew 25,000 colony-forming units (CFU)/mL of a catase-positive, coagulase-negative, novobiocin-resistant gram-positive coccus. What is the most likely pathogen?

a. S. haemolyticus

b. Staphylococcus epidermidis

c. S. intermedius

d. S. saprophyticus

d. S. saprophyticus

This staphylococcus produces zones of beta hemolysis on 5% sheep blood agar.

a. S. aureus

b. Staphylococcus epidermidis

c. S. saprophyticus

d. S. intermedius

a. S. aureus

All of the following is used to describe the colony morphology of Staphylococcus epidermidis, except:

a. small to medium

b. white

c. nonhemolytic

d. B-hemolytic

d. B-hemolytic

Streptococcus agalactiae is a significant cause of

a. vaginitis

b. pharyngitis

c. invasive disease of the newborn

d. cystitis

c. invasive disease of the newborn

Which of the following is the drug of choice for treating most streptococcal infections?

a. penicillin

b. gentamicin

c. cephalothin

d. erythromycin

a. penicillin

Which of the following tests can be used to identify group b streptococci?

a. CAMP

b. Bacitracin

c. Novobiocin

d. Optochin

a. CAMP

Two serious complications of an infection with group A streptococci are:

a. acute glomerulonephritis and rheumatic fever

b. acute glomerulonephritis and necrotizing fasciitis

c. toxic shock syndrome and scarlet fever

d. gangrene and rheumatic fever

a. acute glomerulonephritis and rheumatic fever

What organism on BAP has grayish-white colonies typically surrounded by a small zone of b-hemolysis?

a. viridans strep

b. streptococcus agalactiae

c. enterococcus

d. viridans strep

b. streptococcus agalactiae

What is the drug of choice to treat group a streptococci when the patient cannot tolerate penicillin?

a. penicillin

b. gentamicin

c. cefoxitin

d. erythromycin

d. erythromycin

what is the cellular structure that streptococcus pyogenes relies primarily on for its virulence?

a. S antigens

b. peptidoglycan

c. M proteins

d. lipopolysaccharide

c. M proteins

What test differentiates staphylococci from streptococci?

a. coagulase

b. all of the answers

c. catalse

d. b-hemolysis

c. catalase

what test presumptively differentiates b-hemolytic group A streptococci and nonhemolytic group D enterococci from other streptococcal species?

a. optochin

b. bacitracin

c. hippurate hydrolysis

d. PYR

d. PYR

Which of the following tests can be used to presumptively identify Streptococcus pyogenes?

a. citrate

b. bacitracin

c. nitrate

d. optochin

b. bicitracin