Question 1

The drugs of choice for most Enterococcal infections are:

Accepted Answer

Enterococci are intrinsically resistant to a wide array of antimicrobial agents,and they are generally resistant to killing by any of the single agents (e.g. ,ampicillin,vancomycin)that are bactericidal for most other gram-positive cocci.Therefore,effective bactericidal activity can only be achieved with the combination of a cell wall-active agent,such as ampicillin or vancomycin,and an aminoglycoside,such as gentamicin or streptomycin.

Question 2

Erythrogenic toxin,hyaluronidase enzyme,and hemolysins S and O are extracellular products of:

Accepted Answer

All of these descriptions are true of S.pyogenes.

Question 3

What morphologic feature is a major consideration in determining an identification scheme for streptococci?

Accepted Answer

The cellular arrangement on Gram stain and the type of hemolysis are important considerations in the identification of streptococci.

Question 4

The development of acute rheumatic fever and subsequent valvular heart disease are problems that may be encountered by patients infected with:

Accepted Answer

Acute rheumatic fever and valvular heart disease are sequelae that sometimes develop in patients infected with S.pyogenes.

Question 5

The colonial morphologic features of this organism resemble a donut as it ages,and it has a polysaccharide capsule that is responsible for its virulence.What two characteristics describe this organism?

Accepted Answer

Based on the morphologic features listed,the organism is S.pneumoniae.The organism is α-hemolytic and positive for bile solubility so the only answer that describes this organism is D.

Question 6

Which species of bacteria is responsible for causing diseases such as rheumatic fever,glomerulonephritis,and exudative pharyngitis?

Accepted Answer

S.pyogenes causes all of these diseases.

Question 7

Enterococci can be described as:

Accepted Answer

One characteristic of enterococci that helps identify this organism is its ability to hydrolyze bile esculin.

Question 8

Optochin,PYR,bile solubility,esculin,and 6.5% NaCl are tests most likely performed on a(n)_______ Streptococcus.

Accepted Answer

The tests listed are those used to differentiate various α-hemolytic streptococci.

Question 9

Generally speaking,nutritionally variant streptococci require what ingredient not found in most conventional media?

Accepted Answer

Abiotrophia and Granulicatella will not grow on blood or chocolate agar unless pyridoxal (vitamin B₆)is supplied by the placement of a pyridoxal disk,by cross streaking with Staphylococcus,or by inoculation of vitamin B₆-supplemented culture media.

Question 10

Which of the following organisms best describes a catalase-negative,gram-positive coccus that is β-hemolytic on sheep blood agar,and bacitracin positive?

Accepted Answer

Micrococcaceae spp.and S.epidermidis are catalase-positive,and S.pneumoniae is α-hemolytic.

Question 11

The development of glomerulonephritis is a problem that may be encountered by patients infected with:

Accepted Answer

Glomerulonephritis is a condition that sometimes develops in patients infected with S.pyogenes.

Question 12

The bacterial species that can be described as able to hydrolyze hippurate,is β-hemolytic,is a major cause of neonatal meningitis and sepsis,and is a producer of the Christie,Atkins,Munch-Petersen (CAMP)factor is:

Accepted Answer

S.agalactiae is β-hemolytic,is CAMP and hippurate-positive,and causes neonatal meningitis and sepsis.

Question 13

The bacterial species that can be described as able to grow in 6.5% sodium chloride (NaCl)and 40% bile,is part of the normal fecal flora of animals and humans,displays g hemolysis,and is a major cause of nosocomial infections is:

Accepted Answer

All of the descriptions are true of E.faecalis.

Question 14

What name is given to the type of hemolysis that produces incomplete hemolysis and a greening discoloration of the medium?

Accepted Answer

α hemolysins cause incomplete hemolysis of erythrocytes,making blood agar appear green around the colony.

Question 15

What name is given to the type of hemolysis that produces complete hemolysis and a clearing of the medium?

Accepted Answer

β hemolysins cause complete hemolysis of erythrocytes,making blood agar appear clear around the colony.

Question 16

Bacitracin,CAMP factor,PYR,and hippurate are tests most likely performed on a(n)_______ Streptococcus.

Accepted Answer

The tests listed are those used to differentiate various β-hemolytic streptococci.

Question 17

Differentiation of the pleomorphic strains of streptococci and the similar corynebacteria or lactobacilli can be best accomplished by:

Accepted Answer

All the genera described in this chapter are gram-positive cocci.Microscopically,streptococci are round or oval-shaped,occasionally forming elongated cells that resemble pleomorphic corynebacteria or lactobacilli.Growth in broth should be used to determine its cellular morphologic structure if a question remains regarding the staining characteristics from solid media.

Question 18

When performing the CAMP test,what bacteria is steaked down the middle?

Accepted Answer

The CAMP factor test is used to differentiate S.agalactiae from other β-hemolytic streptococci.S.aureus is streaked down the middle.The unknown bacteria is steaked perpendicular to the S.aureus.The zone of increased lysis assumes the shape of an arrow at the junction of the two streak lines.

Question 19

The major etiologic agent of bacterial endocarditis in the United States is:

Accepted Answer

Viridans streptococci is the etiologic agent in the majority of cases of bacterial endocarditis in the United States.

Question 20

S.pneumoniae can be described as:

Accepted Answer

S.pneumoniae contains an antiphagocytic capsule,is sensitive to bile and optochin,and is catalase-negative.S.agalactiae is CAMP positive.

Quiz 13: Streptococcus, Enterococcus, and Similar Organisms