BOC: Aerobic Gram + Cocci

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90. A urine Gram stain shows gram-positive cocci in clusters. The organism tested catalase positive. To speciate this organism from culture, the technologist should perform a coagulase test and a/am:

Novobiocin susceptibility.

92. The Gram stain from a blood culture shows gram-positive cocci in chains. No growth occurs on blood agar plates incubate aerobically and anaerobically. Additional testing should be done to detect the presence of:

Abiotrophia defectiva

93. A reliable test for distinguishing staphylococcus aureus from other staphylococci is:

Coagulase

94. The optochin (ethylhydrocupreine hydrochloride) disk is used for the identification of:

Streptococcus pneumoniae, is susceptible while other alpha-hemolytic strep are resistant.

95. In the optochin susceptibility test, if there is a zone of inhibition of 19-30 mm surrounding the disk following overnight incubation at 37C, the colony most likely consist of:

Pneumococci

96. Which two diseases are usually preceded by infection with beta-hemolytic streptococci?

Glomerulonephritis and rheumatic fever.

97. The enterotoxin produced by certain strains of hemolytic, coagulase positive Staphylococcus aureus:

Causes one type of bacterial food poisoning.

98. A gamma-hemolytic Streptococcus that blackens bile esculin agar but doesn't grow in 6.5% NaCl broth is most likely:

Group D strep, enterococcus has positive esculin test but it does grow in 6.5% NaCl.

99. Gram stain examination of blood culture bottle shows dark blue, spherical organisms in clusters. Growth on sheep blood agar show small, round, pale yellow colonies. Further tests should include:

Catalase production and coagulase test. All staph catalase positive and coagulase to differentiate S. aureus from coagulase negative staph.

100. Gram positive cocci in chains are seen on a Gram stain from a blood culture. The organism grown as a beta-hemolytic colony. Further tests that could be performed include:

Bile esculin, PYR, bacitracin, and hippurate, all presumptive tests of beta hemolytic strep such as S. pyogenes, S. agalactiae, and Enterococcus.

101. "Nutritionally deficient" streptococci are:

In the genera Granulicatella and Abiotrophia.

102. After 24hrs a blood culture from a newborn grows catalase-negative, gram-positive cocci. The bacterial colonies are small, translucent and beta-hemolytic on a blood agar plate. Biochemical test results of a pure culture are: Bacitracin resistant, CAMP positive, Bile esculin negative, and no grown in 6.5% NaCl broth. Assuming all control react properly and reactions are verified, the next step would be to:

Perform a Streptococcus group typing, the colony description resembles S. agalactiae but confirmed by antigen typing.

103. A beta-hemolytic streptococcus that has been isolated from an ear culture grows up to the edge of a 0.04 unit bacitracin disk. Which of the following tests would help to determine if the organism is Enterococcus?

Growth in 6.5% NaCl broth.

104. The organism most commonly associated with neonatal purulent meningitis is:

Group B streptococci, all listed (Neisseria meningitidis, Strep pneumoniae, and Haemphilus influenza) cause meningitis but group B strep is associated with neonate and elderly meningitis.

105. An important cause of acute exudative pharyngitis is:

Streptococcus pyogenes, causes strep throat.

106. Of the following bacteria, the most frequent cause of prosthetic heart valve infections occurring within 2-3 months after surgery is:

Staphylococcus epidermidis.

108. A catheterized urine is inoculated onto blood and MacConkey agar using a 0.01mL loop. After 48hrs, 68 colonies of a small translucent nonhemolytic organism grew on blood agar but not MAC. Testing reveals small gram-positive, catalase negative cocci. The preliminary report and follow-up testing would be:

Growth of 6,800 colonies/mL of Streptococcus species, esculin hydrolysis and NaCl growth tests to follow.

109. Children who have infections with beta-hemolytic streptococci can develop:

Acute glomerulonephritis.

110. A gram-positive cocci isolated from a blood culture has the following characteristics, Optochin Susceptibility- negative, Bacitracin (0.04 U) Susceptibility- negative, Bile esculin hydrolysis- negative, hippurate hydrolysis positive, catalase- negative. The organism is most likely:

Streptococcus agalactiae

111. A beta hemolytic streptococci that is bacitracin- sensitive and CAMP-negative is:

Group A strep (strep pyogenes is sensitive to bacitracin and CAMP-negative).

112. A beta hemolytic streptococci that is bacitracin- resistant and CAMP-negative is:

Group B streptococci (Strep agalactiae are resistant to bacitracin and CAMP-negative)

113. A beta hemolytic streptococci may be distinguished from other hemolytic streptococci by which of the following procedures:

Latex antigen typing.

114. It is important to differentiate between Enterococcus and group D streptococci because:

Enterococci often show more antibiotic resistance than group D streptococci.

115. Streptococci pneumoniae can be differentiated best from the viridians group of streptococci by:

Bile susceptibility.

116. Characteristically, enterococci are:

Relatively resistant to penicillin.

117. A beta hemolytic, catalase-positive, gram-positive coccus is coagulase-negative, by the slide coagulase test. Which of the following is most appropriate action in identification of this organism?

Do a tube coagulase test to confirm the slide test.

118. Which of the following would best differentiate Streptococcus agalactiae from Streptococcus pyogenes?

Hydrolysis of sodium hippurate, agalactiae is + and pyogenes -.

119. The most critical distinction between Staphylococcus aureus and other Staphylococcus is:

Coagulase production.

120. Which of the following organism is, to date, considered universally susceptible to penicillin?

Streptococcus pyogenes.

121. A beta hemolytic gram-positive coccus was isolated from the CSF of a 2-day-old infant with signs of meningitis. The isolate grew on sheep blood agar under aerobic conditions and was resistant to a bacitracin disc. Which of the following should be performed for the identification of the organism?

Latex antigen typing.

122. How many hours after eating contaminated food do initial symptoms of staphylococcal food poisoning typically occur?

2-6 hours.

123. During the past month, Staphylococcus epidermidis has been isolated from blood cultures at 2-3 times the rate from the previous year. The most logical explanation for the increase in these isolates is that:

There has been a break in proper skin preparation before drawing blood for culture.

125. A yellow colony from a wound culture tested catalase-positive and coagulase-negative. The organism stained as gram-positive cocci in clusters. Which of the following tests would differentiate between a coagulase negative Staphylococcus and Micrococcus?

Furazolidone (100 u/g disc) susceptibility, Staphly susceptible and Micrococcus resistant.

127. An isolate from an unknown beta-hemolytic Streptococcus is streaked perpendicular to a streak of beta-lysin producing Staphylococcus aureus. After incubation a zone of arrowhead hemolysis is noted at the interface of the 2 streaks. What is the name of this test and presumptive identification of the unknown streptococcus?

CAMP test and S. agalactiae

128. Which of the following may be used as a positive QC organism for the bile esculin test?

Enterococcus faecalis.

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