MDL 246 Week 3 - Gram Positive

True or False: Corynebacterium species produce spores.

False

True or False: Pediococcus and Leuconostoc are susceptible to vancomycin.

False

True or False: Staphylococcus aureus is the only staphylococci that is positive for the coagulase test.

False

Describe the Gram stain of Staphylococcus

Gram positive cocci

What does blackening of media in a TSI tube indicate and what species is this typical of?

H2S production Typical of Salmonella, Citrobacter, and Proteus

Are Streptococci catalase positive or negative?

Negative

Are Staphylococci catalase positive or negative?

Positive

What does a K/K TSI tube look like what organism is this typical of?

Red slant/red butt Typical of P. aeruginosa

What does a K/A TSI tube look like and what organism is this typical of?

Red slant/yellow butt Typical of Shigella species

What is the most virulent species of Staphylococcus encountered in the clinical laboratory?

S. aureus

How do you differentiate Staphylococci?

S. aureus is coagulase positive (and typically hemolytic), others are not. S. saprophyticus is resistant to novobiocin, while S. epidermidis is susceptible

How can Streptococci be differentiated?

S. pyogenes and S. agalactiae are both beta hemolytic; S. agalactiae is CAMP positive S. pneumoniae is alpha hemolytic, bile soluble, and optochin sensitive S. viridans are alpha or non-hemolytic

In the CAMP test a single streak of a beta-hemolytic streptococcus is placed perpendicular to a streak of beta-lysin-producing Staphylococcus aureus. After incubation, a zone of increased lysis in the shape of an arrowhead is noted, which indicates the presence of: a. Streptococcus bovis b. Streptococcus agalactiae c. Streptococcus pyogenes d. Streptococcus equines e. Streptococcus mitis

b. Streptococcus agalactiae

An optochin disk test was performed on an unknown gram positive cocci. There was a zone of inhibition greater than 16mm around the disk. The organism also tested positive on the bile solubility test. The most likely identification is: a. Alpha-hemolytic streptococcus b. Streptococcus pneumoniae c. Staphylococcus aureus d. Staphylococcus epidermidis

b. Streptococcus pneumoniae

Clostridium botulinum and Clostridium tetani produce _____________ endospores? a. Terminal b. Subterminal c. Central d. All of the above

b. Subterminal

Which of the following is the key to virulence in Streptococcus pneumoniae? a. coagulase b. capsule c. catalase d. CAMP

b. capsule

A positive bile esculin reaction is ________________? a. red to pink b. dark brown to black c. light yellow to orange d. blue

b. dark brown to black

A urine culture grows Gram-positive cocci in clusters. To SPECIATE this organism, the technician should perform a coagulase test and a(n): a. catalase b. novobiocin disk test c. oxidase d. beta-lactamase

b. novobiocin disk test

The Gram stain procedure manual calls for acetone-alcohol decolorization for 2 minutes. The best course of action for the newly employed technician would be to: a. Perform the stain according to the procedure manuals instruction b. Perform the stain according to the manufacturer's directions c. Ask a supervisor or trainer if this is indeed the timing to be followed d. Change the timing in the procedure manual and change the date

c. Ask a supervisor or trainer if this is indeed the timing to be followed

Which of the following agents typically cause an infection as a result of animal exposure? a. Clostridium perfringens b. Bacillus cereus c. Erysipelothrix rhusiopathiae d. Actinomyces israelii

c. Erysipelothrix rhusiopathiae

The organism Bacillus cereus would BEST be described by the following Gram's stain reaction: a. Gram positive cocci b. Gram negative cocci c. Gram positive rod d. Gram negative rod

c. Gram positive rod

Many enterococci have acquired resistance to vancomycin. The potential for transfer of this gene to what organism genus represents a serious public health threat? a. Micrococcus b. Streptococcus c. Staphylococcus d. Aerococcus

c. Staphylococcus

A beta hemolytic colony on sheep blood agar is stained and found to be Gram positive cocci. The catalase test is positive and the coagulase test is positive. The organism is most likely: a. Enterococcus faecalis b. Staphylococcus epidermidis c. Staphylococcus aureus d. Escherichia coli

c. Staphylococcus aureus

The optochin disk test is used to identify: a. Haemophilus influenzae b. Group A beta-hemolytic streptococci c. Streptococcus pneumoniae d. Alpha-hemolytic streptococci

c. Streptococcus pneumoniae

An organism that grows as a small, clear beta-hemolytic colony on sheep blood agar, stains as a Gram-positive cocci, and is catalase negative is MOST likely to be which of the following? a. Streptococcus pneumoniae b. Staphylococcus epidermidis c. Streptococcus pyogenes d. Enterococcus faecalis

c. Streptococcus pyogenes

Which of the following is known as the "flesh eating" bacteria? a. Streptococcus pneumoniae b. Staphylococcus epidermidis c. Streptococcus pyogenes d. Enterococcus faecalis

c. Streptococcus pyogenes

Which of the following is the most common bacterial cause of acute pharyngitis? a. Streptococcus pneumoniae b. Staphylococcus epidermidis c. Streptococcus pyogenes d. Enterococcus faecalis

c. Streptococcus pyogenes

In the carbohydrate utilization test a positive reaction (yellow color) indicates what? a. the organism does not use the carbohydrate present in the tube b. the phenylalanine in the medium is deaminated to phenylpyruvic acid c. acid production from the carbohydrate present in the tube d. none of the above

c. acid production from the carbohydrate present in the tube

The viridans streptococci are typically _________ or ______ hemolytic. a. alpha or beta b. beta or gamma c. alpha or gamma d. beta or gamma

c. alpha or gamma

The viridans streptococci can be differentiated from Streptococcus pneumoniae by: a. alpha hemolysis b. morphology c. bile solubility d. catalase reaction

c. bile solubility

The most critical distinction between Staphylococcus aureus and most other staphylococci is: a. phosphatase reaction b. DNA production c. coagulase production d. hemolysis

c. coagulase production

In the differential staining technique for bacteria, the primary stain is: a. iodine b. acetone-alcohol c. crystal violet d. safranin

c. crystal violet

Clostridium difficile is associated with: a. Food poisoning b. pharyngitis c. pseudomembraneous colitis d. difficult childbirth

c. pseudomembraneous colitis

Colonies of Staphylococcus aureus will grow in the presence of salt and ferment mannitol producing colonies surrounded by a _______ halo on Mannitol Salt Agar. a. blue b. pink c. yellow d. black

c. yellow

Which of the following have "molar tooth" colony formation on plated media? a. Clostridium perfringens b. Bacillus cereus c. Erysipelothrix rhusiopathiae d. Actinomyces israelii

d. Actinomyces israelii

Abiotrophia species (nutritionally variant streptococci): a. Will not grow on blood agar unless vitamin B6 is supplied b. Grows when blood culture media is cross-streaked with Staphylococcus aureus c. Resemble viridans streptococci d. All of the above e. None of the above

d. All of the above

Which of the following is a pigment seen in Micrococcus species colonies? a. White b. Yellow c. Orange d. All of the above e. none of the above

d. All of the above

Which Bacillus species is most likely to be used as an agent of bioterrorism? a. Bacillus cereus b. Bacillus not-so-serious c. Bacillus subtilis d. Bacillus anthracis

d. Bacillus anthracis

Staphylococcus aureus can be differentiated from Staphylococcus saprophyticus by which of these tests? a. Catalase Test b. Oxidase Test c. Gram stain d. Coagulase Test

d. Coagulase Test

Which feature distinguishes Erysipelothrix rhusiopathiae from other clinically significant non-spore-forming, Gram-positive bacilli? a. "tumbling" motility b. beta-hemolysis c. more pronounced motility at 25C than 37C d. H2S production

d. H2S production

Which two tests are always positive for Enterococcus species usually isolated from humans? a. NaCl broth and catalase b. Group D Antigen and coagulase c. Bile solubility and optochin d. PYR and LAP

d. PYR and LAP

Which of the following are known as anaerobic diphtheroids? a. Peptostreptococcus anaerobius b. Clostridium perfringens c. Lactobacillus species d. Propionibacterium species

d. Propionibacterium species

The ONPG test allows organisms to be classified as lactose fermenters by testing for which of the following? a. permease b. beta-lactamase c. phosphatase d. beta-galactosidase

d. beta-galactosidase

In a positive PYR test, the addition of a cinnamaldehyde reagent causes a __________ color to be produced. a. blue b. green c. yellow d. red

d. red

In the differential staining technique for bacteria, the counterstain is: a. iodine b. acetone-alcohol c. crystal violet d. safranin

d. safranin

The urease test is used to determine the ability of an organism to split urea by the action of an enzyme urease forming two molecules of ammonia. Ammonia increases the pH and its presence is detected a. by the disappearance of the colonies tested. b. by the clotting of the colonies tested. c. using a hydrolysis indicator which turns bright blue. d. using a pH indicator which turns bright pink.

d. using a pH indicator which turns bright pink.

The importance of accurate bacterial identification cannot be overstated because identity is central to diagnostic bacteriology issues, including: a. Determining the clinical significance of a particular pathogen b. Guiding physician care of the patient c. Determining whether laboratory testing for detection of antimicrobial resistance is warranted d. Determining the type of antimicrobial therapy that is appropriate e. All of the above

e. All of the above

What are the Gram-positive bacilli species?

Bacillus, Corynebacterium, Listeria monocytogenes, Erysipelothrix rhusiopathiae, Lactobacillus, Clostridium, Acintomyces

An organism that grows as a small, grey, glistening, alpha-hemolytic colony on sheep blood agar that dips down in the center like a doughnut is MOST likely which of the following? a. Streptococcus pneumoniae b. Staphylococcus epidermidis c. Streptococcus pyogenes d. Enterococcus faecalis

a. Streptococcus pneumoniae

The most common bacteria isolated as a cause of urinary tract infections is Escherichia coli. What is the reaction when E. coli is subjected to the indole test? a. The test would be positive b. The test would be negative c. The test would not be used for E. coli d. none of the above

a. The test would be positive

Colonies of Lactobacillus are: a. alpha hemolytic b. beta hemolytic c. gamma hemolytic d. None of the above

a. alpha hemolytic

You are testing Gram's stain reagent for quality control and you get the following results: Escherichia coli blue bacilli Staphylococcus aureus blue cocci The best interpretation of these results is: a. no decolorizer was added b. the iodine should be replaced c. no mordant was added d. the staining time with the safranin should be increased

a. no decolorizer was added

The potentially lethal intoxication type of food poisoning associated with improperly canned food is caused by: a. Bacillus cereus b. Clostridium botulinum c. Clostridium perfringens d. Staphylococcus aureus

b. Clostridium botulinum

What organism group forms a "string" in the "other" string test when using the bile solubility reagent? a. Lactobacillus species b. Escherichia species c. Streptococcus species d. Enterococcus species

b. Escherichia species

The oxidase test is most often used to differentiate a. Gram positive bacteria b. Gram negative bacteria c. Mycobacteria d. Fungus

b. Gram negative bacteria

Clostridium perfringens is known for ___________ and __________. a. Small rods and gas gangrene b. Large boxcar-shaped rods and a double-zone of hemolysis c. Translucent colonies and alpha hemolysis d. Rods with spores and pharyngitis

b. Large boxcar-shaped rods and a double-zone of hemolysis

In which type of hemolysis seen in streptococci are the red blood cells in the blood agar only partially lysed resulting in a greenish discoloration of the agar?

Alpha

Which Gram positive organisms are seen in pairs and/or chains of cocci?

Streptococcus

On Gram stain, which Gram positive organism are lancet-shaped cocci in pairs?

Streptococcus pneumoniae

An organism that exhibits the satellite phenomenon around colonies of staphylococci is: a. Haemophilus influenzae b. Neisseria meningitidis c. Neisseria gonorrhoeae d. Klebsiella pneumonia

a. Haemophilus influenzae

Morphologically, in Gram stain, Streptococcus pneumoniae exhibits a. Lancet-shaped cocci in pairs b. Coffee-bean shaped cocci in pairs c. Filamentary chains of bacilli d. Small curved rods

a. Lancet-shaped cocci in pairs

Which staphylococcal species is the most virulent encountered in the clinical laboratory? a. Staphylococcus epidermidis b. Staphylococcus aureus c. Staphylococcus haemolyticus d. Staphylococcus saprophyticus

b. Staphylococcus aureus

A Gram-positive bacilli with a narrow zone of hemolysis is isolated from a blood culture. A motility test is performed and an umbrella-shaped motility is seen in semi-solid media. This organism is MOST likely: a. Listeria monocytogenes b. Corynebacterium diphtheriae c. Bacillus anthracis d. Corynebacterium jeikeium

a. Listeria monocytogenes

Which of the following are anaerobic Gram-positive cocci? a. Peptostreptococcus anaerobius b. Clostridium perfringens c. Lactobacillus species d. Propionibacterium species

a. Peptostreptococcus anaerobius

True or False: A positive reaction in the hippurate hydrolysis test is evidenced by the development of a blue color after addition of the ninhydrin reagent.

True

True or False: Bacillus cereus is an endospore-forming Gram-positive rod that has been shown to cause food poisoning.

True

True or False: Clostridium botulinum and Clostridium tetani produce spores.

True

True or False: Corynebacterium diphtheriae is spread by person-to-person contact or may be transferred by exposure to contaminated objects.

True

True or False: Definitive identification of Corynebacterium diphtheriae requires demonstration of toxin production in the isolate in question.

True

True or False: Group B Streptococcus gives a positive arrow of hemolysis in the CAMP test.

True

True or False: Lactobacillus is a necessary bacterium for a healthy balance in the female vaginal tract.

True

True or False: Novobiocin is used to differentiate Staphylococcus saprophyticus from Staphylococcus epidermidis?

True

True or False: On Gram stain, Actinomyces species can be beaded or branching Gram-positive rods.

True

True or False: Staphylococcus aureus produces the toxin-mediated diseases scalded skin syndrome and toxic shock syndrome.

True

True or False: Staphylococcus epidermidis is the most commonly encountered coagulase negative staphylococci and is an opportunistic pathogen.

True

True or False: Streptococcus agalactiae is a Group B beta-hemolytic streptococci.

True

True or False: The PYR test is used to aid in the identification of a catalase negative, Gram positive cocci.

True

True or False: The aerotolerance test is used to determine if an isolate thought to be anaerobic isolate when the initial plate examination is performed is truly anaerobic.

True

What does an A/A TSI tube look like and what organism is this typical of?

Yellow slant/yellow butt Typical of E. coli