IV : Gram Positive Cocci

Sheep blood agar.

When processing throat swabs for a group A Streptococcus culture, the medium of choice is:

Rejected as unacceptable.

A 21 year old patient presents with pharyngitis. A throat swab is collected and submitted for anaerobic culture. This specimen should be:

LIM broth

A vaginal/rectal swab is collected from a pregnant patient to screen for group B Streptococcus colonization. What is the best medium to use for specimen inoculation?

incubated at 56c.

To quality control the autoclave, a vial of Bacillus stearothermophilus is autoclaved and should then be:

Bacterial suspension was not diluted to the proper concentration.

In a quality control procedure on a new batch of Mueller-Hinton plates using a stock culture of staphylococcus aureus, all the disk zone sizes are too small. The most likely reason for this is that the:

Novobiocin susceptibility

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

Abiotrophia defectiva

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

Bile solubility

Viridans streptococci can be differentiated from Streptococcus pneumoniae by:

Coagulase

A reliable test for distinguishing Staphylococcus aureus from other staphylococci is:

Streptococcus pneumoniae

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

Group D Streptococcus

A gamma-hemolytic Streptococcus that blackens bile esculin agar but does not grow in 6.5% NaCl broth is most likely:

Catalse production and coagulase test.

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

Bile esculin, PYR, acitracin, and hippurate.

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

in the genera Granulicatella and Abiotrophia

"Nutritionally deficient" streptococci are:

Group B streptococci

The organism most commonly associated with neonatal purulent meningitis is:

Streptococcus pyogenes

An important cause of acute exudative pharyngitis is:

Acute glomerulonephritis

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

Group A

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

Group B

A beta-hemolytic Streptococcus that is bacitracin-resistant CAMP positive is:

Latex antigen typing.

Group B, beta-hemolytic streptococci may be distinguished from other hemolytic streptococci by which of the following procedures?

Enterococci often show more antibiotic resistance than group D streptococci.

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

Bile solubility

Streptococcus pneumoniae can be differentiated best from the viridans group of streptococci by:

Relatively resistant to penicillin.

Characteristically, enterococci are:

Hydrolysis os sodium hippurate

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

the most critical distinction between Staphylococcus aureus and other Staphylococcus is:

Coagulase production.

Streptococcus pyogenes.

Which of the following organisms is, to date, considered universally susceptible to penicillin?

Latex antigen typing.

A beta-hemolytic gram-positive coccus was isolated from the cerebrospinal fluid 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?

2-6 hours.

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

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

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:

Furazolidone (100 ug/disk) susceptibility.

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?

CAMP test and S agalactiae

An isolate of 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 the test and the presumptive identification of the unknown Streptococcus?

Enterococcus faecalis

Which of the following may be used as a positive quality control organism for the bile esculin test?

gram + cocci in grapelike clusters, non-motile

General morphology of Staphylococci

Micrococcacea (obsolete)

Staphylococci belongs to the family

Staphylococcus saccharolyticus

Staphylococci is Facultative anaerobes EXCEPT

Catalase

A biochemical test used to separate Staphylococci (+) and Micrococci (+) from Streptococci (-)e

rigorous bubbling / effervescence

+RESULT of Catalase

3% H2O2

+of Catalase uses

F

Do not use colonies from blood agar plate (BAP) as it gives a false positive result

Catalase of Staphylococci (t/f)

Do not use colonies from blood agar plate (BAP) as it gives a false negative result

7.5 - 10% NaCl

Staphylococci is able to grow in

0.04 units of Bacitracin

Staphylococci is resistant to

Beta-hemolytic

Staphylococci

_ on BAP

T

Staphylococcus aureus is known as the most virulent spx (t/f)

gold

Staphylococcus aureus

Aureus means

anterior nares & nasopharynx

Staphylococcus aureus

Normal flora of the

Staphylococcus aureus is a facultative anaerobe

Staphylococcus aureus is a facultative aerobe (t/f)

PCR

Staphylococcus aureus

what will enable detection from the nasal swab

Uniform turbidity

GROWTH/ COLONY MORPHOLOGY of Staphylococcus aureus

on broth

creamy, white with pinhead

GROWTH/ COLONY MORPHOLOGY of Staphylococcus aureus

Growth in BAP as

smooth circular and opaque colonies with oil-like butyrous appearance

GROWTH/ COLONY MORPHOLOGY of Staphylococcus aureus

On plates, they produce

Jet black colonies

GROWTH/ COLONY MORPHOLOGY of Staphylococcus aureus

on tellurite agar/ Vogel Johnson medium

1. Coagulase Test

2. Mannitol Salt Agar Test / Mannitol Salt Fermentation Test

3. DNAse / Thermonuclease Test

4. Latex Agglutination Test for Protein A

Test for Identification of Staphylococcus aureus

Coagulase Test

DEFINITIVE TEST for S. aureus; test to differentiate from other Staphylococcus

1. Slide coagulase (screening)

2. Tube coagulase (confirmatory)

2 types of coagulase test

Slide coagulase (screening)

detects cell bounded coagulase/ clumping factor

Rabbit plasma (obtained using EDTA)

Reagent of Slide coagulase (screening)

clumping

+result of Slide coagulase (screening)

Tube coagulase (confirmatory)

Detects the free coagulase

Rabbit plasma

Reagent of Tube coagulase (confirmatory)

clot

+result of Tube coagulase (confirmatory)

selective medium

Mannitol Salt Agar Test / Mannitol Salt Fermentation Test is known to be a _ medium

MSA (1% Mannitol)

media of Mannitol Salt Agar Test / Mannitol Salt Fermentation Test

7.5% NaCl

inhibitor of Mannitol Salt Agar Test / Mannitol Salt Fermentation Test

Phenol Red

pH indicator of of Mannitol Salt Agar Test / Mannitol Salt Fermentation Test

yellow colonies

+result of of Mannitol Salt Agar Test / Mannitol Salt Fermentation Test

DNAse / Thermonuclease Test

detects deoxyribonuclease

DNA + Methyl Green

Dye Method of DNAse / Thermonuclease Test

= clear zone around the colonies

DNA + 0.1 % Toluidine Blue

Dye Method of DNAse / Thermonuclease Test

= pink zone around the colonies

cells are dead

Dye Method of DNAse / Thermonuclease Test

DNA + 0.1 % Toluidine Blue + pink zone =

cells are alive

Dye Method of DNAse / Thermonuclease Test

DNA + 0.1 % Toluidine Blue - blue zone =

clearing of agar around the colonies

Dye Method of DNAse / Thermonuclease Test

HCl PRECIPITATION METHOD + result

1. S - Serratia marcescens

2. M - Moraxella catarrhalis

3. A - Aeromonas

4. S - Streptococcus pyogenes

5. H - Helicobacter pylori

6. V - Vibrio cholerae

7. S - Stenotrophomonas maltophilia

8. S - Staphylococcus aureus

Dye Method of DNAse / Thermonuclease Test

Bacteria which are DNAse test (+)

Latex Agglutination Test for Protein A

Antigen detection

S. aureus with Protein A

has inert particles to which antibody (Fc fragment) binds

Latex Agglutination Test for Protein A

detects specific bacterial antigens

1. S. pneumoniae

2. N. meningitidis

3. H. influenzae

4. N. gonorrhoeae

Latex Agglutination Test for Protein A detects specific bacterial antigens such as

1. Lipase

2. Hyaluronidase / T Factor / Duran-Raynal Factor

3. Beta-lactamase

4. Staphylokinase / Fibrinolysin

5. Coagulase

6. DNAse / Thermonuclease

7. Beta-hemolysin

8. Protein A

9. Gelatinase

VIRULENCE FACTOR of S. aureus

Enzymes:

Lipase

a fat splitting enzyme, associated with SKIN INFECTIONS such as boils, carbuncles, and furuncles

Hyaluronidase / T Factor / Duran-Raynal Factor

a spreading factor that enhances invasion to tissue (joints = arthritis)

Hyaluronidase / T Factor / Duran-Raynal Factor

causes hydrolysis of hyaluronic acid

Beta-lactamase

makes S. aureus resistant to penicillin

Beta-lactamase

hydrolysis of penicillin

Staphylokinase / Fibrinolysin

dissolves fibrin clot and may enable the infection to spread once the clot is dissolved

Coagulase

causes bacteria to agglutinate in plasma;

Coagulase

converts fibrinogen to fibrin;

Coagulase

may coat neutrophils with fibrin formed to protect organisms from phagocytosis

DNAse / Thermonuclease

causes degradation of DNA

DNAse / Thermonuclease

decreases the viscosity of exudate giving organisms more mobility

Beta-hemolysin

causes destruction of RBC;

Beta-hemolysin

responsible for beta-hemolysis of S. aureus; ANEMIA

hemolysin

lyse RBC

Protein A

prevents phagocytosis;

Protein A

has the ability to bind Fc portion on IgG;

Protein A

found on the CELL WALL

Gelatinase

Gelatin-→amino acid

liquefy

Gelatinase

At ref temp: (+) gel will

solidify

Gelatinase

At ref temp: (-) gel will

1. Enterotoxins

2. Exfoliatin A & B / Epidermolytic Toxin A and B

3. Panton-Valentin Leukocidin

Toxins of S. aeureus

Enterotoxins

a group of seven heat-stable proteins (A, B, C, C2, D, E, F).

Enterotoxin A and B

Most staphylococcal-related food poisonings are associated with Enterotoxin -.