Staphylococci Characteristics and Tests

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Questions and Answers

What does a purple colored reaction after adding Kovacs reagent indicate?

Presence of oxidase enzyme (correct)

Presence of glucose

Presence of bile salts

Presence of bacteria

Which characteristic helps differentiate Staphylococcus from Streptococcus?

Shape of organisms

Colony color

Catalase test results (correct)

Presence of spores

What does the presence of bubble formation in the catalase test indicate?

Negative reaction for Micrococci

Positive reaction for Staphylococci (correct)

Positive reaction for Streptococcus

Negative reaction for Coagulase

Which method detects clumping factor in the coagulase test?

Slide Coagulase Method Signup and view all the answers

What does the term 'Gram + cocci' indicate about the organism's morphology?

It forms clusters and is spherical Signup and view all the answers

How can one differentiate Staphylococcus aureus from Coagulase Negative Staphylococci (CoNS)?

Using the Coagulase test Signup and view all the answers

Which characteristic of an organism on a Blood Agar Plate suggests it needs oxygen for growth?

Facultative anaerobism Signup and view all the answers

What color change indicates a positive anaerobic acid production test for Staphylococci?

Yellow Signup and view all the answers

Which feature distinguishes Streptococci during a catalase test?

They do not form bubbles Signup and view all the answers

Which of the following Staphylococcus species is primarily associated with nosocomial infections related to implanted medical devices?

S.epidermidis Signup and view all the answers

What is the purpose of the bacitracin test when differentiating between Staphylococcus and Micrococcus?

It indicates susceptibility to antibiotics. Signup and view all the answers

How does the result of the lysostaphin test correlate with bacitracin results?

They are inversely proportional. Signup and view all the answers

During the oxidase test, which group of bacteria is Staphylococci differentiated from?

Micrococci Signup and view all the answers

What is the color indication in an open/aerobic tube for the glucose medium if no acid is produced?

Purple Signup and view all the answers

Which test is used to assess anaerobic acid production in Staphylococci?

Oxidation-Fermentation test Signup and view all the answers

Which group of coagulase negative staphylococci is commonly associated with urinary tract infections?

S.saprophyticus Signup and view all the answers

Which of the following species is associated with urinary tract infections?

S.saprophyticus Signup and view all the answers

What type of bacteria are staphylococci classified as?

Gram-positive cocci Signup and view all the answers

Which test is primarily used to differentiate Micrococcus from coagulase negative Staphylococcus?

Oxidase test Signup and view all the answers

Which species of coagulase negative staphylococci is known for its potential pathogenicity on human skin?

S.epidermidis Signup and view all the answers

Which statement correctly describes Staphylococcus aureus?

It can produce a positive coagulase test. Signup and view all the answers

What is the general habitat of staphylococci species?

Skin, mucous membranes, and intestines Signup and view all the answers

Which species is categorized under the unspecified group of coagulase negative staphylococci?

S.lugdunensis Signup and view all the answers

Which of the following statements is true regarding S.saccharolyticus?

It is an obligate anaerobe. Signup and view all the answers

What is the most significant virulence factor of Staphylococcus aureus?

Coagulase Signup and view all the answers

Which of the following characteristics is TRUE for Staphylococcus aureus?

It is a halophilic organism Signup and view all the answers

What type of infections is Staphylococcus aureus chiefly responsible for?

Skin, wound, and deep tissue infections Signup and view all the answers

How is Staphylococcus aureus commonly transmitted to humans?

Direct exposure from unwashed hands and inanimate objects Signup and view all the answers

Which of the following statements about food poisoning caused by Staphylococcus aureus is correct?

It involves enterotoxins A and B Signup and view all the answers

What color is Staphylococcus aureus typically associated with when grown on Blood Agar Plate (BAP)?

Golden yellow Signup and view all the answers

Which coagulation property is indicative of Staphylococcus aureus?

True coagulase-positive Signup and view all the answers

Pseudomembranous enterocolitis is mostly associated with which organism?

Clostridium difficile Signup and view all the answers

What is the primary role of Hyaluronidase in S.aureus infections?

It degrades hyaluronic acid, facilitating the spread of infection. Signup and view all the answers

What is a common symptom associated with toxic shock syndrome caused by S.aureus?

Nausea or sickness Signup and view all the answers

Which enzyme produced by S.aureus is responsible for dissolving fibrin clots?

Staphylokinase Signup and view all the answers

What is the purpose of the coagulase test in identifying S.aureus?

To detect cell-bound coagulase or clumping factor Signup and view all the answers

What does β-Lactamase do in S.aureus?

It provides resistance to penicillin and similar antibiotics. Signup and view all the answers

Which toxin is associated with food poisoning from S.aureus?

Enterotoxin A Signup and view all the answers

What effect does Lipase have in the context of S.aureus infections?

It dissolves lipids, allowing bacterial entry. Signup and view all the answers

In which methods is the coagulase detected?

Slide method and tube method Signup and view all the answers

Study Notes

General Characteristics of Staphylococci

Nonmotile, non spore-forming, facultative anaerobes.
Gram-positive cocci have a grape-like appearance and cluster together.
Positive oxidase reaction indicated by purple color with Kovacs reagent.
Blood Agar Plate (BAP) serves as primary media for microbial identification, producing pinhead, creamy, golden colonies.

Catalase Test

Staphylococci are catalase positive; Streptococci are catalase negative.
Bubble formation in the presence of hydrogen peroxide indicates a positive reaction.

Coagulase Test

Differentiates Staphylococcus aureus (coagulase-positive) from Coagulase Negative Staphylococci (CoNS, coagulase-negative).
Clot formation indicates a positive result for S. aureus.
Two methods: slide (presumptive detection) and tube (confirmatory test).

Key Species of Coagulase Negative Staphylococci (CoNS)

S. epidermidis: Associated with nosocomial infections, particularly in implanted medical devices.
S. saprophyticus: Known for causing urinary tract infections (UTIs).
S. lugdunensis: Related to catheter-associated bacteremia and infective endocarditis.
S. haemolyticus: Occasionally linked to native valve infections and septicemia.

Staphylococcus Aureus

Most clinically significant species of Staphylococci.
True coagulase-positive and highly virulent.
Produces coagulase, which forms fibrin clots that help evade host immune response.
Exhibits halophilic properties; grows best in 7.5% to 10% NaCl on Mannitol Salt Agar.
Beta-hemolytic on BAP, appearing golden yellow.

Virulence Factors of S. Aureus

Coagulase: Protects bacteria from phagocytosis by forming fibrin clots.
Hyaluronidase: Acts as a spreading factor, facilitating tissue invasion by degrading hyaluronic acid.
Staphylokinase: Dissolves fibrin clots, aiding in the spread of infection.
Lipase: Breaks down lipids, aiding bacterial entry into tissues.
DNAse: Degrades DNA, contributing to tissue damage.
β-Lactamase: Enzyme conferring resistance to penicillin.

Disease Associations

Commonly responsible for skin, wound, and soft tissue infections.
Associated with food poisoning due to enterotoxins (A, B, C1, C2, D, E, G-J).
May cause toxic shock syndrome (TSST-1) linked to the use of absorbent tampons.

Laboratory Tests for Differentiation

Catalase Test: Differentiate Staphylococcus from Streptococcus.
Coagulase Test: Differentiate S. aureus from other staphylococci.
Oxidase Test: Distinguish Micrococcus from CoNS.
Bacitracin Test: Advanced differentiation of Micrococcus species.

Identification Tests Summary

A combination of tests, including catalase, coagulase, and oxidase, is essential for accurate identification of Staphylococci species in clinical microbiology.

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Description

This quiz covers the general characteristics of Staphylococci, including their catalase and coagulase tests. You'll learn about their identification on media like Blood Agar Plates, and the significance of coagulase-negative Staphylococci. Test your knowledge on these important microbiological concepts.