Staphylococci and Related Diseases

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Questions and Answers

Which of the following Staphylococcus species are coagulase positive?

S. aureus, S. intermedius, S. pseudintermedius (correct)

S. lugdunensis, S. schleiferi, S. epidermidis

S. aureus, S. epidermidis, S. saprophyticus

S. hyicus, S. delphini, S. lugdunensis

Which of the following toxins is considered less toxic to cells?

δ-hemolysin (correct)

β-hemolysin

γ-hemolysin

α-hemolysin

What is the mechanism of action of Protein A?

It acts on sphingomyelin in the plasma membrane of erythrocytes.

It binds to the Fc portion of IgG, inhibiting phagocytosis. (correct)

It directly lyses erythrocytes.

It binds to the Fab portion of IgG, preventing antibody binding.

Which of the following staphylococcal toxins is lethal to polymorphonuclear leukocytes?

Panton-Valentine leukocidin (PVL) (C) Signup and view all the answers

Which of these is NOT a characteristic of Staphylococci?

Spore-forming (D) Signup and view all the answers

Which of the following staphylococcal species is the most common cause of prosthetic valve endocarditis?

S. epidermidis (A) Signup and view all the answers

Which of the following is a common source of hospital-acquired infections?

S. epidermidis (B) Signup and view all the answers

What is the Greek term for "bunches of grapes" which describes Staphylococci's appearance?

Staphle (A) Signup and view all the answers

Which type of toxin is associated with Ritter disease, a skin condition mainly affecting newborns and infants?

Exfoliative toxin (B) Signup and view all the answers

Which of the following staphylococcal species is associated with UTIs in young women?

S. saprophyticus (A) Signup and view all the answers

What is the basis of the slide coagulase test?

Clumping factor causing bacterial cells to agglutinate in plasma (A) Signup and view all the answers

What is the name of the test used to identify Staphylococci based on their ability to coagulate plasma?

Coagulase test (D) Signup and view all the answers

Which of these toxins is associated with Staphylococcal pseudomembranous enterocolitis?

Enterotoxin B (C) Signup and view all the answers

Which of these is NOT a type of hemolysin produced by S. aureus?

Epsilon (C) Signup and view all the answers

Which of these is a potential consequence of TSS caused by Staphylococci?

All of the above (D) Signup and view all the answers

Which of these is a common characteristic of both Staphylococci and Micrococci?

Catalase production (A) Signup and view all the answers

Which of the following is NOT a characteristic of Staphylococcus aureus?

Is typically less virulent than other Staphylococcus species. (D) Signup and view all the answers

What is the mechanism by which Staphylococcus aureus develops resistance to methicillin?

Production of an altered penicillin-binding protein (PBP) called PBP2a. (C) Signup and view all the answers

Which of the following statements is TRUE about Staphylococcus lugdunensis?

It can cause both community-associated and hospital-acquired infections. (A) Signup and view all the answers

What is the name of the gene responsible for methicillin resistance in Staphylococcus aureus?

mecA (C) Signup and view all the answers

What is the 'gold standard' method for detecting methicillin resistance in Staphylococcus aureus?

Detection of the mecA gene by molecular methods. (C) Signup and view all the answers

Which of the following is a TRUE statement about Staphylococcus saprophyticus?

It is a common cause of urinary tract infections in young women. (B) Signup and view all the answers

Which of the following statements is TRUE regarding the treatment of methicillin-resistant Staphylococcus aureus (MRSA)?

Vancomycin remains the primary treatment option. (B) Signup and view all the answers

What is the most appropriate test for determining methicillin resistance in Staphylococcus aureus isolates?

A molecular test for the mecA gene. (D) Signup and view all the answers

Study Notes

Staphylococci

Gram-positive cocci, arranged in clusters ("bunches of grapes")
Nonmotile, non-spore-forming, aerobic or facultatively anaerobic
Catalase-positive
Several species, including S. aureus, S. epidermidis, S. saprophyticus, S. lugdunensis
Important in human infections, often causing food poisoning, skin infections, and other diseases.
S. aureus is the most common and clinically significant species

Staphylococcal Diseases

Food poisoning: Caused by heat-stable enterotoxins
Scalded skin syndrome (SSS): Caused by exfoliative toxins
Toxic shock syndrome (TSS): Caused by toxic shock syndrome toxin-1 (TSST-1)
Impetigo: Superficial skin infection, can progress deeper
Cellulitis: Skin infection, can progress deeper
Carbuncles: Deep skin abscesses

Staphylococcal Toxins

Enterotoxins: Heat-stable, cause vomiting and diarrhea (A-E, G-J groups)
Exfoliative toxins: Cause scalded skin syndrome
Toxic shock syndrome toxin-1 (TSST-1): Causes toxic shock syndrome
Cytolytic toxins (hemolysins and leukocidins): Damage cells
Panton-Valentine leukocidin (PVL): Toxin lethal to polymorphonuclear leukocytes

Coagulase

Enzyme produced by some staphylococci
Positive test results in clot formation in plasma

Differentiation Between Staphylococci and Micrococci

Use tests like modified oxidase, anaerobic acid production from glucose/glycerol, resistance to bacitracin, lysosome/lysostaphin assay.

Antimicrobial Susceptibility

Testing crucial for S. aureus and S. lugdunensis infections
Testing of S. saprophyticus from urine not usually required

Methicillin-Resistant Staphylococci (MRSA)

Isolates resistant to nafcillin or oxacillin
Vancomycin often the treatment of choice for MRSA and MRSE
Screening for MRSA involves oxacillin-salt agar plate and/or detection of the mecA gene

Vancomycin-Resistant Staphylococci

Vancomycin often the drug of choice
Infections may require different approaches, emphasizing prompt testing

Macromolecule Resistance

Modified disk diffusion tests used to assess resistance
Resistance mechanisms can affect treatment pathways

Diagnostic Procedures

Gram stains, catalase tests, coagulase tests
Differentiating tests used to identify specific staphylococcal and micrococcal species

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Description

This quiz covers essential information about Staphylococci, focusing on their characteristics, various species, and the diseases they cause. Learn about the significant role of S. aureus in human infections and the toxins associated with these bacteria. Test your understanding of staphylococcal diseases, including food poisoning and skin infections.