Staphylococcus aureus

Question 1

What is the General characteristics of the genus Staphylococcus.?

Answer 1

Genus: Staphylococcus ,Gram positive cocci ,Non-motile ,Non-sporing ,Facultative anaerobes ,Catalase positive also the Cells occur in grapelike clusters because cells division occurs
along different planes.

Question 2

The Staphylococcus is Divided in two groups based on coagulase production which is

Answer 2

1-:Coagulase-positive Staphylococci (CoPS) Staphylococcus aureus

2- Coagulase-negative Staphylococci (CoNS) Staphylococcus epidermidis
Staphylococcus saprophyticus .

Question 3

Staphylococcus aureus charectrized by

Answer 3

Gram positive cocci, arranged in grape-like clusters.
Catalase and coagulase positive
Facultative anaerobes, grow well on ordinary media at 37 °C.
Sometimes produce a β-hemolytic appearance on blood agar (clear zone
around colony due to lysis of red cells).
They can tolerate high concentrations of salt (5-10%) in culture media.
The most clinically significant species of staphylococcus  Responsible for a number of infections

Question 4

Staphylococcus aureus can cause a lot infection, mention 5 .

Answer 4

 Skin infections
 Wound infection
 Food poisoning
 Pneumonia
 Bacteremia
 Toxic shock syndrome (TSS)

Question 5

Mention 4 virulence ( enzyme ) and there activity?

Answer 5

Coagulase : Converts fibrinogen to fibrin in plasma
Deoxyribonuclease (Dnase) : Breaks down DNA
Staphylokinase : Breaks down fibrin
Lipase :Break down the lipid

Question 6

Mention 4 Virulence factor (toxins) and there activity?

Answer 6

Enterotoxins: Causes vomiting and diarrhoea
Haemolysin: RBCs lysis
toxin (TSST): servals condition fever, hypotension and shock can leads to death .

Question 7

What is the type of specimen

Answer 7

Skin or wound swab, Blood or Sputum Nose swab ( for MRSA screening)

Question 8

Culture.?

Answer 8

Blood agar or Mannitol salt agar (MSA) Incubate at 37°C overnight

Question 9

Colony morphology

Answer 9

Blood agar: Golden colonies (sometimes β-hemolytic)

MSA: growth, yellow colonies

Question 10

Identification tests

Answer 10

Gram stain:Gram positive cocci in clusters
Catalase:positive
Coagulase: positive
DNase: positive

Question 11

What is the Treatment

Answer 11

cephalosporins, oxacillin or flucloxacillin.

Question 12

Any antibiotics resistance ?

Answer 12

penicillins and cephalosporins.and in 2002 , vancomycin-resistant Staphylococcus aureus

Question 13

What is Control and prevention of staphylococcal infections

Answer 13

The screening of infected and colonised patients
The early detection of MRSA
Improved hand hygiene
The prudent use of antibiotics