Gram positive bacteria

• What type of bacteria is Staphylococcus?

  Gram positive bacteria
• How many species of staphylococci are there?

  Approximately 30 species
• What are the metabolic capabilities of staphylococci?

  They are facultative anaerobes capable of both fermentation and respiration
• How can staphylococci be distinguished from streptococcus?

  By their catalase positive reaction with 3% H2O2
• What is one of the major products formed when staphylococci ferment sugars?

  Lactic acid
• What is the G+C content of staphylococci similar to?

  Lactic acid bacteria
• How do staphylococci appear under the microscope?

  In grape-like clusters of cocci
• What does the term "staphylococcus" derive from?

  It comes from the Greek word "staphyle," meaning bunch of grapes
• What type of hemolysis does Staphylococcus aureus exhibit on blood agar?

  Beta-hemolysis
• What is the coagulation reaction associated with Staphylococcus aureus?

  It causes plasma to clot by converting fibrinogen to fibrin
• What distinguishes Staphylococcus aureus from Staphylococcus epidermidis and Micrococcus?

  It is coagulase positive
• What is a common method used to perform the coagulase test for Staphylococcus aureus?

  Latex bead agglutination
• Where is Staphylococcus aureus commonly found in the human body?

  As a major component of normal flora in the skin and nose
• What types of infections can Staphylococcus aureus cause in newborns and immunocompromised patients?

  Pneumonia and septicaemia
• How does Staphylococcus aureus invade subcutaneous tissue during skin infections?

  With the aid of lipases
• What is the sequence of events in a skin infection caused by Staphylococcus aureus?

  Inflammation → white blood cells → toxins kill cells → pus formation → coagulate forms a fibrin barrier
• What are some skin conditions caused by Staphylococcus aureus?

  Boils, carbuncles, and impetigo
• What is septic arthritis and how is it related to Staphylococcus aureus?

  It is an infection of the joint, often seen in babies and young children caused by Staphylococcus aureus
• How can bacteria gain access to joints to cause septic arthritis?

  Via bloodstream, from an injury, or during surgery
• What is osteomyelitis?

  It is an infection of the bone
• How can bacteria be introduced to bones to cause osteomyelitis?

  Through direct inoculation during trauma or surgery
• What is hematogenous osteomyelitis?

  It is an infection of the bone that occurs via the bloodstream
• What is scalded skin syndrome (SSSS) and what causes it?

  It is caused by a toxin produced by phage group 2 Staphylococcus aureus, leading to desquamation
• What is the role of exfoliative toxins in SSSS?

  They affect the skin at remote sites leading to desquamation
• Who is most affected by scalded skin syndrome?

  Mostly young children, particularly neonates
• What are hemolysins and their effect?

  They are toxins that lyse erythrocytes and damage various cell types
• What is the function of leukocidin produced by Staphylococcus aureus?

  It kills white blood cells to allow bacteria to survive
• What is the effect of enterotoxins A, B, and D?

  They cause food poisoning with severe diarrhea and vomiting
• What is TSST-1 and its role?

  It is a superantigen that stimulates T-cells to release TNF, causing shock
• What is the role of lipases produced by Staphylococcus aureus?

  They are lipid hydrolyzing enzymes that allow organisms to invade tissues
• What is fibrolysin and its function?

  It dissolves fibrin clots, aiding in the spread of bacteria
• What is the significance of extracellular coagulase?

  It may be involved in forming the fibrin wall of abscesses
• What is Panton-Valentine leukocidin and its association?

  It is produced by strains carrying the lukF and lukS genes and is associated with community-acquired infections
• How does food poisoning occur with Staphylococcus aureus?

  It is caused by ingestion of preformed toxin from contaminated food
• What is the onset and recovery time for food poisoning caused by Staphylococcus aureus?

  Both occur within a few hours
• What is the effect of the enterotoxin on the gastrointestinal system?

  It inhibits water absorption, leading to explosive diarrhea
• What is the treatment for Staphylococcus aureus infections?

  Standard treatment includes synthetic penicillins like oxacillin and methicillin
• What is MRSA and how did it evolve?

  MRSA is methicillin-resistant Staphylococcus aureus that evolved due to altered penicillin-binding proteins and penicillinase production
• When was the first MRSA isolated?

  In the 1960s
• What has been the trend in MRSA infection rates in hospitals since the 1990s?

  Rates have stabilized after a significant increase