Chain of Infection: S. Aureus

Question 1

Why is S. Aureus relevant in dentistry?

Answer 1

• classic pathogen for HAIs
• overlooked source of carriage and infection
• can be detected in the dental surgery environment
• can be detected in dental instruments

Question 2

What are the 6 links in the chain of infection?

Answer 2

• infectious agent
• reservoir
• portal of exit
• mode of transmission
• portal of entry
• susceptible host

Question 3

Describe the type of bacteria staphylococcus aureus is

Answer 3

gram positive cocci prone to clumping

Question 4

Name a virulence factor associated with staphylococcus aureus and how it works

Answer 4

• PVL toxic
  
  • Panton Valentine Leucocidin
  • kills white blood cells
    
    • penetrates the membrane
    • cascade of inflammatory event

Question 5

What is the characteristic appearance of a PVL+ staphylococcus aureus infection

Answer 5

• ‘spider bite’ like
  
  • well circumscribed
  • soft tissue boils
• difficult to treat
  
  • recurrent

Question 6

What are the two strains of staphylococcus aureus in terms of antimicrobial susceptibility?

Answer 6

• flucloxacillin sensitive (MSSA)
  
  • can treat with flucloxacillin
    
    • methicillin is laboratory equivalent
• flucloxacillin resistant (MRSA)
  
  • treat with vancomycin
    
    • for severe infections
  • oral options for less severe infections

Question 7

Where does the majority of staphylococcus aureus reside?

Answer 7

• nose - 27%
• hand - 27%
• pharynx - 10-20%

Question 8

Provide examples of oral infections with staphylococci

Answer 8

• angular cheilitis
• staphylococcal mucositis
• parotitis
• endodontic and implant infections
• osteomyelitis

Question 9

What are possible exogenous sources of staphylococcus aureus?

Answer 9

• air/water syringe
• dental chair
• dental impression gun
• dental appliances
• dental handpieces

Question 10

What are the most common portals of exit for staphylococcus aureus?

Answer 10

• hands
• aerosols from handpieces

Question 11

What are the most common modes of transmission for staphylococcus aureus?

Answer 11

• hands/environment
• inadequately decontaminated handpieces

Question 12

What are the possible portals of entry for staphylococcus aureus?

Answer 12

• depends on the reservoir/mode of transmission
  
  • surgical procedures

Question 13

Who are the susceptible hosts for staphylococcus aureus?

Answer 13

• all patients undergoing surgical treatment
• patients with higher carriage rates of s. aureus
  
  • antibiotic users
• patients more susceptible to infections