staphlococcus

Question 1

when identifying the species of a bacterial infection, how do you get to staphlococcus?

Answer 1

once you get to gram positive
- identify if its a cocci
- in clusters
(chains is strep)

Question 2

once you have identified the infection as staphlococci, how do you find out further what species it is?

Answer 2

• carry out a coagulase or a dnase test
• coag positive = S. aureaus
• coag negative = coagulase negative staphlococcus eg S. epidermidis

Question 3

what is the main coagulase positive staph?

Answer 3

S. aureaus

Question 4

how is S. aureaus spread?

Answer 4

aeresol and touch
- can shed skin - also this way

Question 5

what are the virulence factors of S. aureas? (how it causes disease)

Answer 5

• pore-forming toxins
• proteases break down dna and proteins
• toxic shock syndrome - mass cytokine release
• protein A binds to Ig in wrong orientation

Question 6

what is meant by “toxin mediated” and “pyogenic” effects caused by S. aeureas?

Answer 6

• toxin-mediated means the effects caused by the toxins released by the bacteria and not directly because of the bacterias invasion
• pyogenic means the direct effects caused by the bacterias invasion

Question 7

name the toxin-mediated effects of S. aureaus.

Answer 7

• scolded skin
• toxic shock syndrome
• food poisoning

Question 8

name the pyogenic effects of S. aureaus.

Answer 8

• wound infections
• absesses
• impetigo - wound crust or boils
• septicaemia - sepsis
• osteomyelitis - bone infection
• pneumonia - lung infection
• endocarditis - heart valve infection

Question 9

outline the drugs we use to treat S. aureus and make note of the species resistance.

Answer 9

• usually we can treat with B-lactams
• however it can become resistant as is known as methicillin-resistant staph aureus (MRSA)
• it is therefore resistant to:
• B-lactams
• gentamicin
• erythromycin
• tetracycline

in this case we treat with:
- vancomycin, linezolid, daptomycin.

Question 10

name the 2 important coagulase negative staphlococci.

Answer 10

• S. epidermidis
• S. saprophyticus

Question 11

outline the species S. epidermidis and its virulence factors.

Answer 11

• normal bacteria in flora on the skin
• infection common in prosthetics

virulence:
- forms biofim

Question 12

what medication is used to treat S. epidermidis?

Answer 12

vancomycin
however highly resistant to certain things

Question 13

what medication is used to treat S. saprophyticnus?

Answer 13

its not as resistant so treated with nitrofuranotin

Question 14

outline the species S. saprophyticus and its virulence factors.

Answer 14

• acute cystic
• second most common baccyT in UTIs

virulence factors:
- contains haemoagglutination for adherance to uroepithelium
- contains urease which breaks down urea - making the environment more acidic