IDT201 Flashcards
What shape does S.aureus appear under light microscopy?
grape-like structures
how does S.aureus look when grown on agar?
1) round golden-yellow colonies
2) hemolysis when on blood agar
what does it mean to be catalase positive?
produces the enzyme “catalase” and is able to convert hydrogen peroxide to water and oxygen.
Why is a catalase test useful in distinguishing staphylococci from streptococci and enterococci?
S. aureus is catalase positive and others are not.
is S. aureus coagulase-positive?
YES. Other staphylococcus species like S.epidermidis are coagulase-negative
what does it mean to be coagulase-positive?
produces the enzyme coagulase
Where is S.aureus found?
colonizes the nose (anterior nares), throat, and/or skin of individuals. Approx 10-20% of the population are long-term carriers of S.aureus.
Where is S.epidermidis normally found?
normal flora on the skin of individuals
Where is S. saprophyticus normally found?
found on the skin surrounding the genitourinary tract. (eg. vagina)
S. aureus infections are normally classed as inflammatory or toxigenic. What is the difference?
inflammatory: skin and skin structure infections. Abscesses
toxigenic: food poisoning
There is an infection at an indwelling catheter. What is the most likely bacteria present at the infection site?
S. epidermidis. It is described as an opportunistic pathogen and likely seen with infections of foreign bodies like IV, catheters, prosthetic implants and shunts.
A young sexually active woman has an infection in her urinary tract. What bacteria is most likely present at the infection site?
S. saprophyticus
What is hyaluronidase?
breaks down hyaluronic acids present in the acellular matrix of connective tissue.
List enzymatic virulence factors
1) coagulase
2) catalase
3) hyaluronidase
4) beta-lactamases
5) nuclease
6) lipase
how is S. aureus spread?
infections can be spread through
1) contact with pus from an infected wound,
2) skin-to-skin contact with an infected person and
3) contact with contaminated objects such as towels sheets, clothing or athletic equipment
