Bacteriology - Staphylococcus Flashcards
What is the etiology for “Staphylococcus”?
Greek: staphyle - bunch of grapes, kokkos - grain or berry
What are the main characteristics of the Staphylococcus genus?
Staphylococci are:
- Facultative anaerobes
- Catalase positive
- Gram positive
How are Staphylococci suited to their environment?
- Resistant to dry conditions
- Resistant to high salt concentrations
- Well suited to living on skin
- Can survive long periods in the environment
- Part of the normal flora of the URT
What are the medically important species of Staphylococcus? [3]
There are >30 species of Staphylococcus, however only 3 are medically important:
- Staphylococcus aureus
- Staphylococcus epidermidis
- Staphylococcus saprophyticus
Define faculative anaerobe.
A facultative anaerobe is an organism that makes ATP by aerobic respiration if oxygen is present, but is capable of switching to fermentation or anaerobic respiration if oxygen is absent.
Name the pathogenic coagulase-negative Staphylococci species. [2]
- Staphylococcus epidermidis
- Staphylococcus saprophyticus
What diseases do the main Staphylococci species cause?
- Staph. aureus: wide range of major and minor infections
- Staph. epidermidis: opportunistic infection, especially associated with foreign bodies
- Staph. saprophyticus: UTIs
Outline the characteristics of Staphylococcus aureus.
- Gram positive coccus
- 1 μm diameter
- Arranged in grape-like clusters
- Non-sporing
- Non-motile
- Usually non-capsulate
- Colonies: circular, 2-3 mm diameter, smooth, shiny surface, opaque, golden-yellow.
What are the main diagnostic features of Staphylococcus aureus?
- Production of extracellular enzyme, coagulase, which converts plasma fibrinogen into fibrin, aided by an activator present in plasma.
- Production of thermostable nucleases that break down DNA.
- Production of a surface-associated protein known as clumping factor or bound coagulase that reacts with fibrinogen.
