Staph & Strep Flashcards
What does the catalase test detect the presence of?
Catalase enzyme in aerobic organisms
What can the catalase test differentiate?
Staphylococci from streptococci and helps to confirm gram stain observations
What are the two recognised stphylococci used of medical importance?
Staphylococcus aureus
Staphylococcus epidermidis
Are staphylococci pathogenic?
Not always they are a normal part of the flora of URTI and skin
how to differentiate the two staphylococci?
A diagnosis on manitol salts agar
S.aureus ferments mannitol, creating acid, changing pH, changes from yellow to red
How is S. aureus disease transmitted?
Touch from an infected but asymptomatic person to a susceptible individual
Also from contaminated food
What is S. aureus caused by?
Acne, boils, pimples, pneumonia, carditic, meningitis
Are most staphylococcal infections pus forming?
Yes
Is alpha toxin hemolysin from S. aureus pore forming?
Yes
What does hemolysin do when infected?
Lyses red blood cells by inserting into their membrane and forming a hole
Host cell contents leak
What does S. aureus produce?
Coagulase, a tissue destroying enzyme
What is the coagulase test?
Test to see if an organism converts fibrin to fibrinogen
What is S. aureus leucocidin?
Another toxin that seperates the components that cats together to damage membranes
What does S. aureus leucocidin target?
White bloods cells
Attcking against the immune system
What is toxic shock syndrome?
A complication of S . aureus infection
What are the symptoms of toxic shock?
High fever
Rash
Vomiting
Diarroea
Death
What is the cause of toxic shock?
The use of highly absobant tampons
What is a treatment of S. aureus?
Penicillin and cephalosporin
How do the treatments work?
Inhibit bacterial cell wall biosynthesis and prevent cross-linking in the peptidoglycan layer
What is beta-lactamases?
Enzymes produced by bacteria
(mechanism of resistance)
What does MRSA stand for?
Methicillin resistant staphylococcus aureus
What is MRSA?
Infections that are resistant to many drugs
How to prevent S. aureus infection?
Imposible to prevent
People carry it without knowing
Good hygiene
Avoiding contact
Keeping wounds covered
What distance is the best fro pathogens to trnasmit?
Short distances
Does stretococci and staphylococcus areus have a thin ot thick cell and does it dry easily?
They have thich cell walls and are more resistant to drying
What are the symptoms of URTI?
Common cold
Annoying but not life threatning
What are the symptoms of LRTI?
problematic
Bacterial / pneumonia
Big issue for the immunocompromised or elderly
What does URTI stand for?
Upper respiratory tract infection
Is URTI streptococci gram positive and what is the shape?
Gram positive and spherical bacteria in chains not clusters
What does streptococci commonly cause?
Strep throat
How can streptococcus be differentiated from staphylococcus?
Gram stain arrangement
Catalase test
Blood agar homolysis
What can stretococci also produce?
Homolysins
What are homolysins?
Lysis of red blood cells
What are the types of hemolysis?
Alpha
Beta
Gamma
What is alpha haemolysis?
Partial or green haemolysis
What is beta haemolysis?
Complete lysis of red blood cells
What is gamma haemolysis?
Not showing typical alpha or beta haemolysis
What is strep throat?
A bacterial infection of the throat, inflammation and pain, severe sore throat
What do S. pyogenes produce in strep throat?
Hemolysin
Lyses red blood cells which cause beta-hemolysis on blood agr pkates
What are the symptoms of strep throat?
Enlarged tonsils
Red spots on the palate
Mild fever
Generally feeling unwell
Tender lymph nodes
What are some treatments of strep throat?
Antibiotics
How to diagnose strep throat?
Rapid antigen detection systems
Culture in a blood agar plate
What is scarlet fever?
Exotoxins from streptococcus acts as superantigens, causing host inflammation and tissue destruction
What are the symptoms of scarlet fever?
A body wide infection
Severe sore throat
Fever
Characteristic rash
How is scarlet fever treated?
Antibiotics or can get better on its own
What are the complications to strep throat?
Rheumatic fever
Why is rheumatic fever bad?
The immune response to streptococcus infection can generate antibodies that cross react with human cells
What are the symptoms of rheumatic fever?
Fever
Painful and tender joints
Red, hot or swollen joints
Small, painess bumps beneath the skin
Chest pain
Heart murmur
Fatigue
Outbursts of unusual behaviour
What is streptococcus pneumoniae?
An invasive lung disease
What does streptococcus pneumoniae do?
When the aveoli, an inflammatory response is stimulated causing plasma, blood and white blood cells to fill the alveoli
