Gram Positive Bacteria Flashcards
What makes a gram positive bacteria differnet from a gram negative?
A thick peptidoglycan layer
No outer Lipopolysaccharide layer.
Why is gram staining useful?
- Some antibiotics are effective against gram +ve or gram -ve.
- gram staining gives us an early indication of the type of bacteria which may be causing infection
What are the 3 types of gram +ve Cocci?
Staphylococci (clusters)
Streptococci (Chains)
Enterococci
What are the subtypes of Staphylococci?
Coagulase postive & coagulase negative
What is the main coagulase postive staphylococci?
Staphylocci Aureus
A commensal microbe in the nose, axilla & perineum.
Major pathogen
Why is Staphylococci Aureus commonly resistant to penicillin?
Beta-lactamase causes penicillin resistance.
Where are coagulase negative staphylococci?
Theyre commensals in the skin
How do coagulase negative staphylococci become pathogenic?
In the prescence of foreign bodies or prostheses.
What are the 2 subtypes of Streptococci?
Alpha- (partial haemolysis) & Beta-haemolytic (complete haemolysis).
What culture is used to distinguish between alpha- & beta-haemolytic streptococci?
Blood Agar culture
alpha-haemolytic turns it green
beta-haemolytic turns it clear
Name and detail an example of alpha-haemolytic streptococci?
Streptococci Pneumoniae
- normal mouth flora (commensal)
- Causes infective endocarditis
How are beta-haemolytic streptococci further divided?
Into groups A-G.
A,B & D are clinically significant
Name and detail a common Group A beta-haemolytic streptococci?
Streptococcus Pyogenes
A major pathogen causing sore throat & cellulitis.
Name & detail a common group B beta-haemolytic streptococci?
Streptococcus Agalactiae
Causes neonatal sepsis with meningitis & bacteraemia.
Commonly carried in women’s genital tract.
What is special about group D beta-haemolytic streptococcus?
Theyre actually non-haemolytic (SHOCKER).
known as enterococci.
Name & detail a common enterococcus
Enterococcus Faecalis
A normal gut commensal that can cause UTI’s.
Name the 3 common types of Anaerobic Gram-Positive Bacilli?
- Clostridium Difficile
- Clostridium Perfringens
- Clostridium Tetani
Can Clostridium Difficile be cultured?
TEchnically yes but its very difficult
What does clostridium difficile infection cause?
It produces toxins that cause diarrhoea & pseudomembranous colitis (inflammation of the wall of the colon)
How does clostridium difficile spread?
Via spores, often in hospitals.
What increases risk of pathogenic clostridium difficle infection?
Anything that disrupts normal gut flora, such as antibiotic use.
How is a clostridium difficile infection detected?
Antigen & toxin can be detected in a stool sample
Where is clostridium perfringens found?
In the gut as a normal commensal.
Also in food & wounds
What does clostridium perfringens cause?
“Gas Gangrene” in wounds.
Food poisoning in food.
