Bacteria iSoc Flashcards
What is alpha haemolysis? (3)
Partial breakdown of cells
Appears green
E.g. Streptococcus pneumonia
What is beta haemolysis? (3)
Complete breakdown of cells
Appears brightened
E.g. group A Strep (aka Strep. pyogenes), Staph. aureus
What is gamma haemolysis? (3)
No breakdown of cells Looks ‘vague’
Staph. epidermis
What does ‘streptococci’ indicate? (2)
Twisted chain (strep) Spherical (cocci)
What does ‘staphylococci’ indicate? (2)
Grape-like (staph)
Cocci (spherical)
What are Koch’s postulates? (4)
Causative agent has to be present in all cases of infection
Can cultured from cases in vitro (not possible in all cases e.g. leprosy)
Can reproduce disease in animal model
Can be isolated from infected animal
What is virulence? (1)
The ability of a microorganism to cause disease
A patient is found to have a yellowy liquid in their
abdomen. They also report abdominal pain and have a fever of
39oC. What organism could have caused this? (3)
Meningococci, staphylococci, streptococci
Organism must be pyogenic as it produces pus
Pus is a collection of WBCs (mainly neutrophils), bacteria + dead cells
Which tissue surfaces do not possess bacterial flora, under normal circumstances? (7)
Lower resp tract Sinuses Middle ear Brain Blood Muscle CSF
Which cytokines are produced by macrophages in response to endotoxin exposure? (3)
IL-1, IL-6 + TNF
What are endotoxins? (4)
Integral part of bacterial cell wall
Only present in gram -ve bacteria e.g. E.coli
Usually only released when bacterial cell is damaged
Results in variety of effects @ many diff sites
You examine a patient and notice they have
cellulitis on their right lower leg. Which organism and
which enzyme can result in this presentation? (4)
Streptococcus (gram +ve) and hyaluronidase
Breaks down hyaluronic acid
Disrupts tissue mosaic + allows bacterial + inflammatory exudate to spread deeper
Why do only gram -ve bacteria produce endotoxins? (1)
Lipid A/lipid polysaccharide (LPS) is present on outer cell wall of gram -ve but not gram +ve
What type of bacteria is Clostridium perfringens + what enzyme does it contain? (4)
Gram +ve bacillus
Alpha-lecithinase
Splits lecithin (on surface of many cells)
Major tissue damage
Bacterial causes of meningitis? (3)
Strep. pneumoniae (gram +ve diplococci) Neisseria meningitidis (gram -ve diplocci) Haemophilus infleunzae (gram -ve bacilli)
