Theme 1: Lecture 1- Bacterial pathogens Flashcards
Which bacteria have thicker walls - gram +ve or -ve?
+ve
What colour do gram +ve cells turn following a gram stain and why?
blue/ purple
thicker wall allows colour to be retained
What colour do gram -ve cells turn following a gram stain and why?
red/pink
thin outer membrane does not retain the blue colouring
What factors allow certain bacteria to cause infections?
- Host factors - devices, immune system
- Opportunity - exposure, normal flora
- Bacterial factors - virulence, resistance, environmental survival
Why is E.coli the most common cause of UTIs?
- able to adhere to uroepithelial cells/ urinary catheter materials
- triggers host inflammatory response
- able to develop resistance to antibiotics
How would S.aureus cause skin infections?
- nasal carriage in up to 50% of people
- able to adhere to damaged skin
- produces exoenzymes and toxins that can damage tissues and provoke host response e.g pus formation
Is staphylococcus aureus gram +ve or -ve?
+ve
What infections can S.aureus cause?
- skin/soft tissue infections - commonest
- more severe infections - bacteraemia, septicaemia
- osteomyelitis/ septic arthritis
- rarely- endocarditis, pneumonia, UTI and meningitis
What are opportunistic pathogens?
microorganisms that do not usually infect healthy hosts but produce infections in hospitals, to immunosuppressed persons or those patients presenting underlying diseases
What is staphylococcus epidermis?
- gram +ve
- opportunistic pathogen
- most people carry on skin
- causes infection in association with ‘foreign bodies’ e.g catheters, prosthetics
- adheres to plastics/metals using glycocalyx (‘slime’)
What is the commonest cause of bacterial sore throat?
streptococcus pyogenes
What is another word for streptococcus progenies and what conditions can it cause
- group A strep
- scarlet fever, necrotising fasciitis, other SSTIs, pneumonia, puerperal sepsis, glomerulonephritis
what is puerperal sepsis?
infections in lower reproductive tract after women has given birth
Which bacteria is responsible for causing ‘strawberry tougue’ presentation in scarlet fever?
streptococcus pyogenes
How can you tell apart staph infections from strep infections under a microscope?
"staphylo" = 'bunch of grapes' "strepto" = 'chain'
What is the commonest cause of bacterial pneumonia and bacterial meningitis?
streptococcus pneumonia
What is the commonest cause of bacterial meningitis and sepsis in neonates?
streptococcus agalactiae a.k.a ‘group B strep’
Which gram +ve species of pus-forming streptococci is associated with abscesses? (dental, lung, liver, brain etc)
streptococcus milleri complex
What is viridans streptococci?
- gram +ve
- collective name for number of α-haemolytic streptococci that inhabit the upper respiratory tract e.g S.oralis, S.mitis
- classic caușe of sub-acute bacterial endocarditis
What condition is S.mitis associated with?
rotting teeth/dental care
What is streptococcus gallolyticus? a.k.a streptococcus bovis
- a type of α- haemolytic streptococcus that forms part of bowel flora
- bacteraemia with this organism can be associated with colonic malignancies
What is zoonosis?
diseases that can be passed from animals to humans
What is listeria monocytogenes?
- gram +ve bacillus
- rare but significant cause of sepsis and meningitis in pregnancy, neonates and immunosuppressed patients
Which gram +ve bacteria is associated with consuming cheese made from unpasteurised milk and other foodstuffs?
listeria monocytogenes
