Bacterial Pathogens Flashcards
Why do certain bacteria cause particular infections?
Opportunistic infections from exposure to normal flora Host factors Devices Immune system Bacterial factors Virulence Resistance Bacterial factors Environmental survival
Why is E.coli likely to cause UTIs
Part of normal bowel flora in most humans
Colonisation of urethral meatus and surrounding area
Short urethra in females
Able to adhere to uroepithelial cells/urinary catheter materials
Triggers host inflammatory response
Able to develop resistance to antibiotics
S.aureus and skin infections
Nasal carriage in up to 50% of people
Able to adhere to damage skin
Produces exoenzymes and toxins that can damage tissues and provoke host response (e.g.pus formation)
What is staphylococcus aureus
Primary pathogen
30-50% carry in nose
causes skin/soft tissue infections
What are common infections caused by stap aureus
Bacteraemia/septicaemia Osteomyelitis/septic Arthritis endocarditis pneumonia UTI Meningitis
What’s the commonest cause of a Staph aureus infection
including of surgical site of infections
What is Staphylococcus epidermidis?
Opportunistic pathogen
Skin commensal
Most people will carry it on their skin
One of 20+ species of ‘coagulase negative staphylococci’
What does Staph epidermidis cause infections in association with?
Foreign bodies such as intravascular catheters, prosthetic joints, prosthetic cardiac valves etc.
What does Staph epidermidis adhere to?
Plastic/metals using glycocalyx (slime), forming biofilms
What is Streptococus pyogenes?
also called ‘Group A Strep’
Commonest cause of bacterial sore throat
What does Strep pyogenes also cause?
Scarlet Fever Necrotising fasciitis (flesh eating bug' Other SSTIs Invasive infections such as pneumonia Puerperal sepsis Also associated with secondary immunological presentations such as glomerulonephritis
What is Streptococcus pneumoniae
Commonest cause of bacterial pneumonia
Commonest cause of bacterial meningitis (except in neonates)
Can also cause other common childhood infections such as otitis media
What is Streptococcus agalactiae?
Can also be referred to as ‘Group B strep’
Commonest cause of bacterial meningitis and sepsis in neonates (babies aged under three months)
What is Streptococcus milleri complex?
Three closely related species of pus-forming streptococci
Associated with abscesses : dental, lung, liver, brain and others
What is Viridans streptococci?
Collective name for a number of species of alpha-haemolytic streptococci that inhabit the upper resp tract e.g. S.oralis, S mitis
Classic cause of sub-acute bacterial endocarditis
