Pathogenic Bacteria 2 Flashcards
What is a key feature of gram-negative bacteria and what does it allow?
It has a thinner peptidoglycan cell wall and thick lipopolysaccharide outer membrane layer, so is less readily exposed to the external environment.
What is a useful prelimary test to classify gram negative bacilli?
Lactose fermentation.
Define coliforms.
Organisms which are in the family Enterobacteriaceae.
Where are gram negative bacilli mainly found?
Mainly commensals of the human large intestine.
State Strict, aerobic bacilli.
Pseudomonas spp
- May contaminate medical equipment and is a hospital acquired cause of sepsis i.e. UTI, bacteraemia, pneumonia
- Feared respiratory pathogen in cystic fibrosis
- Multi-drug resistance mechanisms
- Limited treatment options
What is Aerobic Gram-negative cocci:
Neisseria spp
- Neisseria meningitidis causes meningitis. Often life threatening.
- Neisseria gonorrhoeae Causes gonorrhoeae, which causes urethritis in men and pelvic inflammatory disease in women. Spread by sexual contact.
Outline Small aerobic bacilli.
Haemophilus influenzae
- Causes respiratory tract infection (second to S. pneumoniae)
- Capsulate form (type B) was formerly an important cause of meningitis in children (Hib conjugate vaccine)
Outline examples of coliforms of aerobic gram- negative bacteria.
Escherichia coli, salmonella app
other coliform- shigella spp, klebsiella spp, proteus spp
Outline Escherichia coli and the infection it causes.
- Ferments lactose
- Several virulence mechanisms i.e. pili, capsule, endotoxin and exotoxins
- Strains vary considerably in disease potential
- Important cause of UTI
What does - Enterotoxogenic E.coli cause?
traveller’s diarrhoea
What does - Enterohaemorrhagic E.coli cause?
bloody diarrhoea and haemolytic uraemic syndrome.
What can salmonella spp. not do?
- Does not ferment lactose
- Can be invasive i.e. enters bloodstream
What does Salmonella enterica cause?
cause bacterial diarrhoea
What does Salmonella typhi causes?
causes typhoid fever
What do the other coliform shigella spp, klebsiella spp, proteus spp cause?
- Shigella spp: another cause of diarrhoea, dysentery
- Klebsiella spp: cause of UTI
- Proteus spp: cause of UTI, often associated with stones
