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
Outline examples of microaerophilic bacilli.
- Curved bacilli Campylobacter spp
- Spiral bacilli- Helicobacter pylori
Describe microaerophilic Curved bacilli Campylobacter spp/
- Source: domestic animals and chickens
- Spread via faecal-oral route
- Commonest cause of bacterial diarrhoea in UK.
Describe microaerophilic Spiral bacilli- Helicobacter pylori?
- Curved rods
- human stomach habitat
- Damages mucosa and causes ulcers
- Strong risk factor for gastric adenocarcinoma
What is an example of strictly anaerobic gram-negative bacilli?
Bacteroides
What are Anaerobes and examples?
They are often part of a polymicrobial infection
Examples: Bacteriodes spp., Prevotella, Porphyromonas
Outline Bacteriodes spp., anaerobe.
Bacteroides fragilis- part of normal colonic flora. Cause intra-abdominal abscess and may spread to other sites.
Outline prevotella, porphyromonas anaerobes.
They are oral anaerobes.
- Important in aetiology of periodontal disease and may be part of polymicrobial dental abscesses.
- Role in aspiration pneumonia.
- Human and animal bite infections.
List the Miscellaneous bacteria.
Mycobacteria, Spirochaetes, Chlamydia, Mycoplasma.
How are these miscellaneous bacteria visualised?
Resistant to decolourisation by acid or alcohol after staining with carbol fuchsin.
How is Mycobacteria identified?
Visualised with special stains e.g. Ziehl-Neelsen or Auramine phenol.
However, it doesn’t identify the species.
Culture required for ID. Growth takes weeks.
Molecular detection and identification of MTB if possible.
