Micro-organisms: Bacteria Flashcards
What type of E.coli causes food poisoning/ haemolytic uraemia?
O157:H7
What family of bacteria does E.coli come from?
Enterobacteriaceae
What bacteria is a causative agent of anthrax?
Bacillus anthracis
What condition does Neisseria gonorrhoeae cause?
Gonorrhoeae
What cellular structures will all bacteria have?
Cell wall
Cytoplasm
Ribosomes
Genetic material
How does Helicobacter Pylori deal with the stomach’s acidic environment?
Releases urease, converting urea into bicarbonate and ammonia-> cloud of neutralising chemicals protecting it from acid and immune response
What structure determines whether a bacterium is Gr- or Gr+?
Cell wall
How does gram staining work?
Crystal violet
Wash out with alcohol.
If bacteria is G+, it will retain a purple stain.
Counterstain bacteria with fuchsin.
If the bacteria isn’t Gr+ it will retain a pink stain.
Which type of bacteria has the more complex cell wall structure?
Gram negative
How would acid-fast bacteria stain?
Gram negative
What staining does mycobacterium tuberculosis require?
Ziehl Neelson
Carbolfusion stain
Do Chlamydia and Mycoplasma stain?
No
What is M.tuberculosis’ mechanism of action?
Inhabit and proliferate within unactivated macrophages in alveoli
Granuloma formation
What endotoxin alerts the host’s immune system of TB?
Mycolic acids
Why does Klebsiella pneumoniae take on its stringy texture in culture?
The bacterium has a capsule
What bacterium is the causative agent to Lyme disease?
Borrelia burgdorferi
What shape is the bacterium Borrelia burgdorferi?
Spirochete
What appearance do cocci bacteria have?
Chains
Which Gram+ species are spore forming?
C. difficile
C. botulinum
What do all bacteria require?
Carbon Nitrogen Phosphate Sulphate Minerals Trace elements like iron
How is PCR used with relation to a bacterial genome?
Probing for presence of pathogen’s DNA
Probing for presence/absence of antibiotic resistance genes
How does diversity of bacteria arise?
Mutations
Genetic exchange
Natural selection
What are the different forms of horizontal gene transfer?
Transformation
Transduction
Conjugation
Transposons
What is transformation in relation to gene transfer?
Uptake of short DNA fragments by naturally transformable bacteria
What is transduction in relation to gene transfer?
Bacteriophages mediate transfer of DNA from one bacterium to another
What is conjugation in relation to gene transfer?
Bacteria having sex through pili; cell-to-cell contact results in DNA transfer
What is transposition in relation to gene transfer?
Transposons move DNA from one site to another, it can deactivate genes onto which the DNA inserts
How do bacteria replicate?
Binary fission
What is the definition of a pathogen?
Organism capable of causing disease
What does ‘Koch’s postulates’ mean?
He proved that a specific microorganism causes a specific disease
What areas of the body should be microbe free?
Blood CSF Urine Muscles Glands Brain Inner Ear
What does ‘lethal dose 50’ mean?
The dosage that causes 50% mortality in an animal model
What are overt pathogens?
Pathogens that are only associated with disease; can’t be healthy microbial flora
What is an opportunistic pathogen?
Normal flora that can cause disease when introduced tp unprotected sites
What is a facultative pathogen?
A pathogen that can grow and survive in the environment as well as in the host (accidental host)
What are sub clinical infections?
The presence of bacteria but no pathology (yet)
What are examples of bacterial virulence factors?
Adhesins Flagella Factors to help obtain nutrients Toxins Capsule Type III secreted molecules (stuff that's secreted directly into the host cell by the bacterium)
What are the virulence factors of S .pneumoniae?
Capsule prevents phagocytosis Adhesins attach to respiratory lining. IgA protease cleaves IgA ans promotes infection spread Neuroaminifase Pneumolysins- pore forming
What are exotoxins?
Proteins released extracellularly
What are enterotoxins?
Exotoxins that act on the small intestine -> change in intestinal permeability -> diarrhoea
What type of bacterium is clostridium botulinum?
Gram+ Anaerobia Spore forming Neurotoxin -> botox, resp. arrest Used to relieve spasticity
What type of bacterium is Salmonella enterica?
Gram-
Food borne-> gastroenteritis
Hides from immune system in immune cells
What type of bacterium is listeria monocytogenes?
Gram+ Rod Food born -> cheese/ pate Affects mainly pregnant women/ immunocompromised patients Can lead to meningitis Virulence- vacuole escape
What are pathogen strategies for immune evasion?
Hiding in immune cells
Changing antigens
Decorate outside of cell with molecules similar to the host -> autoimmunity
Blocking/ changing immune response
What does ‘dysbiosis’ mean?
Imbalance of normal gut microbiota composition
Usually has harmful effects on the host
What does ‘probiotics’ mean?
Non-pathogenic organisms used as food ingredients to benefit the host’s health
E.g. Yakult
What does ‘prebiotics’ mean?
Non-digestible food ingredient that benefits the host by selectively stimulating the growth and/or activity of one/ a limited number of bacteria in the colon -> improving health
What is the hygiene hypothesis?
Exposure to more dirt strengthens the immune system.
How can you change your intestinal microbiome?
Antibiotics Lifestyle Diet Hygiene Chronic inflammation Metabolic dysfunction
How do commensal species cause infection?
Spread into sterile parts of the body
Expand population size numbers
How do microbial protectors challenge Koch’s postulate?
An organism is present that can compete against the pathogen
Indirectly:
Inducting the immune system
It’s metabolic products
Directly:
Competing for nutrients
Direct toxicity
