Things I Struggle With Flashcards
How can we detect growth in lactose medium
Note: not macconkey that’s somet else
pH changes and oxygen is produced
Solution turns from red -> yellow
What infection is known to produce insoluble hydrogen sulphide
Salmonella
What do bile salts in macconkey agar prevent the growth of
Gram positives
What type of bacteria contain endospores
Gram positives
What are the 3 components of a gram-negative cell wall
Lipopolysaccharide
Porin
Periplasm
What is a heterotroph
A bacteria that fix their carbon using sugars
What are autotrophs
Bacteria that fix inorganic carbon
Give an example of a autotroph
Guild F = green & purple sulphur bacteria
Give an example of a heterotroph
Guild B = gliding bacteria
Where do organotrophs source electrons
Organic matter
Where do lithotrophs source electrons
Inorganic compounds
What are guild D bacteria used for
Used to leach materials & oxidise iron
What are pathobionts
Normal flora that become pathogenic
Draw the difference between laminar flow and turbulent flow
Straight lines = laminar Flor
Turbulent flow = lots of mixing, no discrete lines
What provides structure and integrity to the biofilm matrix
Exopolymeric substances
What are 3 components of exopolymeric substances
Lipids
Polysaccharides
Proteins
Extracellular DNA
Name 3 examples of biofilms
Skin
Teeth (plaque)
Mucosa (respiratory tract)
What sloughs cells from a biofilm
Phagocytes (amoeba) grazing on the surface
What does lux R and lux I do
Lux R = recruits rna polymerase to transcribe the operon when conc of autoinducer is high
Lux I = produces autoinducer
What do the police of Neisseria gonorrhoea bind to
Galactose
What bacteria uses collagenase
Clostridium
Give an example of a cytolytic toxin
Staph aureus alpha toxin
- inserts into host membrane forming a pore which cell contents flow out of
Give an example of a A-B toxin
Clostridium botulinum
- binds to pre synaptic membrane preventing ach release
What do B subunits bind to in A-B toxin
Glycans in cell wall
Give an example of a superantigen
Staph aureus toxic shock syndrome toxin 1
- secretion of fluids and electrolytes
How do superantigens work
Stimulate immune cells to produce cytokines = severe inflammation, shock and organ failure
How does the gastroenteritis toxin work
Toxin is endocytosed into the cell where it is transported to the ER via phagosome
Causes CAMP increase and electrolyte imbalance
= water leaves causing dehydration & diarrhoea
Give 3 examples of PAMPs
Adhesions
O antigens of LPS
Peptidoglycan
What type of receptors do amoeba have
- how do they work?
Pattern recognition receptors
- binding directly induces phagocytosis 
How do bacteria avoid ingestion;
Altering PAMPS
Offensive & defensive virulence factors
How do bacteria avoid digestion
- Leave food vacuole and divide in cytoplasm
- Produce chaperonins that re-fold incorrectly folded polypeptides
- Produce protease that disrupts host superoxide anion generation
What do aminoglycosides target
Mainly gram negative bacteria
Name two ribosomal protection proteins
Tet M
Tet O
How do ribosomal protection proteins work
Find to the ribosome changing its confirmation, prevents tetracycline from binding without stopping synthesis
What does Tet X gene do
Produces a protein that chemically modifies tetra cycling in the presence of oxygen and NADPH
Name three mechanisms of tetracycline resistance
Tetracycline efflux
Ribosomal protection proteins
Tetracycline inactivation
What are the two types of resistance to antibiotics
Intrinsic resistance which is naturally occurring
Acquired resistance e.g. genetic transfer
How do bacteria biofilm resist antibiotics
Covered in polymeric substance that prevents antibiotic penetration
How can a phage induce antibiotic resistance in a population
Bacteriophage infect bacterial cells and break down the host chromosome
Sometimes host DNA is repackaged into the phage genome
Phage is released and reinfects another cell where recombination occurs (lysogenic life cycle)
What do beta lactams bind to which weakens the cell wall
Bind to penicillin binding proteins = weakening cell wall
What gene confers resistance in MRSA
Mec A
What is the mortality rate for postsplenectomy sepsis
50-70%
How can we prevent aspergillus
Filter hospital air
Give respiratory protection to vulnerable patients
How can we prevent legionella
Prohibit showers = sponge baths
Monitor the water supply
Surveillance on cases
Why does diabetes affect necrotising fasciitis
Reduce blood flow to extremities means it’s harder to mobilise the immune system
How many organisms are Manuka honey effective against
80
Describe the new properties of teixobactin 
New antibiotic that treats gram-positive infections (via disturbing cell wall synthesis)
Effective at low-dose, not yet approved
Describe the life cycle of leishmaniasis
Sandfly ejects infected stage
Promastigotes phagocytosed by macrophage
Transform into amastigotes = multiply
Infected macrophages are consumed in blood meal
What test can be used to diagnose L. Donovani & L. Infantum
Immunochromatographic strip
= nitrocellulose with antigens that detects any antibodies
X - lots of false positives
What happens to ingested giardia cysts
Excyststion in small intestine
= trophozoites which multiply
Encystation towards the colon
= cysts pass in faeces
Life cycle of cryptosporidium
Ingest oocyst & excystation
Sporozoites parasitise epithelial cells of gut
2 types of oocysts produced = thick walled excreted from host
Gold standard for detecting cryptosporidium
Direct fluorescence assay
Antigen & conjugated antibody
What are subunits that make a capsid called
Capsomers
Describe the replication cycle of a virus
Adhesion, entry and uncoating
Viruses with ssRNA form ds intermediate using RNA polymerase = allows mRNA to be formed
Translation occurs using host machinery
Assembly of new virus in the nucleus
Pinches off by budding
What did Fraenkel find
RNA is the genetic material of TMV
Average latent period for covid-19
5.6 days
Describe measles
R0 = 15
Respiratory disease that can spread to the rest of the body
Describe the stages of HIV infection
Flu like symptoms
CD4 T cells decline and immune system declines anti-HIV antibodies rise
anti-HIV can no longer be produced virus becomes prevalent and can survive outside of T cells
Virus reproduces uncontrollably = fatal
How does Dicer work
Double stranded RNA genomes are recognised by DICER proteins
These are cleaved into pieces and catalysed further by RISC or Argonaut
How do PAMPs work
Detect infection and recruit adaptor molecules
Phosphorylation of Irf3 forms a dimer that binds to the promoter region and causes gene expression
Process encodes interferons
What do interferons do
Bind to receptors in adjacent cells activating STAT pathway
Priming the cells to fight viruses that have not yet arrived
What produces interleukin 4, what does it do
T-helper type 1 cells
Converts naive t helper cells into t helper type 2 cells
Negative inhibition= prevents cytokine storm
Since 2000 how many cases of polio in 21 cases
760
Most being vaccine derived polio
What does acyclovir do
Inhibits viral DNA synthesis
