Proteins: Bacterial Infection Flashcards
What is bacteria?
Diverse and ubiquitous group of small, unicellular prokaryotes.
What’s the difference between good ‘friendly’ bacteria and bad bacteria?
Good is useful for the ecosystem and food production as a source of useful compounds whereas bad is disease causing, causes food spoilage and bio fouling/corrosion.
What are the four Koch’s postulates?
- The microorganism must be present in every case of the disease (not in healthy animals)
- The microorganism must be isolated from the diseases host and grown in pure culture
- The specific disease must be isolated when a pure culture of the microorganism is inoculated into a health susceptible host
- The microorganism must be recoverable from the experimentally infected host and shown to be identical to the original causative agent.
What are Koch’s postulates?
Guidelines to what a bacterium is, although not all are met all of the time.
What’s a) pathogenic, b) opportunistic/ conditionally pathogenic and c) non-pathogenic in terms of bacteria?
Pathogenic: disease causing
Opportunistic/conditionally pathogenic: sometimes disease causing
Non-pathogenic: harmless
How do diseases come about?
Some bacteria are entirely pathogenic, some bacteria acquire extra virulence factors which make them pathogenic, some bacteria from normal flora can cause disease if they gain access to deep tissue (especially if associated with a foreign body) or in immunocompromised patients many free-living bacteria and components of the normal flora can cause disease.
What is the normal flora?
All body surfaces possess a rich normal flora, the nose, mouth, GI, urogenital tract and skin in particular. It provides colonisation resistance and includes numerous conditional pathogens.
What type of infection can normal flora cause?
Endogenous infection
What is zoonosis?
An infectious disease that can be transmitted from animal to human, which may or may not cause disease.
What percentage of known human pathogens are zoonotic?
~60%
What is disease invasion?
The movement of a pathogen into a new host
Discuss tuberculosis?
Caused by mycobacterium tuberculosis, an infection of the lungs. Causes a cough, chest pain, fever, weight loss, fatigue etc. 1/3 of the worlds population is latently infected, 1/10 of latent infections become active diseases. Untreated it kills 50% infected.
Describe pneumonia?
Most commonly caused by streptococcus pneumoniae but also caused by other bacteria. Symptoms include cough, fever and chest pains due to compromised oxygen transport through the alveoli due to bacteria nucleophiles and fluid from damage. Major cause of death in young and old.
What does synergy between viral and bacterial diseases mean?
When they both infect together and become lethal. Eg. Flu and pneumonia or HIV and tuberculosis
How much more likely are you to develop active tuberculosis if you have HIV?
x800
What is a major cause of food poisoning?
Bacteria, 1 million cases per year and ~ 500 deaths.
What does the term exotoxin- mediated disease mean?
Caused by bacterial toxins grown outside the body but ingested.
Describe cholera?
An exotoxin-mediated disease, caused by vibrio cholerae. Causes rapid dehydration and electrolyte imbalance which causes rice-water diarrhoea and vomiting. Around 5 million cases per year and 100 000 deaths. Treatment is rehydration therapy-fluid and electrolytes.
What is the mechanism by which Choleragen works?
The toxin binds to GM1 ganglioside recepto tom enterocytes via b subunits. The a subunit undergoes receptor mediated endocytosis and catalyses ADP-ribosylation of the Gs protein. This stimulate adenylate cyclase and overproduction of cAMP which in turn stimulates the secretion of ions from cells to lumen and a large scale movement of water into the lumen.
What is septic shock?
Lipopolysaccharides (contains lipid and sugar portions) are endotoxins which cause septic shock. The symptoms are raised temperature, fever, hypotension, coagulation and leads to multiple organ failure and death in over 50% of cases.
What are some methods of preventing bacterial disease?
Disinfection/sterilisation, aseptic technique, decolonisation and prophylactic antibacterials and vaccination.
How are bacterial diseases treated?
Antibacterial chemotherapy, anti-toxin, surgery, electrolyte replacement etc.
What are cell walls common to?
Plants, bacteria and fungi but not found in protozoa and animals
How do cell walls vary?
Different biological kingdoms have difference cells walls which are comprised of polymers of repeating subunits.
What are the repeating units that make cells walls in plants?
Cellulose (a glucose polymer)
What are the repeating units that make cells walls in bacteria?
Peptidoglycan (a polymer of two sugars cross-linked by peptides)
What are cell walls required for?
Structural protection from osmotic pressure, enables cells to survive hypotonic environments, a scaffold for anchoring extra cellular proteins, roles in virulence, immune system recognition, major antibiotic targets and fundamental biological interest.
What is the structure of peptidoglycan?
Made of N-acetyl muramic acid and N-acetyl glucosamine linked by peptide bridges.
What are other terms for a) N-acetyl muramic acid and B) N-acetyl glucosamine?
A) NAM or MurNAc
B) NAG or GlcNAc
How does he peptidoglycan vary?
Many variations in the stem peptide (originally 5 amino acids long but cleavage between 4 and 5 is required for energy) region. Position 4 is always D-alanine.
In E.coli meso-diaminopimelate (an amino acids related to Lysine) is at position 3.
In S.aureus L-Lysine is present at position 3.
