Infectious Diseases & Pathogenicity Flashcards
What are the 2 shapes/morphologies of bacteria - single-celled?
-Cocci (round cells)
-Rod-shaped cells (bacilli)
How are cocci named alone & multiple?
single = monococcus
paired = diplococcus
grouped = staphylococcus
chained = streptococcus
What rod-shaped bacteria do you get?
single rod = bacillus
grouped/clustered
chains
Label this prok cell.
-Outer memb = (some)
-Cell wall = (most)
-Inner memb
–> ALL 3 = cell wall complex
Mebs used to create potential = ATP
-Fimbriae/Pili = (some)help w/ adhesion & sometimes motility
-Flagella = motility - spin
-Capsule = sticky - prevents phagocytosis
-Ribosomes = 70s
-Plasmids = extra chromosomal DNA - antibiotic resistance genes, can move between bacteria
-Nucleoid = nuc acid & histone-like prots - folds
-Cytoplasm = contains inclusion bodies e.g.,
Ca2+
What are the 2 types of bacteria shown from gram staining?
-Gram -ve
-Gram +ve
What are gram -ve bacteria?
-Small amount of peptidoglycan
-Has 2 membs - inner & outer
–> so has x2 periplasmic spaces
–> so is more selective
-Have bulk transporters on OM - move groups of things in (little selectivity)
-OM transports stuff into periplasmic space - enzymes degrade polymers = monomers - taken up by IM
-Greater time for enz to act on material as are x2
What are gram +ve bacteria?
-Have lots of cell wall material - peptidoglycan
-Has inner memb only
–> so has x1 periplasmic space - enzymes here = break down material before get into cell & capture enzs
What is peptidoglycan?
-Cross-linked chain of carbs (hexose sugars) w/ peptides (AAs)
–> gives rigidity to cell wall (due to cross-linking)
-Mesh-like structure
What is periplasmic space?
-Gaps in bacteria cell wall complex - where enzymes are secreted by bacteria
-These enzymes degrade polymers & antibiotics
What are spores?
-Produced by some bacteria
-Dormant form of bacteria
-Lacks water
-Stain bacteria - spore positioning = help identify bacteria species
-Can survive in extreme envs
-Able to germinate to = new bacterial cell
-Removes water from its components - DNA & RNA - so spores can survive for long time
-Dehydrate spore - where is lots of water & nutrients - rehydrate so spore can germinate
What are some positionings of spores of bacteria - used to identify bacteria species?
Why are spores an issue for infection control?
-Responsible for transmission
-Effect treatment - drugs only kill viable things - not spores
-Difficult to kill - no water (often target water to kill things)
-Small = easily spread - infection control = hard
Example of spore forming bacteria & description of it?
Clostridium difficile
= gram +ve
= rod shaped
-Link to elderly & antibiotic use
-Sub type - makes toxin = diarrhoea & organ failure
-Spore production - effects management - isolation, barrier nursing, inc cleaning of rooms (Cl based disinfectants)
What to do with patient if think has infection - Infectious Disease Diagnosis & Control?
Sequence of treatment
* Observation of patient - symptoms
* Sampling
* Laboratory observation & culture
* Identification tests
* Treatment - e.g. antibiotic therapy
* Observation of population (epidemiology)
* Prevention of transmission
What is empirical prescribing?
-Prescribing based on symptoms (prescribe before diagnose)
-Bets guess
-Don’t know exactly what is but know symptoms indicate sometime a specific antibiotic will treat
Why are hospital acquired infections & community acquired infections different?
In hospital = more likely to be antibiotic resistance (more likely to diagnose) & closed env
What does disease mean?
A disturbance in the state of health where the body cannot carry out all its normal functions
What does infectious disease mean?
Due to infection by pathogenic microorganisms
What does infection mean?
Invasion by and multiplication of a pathogenic microbe within or on a host
What does contamination mean?
The presence of microbes in a location/env
What are Koch’s Postulates?
-To link presence of pathogens in someone w/ a disease to that disease
-Concept of linking an organism to a disease
- Causative agent must be observed in every case of the disease
- The agent must be isolated from a diseased host & grown in pure culture
- When the agent from the pure culture is
inoculated into healthy, but susceptible, hosts the agent must cause the same disease - The agent must be re-isolated from the inoculated, diseased host & identified as identical to the original specific causative agent
Why are Koch’s postulates less useful now?
-Organism = diff types of disease in diff people - due to genetics
-Some infectious agents - can’t isolate & grow (worked well for most bacteria but not for viruses)
Do organisms only affect 1 site?
No - some can affect many across body - e.g., staphylococcus aureus
-Some sites can be affected by many types of organisms
What is the iceberg concept of infectious diseases?
-Severe = symptoms are impacting greatly on you - more likely to go to GP
-Mild = less likely to go to GP
…
(not all infected show symptoms!)
-Only people presenting to clinicians = at top of iceberg - at bottom don’t see - these spread disease
Describe how a disease progresses?
-Microbe encounters host (human)
-Encounter
-Transition - between contact & impact (stages which lead to entry/estab - most pathogens don’t get through as we manage them beforehand)
-Entry/establishment - adheres to cells
-Colonise - pathogen now on tissues & SOME pathogens spread from initial site to other organs via bloodstream:
.Spread
.Multiply
.Damage
.Outcome of infection (spread to others & impact on us - our recovery)
-Commensals (normal flora - on body surfaces) - produce antimicrobial peptides - to stop colonisation by pathogens - as stop establishment. In return these ‘want’ nutrients
-OR CAN BE ASYMPTOMATIC
How can bacteria attach to host cells?
-Adhesins on tip of pili or fimbriae = interact w/ glycoprots recs on host cell memb
-Alternatively on bact cell memb can have adhesins containing glycocalyx
(Glycocalyx = outer viscous covering of fibers extending from bact)
-More pili = more adhesive
-Capsules - sticky - carb based - viscous (polymeric) - so adhere to host too
What do alpha haemolytic streptococci release (toxin) - what does this cause?
-Haemolysins
–> causes incomplete lysis (haemolysis) - targeted to RBCs - releases haemoglobin i.e., iron (source of iron, once remove AAs)
- leaky RBCs - not fully
-Can’t read though these RBCs (paper underneath)
What do beta haemolytic streptococci release (toxin) - what does this cause?
-Haemolysins
–> causes complete lysis (haemolysis) of RBCs - haemoglobin released - obtain iron from AAs
-Can read through these RBCs (paper underneath)
