Infection And Immunity Workshops Flashcards
Where do polymixins work? How do they work?
Only work on gram negative bacterias Outer membrane
Work on LPS
They bind to the lipid A component of LPS
They increases the outermembranes permeability
May also interact with the cytoplasmic, inner membrane
Interact with phospholipids here and increase permeability
What’s the difference between polyenes and polymixins?
Polymixins work in bacteria (antibiotic)
Polyenes work in fungi (antifungal)
Both Work on cell membranes/ outer membrane
How could a bacteria become resistant to polymixin antibiotics ?
A change in the LPS of the bacteria (in the lipid A component) results in polymyxins being unable to bind.
This resistance is quite rare
Where in a bacteria does chloramphenicol act?
Bacterial ribosomes
It binds to the 50S subunit and decreases peptide bond formation between amino acids so inhibits bacteria protein synthesis
How could a bacteria become resistant to chloramphenicol?
Through CAT genes
Chloramphenicol Acyl transferase genes
This enzyme will inactivate chloramphenicol
What antibiotic targets the nucleoid in bacterial cells?
Trimethoprim
How does trimethoprim work?
Works in the nucleus
It inhibits dihydrofolate reductase enzyme
This enzyme is needed to convert dihydrofolic acid into trihydrofolate, and trihydrofolic acid is needed to make bases in the bacteria. So it stops bacterial DNA being formed.
How could a bacteria become resistant to trimethoprim?
Alterations in dihydrofolate reductase enzyme so that trimethoprim can no longer bind
Also alterations in the uptake of the antibiotic into the bacteria
Glycopeptides act at the cell wall of bacteria. How do they work?
Bind to the d-ala d-ala sequence
Therefore inhibit binding of more monomers to the peptidoglycan chains; stop these stop these from Crosslinking so decrease stability in the cell wall of bacteria
How could a bacteria become resistant to glycopeptides?
Mutation in d-ala d-ala becoming d-ala d-lactate
Glycopeptides can no longer bind
This mutation is common in Enterococci
What bacteria cause catheter associated UTIs? Which is most common?
E.coli (most common) Enterococcus faecilis (quite common) Both these are from the gut Staph epidermis, staph aureus (quite common) Psudomonas Klebsiella Proteus
What do we use to treat catheter associated UTIs?
All the bacteria that cause this are a mixture of gram positive and negative. Therefore need to treat with broad spectrum antibiotics.
IV antibiotics used:
Gentamicin (1st choice) + amoxicillin and Coamoxiclav to fight resistant bacteria
Or
Vancomycin
Ciprofloxacin
What TYPICAL agents cause community aquired pneumonia?
Streptococcus pneumoniae
Haemophillus influenza
Streptococcus pyogenes
What ATYPICAL agents may cause intracellular infections?
Legionella pneumophila
Mycoplasma pneumonia
Chlamydia pneumonia
Cause intracellular infections so need to choose antibiotics that GET into cells
What Do we use to treat community aquired pneumonia?
Amoxicillin/ co-amoxiclav orally
Or if patient is allergic to penicillin: Clarithromycin
Doxycycline
What is Cellulits?
Inflammation of the skin
May occur from an insect bite
Or an operation opening up the skin
Could get in the blood stream and affect the heart: endocarditic Cellulitis
What organisms cause cellulitis?
Staph aureus
Streptococcus pyogenes
Staph epidermis
(Remember it’s the staphs and streps: common on the skin!!)
What do we use to treat cellulitis ?
Flucloxacillin (oral/ IV)
Vancomycin (IV)
Could maybe chose Clarithromycin or doxycycline or penicillin V
What microorganisms can cause acute exacerbations in COPD?
Haemophilus influenzae
Streptoccocus pneumonia
Staph aureus
Remember it’s the ones you’d expect in the lungs: influenzae and pneumonia
What can we use to treat COPD?
Doxycycline good as it works against all three
Amoxicillin (if you suspect resistance then give co-amoxiclav which contains a beta lactamase inhibitor)
Clarithromycin
Meningitis is the inflammation of the membranes lining the brain and spinal chord. It is rarely caused by bacteria, but when it does, what happens if you don’t treat it rapidly with antibiotics?
Death
Where do bacteria invade in meningitis?
It is inflammation of the membranes lining the brain and spinal cord
They invade the back of the throat, pass into the blood stream and invade the CSF
Bacteria that cause meningitis live in the back of the nose and throat in 1/10 people.
But most people who carry these bacteria become immune to them so they don’t usually cause disease.
The germs can be spread by secretions from nose and throat. But must have had close contact with the person or occasionally passed through respiratory droplets
Symptoms of meningitis occur suddenly after an incubation period of ______ days
1-3 days
What does the rash look like that’s associated with meningitis?
Rash of tiny red/ purple pin prick spots
May spread to look like fresh burning
If you press on the rash- it doesn’t go away!!
It’s a result from bleeding capillaries close to the surface, as bacteria release toxins in the blood which break down blood vessel walls
What is meningococcal septicaemia?
Blood poisoning
Occurs when bacteria in the blood multiply uncontrollably
Meningococcal disease can appear as meningococcal meningitis or meningococcal septicaemia
Or a combination of both of these
What will very severe cases of meningitis go on to cause?
Hearing loss
Damage to the brain
Learning impairments
Epilepsy
What can septicemia cause in the long run?
Scarring to skin
Amputations
What is first line treatment if bacterial meningitis is suspected?
High dose benzyl penicillin IV
Or a high dose 3rd generation cephalosporin such as ceftriaxone (IV) or cefotaxime (IV)
What shall I use to treat meningitis if my patient has anaphylaxis with penicillins or rash with cephalosporins?
IV chloramphenicol 12.5mg/kg QDS
Why is benzyl penicillium a good first line treatment for bacterial meningitis?
It has a broad spectrum
Rapidly absorbed into blood stream
Non toxic at high concentration
Good penetration into CSF
This is the same for cephalosporins
What is the most common bacteria causing meningitis?
Neisseria meningitidis (meningococcal meningitis) most common
Type B accounts for most cases
Mostly in under 5 years olds or 15-24s
It’s a gram negative bacteria so uses LPS LIpid A which is very toxic so can cause septic shock
What other bacteria can cause meningitis?
Streptococcus pneumonia (2nd most common) In under 2s and over 65s and immunocompromised It's the most dangerous type: 20% mortality whereas N.menigtiis is 10%
Haemophilus influenza B in under 5s
Less common: Staph aureus Listeria monocytogenes Mycobacterium tuberculosis E.coli
What antibiotic can we use for N.meningitis?
Penicillin G or ampicillin
Or if penicillin resistant: use 3rd generation cephalosporin like ceftriaxone or cefotaxime
Sensitive to both these: then chloramphenicol
What can we treat strep pneumonia bacterial meningitis with?
Ceftriaxone or cefotaxime IV
If penicillin resistant or pneumonococci suspected add in rifampicin or vancomycin
Sometimes with bacterial meningitis, relatives should be treated as prophylaxis. What can be given as prophylaxis for N.meningitis?
Rifampicin
Or ciprofloxacin
These are different to the actual treatments as we want to decrease chance of resistance
What prophylaxis can be used for bacteria caused by s. Pneumoniae?
No prophylaxis
What prophylaxis should be given for haemophilus influzae meningitis?
If patient lives with unvaccinated child under 4, the entire household should be given Rifampicin as prophylaxis
What vaccines are available for meningitis?
HiB vaccine (H. Influenzae type B) N.meningitidis Type C (Men C) N. Meningitidis type A, C, Y, W135 N. Meningitidis type B S.pneumonia vaccines
