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Flashcards in Infection And Immunity Workshops Deck (95)
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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


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


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?



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)


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


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


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)



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?



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

What can septicemia cause in the long run?
Scarring to skin


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

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