Anti infectives Flashcards
What is the difference between antimicrobials and antibiotics?
Antimicrobials is an umbrella term for any substance that fights against micro-organisms
Antibiotics refers to substances that are derived from or produced by micro-organisms which destroy bacteria or inhibit their growth
How do bacterial spores form?
Via spormulation inside the cell, release on bursting of the cell
How can anti-bacterial resistance occur?
Spontaneous mutation
Reduced drug affinity to the bacterial binding site
Bacterial enzymes able to deactivate drug
When does anti-bacterial resistance occur?
When not all micro-organisms are destroyed, allowing them to overcome the drug
How should bacteria be identified?
Signs and sxs
Subculture (microscope or staining)
Test antibiotic sensitivity
What colour does gram positive bacteria stain?
Purple
What colour does gram negative bacteria stain?
Pink/red
What type of bacteria tends to have a more serious infection and why?
Gram negative
Due to extra outer membrane, it’s more resistant to immune defence and drugs
What are the types of bacterial infections commonly seen in practice?
Blepharitis
Bacterial conjunctivitis
Stye
Chalazion
Corneal ulcer
Keratitis
Orbital cellulitis
Dacrocystitis
Is Staphylococcus Aureus gram positive or negative?
Gram positive
Give some examples of Staphylococcus Aureus infections
Blepharitis
Central and marginal coreal ulcers
Mucopurulent conjunctivitis
Stye
Dacrocystitis
Orbital cellulitis
Is Streptococcus gram positive or negative?
Gram positive
Give examples of a Streptococcus infection
Mucopurulent conjunctivitis
Dacrocystitis
Central corneal ulcers
Orbital cellulitis
Is Pseudomonas Aeruginosa gram positive or negative?
Gram negative
When are you likely to pick up an Pseudomonas Aeruginosa infection?
From plants, soil and water - it’s opportunistic
What could happen with a Pseudomonas Aeruginosa infection?
Sight loss
Give examples of a Pseudomonas Aeruginosa infection
Endophthalmitis
Central corneal ulcers
Is Moraxella Lacunata gram positive or negative?
Gram negative
Give examples of a Moraxella Lacunata infection
Conjunctivitis
Central/peripheral corneal ulcers
Are E-coli, neisseria, salmonella and haemophilus influenzae gram positive or negative?
Gram negative
Give examples of infections that E-coli, neisseria, salmonella and haemophilus influenzae would cause
Conjunctivitis
Central corneal ulcers
What are the two bacteria most likely to cause bacterial conjunctivitis?
Staphylococcus and streptococcus
How should a bacterial infection be treated?
- Identify bacteria with clinical/lab diagnosis
- Select effective antibacterial
- Use antibacterial at an effective dose for long enough in the right place to fight infection
- Use other non-pharma treatments to aid symptoms (e.g. hot compress)
What are the types of antibacterial drugs?
Chloramphenicol
Tetracyclines
Fusidic Acid
Penicillins
Polymixin
Aminoglyosides
Fluoroquinalones
Isetionates
How can antibacterial drugs work? i.e. what are the possible mechanisms?
Inhibit protein synthesis
Inhibit nucleic acid synthesis
Inhibit bacterial cell wall synthesis
Disrupt bacterial cell plasma membrane
Which drugs inhibit protein synthesis?
Chloramphenicol
Fusidic acid
Propamidine isetionate
Aminoglycosides
Tetracyclines
How does protein synthesis inhibition work?
Ribosomal subunits selectively targeted, preventing assembly of new proteins within the bacterial cell by toxicity from the drug
When can chloramphenicol be given?
With a signed order as a POM
As a P OTC as long as px is over 2, is used to treat acute bacterial conjunctivitis for a max of 5 days
Which ribosomal subunit is chloramphenicol toxic to?
50S
What bacteria is chloramphenicol effective against?
Gram positive and negative
Some funghi
What forms is chloramphenicol available in? How should it be stored?
0.5% drops and minims
1% ointment
Must be kept in fridge
What cautions do you need to be aware of with chloramphenicol?
If using systemically: aplastic anaemia or grey baby syndrome can occur
Most Pseudomonas aeruginosas resistant
Refrain from use unless infection not clearing up (after 72 hours with lid hygiene advice)
When would chloramphenicol be indicated?
Superficial eye infections
Is chloramphenicol bacteriostatic or bacteriocidal?
Bacteriostatic
Is Fusidic acid bacteriostatic or bacteriocidal?
Bacteriostatic (mostly)
Can be bacteriocidal if conc high enough
What is fusidic acid available as?
1% modified-release eye drops: ophthalmic gel (liquifies on contact)
2x daily
POM
When is fusidic acid indicated?
Bacterial conjunctivitis
What bacteria is fusidic acid effective against?
Gram positive cocci
What is the mode of action for propamidine isetionate and diprompropamidine isetionate?
Bacteriostatic
Not fully clear - modify protein/DNA synthesis
When is propamidine isetionate and diprompropamidine isetionate indicated?
Acanthamoeba keratitis
Effective against staph and strep
What is resistant to propamidine isetionate and diprompropamidine isetionate?
Pseudomonas aeruginosa
What is propamidine isetionate and diprompropamidine isetionate available as?
Drops 0.1% (propamidine)
Ointment 0.15% (diprompropmidine)
What type of antibiotic is Gentamicin?
Aminoglycoside
What is Gentamicin effective against?
Pseudomonas aeruginosa!!
Many other bacteria (gram positive and negative)
Which is Gentamicin’s mode of action?
Inhibits protein synthesis by targeting 30S subunit
Who can prescribe Gentamicin?
IP OOs and ophthalmologists
What is gentamicin used to treat?
Conjunctivitis
Serious bleph infections
What is Gentamicin available as?
0.3% drops, sometimes with BK chloride
What’s the dose for Gentamicin?
1 drop every 2 hours initially, reduce dose until 48 hours after healing
Name another aminoglycoside
Framycetin
What is Polymixin B’s mode of action?
Bactericidal, disrupting on the cell plasma membrane of gram negative bacteria
When is Polymixin B indicated?
Superficial bacterial infections
(conjunctivitis, blepharitis)
What is Polymixin B available as?
Maxitrol drops or ointment (with dexamethasone and neomycin)
What drugs prevent cell wall synthesis?
Penicillins
Vancomycin
Who can prescribe Polymixin B?
IP OOs
What should you do with a fungal infection?
Refer, no drugs available to OOs
Whats the difference between moulds and yeasts?
Moulds - multicellular, spore to reproduce, infection usually trauma related
Yeasts - unicellular, bud to reproduce, infection usually due to chronic/systemic causes
What are the RFs for fungal infections?
Exposure (e.g. gardening)
Immunocompromised
Hot/humid climate
Increased Age
Give an example of a fungi
Candida albicans
Give an example of a fungal infection
Fungal keratitis
Endophthalmitis
Give an example of an antifungal
Nystatin
Amphotericin
Fluctyosine
What is used to treat Chlamydiae?
Tetracyclines
How do tetracyclines work?
Prevent protein synthesis by binding to ribosomal subunit 30S
When are tetracyclines contraindicated?
<12 year olds bc deposits in teeth and bones
How do modern antivirals work?
Utilise chemical signals specific to target virus - strengthens drug activity and minimises effect on host cells
What are some types of viral infection?
HSV 1 - dendritic ulcers, keratoconjunctivis and cold cores
Herpes zoster - chicken pox, shingles
Adenovirus - epidemic keratoconjunctivitis
HIV
Rubella - congenital cataracts and microphthalmos
What ophthalmic effects can shingles have?
Corneal oedema and inflammation
Reduced corneal sensitivity
Corneal ulcers and scarring
What does Aciclovir treat?
HSV (local and systemic)
Herpes zoster (systemic)
How does Aciclovir work?
Prevents viral DNA replication
Inactive form until activated by thymidine kinase
What is Aciclovir available as?
3% ointment
Systemic tablets (or if ocular infection stromal or deeper)
What does Ganciclovir treat?
Herpetic keratitis
CMV for AIDs pxs
How does Ganciclovir work?
Stops viral DNA replication
What is Ganciclovir available as?
0.15% gel with BK chloride
What’s the dose for Ganciclovir?
5x daily until epithelium healed, then 3x daily for 7 days
Who can prescribe Ganciclovir?
IP OOs if infection is unilateral and epithelial only
When is it ideal to treat acanthamoeba keratitis?
Before formation of cysts
What is acanthamoeba keratitis treated with?
Aggressive combination therapy
(polyhexanide or chlorhexidine and propamidine)
