Anti-infective Drugs Flashcards
Why do anti infective medication fight bacteria and not a human’s own cells?
There is a difference in the structure of bacteria and human cell and therefore they are only toxic to
What part a bacteria does Pencillin affect?
Cell wall synthesis
With majority of ophthalmic use, what part of the bacteria do anti-infective drugs affect?
Inhibiting bacterial protein synthesis
How does fluoroquinolones work?
Inhabits bacterial DNA synthesis :
DNA gyrase
What are four general consideration you should consider when thinking of what antibiotic to use?
1) Spectrum of cover (e.g should it have a broad or narrow specificity + should it be used on its own singularly or should it be used in combination)
2) Appropriate penetration ( topical or ointment or orally)
3) Rout of administration
4) Side effects (safe for pregnant women/breast feeding woman/ antibiotic resistance)
Normally how is which type of antibiotic chosen?
By clinical presentations and also a differential diagnosis
In what case would an antibiotic sensitivity test be used?
If a px does not tend to be responding well to a particular antibiotic
Give an example of an antibiotic sensitivity test and how is it carried out?
KIRBY-BAUER ANTIBIOTIC SENSITIVITY TEST
Sample of bacteria taken through a biopsy, bacteria plated on to an agar plate, paper inpreganated antibiotic discs are placed on top of the culture median. The bacteria begins to grown in an incubator at 37 degrees for 18 hours but due to the antibiotic, a zone is formed and the area of bacterial inhibition are measured to see which is most appropriate
Which three anti infective drugs are available to all registered optometrists?
1) Chloramphenicol POM & P- antibiotic
2) Fusidic acid POM - antibiotic
3) Propamidine P medicine - disinfect agent
Under which act can an optometrist administer chloramphenicol and Fusidic acid ?
Medicine Act Exemption
Can an additional supply administrate Polymyxin B?
No- it has been discontinued
What is P chloramphenicol used for ?
Bacterial conjunctivitis
What is POM chloramphenicol used for?
Prophylactic use- corneal abrasions, superficial infective
Is POM chloramphenicol a broad or narrow spectrum antibiotic?
Broad spectrum but NOT effective against pseudomonas
What can two diseases can occur from chloramphenicol not being used topically?
Aplastic anaemia and Grey Baby syndrome (in new born babies)
What is the licensed use for POM chloramphenicol?
Superficial infections like bacterial conjunctivitis, infective blepharitis, prophylaxis following trauma
What are the formulation as that chloramphenicol is used in?
Chloramphenicol 0.5% eye drops
Chloramphenicol 1.0% ophthalmic ointment
Minims Chloramphenicol 0.5% unit does eye drops
What happened in 2005 in relation to OTC Chloramphenicol?
The OTC Chloramphenicol eye drops were re classified from POM to P medicine for treatment of acute bacterial conjunctivitis
What is the mode of action of Chloramphenicol?
Inhibits protein synthesis through binding to the enzyme peptidyl transferase on the 50s ribosomal subunit, this blocking of the enzyme prevents the incorporation of new amino acids into growing peptide chain
Which two bacterias is the usual cause of bacterial conjunctivitis?
Staphe (staph epidermidis) and Stapha (staph. Aureus)
Which type of organisms are POM Fusidic acid effective against?
Gram +ve organisms (esp staph. Aureus) + slows bacteria growth= bacteriostatic
What is POM Fusidic acid licences for?
Bacterial conjunctivitis
Why is Fusidic acid sometimes not used for acute bacterial Conjunctivitis for children?
Ineffective against gram -ve H.influenza which is the most causative pathogen in this population
What are some off licence uses of POM Fusidic acid?
Prophylaxis from a corneal abrasion or blepharitis
What is the only formulation of Fusidic acid and how many times a day should it be used?
Fusidic acid 1% and twice daily
Is Fusidic acid viscous?
Yes and it does not penetrate ocualr tissues very readily
Which organism does Fusidic acid have a good sensitivity against?
Staphylococcus
What is more expensive chloramphenicol or Fusidic acid?
Fusidic acid
How does polymyxin B work?
Interferes with the functioning cell membrane of aerobic gram negative bacteria and inhibits with synthesis of the cell wall
What is a Propamidine?
It is a disinfectant which is active against gram +ve.
It has anti fungal and anti amoebic properties which could be treated for conjunctivitis and bleph
P medicine
What are the formations that propamidine comes in?
Brolene and gold eye ointment treatment
*note- it is not really used as chloramphenicol is preferred
How many times a day should propamidine be used?
4 times a day 1-2 drops
In which instance would you administer fluoroquinolones?
Bacterial keratitis
Which organism is fluoroquinolone effective against?
Gram negative bacteria
What is a major risk factor of bacterial keratitis?
CONTACT LENSES
What are the four fluoroquinolone ophthalmic drugs that are available?
BROAD SPECTRUM DRUGS
Ofloxacin
Ciprofloxain
Levofloxacin
Moxifloxacin
How does aminoglycosides work?
They inhibit protein synthesis
What are three examples of aminoglycosides?
BROAD SPECTRUM
Gentamycin
Neomycin
Tobramycin
Which bacteria is aminoglycosides effective against?
Gram negative and gram positive
why are aminoglycosides used less readily than fluoroquinolones?
With some px they can get corneal epithelial toxicity
Are tetracyclines delivered systematically or topically?
Systemically
What is the indication of using tetracycline and how does it help this?
Treating meibomian disease by reduces bacterial load on the lid margins
How does tetracyclines work?
Inhibits protein synthesis by blocking the attachment of the transfer RNA-amino acid to the ribosome
What is the first line treatment of lid margin disease?
Lid hygiene
What are organism is lid margin disease associated with?
Staphylococcus
What are two examples of tetracyclines?
Doxycycline and minocycline
Why does tetracycline supposedly help lid margin disease?
Staphylococci produce toxins which leads to an inflammatory response. So by reducing the bacterial load you reduce inflammation
What is azithromycin used to treat?
Trachoma (which is prevalent with chlamydia) and acute bacterial conjunctivitis and off-licence use is blepharitis
What is the life cycle of a virus?
It can only replicate within living cells, it has a capsid protein which surrounds the viral RNA and DNA (nucleic acid). When virus is bound to target this viral DNA is released which is replicated and exits the cells to infect other cells - READ UP ON THIS
What kind of virus is a herpes virus?
DNA virus
What are three example of herpes virus?
Herpes simplex, varicella zoster and cytomegalovirus
What disease is associated with varicella zoster and what can it cause if reactivated?
Chicken pox then left dormant, it can be reactivated to cause shingles
What is typical of a herpes simplex viral Keratitis?
Dendritic ulcer
What is potentially problematic about ophthalmic shingles?
It tends to affects the trigeminal nerve but can effect the ophthalmic nerve too which could lead to corneal involvement and being sight threatening
What kind of people is cytomegalovirus more prevalent in?
Immunosuppressed px
In what part of the eye what does cytomegalovirus effect?
The retina- viral necrotising retinitis
What is an example of an anti-viral drug?
Acyclovir
How does acyclovir work?
-Enters the cell and converted into aciclovir monophosphate by the herpes simplex virus enzyme thymidine kinase
- This enzyme adds a phosphate group which is why it becomes monophosphate
- The enzyme adds another 2 phosphates to make the drug in its active form of aciclovir triphosphate
- This competes with natural molecule “deoxyguanosine triphosphate (dGTP)” which is a building block of DNA
- This drugs inhibits DNA synthesis by taking over the natural molecule
What is the ophthalmic version of acyclovir?
Ganciclovir eye gel (Virgan)
How is sight threatening cytomegalovirus (CMV) retinitis treated?
A slow release ocular implant is inserted into the vitreous that is impregnated with ganciclovir
What is the epidemiology of acanthamoeba?
Free living amoeba and water/ soil
What is the treatment for acanthamoeba keratitis?
- Propamidine 0.1%
- Polyhexamethylene biguanide (PHMB) 0.02% OR chlorhexide 0.02%
^Disinfectants
Administered day and night hourly for 2 days minimum ; in HOS ward.
given until it is gone
