anti-infectives Flashcards
what are the three antinfectives?
-antibacterials
-antivirals
antifungals
what makes up the basic structure of a bacterial cell?
-DNA in the form of plasmid
-Cell wall
-ribosomes
-cytoplasm
-granule
-plasma membrane
name 2 types of bacteria that produce bacterial spores
-bacillus
-clostridium
why are bacterial spores dangerous
they are able to withstand extreme environments for a length of time mainly due to the thick cell wall.
when do bacterial spores get released?
when a bacterial cell bursts
what are the three mechanisms of micro-organism resistance to anti-infective drug?
-Spontaneous mutation of micro-organism
– Deactivation of drug by bacterial enzymes
– Decreased affinity between drug and binding site on bacteria
give a difference in the infections caused by gram negative and gram positive bactera
gram negative cause more nasty infection because they are more resistant to antibiotics due to them usually having an extra outer membrane
how do you identify type of bacterial infection?
-signs and symptoms
-do a microscopic examination
-gram staining
-test sensitivity to antibiotics
what colour do gram positive bacteria look?
purple as they retain gram stain
what colour do gram negative bacteria look?
colour of gram stain (usually pink) because it looses the gram stain following decolourisation and counterstaining
name 8 typical bacterial infections seen in practise
- Stye, “hordeolum”
- Blepharitis
- Chalazion
- Dacryocystitis
- Conjunctivitis
- Corneal Ulcer
- Keratitis
- (Orbital Cellulitis)
name two common bacteria seen in bacterial infections in practise
-staphylococcus aureus
-streptococcus
what kind of bacteria is staphylococcus aureus and what infections does it cause
-gram positive
– Blepharitis, mucopurulent conjunctivitis, dacryocystitis,
hordeola, central & marginal corneal ulcers, orbital cellulitis
what kind of bacteria is streptococcus and what infection does it?
-gram positive
-Mucopurulent conjunctivitis, dacryocystitis, central
corneal ulcers, orbital cellulitis
for psedomonas aeruginosa,
what kind of bacteria is it and what infecion does it cause?
– Gram negative
– Central corneal ulcers, endophthalmitis
for Escherichia coli, Neisseria, Salmonella,
Haemophilus influenzae, etc.
what kind of bacteria is it and what infecion does it cause?
– Gram negative
– Conjunctivitis, central corneal ulcers
for moraxella lacunata,
what kind of bacteria is it and what infecion does it cause?
– Gram negative
– Conjunctivitis, central & peripheral corneal ulcers
what 4 bacteria cause bacterial conjunctivitis in order from most common to least common
– Staphylococcus
– Streptococcus
– Haemophilus influenza
– Moraxella
What is the treatment process when using antibacterial drugs?
1.Establish clinical & laboratory diagnosis
2.Select antibacterial to which microorganism is
sensitive
3. Maintain effective dose at site of infection for
sufficient length of time
4. Augment drug therapy with physical treatment
give 4 mechanisms by which antibacterial drugs work
– Inhibition of protein synthesis within bacterial cell
– Inhibition of nucleic acid synthesis within bacterial cell
– Inhibition of bacterial cell wall synthesis
– Disruption of bacterial cell plasma membrane
how do antibacterial drugs inhibit protein synthesis?
- bacterial protein synthesis involves the building of peptide chains from amino acids
- Antibacterial drugs show selective toxicity for 30S and 50S ribosomal sub-units
- Prevents assembly of new proteins that are essential for bacterial cell growth and replication
what is dacryocystitis?
infection of the lacrimal sac
what are bacteriostatic drugs?
drugs that slow down or stop the replication of bacteria
what are bactericidal drugs?
drugs that kill bacteria
what’s the difference between a prophylactic drug and a therapeutic drug?
a prophylactic drug is a drug used to prevent an infection in a situation where infection is a risk whereas a therapeutic drug is a drug used for treatment of an existing infection
where does chloramphenicol need to be stored?
in the fridge
what is the first drug to give when treating an eye infection?
chloramphenicol due to its broad spectrum of activity
what are the three categories of anti infective drugs
– Antibacterials
– Antivirals
– Antifungals
Name 4 drugs that inhibit protein synthesis
- Chloramphenicol
- Fusidic acid
- Propamidine isetionate
- Aminoglycosides
- Tetracyclines
give 3 examples of aminoglycosides
-framycetin
-gentamicin
-neomycin
what action does chloramphenicol work by and how des it work?
– Bacteriostatic action
– Binds to 50S ribosomal sub-unit which Inhibits protein synthesis
what microorganisms is chloramphenicol effective against?
-gram + and gram - bacteria
-some fungi
when can chloramphenicol be obtained by a patient?
-when it’s used in practise
-supplied in an emergency
-when they have a written prescription for the pharmacy
what forms is chloramphenicol available as?
– 0.5% eye drops (various brands)
– 1% ointment (various brands)
– Minims Chloramphenicol 0.5%
what are the risks of chlormaphenicol?
-aplastic anaemia (rare)
-grey baby syndrome so babies need serum to be kept at low levels of 15-25 mg/litre
how does fusidic acid work?
inhibits protein synthesis via bacteriostatic action but can be bactericidal at higher concs
what type of bacteria is fusidic acid effective against?
gram + cocci especially staphyloccoci
what is the spectrum of activity like for fusidic acid?
narrow spectrum of activity
what form of drug is fusidic acid available under?
fusidic acid 1% Modified-Release Eye Drops: ophthalmic gel
this gel liquifies on contact with the eye
do you need a prescription to get fusidic acid drops?
yes
how does Propamidine isetionate work?
inhibits protein synthesis via bacteriostatic action
what bacteria is Propamidine isetionate
/Dibrompropamidine isetionate active against?
– Specific for the treatment of Acanthamoeba keratitis
– active against Staphylococcus aureus & Streptococcus pyogenes
– Pseudomonas aeruginosa is resistant
what ways are propamidine isetionate/ dibrompropamidine isetionate avaliable as to patients?
– Brolene eye drops 0.1%
* Propamidine isetionate
– Golden Eye drops 0.1%
* Propamidine isetionate
– Golden Eye Ointment 0.15%
* dibrompropamidine isetionate
Drugs that inhibit protein synthesis
who can use gentamicin?
ophthalmologists and IP optoms only
what kind of chemical is gentamicin?
an aminoglycoside antibiotic
Explain how gentamicin works and by what action?
inhibits protein synthesis by binding to the 30S subunit of the bacterial ribosome via bacteriostatic action
what kind of bacteria is gentamicin active against and name a specific bacteria its effective against
-wide range of gram + and gram -
-effective against Pseudomonas Aeruginosa
what is gentamicin avaliable as to the patient?
0.3% eye drops
how should gentamicin drops be administered?
1 drop every 2 hours, then reduce frequency, continue for 48 hours after healing due to poor cornea and systemic absorption
name 2 aminoglycosides used in eye treatment
framycetin and gentamicin
what is framycetin available as to the patient?
in eye drops as “Sofradex”, a combined drug with dexamethasone and
gramicidin
name 3 drugs that inhibit nucleic acid synthesis
Fluoroquinolones
Sulphonamides
Trimethoprim
how can ciprofloxacin be given to patients and what is it used to treat?
-Ciloxan 0.3% eye drops and ointment
– Superficial bacterial infections and corneal ulcers
how can ofloxacin be given to patients and what is it used to treat?
– Exocin 0.3% eye drops
– Superficial bacterial infections and corneal ulcers
how does polymyxin B work?
acts on cell plasma membrane via bactericidal action
what kind of bacteria is polymyxin B active against?
gram -ve bacteria
what is polymyxin B used for
superficial bacterial infections like conjunctivitis, keratitis, corneal ulceration and blepharitis
what is polymyxin B available as?
Maxitrol in combination with dexamethasone and
neomycin as eye drops or ointment
name 3 drugs that act on the bacterial cell wall used to treat bacterial ocular infections
-polymyxin B
-penicillins (not as common use)
-vancomycin (not very common again)
what are the two types of fungi?
-moulds which have hyphae and produce spores
-yeasts which are unicellular an reproduce by budding
what microbe is the most common cause of mucopurulent conjunctivitis?
staphylococcus bacteria
what is fusarium solani and what can it cause?
a type of fungi that can cause keratitis and endophthalmitis
what are the risk factors of contracting a fungal eye disease
– Exposure to pathogen like vegetable matter
– Immunocompromise
– Hot and humid climate
– Increased age
name 3 examples of fungi that can cause ocular infections
– Candida albicans
– Aspergillus
– Fusarium solani
what are the risks of having specifically an ocular yeast infection?
*Chronic ocular surface diseases
*Chronic mucocutaneous candidiasis
*Immunosuppression, including AIDS
*Corneal anesthetic abuse
what are the clinical features of eye disease caused by moulds
*Stromal infiltrates have minimal
cellular reaction and rough texture.
*The epithelial surface looks dry, grey
and may be either above the level of
the corneal surface or ulcerated.
*Feathery infiltrates. Sometimes
pigmented fungal elements can be
recognized
*Satellite lesions or multifocal
microabscesses are also seen
what are the clinical features of eye disease caused by yeasts
Small, oval, sharply demarcated
ulcerations with a “colour button”
configuration
*Extensive stromal inflammation and
edema
*May be indistinguishable from
Gram-positive bacterial keratitis
name 3 antifungals and how they work
- Nystatin
– Affects fungal cell membranes causing loss of potassium and magnesium ions and consequently affects metabolism - Amphotericin
– Increases permeability of fungal cell membrane so has effect more potent in fungal cells compared to host cells - Flucytosine
– Narrow spectrum of activity against yeasts and only works by inhibiting RNA function and DNA synthesis
how do chlamydiae cause disease
by attacking mucous membranes
what species of chlamydia affects humans?
C. trachomatis
name an anti chlamydial drug and how it works
tetracyclines work by preventing protein synthesis by binding to the 30S subunit of ribosomes
you have a 12 year old child who seems to have an infection caused by chlamydia, what should you not give them and why
any tetracycline as it binds to calcium which gets deposited in teeth and bone leading to discoloration and slowed growth
name 6 viruses and diseases they cause
-herpes simplex virus type 1: dendritic ulcers, keratoconjunctivitis and herpes simplex keratitis
-herpes zoster (varicella): causes chicken pox and shingles
-cytomegalovirus (CMV): retinitis
-Adenovirus: Epidemic keratoconjunctivitis (EKC). Highly contagious!
-Human Immunodeficiencey Virus (HIV) :AIDS and is associated with CMV infection
-Rubella (a “Toga virus”): Congenital microphthalmos, congenital cataracts
name 2 antiviral drugs
aciclovir and ganciclovir
what can aciclovir be used to treat
-herpes simplex and herpes zoster
how does aciclovir work?
1.Viral thymidine kinase activates the drug
2. aciclovir to aciclovir
triphosphate
3. this prevents replication of viral DNA
what is aciclovir avaliable as?
– Aciclovir 3% eye ointment
– Aciclovir tablets for systemic treatment of herpes simplex
and varicella zoster
Antiviral drugs
what is ganciclovir used to treat?
acute herpetic keratitis, and for the treatment of cytomegalovirus retinitis (CMV) in AIDS patients
what is ganciclovir available as?
Virgan, 0.15% ganciclovir gel, with benzalkonium chloride
