Microbiology and Pharmacology Flashcards
What are the main virulence factors and their functions?
- adhesin: enables the binding of organism to the host tissue
- impedin: enables the organism to avoid host defence
- aggressin: damage to host directly
What are the main features of Staph?
- colonises skin and mucous membranes
- can cause superficial lesions and systemic issues such as toxic shock which is caused by TSST-1
- PVL is in extreme skin infections and leads to sepsis and necrotising fasciitis
What are the main features of TSST-1?
this is a super antigen which stabilises immune reaction and causes both release of cytokines and toxic menstrual shock
What are the main features of Strep?
- normally in the pharynx
- Lancefield classification of surface antigens
- is bacterial sore throat, impetigo, cellulitis and necrotising fasciitis (strep A destroys connective tissue)
How do drugs move into the skin?
if the drug is hydrophobic then it can move in by massive diffusion and remain in the lipid layer around the corneocytes
How is the rate of drug absorption described mathematically?
by Fick’s Law according to the vehicle
What is an excipient?
this is a substance that can be put in the vehicle that can enhance solubility
What is a good way to administer a drug for a long time at a steady plasma concentration?
trans-dermal patch
What is the best way to improve partitioning?
- hydration of the skin by occlusion with type of vehicle or cling film
- inclusion of excipients to increase solubility of the drug
What effects do glucocorticoids have on the skin?
- anti-inflammatory
- immunosuppressive
- vasoconstricting
What conditions are glucocorticoids used to treat?
atopic eczema, psoriasis and pruritus
What are the side-effects of long-term steroid use?
- steroid rebound
- skin atrophy
- systemic effects
- infection
- steroid rosacea
- stretch marks
How do glucocorticoids act?
- signal via GRalpha receptors
- enter cells by diffusion and then they combine with GRa
- the receptor moves to nucleus and assembles into a homodimer
- binds to glucocorticoid response elements in the promoter region
- switch on or off of genes
What is TTD?
transdermal drug delivery is good for steady state drug delivery and avoids first-pass metabolism
however, only some drugs are suitable
What are the + and - for subcutaneous drug administration?
+ slow absorption
+ slow constant release
- injection volume limited
What are the advantages of topical treatments?
there is direct application and reduced systemic effects
What are the disadvantages of topical treatments?
they are time consuming, correct dosage can be difficult and they are messy
What are the features of creams?
- non-greasy
- semisolid emulsion of oil in water
- high water content
What are the features of ointments?
- semi-solid grease or oil
- no preservative
- occlusive and restrict water loss from the skin
- very greasy
What are the features of lotions?
- liquid
- might sting
- good for scalp or hair-bearing areas
What are the features of gels?
- thickened solutions
- semi-solid
- treat scalp, face and other hair-bearing areas
What are the features of pastes?
- semi-solid
- contain finely powdered material
- stiff and greasy to hard to apply
- protective, occlusive and hydrating
What are the features of foams?
- colloid with 2 or 3 phases
- increased penetration of active agents
- can spread easily
What are emollients?
they enhance the rehydration of the epidermis for dry conditions esp eczema
What are the risks of emollients?
- skin is slippy
- risk of fire from paraffin content
What are the actions of topical steroids?
- vasoconstrictive
- anti-inflammatory
- antiproliferative
What are topical steroids used for?
- eczema
- psoriasis
- keloid scars
- other non-infective dermatoses
How many grams of steroid for a whole adult?
20-30g
What are the most common side-effects of topical steroids?
- skin thinning
- pupura
- stretch marks
- rosacea
- acne
- telangiectasia
What do calcineurin inhibitors do?
they suppress lymphocyte activation so are used in eczema treatment
What do antiseptics do?
they are used for recurrent infections, antibiotic resistance and wound irrigation
What are antiviral agents used for?
herpes simplex, herpes zoster and eczema herpeticum
What are topical antifungals used for?
candida, dermatophytes (ringworm) and pityriasis versicolor
What are keratolyticxs used for?
to soften keratin eg in corns or viral warts
What is the treatment for warts?
keratolytics and mechanical paring
What is the treatment for psoriasis?
emollients plus tar, vit D, keratolytic, topical steroid and dithranol
What can scalp psoriasis be treated with?
greasy ointments, tar shampoo, steroids in alcohol base or vet D analogues
What colours are the different types of Staph on agar plates?
- S.aureus is golden on agar
- Coagulase negative staph is white on agar
What is the only coagulase positive Staph?
S. aureus
What is the best drug for a Staph aureus infection?
flucloxacillin
What are two extra things that S. aureus can have that can make the infection worse?
- SSSST which is staphylococcal scalded skin syndrome toxin
- PVL producing staph is a worse infection due to toxins
What are some examples of skin diseases caused by staph aureus?
cellulitis, infected eczema or impetigo
What is the treatment for MRSA?
vancomycin
and co-trimoxazole or doxycycline
When should S.epidermidis be considered?
if it is in association with an implanted artificial material that is causing recurrence of infection
What is the most relevant strep to skin?
beta haemolytic (split into A and B based on antigenic structure)
What diseases are group A strep associated with?
infected eczema
impetigo
cellulitis
What is the classical disease caused by group A beta haemolytic strep?
erysipelas
When do you take swabs of an ulcer?
ONLY if there are signs of infection or cellulitis
What are the main features of a tinea infection?
- this is ringworm
- found when the skin is soggy and it is in keratinised tissues
- it heals from the inside out so gives a ring appearance
- males
What is the most common microbiological cause of tinea?
trichophyton rubrum
What is the treatment for tinea?
clotrimazole cream or a topical nail paint
Where is candida usually seen and how is it treated?
- skin folds, under the breasts, nappy area of babies
- treatment is clotrimazole cream
What is the treatment for scabies?
malathion lotion
What is the most common cause of a UTI in a woman of child bearing age?
Staph saprophyticus
