Infection Flashcards
What is virulence
The degree of pathogenicity within a group of parasites as indicated by fatality and ability to invade a host’s tissues
5 stages of how microorganisms cause disease
Exposure Invasion Adherence Multiplication Dissemination
Pathogenicity
Ability to cause disease. Determined by virulence factors
List some virulence factors
Exotoxins Endotoxins
What is a bacteriophage
Virus which infects and replicates within a bacterium
What is a cluster of cocci called?
Staphylococci
What is a chain of cocci called?
Streptococci
What is in the infection model?
Patient - person, time, place Mechanism of infection - type of spread Infection - attachemnt? Toxins? Host defences? Inflammation? Damage? Management - diagnosis based in history, examination and investigations, treatment, infection prevention
What is specific treatment?
A medicine that has properties especially useful for treatment of a disease eg antimicrobials, surgery
What is supportive treatment?
Aimed at reinforcing patient’s own defences in overcoming a disease eg fluids
Classification of antibiotics?
Antibacterials, antivirals, antifungals, antiprotozoa
Classify further antibacterials
Bactericidal/bacteriostatic
Spectrum - broad, narrow
Target site/mechanism of action
Chemical structure
Ideal features of antibiotics
Get to site of infection
Selective toxicity
Few adverse effects
Easy to take/administer (oral/IV)
Long half-life
No inteference with other drugs
Give the classifications of antibiotics based on their mechansim of action
Protein synthesis
Cell wall synthesis
Nucleic acid synthesis
Cell membrane function
What do beta-lactams do?
Inhibit petidoglycan cross-linking in cell walls. B-lactam ring binds to an enzyme which would normally do the cross-linking
Examples of beta-lactams?
Penicillins
- Amoxicillin
- Penicillin
- Flucloxacillin
What bacteria does amoxicillin target?
Gram positive mostly, some Gram negative
Upper respiratory tract infections
Streptococcus pneumoniae
Haemophilus influenzae
Enterococcus faecalis (endocarditis, UTIs)
Beta haemolytic streptococci
NOT ACTIVE AGAINST STAPH AUREUS
Give some examples of antibiotics that inhibit cell wall synthesis
Penicillins and glycopeptides
What do glycopeptides do?
Bind to amino acids in the cell wall preventing peptidoglycan cross-links
Affect Gram positive only
Examples of glycopeptides
Vancomycin
Teicoplanin
What bacteria does vancomycin affect?
Staph aureus (including MRSA)
Streptococci
Enterococci
C. diff
Examples of antibiotics that affect protein synthesis?
Tetracyclines, aminoglycosides, macrolides
How do tetracyclines work?
Lock tRNA to septal site of mRNA, blocking translation.
Which bacteria do tetracyclines have an effect on?
Many Gram positives and some Gram negatives.
How do aminoglycosides work?
Stop translation
Potentially nephrotoxic and ototoxic
What are aminoglycosides used to treat?
Endocarditis, UTIs, staph aureus, E. coli
How do macrolides work? Which bacteria do they affect?
Bind to 50S ribosome, intefering with protein synthesis. Affect Gram positive cocci, chlamydia, anaerobes
Which antibiotics affect cell membrane function and how?
Polymixins
Interact with phospholipids so that cations and nucleic acids can leak out.
Which bacteria do polymixins affect?
Gram negative
3 methods of antibiotic resistance
Altered uptake
Drug inactivating enzymes
Altered target
How does altered target work in drug resistance?
Lower affinity of target enzymes due to mutations
How does altered uptake work in drug resistance?
Make themselves impermeable to drugs
Eg E. coli is resistant to tetracyclines by acquisition of an efflux pump.
How do drug-inactivating enzymes work?
Eg Staph aureus produce beta-lactamase breaking down beta-lactam ring in penicillin.
Or add a chemical group to drugs eg aminoglycosides
How do polyenes work?
Inhibit cell membrane function in fungal infections
Give two types of polyenes and what they are used to treat
Nystatin - Candida
Amphotericin - Sytemic fungal infections through an IV
How do azoles work?
Used to treat yeasts and moulds. Inhibit cell membrane synthesis
What does aciclovir do?
Inhibits viral DNA polymerase.
What is aciclovir used against?
Herpes simplex
Varicella zoster (chicken pox and shingles)
