Antibiotics Flashcards
Microbe
Microorganism which usually results to disease
Why use antimicrobial chemotherapy
treat infections caused by microorganisms such as bacteria, viruses, fungi, and parasites. The goal of antimicrobial chemotherapy is to selectively target and destroy these harmful pathogens without causing significant harm to the host.
Can also be used as a prophylaxis (prevents infection in those at high risk e.g. immunosuppressed)
Where do antibiotics come from and do
Usually comes from bacteria and fungi that produce these compounds to kill or inhibit the growth of other microorganisms
What is the difference between Bacteriocidal and bacteriostatic
Bacteriocidal:
Kill bacteria
Destroy cell wall
Bacteriostatic:
Stop cell replication
Inhibit protein and nucleic acid synthesis
What does Penicillin do
-inhibit cell division
-inhibit cell wall formation
-causes cell death
Inherent resistance
Particular grams stains are resistant to antibiotics owing to their wall structure.
Acquired resistance
Induced resistance of a bacteria to an antibiotic it was originally sensitive to the antibiotics.
How can bacteria become resistant
- Change target / replace sensitive pathway
- Reduced membrane permeability
- Pump the antibiotic out
- Destroy the antibiotic
Occurs through
* Mutation of genes
* Acquisition of genes
What is MRSA
Methicillin-Resistant Staphylococcus aureus. It is a type of bacteria that is resistant to many common antibiotics, including methicillin, penicillin, and other beta-lactam antibiotics.
How does MRSA cause resistance?
(mecA gene)
Acquisition of mecA gene which encodes for PBP2a (penicillin binding protein 2a). Normally anitbioitcs target PBPs which are enzymes that result in bacterial cell wall synthesis.
Antibiotic binds to PBPs and inhibit formation of cell wall, leading to cell death.
But in mecA gene PBP2a is different structure to PBP so antibiotics don’t bind effectively so cell wall formation continues
How does MRSA cause resistance to antibiotics (beta-lactamase)
Bacteria possess an enzyme
known as beta-lactamase that destroys the antibiotic
Overcoming bacterial resistance
(Beta lactamase inhibitors)
Adding beta lactam ring such as clavulanic acid and amoxillcin allows for beta lactamase inhibitors.
Other beta lactamase inhibitors include:
* Piperacillin and Tazobactam (Zosyn®)
* Ticarcillin and Clavulanate (Timentin®)
How is an antibiotic chosen
Patient
Allergies / renal & hepatic function / susceptibility / age / severity of illness / pregnancy / breastfeeding / tolerate oral drugs?
Organism
Local bugs / multi-drug resistance (MDR)
PO or IV
Why multiple Antibiotic
To prevent the emergence of resistant strains
To treat mixed infections
To treat emergency / life threatening cases before a firm diagnosis
To take advantage of antibiotic synergism
To use lower doses of a toxic drug
Side effect of antibiotics
Continuous Antibiotic use destroys gut flora:
Diarrhoea
Reduced absorption of nutrients
Anaemia due to abnormal absorption of vitamin B12
Allergic reactions / Anaphylaxis
Toxicity:
renal / hepatic
