Antibiotics Flashcards
Define infection
Invasion and multiplication of pathogenic microbes
Define antibiotic
Antibacterial medication
Define anti-bacterial
Kills or inhibits growth of bacteria
Define bactericidal
Kills bacteria
Define bacteriostatic
Inhibits growth of bacteria (by affecting RNA and DNA)
What is the minimum bacterial concentration (MBC)?
Lowest concentration that kills 99.9% of a population
What is the minimum inhibitory concentration (MIC)?
Lowest concentration which inhibits visible growth of bacteria
What is the breakpoint?
MIC cut-off which separates strains where there is a high likelihood of treatment succeeding from those where treatment is more likely to fail
Name 4 features of bacteria
1-10 um in size
DNA as a single chromosome (prokaryotes)
Independent metabolism and no organelles
Cell wall (differs from cell membrane)
Describe the cell wall of a gram +ve bacteria
Peptidoglycan cell wall
If a bacteria has a peptidoglycan cell wall, is it gram +ve or -ve?
Gram +ve
Describe the cell wall of a gram -ve bacteria
Lipopolysaccharide cell wall
If a bacteria has a lipopolysaccharide cell wall, is it gram +ve or -ve?
Gram -ve
Which cell wall is thicker, gram +ve or gram -ve?
Gram +ve
Has several layers of peptidoglycans
List the 4 classifications of bacteria
Gram positive cocci
Gram positive bacilli
Gram negative cocci
Gram negative bacilli
Give an example of a gram positive cocci bacteria
Staphylococcus species
Streptococcus
Give an example of a gram positive bacilli bacteria
Bacillus anthracis
Lactobacilli species
Give an example of a gram negative cocci bacteria
Neisseria meningitidis
Haemophilus influenzae
Give an example of a gram negative bacilli bacteria
Escherichia coli
Salmonella species
What classification of bacteria are E. coli and salmonella?
Gram negative bacilli
What classification of bacteria are Staphylococcus and Streptococcus species?
Gram positive cocci
What are the 4 potential targets for antibiotic therapy?
Bacterial cell wall
Bacterial RNA & protein synthesis
Bacterial DNA structure & function
Folic acid synthesis
What 2 classes of drugs target the bacterial cell wall?
What effect does this have on the bacteria?
Beta-lactams (penicillins, cephalosporins, carbapenems)
Glycopeptides
(Bactericidal)
What 3 classes of drugs target RNA and protein synthesis?
What effect does this have on the bacteria?
Macrolides
Tetracyclines
Aminoglycosides
(Bacteriostatic)
What 3 classes of drugs target bacterial DNA structure and function?
Quiolones
Nitroimidazoles
Nitofurantoin
(Bactericidal)
What 2 classes of drugs target folic acid synthesis?
Trimethoprim
Sulphonamides
(Bacteriostatic)
Why are cephalosporins now not used so much?
Broad spectrum of activity and kill more natural flora
Likely to cause C. diff
What is the CURB-65 scale?
What actions are taken on the basis of this scale?
Confusion
Urea >7mmol/L
Respiratory rate >30 minute
BP <90mmHg systolic OR <60mHg diastolic
65 yrs >/=
Score > 1 - admit
Score >2 - IV treatment
What is the bacterial target of beta-lactams?
What 3 types of drugs are in this family?
Bacterial cell wall
Penicillins
Cephalosporins
Carbapenums
What class of drugs are fluclox/co-amox/taz in?
What are they used to treat?
Penicillins - beta-lactams - cell wall synthesis
Flucloxicillin - SSTI
Co-amoxiclav - mixed infections
Pipirecillin-tazobactum - anti-pseudomonal
What class of drugs are ceftriaxone and ceftazidime in?
What are they used to treat?
What is a serious side effect?
Cephalasporins
Ceftriaxone - bacterial meningitis, ortho infections
Ceftazidime - LRTIs
Broad spectrum antibiotic, kill natural flora. High risk of C diff
What class of drugs are erythromycin, clarithromycin and azithromycin in?
What are they used to treat?
Macrolides - RNA + protein synthesis
What class of drugs is doxycycline in?
What is it used to treat?
Tetracycline - RNA + protein synthesis
Atypical bacterial with unusual cell wall e.g. chlamydia
What class of drugs is gentamicin in?
What is it used to treat?
What is a caution with using this drug?
Aminoglycosides - RNA + protein synthesis
Severe gram -ve infections
Renal toxicity and therapeutic dosing
Only given IV
What class of drugs is meropenum in?
What is it used to treat?
Carbapenums - beta-lactams - cell wall
ITU infections, drug resistant UTIs
What class of drugs are ciprofloxacin and levofloxacin in?
What are they used to treat?
Quinolones - DNA structure and function
Anaerobic gram -ve infections
MRSA
LRTIs
What class of drugs is metronidazole in?
What is it used to treat?
Nitromadazoles - DNA structure and function
Anaerobic infections e.g. abcess
Discuss nitrofurantoin
Acts on bacterial DNA structure and function
Used to treat uncomplicated UTIs
Poor systemic bioavailability but concentrated in urine
Discuss trimethoprim
Acts on bacterial folic acid synthesis
Used to treat uncomplicated UTIs
Not to be used in pregnancy
What patient factors may affect your choice of antibiotics?
Allergy/intolerance
Renal/liver function
Immunocompromised/severity of infection
Route of administration
Polypharmacy
Age, ethnic group
Pregnant, breastfeeding, oral contraceptive
Why are antibiotic guidelines useful?
Useful when deciding on empirical treatment
The BNF can be useful but most hospital trusts develop their own guidelines based on cost, epidemiology etc.
