Antibiotics Flashcards
What should you think about before initiating antimicrobials?
- Allergies
- Route
- Is the antimicrobial going to reach the infection site?\
- Renal impairment
- Hepatic impairment
- Pregnancy or breast feeding?
- Immunocompromised?
- MRSA carrier?
- Duration?
- Drug interactions
- Community or hospital acquired infection
Does P have a collection that can be drained?
Recent travel Hx
Contact with pets or other animals
Could work be a source of infection?
What does NKDA stand for on a drug chart?
No known drug allergies
Which organisms are commonly implicated in CAP?
Strep pneumoniae
Haemophilius influenza
Klebsiella pneumoniae
S. aureus
Atypicals
Virus (13%)
What clinical investigations would you carry out for CAP?
CXR
Serum and urine cultures = for pneumococcal and legionella testing
Sputum sample
Throat swap for viral culture if thinking influence virus
What score is an indicate for the severity of pneumonia?
CURB-65
C - Confusion
U - Urea (>7mmol)
R - RR (>30)
B - BP <90 S or <60 D
65 YO
+1 for each of these
0-1 = low risk
2 = intermediate risk
3-5 = high risk (mort >15%)
What is the calculation for ideal body weight?
IBW Men = 50kg + (2.3 x every inch over 5ft)
IBW Female = 45.5kg + (2.3 x every inch over 5ft)
How many inches are in a foot?
12 inches
When do we use corrected body weight?
If the actual body weight is greater than 20% of the ideal body weight
What is the calculation for corrected body weight?
CBW = IBW + (0.4 x Extra Body Weight)
Extra Body Weight = Actual Body Weight - Ideal Body Weight
How do we work out Extra Body Weight?
Extra Body Weight = Actual Body Weight - Ideal Body Weight
82yo M, 5ft 3in, 94 kg
Calculate
Ideal Body Weight
Extra Body Weight
Corrected Body Weight
Ideal Body Weight = 50kg + (2.3 x 3) = 56.9kg
Extra Body Weight = 94kg - 56.9kg = 37.1kg
Corrected Body Weight = 71.74kg
What is the calculation for renal function with creatinine clearance?
Men CrCl = (1.23 x (140-age) x IBW ) / Serum Creatinine
Women CrCl = (1.04 x (140-age) x IBW) / Serum Creatinine
What are the risks of gentamicin?
Ototoxicity
Nephrotoxicity
What are the two broad types of antibiotics?
Bacteriostatic
Bacteriocidal
What type of antibiotic should immunocompromised Ps always have?
Bacteriacidal
Why are mycobacteria different to other bacteria?
Mycobacteria are a group of bacteria belonging to the genus Mycobacterium. They are characterized by their unique cell wall structure, which contains a high lipid content, particularly mycolic acids. This distinctive cell wall structure gives mycobacteria several unique properties, including resistance to many antibiotics and disinfectants, as well as the ability to survive for long periods in the environment.
What are the four classes of bacteria?
Gram +ve
Gram -ve
Anaerobes
Atypicals
How do β lactams work?
They prevent cross-linking of peptides in the cell wall of the bacteria -> cell lysis
Uses a β lactam ring to do this.
Which types of ABs are β lactams?
Penicillins
Cyclosporins
Carbapenems
Monobactems
How do bacteria start to resist β lactams? How was this overcome?
The bacteria developed enzymes which caused hydrolysis of the β lactam ring.
Was overcome by adding clauvanic acid - very similar to the β lactam ring and the enzyme binds to it irreversibly
If a P has an allergy to a β lactam - which group of Abx can be used instead?
Macrolides
Which penicillin is resistant to β lactamases?
Flucloxacillin
Temocillin
Which is the most broad spectrum penicillin?
Amoxicillin
Ampicillin
Which penicillin can be used for pseudmonal infections?
Piperacillin
Ticarcillin
Why are pseudomonas bacteria hard to treat?
They are gram negative rods
What type of drugs are ticarcillin and piperacillin?
Extended spectrum penicillins (β lactam Abx)
What type of drug is cephalexin?
Cephalosporin (β lactam Abx)
What type of drug is meropenem?
Carbapenem (β lactam Abx)
What are glycopeptides used for?
Serious Gram +VE which produce β-lactamases or not responding to other Abx.
Which drug is used to treat C Diff infection?
Vancomycin
What are the important side effects of glycopeptides?
Are nephrotoxic
What are the important side effects of Vancomycin?
Nephrotoxic
Ototoxic
Also narrow therapeutic window - dose by drug levels in blood
Which drug can be used to Rx resistant strains of MRSA?
Vancomycin
What type of bacteria are affected by vancomycin?
Gram positive
Which ribosomes do bacteria use for protein synthesis?
50S and 30S
Erythromycin
Clarithromycin
Azithromycin
are all examples of what type of Abx?
Macrolides
Which bacteria are targeted by macrolides?
Gram +ves
Gram -ves
Cell wall deficient bacteria
Are broad spectrum
Give an example of a cell wall deficient bacteria.
Chlamydia
How is vancomycin metabolised?
How is it excreted?
It isn’t.
Excreted in the urine
How is clarithromycin metabolised?
How is it excreted?
Hepatic
Metabolites excreted in bileWh
What are the adverse effects of clarithromycin?
N&D
Arrhythmias (alters cardiac conduction)
What is amoxicillin used for?
Sore throat & skin infection - S pyrogenes
Respiratory tract - Pneumococcal
UTI - Coliform infection
What illness is clarithromycin used for?
Similar to amoxicillin
Sore throat & skin infection - S pyrogenes
Resp tract - pneumococcus
UTI - coliform
Chlamydia
What type of drug is Gentamicin?
Aminoglycoside
How does Gentamicin have to be given?
Direct to the blood - is not active orally
What are the adverse effects of gentamicin?
Nephrotoxicity
Ototoxicity
What type of drug is Doxycycline and Minocycline?
Tetracyclines
Are tetracyclines bactericidal or bacteriostatic?
Bacteriostatic
Are aminoglycosides bactericidal or bacteriostatic?
Bactericidal
What are the AEs are tetracyclines?
Phototoxicity
Chelation of metal ions -> deposition in teeth
Bone growth inhibition
What type of Abx are Ciprofloxacin, Nalidixic acid, Norfloxacin and Ofloxacin?
Quinolones
How do Quinolones work?
Inhibit DNA gyrases in bacteria - prevent DNA replication = rapid cell death
Which types of bacteria do Quinolones work on?
Lots - G+ve, G-ve, Mycoplasma, anaerobes, chlamydia.
What illnesses are Quinolones used for?
UTI
Pseudomonal infection
GI infections
Prostatitis
STDs
What are the adverse effects of Quinolones?
Lots of interactions with other meds
Caution in children
poss inc resistant bacteria
Are quinolones bacteriostatic or bacteriocidal?
Bacteriocidal
Is metronidazole bacteriostatic or bacteriocidal?
Bacteriocidal
How does metronidazole work?
Metabolites are toxic to DNA of bacteria
What are the AEs of metronidazole?
Potentially mutagenic
Carcinogenic
Teratogenic
= use for 10 days only.
Is Rifampicin bacteriostatic or bacteriocidal?
Bacteriocidal
Which bacteria is rifampicin used for?
Mycobacteria
- M. tuberculosis
- M. leprae
How does Rifampicin work?
Binds to RNA polymerase - inhibits RNA synthesis
What do you need to remember about Rifampicin?
Strong inducer of CP450 - beware other drugs that can be affected. (esp contraceptive pill)
Also - can turn saliva, tears and sweat orange.
Which Abx affect the bacterial cell wall?
β lactams
Glycopeptides
Which Abx affect protein synthesis?
Macrolides
Aminoglycosides
Tetracyclines
Which Abx affect DNA replication?
Quinolones
Metronidazole
Which Abx affects RNA synthesis?
Rifampicin
Which ABx are anti-metabolites?
Trimethoprim
Sulphonamides
Are sulphonamides and trimethoprim bactericidal or bacteriostatic?
Bacteriostatic
How do sulphonamides and trimethoprim work?
They are chemically similar to bacterial metabolites and interfere with normal metabolic pathways - inhibit synthesis of purines, prevent tetrahydrofolate being made = no production of RNA.
What is the AE of trimethoprim?
May cause folate deficiency if given for a long time.
Which bacteria have resistance?
MRSA
Vancomycin resistant enterococcus (VRE)
Extended spectrum β lactase producing organisms (ESBL/AMPC)
TB
Acinetobacter
What affects the penetration by Abx into the CSF?
Lipid solubility
Molecular weight
Protein binding
Susceptibility to transporters or efflux pumps
What are the RF for ABx resistant infections?
What is the organisational or healthcare system wide approach to promoting good use of antimicrobials to preserve their future effectiveness called?
Antimicrobial stewardship
In primary care - when should you prescribe Abx
If there is clear clinical benefit.
Not for acute self-limiting URTIs.
Avoid prescribing over phone
Avoid broad-spectrum Abx
When should you prescribe Abx in secondary care?
No evidence of infection clinically = NO ABX
Use guidelines, obtain cultures
Can give single dose prophylaxis if ABx have been shown to be effective.
When should you review Abx in secondary care?
You need to review the clinical diagnosis and whether Abx are needed to continue within 48 hours of the first dose
Which of the following are considered broad or narrow spectrum?
β lactams
glycopeptides
macrolides
aminoglycosides
tetracyclines
quinolones
metronidazole
rifampicin
trimethoprim
sulphonamides
Broad:
β lactams
macrolides
aminoglycosides
tetracyclines
quinolones
rifampicin
Glycopeptides (Vanc) = narrow
Metronidazole - primarily anaerobes
Trimethoprim & sulphonamides = narrow -> broad
What are the most common causative pathogens of acute pyelonephritis?
Gram negative bacteria!
E coli (60-80%)
Klebsiella
Proteus mirablis
Psuedomonas
Enterobacter
What patient factors may impact on Abx prescribing?
Immune system
Renal and hepatic function
Perfusion
Age
Pregnancy
Which is the first choice oral Abx for acute pyelonephritis?
Cefalexin
Co-amox - if culture results available and shows susceptibility
Ciprofloxacin
What is the first line IV Abx for acute pyelonephritis?
Co-amox (if culture results available and susceptible)
Cefuroxime
Ceftrixaone
Gentamicin
Which is the first oral ABx if the patient is pregnant?
Cefalexin
Cefuroxime
What type of Abx is Cefalexin?
Cyclosporin (β lactam)
What is the MOA of Cefalexin?
Inhibits bacterial cell wall synthesis
Which generation of cephalosporins in cefalexin?
First generation
Which bacteria is cefalexin effective against?
G+ve cocci
- S. aureus
- S. epidermidis
- Strep. pneumoniae
- Strep. pyrogens
- Anaerobic streptococci
G-ve rods
- E. coli
- Kliebsella pneumoniae
- Proteus mirablis
What illnesses can Cefalexin be used for?
Acute pyelonephritis
Lower UTI
HAP
Infections if susceptible - RTI, otitis media skin and bone infections
What are the AEs of Cephalexin?
Allergy
Abdo pain
Diarrhoea
Leucopenia
What are the drug interactions to be wary of with Cephalexin?
Can be nephrotoxic with gentamicin, ibuprofen and celecoxib
Is Cefalexin harmful in breastfeeding or pregancy?
No
Which are the Abx of choice in breastfeeding women?
What are the most common causative bacteria of cellulitis?
Strep pyogenes (G+ve)
Staph aureus (G+ve cocci)
also
Strep pneumoniae
Haemophilus influenzae
(both G -ve anaerobes)
What is the first choice ABx for cellulitis?
Flucloxacillin
If allergy - Clarithromycin, Erythromycin. Doxycycline
If MRSA resistant = Vancomycin
If flucloxacillin broad or narrow spectrum?
Broad
What illnesses is fluclox used for?
Sore throat & skin - S. pyogenes
Resp tract - pneumococcus
UTI - Coliform
What is the MOA of Fluclox?
Inhibits bacterial cell wall synthesis
What are the AEs of Fluclox?
Allergy
Diarrhoea
Skin reactions
GI disturbance
Opportunistic infections - Candida albicans
What interactions can Fluclox have?
Can inc levels of other protein bound drugs
In ribosome subunits - which subunit does Chloramphenicol and Macrolides bind to?
Which do tetracyclines bind to?
Chloramphenicol and macrolide - bind to 50S
Tetracyclines - bind to 30S
When is Vancoymycin given by oral route? Why?
Given by oral route for Rx of C Diff
- Not otherwise given orally as not absorbed
What interactions does clarithromycin have?
Inhibits the P450 enzyme system
What are the indications for use of Clarithromycin?
Cellulitis
Mild diabetic foot infection
CAP
HAP
H-Pylori eradication
Is Chloramphenicol broad or narrow spectrum?
Broad spectrum
Is chloramphenicol bacteriostatic or bacteriacidal?
Bacteriostatic mostly
Does kill H influenzae
What is the MOA of Chloramphenicol?
Inhibits protein synthesis - binds to 50S subunit.
What are the adverse effects of chloramphenicol?
Pancytopenia
Gray baby syndrome (mort 40%) - beware use in newborms
What interactions does chloramphenicol have?
Inhibits CYP3A4 and CYP2C19 preventing metabolism of certain drugs
What organisms is Doxycycline effective against?
Broad spectrum
- G+ve
- G-ve
Protozoa
Mycobacteria
What is the MOA of Doxycycline?
Binds to 30S ribosome subunit - this inhibits protein synthesis.
What interactions can Doxycycline have?
Competes for protein binding
Can enhance the anticoagulant effect of warfarin - likely due to competitive interaction for albumin binding.
Why is gentamicin given as IV?
Is not absorbed from the gut
Is Gentamicin broad or narrow spectrum?
Broad spectrum - however inactive against anaerobes.
Poor against haemolytic strep & pneumococci.
What is the MOA of Gentamicin?
Binds to the 30S ribosome and inhibits protein synthesis
Which of the following ABx should not be given to children less than 8 due to its deposition in bone and teeth?
A - Clarithromycin
B - Doxycycline
C - Vancomycin
D - Amoxicillin
A 26 yo marathon runner reports to the clinic with acute Achilles tendon rupture. They recently took an Abx. Which of the following may have contributed to tendon rupture?
- Co-Amox
- Cefalexin
- Ciprofloxacin
- Minocycline
Which atypicals is Ciprofloxacin active against?
Chlamydia
Legionella
Mycoplasma
What interactions does Ciprofloxacin have?
Prolongs QT interval
Inhibits CYP1A2 and poss CYP3A4 metabolism
Avoid with dairy products
What is the MOA of Ciprofloxacin?
Inhibits DNA gyrases - prevents bacterial DNA replication. Rapid cell death.
What are the AEs of Ciprofloxacin?
N&V
Headache & dizziness
Tendinitis, tendon rupture
Peripheral neuropathy
CNS - hallucination, anxiety, insomnia, confusion and seizures
Phototoxicity
