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Antibiotics Flashcards

1
Q

Q-SOFA

A

Resp rate >22
Altered GCS
Systolic BP <100

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2
Q

Sepsis

A

If vasopressors required to maintain MAP >65 +

Serum lactate > 2

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3
Q

Abnormalities in sepsis

A

FBC = WBC >12 or <4, Plt <100
U+E = Cr >310, acute oliguria <0.5ml/kg/hr
Lactate >2
Coag = PTT > 60, INR >1.5

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4
Q

Gram +ve bacteria

A

Cocci - staphylococcus (aureus and epidermis), streptococcus (pyogenes and pneumoniae), enterococcus

Rods - listeria, bacillus

Stain purple on gram stain

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5
Q

Gram -ve bacteria

A

Cocci - nessieria meningitides, gonorrhoea, bordetella
Rods - e.coli, Hib, pseudomonas, klebsiella
coliforms - enterococcus, salmonella, shigella

Stain pink

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6
Q

Don’t gram stain

A

Lack of a cell wall - mycoplasma, chlamydia, and mycobacterium TB

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7
Q

Antibiotic targets

A

Cell wall - B lactams, glycopeptides
Protein synthesis - macrocodes, tetracyclines, ahminoglycosides and clindamycin
Folate (DNA synthesis) - trimethoprim and sulphonamides
Nucleic acids - DNA = metronidazole, RNA - rifampicin

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8
Q

B-lactams

A

Encompasses the penicillins, cephalosporins and the carbopenams. All act to inhibit cell wall formation by inhibition of NAMA and NAG cross linking peptoglycan. This leads to weakness and lysis of the cell

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9
Q

Uses of penicillins

A

Flucloxicillin = cellulitis and skin infections
Amox/coamox = LRTI, UTI, URTI
Sepsis = Tazocin
Bacterial meningitis = Ben Pen

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10
Q

SE of penicillins

A

Generally well tolerated - GI upset diarrhoea and risk of c.diff esp with co-amox.

Hypersensitivity - skin rash, anaphylaxis, SJS, TIN

Fluxcloxicillin + coamoxiclav - cholestatic jaundice

Amoxicillin + EBV (glandular fever) = widespread maculopapular rash

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11
Q

Interactions of penicillins

A

Reduce efficacy of COCP, may increase INR due CY450 inhibitor effects

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12
Q

Generations of cephalosporins

A

1st - ceflaxin
2nd - cefuroxime
3rd - cefotaxime and ceftriaxone

1st generations = good cover against gram +ve
3rd = increased gram -ve cover

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13
Q

Indications of cephalosporins

A

Ceftriaxone - bacterial meningitis will penetrate meninges if they are inflamed

Bilary tract - cefuroxime
LRTI and epiglottis - cefotaxime

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14
Q

SE cephalosporins

A

10% cross reactivity with penicillin allergic!
Hypersensitivity - SJS and TEN
High c.diff risk!

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15
Q

Carbopenams

A

Meropenam and ertapenam. Broadest spectrum Abx against gram +ve, gram -ve and anaerobes

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16
Q

Indications for carbopenams

A

Pseudomonas infection

Complicated UTI/URTI

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17
Q

SE of carbopenams

A

N/V and diarrhoea - 5%, neurotoxicity and seizures esp in high doses or renal failure

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18
Q

Tetracyclines MOA

A

Target 30s ribosomal subunit reversibly binds blocking tRNA binding. It dose this by inhibiting aminoacyl tRNA and mRNA complex formation. Bacteriostatic - prevents replication

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19
Q

Indications for tetracyclines

A

Malaria prophylaxis
Mixed respiratory tract infections
Lymes(c.burnetti), brucella, chlamydia
Acne vulgaris/rosacea

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20
Q

Interactions of tetracyclines

A

Antacids, oral iron replacement and dairy products reduces their absorption and therefore efficacy
Risk of idiopathic intracranial HTN with retinoids
CYP450 inhibitors

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21
Q

SE tetracyclins

A

CI in children and pregnancy due to dental hypoplasia causing brown stained teeth and weak bones
Photosensitivity
Can cause oesophageal irritation and dysphagia

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22
Q

Aminoglycosides

A

Gentamicin and streptomycin

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23
Q

MOA aminoglycosides

A

Inhibit protein synthesis by triple blockade
i - misreading of mRNA
ii - block formation of initiation complex of peptide chain on 30s subunit
iii - block translocation of mRNA breaking up ribosomal clusters

Complete protein synthesis blockage. However ineffective against anaerobes as they need o2 dependent transporter to enter the cell

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24
Q

SE aminoglycosides

A

Ototoxic (Irreversible)
Nephrotoxic - usually reversible once stopped

Dose monitoring is crucial serum drug levels are taken 6-14hrs post dose when given OD, nomogram is then used to dictate subsequent frequency and dose.

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25
Interactions of aminoglycosides
Increased risk of nephrotoxicity with NSAIDs, ACEi, increased risk of ototoxicity with vancomycin, diuretics
26
CI aminoglycosides
Renal failure, myasthenia gravis
27
Indications aminoglycosides
Endocarditis Bilary infections and pyelonephritis Pseudomonas infections Sepsis
28
Macrolides
Clarthromycin, erythromycin and azithromycin
29
MOA macrolides
Target 50s subunit of ribosome preventing the transfer of bacterial tRNA from A site to P site on the ribosome thus preventing elongation of the polypeptide chain
30
Indications of macrolides
Good against gram +ve, gram -ve and atypical organisms as doesn't act on the cell wall Atypical LRTI (legionella, mycoplasma) and otitis media H.pylori eradication therapy Chlamydia trachomatis Bordatella pertussis
31
SE of macrolides
QT prolongation with possibility of degeneration to torsdes de pointes Hepatotoxic N/V, diarrhoea and abdo pain
32
Interactions of macrolides
CYP450 enzyme inhibitors preventing breakdown of drugs leading to increased levels - esp warfarin, theophylline, carbamazepine, digoxin Statins = increased risk of myopathy. If myalgia stop immediate and monitor CK
33
Glycopeptides
Vancomycin and teicoplanin
34
MOA glycopeptides
Irreversibly block the elongation of peptidoglycan chains by preventing incorporation of NAMA and NAG subunits this prevents cell wall synthesis
35
Indications of glycopeptides
Oral vancomycin = c.diff Endocarditis MRSA infections Active against aerobic and anaerobic gram +ve bacteria! High molecular weight means they are unable to penetrate cell walls of gram -ve organisms
36
SE glycopeptides
Nephrotoxicity and Ototoxicity thus pre-dose trough and 1hr post dose peak should be monitored Thrombophlebitis and necrosis @ injection site if extravasation Rapid infusion can lead to mass histamine release causing red man syndrome
37
Quinolones
Ciprofloacin and moxifloxacin
38
MOA quinolones
Inhibit DNA gyrase and topoisomerase IV this prevents supercoiling of the bacterial DNA. Unable to do this leads to inability to replicate DNA.
39
Indications for quinolones
Gram -ve, pseudomonas and atypicals UTI, STI - gonorrhoea GI infections and typhoid
40
SE of quniolones
N/V, diarrhoea esp c.diff tendon rupture and damage depression, anxiety - neurotoxicity QT prolongation esp with other drugs
41
Interactions of quinilones
CYP450 inhibitors leading to increase concentrations of drugs. High risk of theophylline toxicity Risk of tornadoes de pointes with other QT prolonging drugs
42
CI quinolones
Tendon rupture or tendonitis Pregnancy or adolescent due to neurotoxicity and c.diff Avoid in CNS/MH
43
Trimethoprim MOA
Targets dihydrofolate reductase by inhibiting its reduction to tetrahydrofolic acid. This is an essential precursor in the thymidine synthesis pathway
44
Sulphonamides
Block thymidine and purine synthesis by inhibiting folic acid synthesis. SE = high incidence of SJS, TEN can cause macrocytic anaemia in prolonged use due to folate deficiency
45
Indications for trimethoprim
1st line for UTI, cotriamozole for PCP in HIV +ve pts
46
SE of trimethoprim
hyperkalemia due to similar structure to potassium sparing diuretic amiloride. SJS, TEN, angioedema
47
Interactions of trimethoprim
ACEi and ARB = increased risk of hyperkalemia | methotrexate = increased risk of haematological toxicity
48
Chloramphenicol SE
Severe irreversible BM suppression
49
Nitrofurantoin MOA
Reactive nitrofurantoin metabolites damage a number of macromolecules within bacterial cells including ribosomal proteins and DNA. Used for UTI - avoid in renal failure due to total renal excretion
50
SE nitrofurantoin
N/V, diarrhoea Peripheral neuropathy Hepatic failure/ dysfunction Pulmonary fibrosis
51
CI nitrofurantoin
Renal function <60 consult specialist | Pregnancy @ term or infants <3months = haemorraghic disease of newborn
52
CI trimethoprim
Pregnancy 1st trimester
53
Metronidazole MOA
After reduction of their nitro group to a nitrosohydroxyl amino group they become trapped within the intracellular compartment of anaerobic organisms causing DNA strand breaks
54
Indications for metronidazole
Anaerobes!! H.pylori eradication, c.diff Surgical prophylaxis and abdo sepsis
55
SE metronidazole
metallic taste in mouth, pancreatitis and hepatitis
56
Interactions of metronidazole
Alcohol abstinence for length of course and 48hrs post. Otherwise hypotension, vominting and flushing
57
Clindamycin
Inhibits ribosomal translocation by binding to 50s rNA of large bacterial subunit. Used for MRSA skin infections, toxic shock syndrome High risk of c.diff
58
Choosing Abx
Pt factors - allergies? pregnancy? renal impairment? Drug - route, dose and SE Disease - pathogen, site and severity Cultures 1st before prescribing.
59
Reviewing Abx
Review every 48hrs. Options are to | stop, change from IV to oral, change Abx if cultures/not effective, continue, outpatient therapy
60
OPAT
Outpatient parenteral Ab therapy - Safe way to administer IV antibiotics in an outpatient or home setting. Used for chronic infections such a endocarditis, bone/joint, soft tissue, abcesses and TB
61
Cellulitis
PC = fever, hot red swollen superficial skin wound. Causes by staph aureus, pseudomonas, strep pyogenes
62
Anaerobes
Clostridium perfringes, difficile
63
Risk factors for skin infections
Obesity, DM, PVD, ulcers or chronic oedema
64
Mx cellulitis
IV fluxcloxicllin 48-72hrs (if MRSA = vancomycin IV)
65
Meningitis Mx
``` GP = 1.2mg benzylpenicillin stat A&E = IV ceftriaxone 2g stat +/- co-amoxiclav if >55 y/o to cover for listeria ``` Give corticosteroids if bacterial meningitis suspected! If signs of increased ICP = CT scan, if no signs of increased ICP = LP stat
66
Meningitis PC
Fever, headache and neck stiffness. May elicit photophobia, confusion, petichal non blanching rash, Kernigs and Brudinskis sign +ve
67
Pathogen meningitis
Neonates - e.coli, group B strep Adults - n. meningitides, strep pneumonia Elderly - increase in listeria and Hib
68
Signs of increasing ICP
``` Cushing reflex = dropping HR, rising BP Papilloedema, dilated pupils Focal neurology Vomiting and seizures Falling GCS ```
69
Complications of meningitis
Hemiparesis, blindness, hearing loss, loss of sense of smell, cognitive impairment and seizures. Cerebral abcess
70
Notification of meningitis
Notify health protection england! Isolate pt for 24hrs Chemoprophylaxis for all close contacts! - Rifampicin BD 2 days, Ciprofloxicin 500mg PO stat
71
Endocarditis
Inflammation of the inner surface of the heart commonly the valves. The vegetations which subsequently form can lead to embolic consequences
72
Risk factors for endocarditis
Previous cardiac surgery and valve defects IVDU Mechanical heart valves
73
Complications of endocarditis
Heart failure due to valve prolapse Mycotic abcess in the the brain Renal failure due to immune complex deposition Stroke/acute limb ischemia
74
PC and inv endocarditis
low grade pyrexia, new murmur, mitral stenosis 3 sets of blood cultures from 2x sites @ fever spike Transoesophageal echo
75
Dukes Criteria
2 major, 1 major and 1 minor, 3x minor Major = echo result +ve (transoesophageal), 2 +ve blood cultures for typical organisms Minor fever >38, IVDU, high CRP/ESR Immune complex - Roth spots, osler nodes, GN Embolic - septic emboli, Janeway, conjunctival haemorrhage, splinter haemorrhage
76
Janeway vs Oslers
``` Janeway = non tender macules on palms and soles Osler = palpable painful nodules on distal pads of fingers ```
77
Pathogens for endocarditis
Native valve - strep viridans Prosthetic valve - staph aureus Others = epidermis, HACEK, MRSA
78
Mx endocarditis
Benzylpenicillin + gentamicin = strep viridans Fluxcloxicillin + rifampicin = staph aureus Vancomycin + gentamicin = MRSA Prophylaxis only offer in high risk group!
79
Aims for gentamicin and vancomycin levels
Gent trough <1mg/L Vancomycin trough 10-15mg/L If below hardford nomogram can be used to adjust dose or increase frequency

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