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Clinical Approach To Antimicrobial Therapy Flashcards

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1
Q

Factors involved in choosing abx: infective agent

A

Pathogenicity; virulence; invasiveness; adherence; toxin production; transmissibility; growth requirements; antibiotic susceptibility in vitro.

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2
Q

Factors involved in choosing antibiotics: host resistance

A

State of health or debility; nutritional state; immune status; underlying illness; implants/foreign bodies; portal of entry; normal flora; antibiotic therapy augment host resistance

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3
Q

Define sepsis

A

Combination of symptoms and signs of a localised primary site of infection

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4
Q

Define SIRS

A

Systemic inflammatory response syndrome

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5
Q

What is SIRS the first sign of?

A

That infection is spreading form the primary site of infection and the patient may be bacteraemic.

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6
Q

Other non infective causes of SIRS

A

Trauma, chronic inflammation, malignancy

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7
Q

What are the criteria for SIRS (at least 2 of)?

A

Temperature: >38C (febrile/pyrexial) or 90 beats/min (tachycardia)
Respiratory rate: >20 breaths/min or PaCO2 12000 cells/mm3 or

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8
Q

What are the features of SEVERE sepsis?

A

Temperature: >38C (febrile/pyrexial) or 90 beats/min (tachycardia)
Respiratory rate: >20 breaths/min or PaCO2 12000 cells/mm3 or

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9
Q

When is prophylactic use of antibiotics indicated?

A

When infection is a serious complication of surgery or of a medical condition e.g. If a non-sterile site will be breeched in surgery

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10
Q

When is therapeutic use of antibiotics indicated?

A

When infection is suspected or confirmed by:

  • Clinical diagnosis (disease or site) or
  • microbiological diagnosis I.e. laboratory confirmed
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11
Q

What information is necessary when deciding what antibiotics to use on a patient with suspected or confirmed bacterial infection?

A
  • location/source of infection
  • severity of infectious process
  • epidemiological setting of patient
  • pre-existing medical contain or problems that could pre-dispose patient to an infection
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12
Q

What information does the anatomical location of an infection give when prescribing antibiotics?

A

Allows most likely organism to be determined and allows pattern of susceptibility to be reasonably predicted (local surveillance)
Allows use of appropriate empirical therapy.
Also determines route if therapy administration .

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13
Q

What are some examples of the epidemiological factors of a patient that impact on the likelihood of an organism?

A

Age; sex; location; travel; IVDU; pets;

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14
Q

What are some pre-existing medical conditions that could pre-dispose a patient to infection?

A

Prosthesis; valvular heart disease; immunosuppressions; diabetes mellitus

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15
Q

What are the implications for a narrow spectrum abx?

A

Targeted therapy - organism defined

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16
Q

What are the implications for use of broad spectrum abx?

A

Empirical or best guess therapy - microbiology is uncertain.
Site directed.
Associated side effects: spread of resistance etc

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17
Q

Factors involved in shaping guidelines for choosing empirical antibiotic treatment

A 
Site of infection
Seriousness 
Likely organisms
Patient factors & circumstances
Cost
Toxicity and side effects
Local/national resistance rates 
Other underlying medical conditions 
Contraindications
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18
Q

Why is picking the correct route of abx administration essential?

A

To ensure effective drug concentrations at the site of infection.

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19
Q

Choices for route if administration of abx

A

Oral
IV
IM
Topical

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20
Q

What can effect oral absorption of abx?

A

Food - abx poorly absorbed or less stable

Drugs - calcium antacids and iron interfere with tetracycline uptake

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21
Q

What are the pharmacokinetic factors that can effect can an abx and its usefulness?

A 
Serum concentrations 
Half life (t 1/2) 
Tissue concentrations 
Protein binding 
Crossing natural boundaries e.g CSF, joint fluid 
Metabolism 
Excretion. (Liver/kidney)
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22
Q

Situations where cidal agents preferred

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A

Immunocompromised- seriously ill or steroid therapy
Immunodeficiency - neutropenia, HIV
Difficult sites - endocarditis and meningitis

NEED TO KNOW KILLING ORGANISM NOT JUST INHIBITING GROWTH

23
Q

How long to treat a UTI/cystitis for

24
Q

How long to treat streptococcal pharyngitis for?

25
How long to treat pulmonary TB for?
6 months
26
How long to treat endocarditis for?
4-6 weeks
27
Most infections responds to how many days treatment according to severity of condition?
5-7 (10) days
28
What signs should be looked for to show treatment of micro-orgs can be stopped?
Clinical observations Resolution of inflammatory process (WBC, CRP, temp = normal) Repeat micro cultures clear Imaging to see if abscess/ collection resolved
29
Advantages of IV to oral switch
Reductions in HA- bacteraemias and infected lines Saves medical and nursing time Reduces discomfort of patients and enables improved mobility and earlier discharge Reduced treatment costs Patient more likely to receive abx at correct time Potential to reduce risk of adverse effects (more error in parental drugs)
30
Why might deep seated infections require initial 2 weeks of IV therapy? Examples
``` Allows correct concentration to reach deep areas Liver abscess Osteomyelitis, septic arthritis Empyema, Cavitating pneumonia ```
31
Advantages of using tWo drugs together (synergy)
To prevent relapse To prevent resistance arising Provides broad spectrum cover
32
Some examples where two abx are used synergistically in the treatment of infection to prevent resistance or relapse
TB: isoniazid and Rifampicin 6 months Endocarditis : penicillin and Aminoglycoside Deep bone and joint: Rifampicin and anti-staph agent Enterococcal infections: penicillin and gentamicin
33
High risk infections requiring prolonged IV therapy
``` S.aureus bacteraemia Severe necrotising soft tissue infection Infected implants/prosthesis Meningitis/encephalitis Intracranial abscess Endocarditis Exacerbation of CF/ Bronchiectasis Inadequately drained abscess or empyema Severe infections related to chemotherapy induced neutropenia ```
34
OPAT
Outpatient parental antimicrobial therapy
35
What is OPAT?
Allows safe administration of IV drugs at home using once daily agents
36
What are the requirements for OPAT?
Patient: clinical stable, capable of self management, good IV access. Need to be reviewed once a week and managed by MDT
37
Advantages of OPAT
Reduce the no of hospital bed days e.g. CF children or adults with endocarditis Patient care in their own home Reduction in the risk of acquisition of nosocomial infection
38
Disadvantages of OPAT
Risk of developing acute, sub-acute or life threatening complications e.g. Anaphylaxis, other drug toxicity, line infection. Failure to resolve underlying infection.
39
Disadvantage of using two drugs together
Increases cost | Increased risk of toxicity
40
What should be considered in terms of drug safety in patient?
Known hypersensitivity or intolerance Impaired excretion (renal/liver failure) Drug interactions e.g. Ciprofloxacin and theophylline Higher risk of toxicity e.g. BM toxicity effects in transplant patients; pre existing liver disease; CNS toxicity in epilepsy Risk of antibiotic associated diarrhoea
41
What causes antibiotic associated diarrhoea?
Abx can disrupt normal flora of gut -> germination of C. Difficile spores -> diarrhoea and colitis caused by toxin positive c.diff.
42
Who are at high risk of antibiotic associated diarrhoea or c.diff?
In patients and elderly
43
What is a penicillin intolerance and what implications does it have?
GI upset, sickness. Very common Penicillins and beta lactams can be used
44
What is penicillin anaphylaxis and what are its consequences?
Severe and immediate skin rash, other anaphylactic symptoms. All beta lactams should be avoided. Replace with Macrolide/quinolone/glycopeptide
45
What are the implications of a skin rash after penicillin
No penicillins but may use other beta lactams I.e. cephalosporins, monobactams and carbapenems, as low risk of cross reaction occurring.
46
What are the possible causes of antibiotic treatment failure ?
Wrong diagnosis (not infectious or could be viral/fungal) Wrong choice of abx - reconsider site and possible orgs; ?source Inadequate dose Antibiotic given by wrong route - IV/ oral vanc Host factors - neutropenic patient require cidal agent Drug resistance developing during treatment (repeat AST) Pus requiring drainage; necrotic material with bio films or foreign body needs removing
47
What are the two goals of antimicrobial stewardship "start smart, then focus" guidance
Effective, timely treatment of infection | Minimise collateral damage of abx use.
48
Principles of "start smart"
Take hx of relevant allergies Prompt effective abx treatment within one hour of dx or ASAP if life threatening Comply with local prescribing guidelines Document clinical indication and dies on drug chart AND in clinical notes Include review/stop date or duration Relevant micro samples taken
49
Principles of "then focus":
Clinical review and decision at 48 hours: 1. STOP - not infections 2. IV/oral switch - nice clinical response 3. Change to narrow spectrum abx 4. Continue and review again after 24 hours 5. OPAT DOCUMENT DECISION
50
Define selective toxicity
Therapeutic agents that target pathogenic organisms, not pathological processes from cells/tissues.
51
Which special groups of patients require different prescribing guidelines?
``` Newborns; Pregnant; Lactating; Elderly; Immunosuppressed. ```
52
Why do newborns, the elderly, pregnant or breastfeeding women and immunosuppressed patients require special prescribing?
There are specific infectious processes which may be specific to these people. They have different physiologies therefore agents are ltd.
53
Which special group of Patients are the most complicated for prescribing and why?
Elderly. | Least homogenous; comorbidities; drug interactions; physiology; compliance and need for written directions.
54
Principles of of prescribing in community care
Empirical treatment, syndrome based. Minimise emergence of bacterial resistance - simple generic agents, avoid broad spectrum abx. Safe, effective and economic use of abx - limit telephone prescribing; no or delayed abx strategy I.e. Frequently viral Referral to hospital if GP suspects immunosuppressive illness or if requires further investigations/hospital admission.

Antimicrobial Therapy (5 decks)

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