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Kat's Pathology > Antimicrobial Agents > Flashcards

Antimicrobial Agents Flashcards

1
Q

What are some mis-uses of anitmicrobials (5)

A 
No infection present 
Selection of incorrect drug 
Inadequate or excessive dose 
Inappropriate duration of therapy 
Expensive agent used when cheaper is available
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2
Q

What are some adverse effects associated with antimicrobials (5)

A 
GI upset
Fever and rash 
Renal dysfunction 
Acute anaphylaxis 
Hepatitis
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3
Q

What does CHAOS refer to when talking about antibiotics (5)

A 
CHOICE of the correct antimicrobial depends upon then...
HOST characteristics
ANTIMICROBIAL susceptibilities of the...
ORGANISM itself and also the...
SITE of the infection
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4
Q

What influences the choice of antibiotic (9)

A

Use narrow spectrum if possible
Use bactericidal drugs if possible
Ideally choice should be based upon a bacteriological diagnosis (otherwise best guess, based upon likely differential diagnosis)
Consider local sensitivity patterns
Patient characteristics
Cost
Pharmakokinetics (absorption, distribution, elimination)
Route of administration (IV for serious infection or if patient not absorbing PO, or need to access deep sites of CNS)
Dosage (age, renal.hepatic function, drug monitoring, allergy)

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5
Q

What host factors influence drug choice (5)

A 
Allergy
Renal function 
Hepatic function 
Age 
Genetics
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6
Q

What is the agar disc diffusion method used for

A

Determine bacterial susceptibilities.
Antibiotic-impregnated disc absorbs moisture from the agar; antibiotic diffuses into the agar medium.
As distance from the disc increases, there is a logarathmic reduction in the [antibiotic].
[diffused antibiotic] at the interface of growing and inhibited bacteria ~ MIC

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7
Q

When should specimens for culture be collected

A

Prior to starting antibiotics

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8
Q

What antibiotic choice is appropriate for nosocomial pneumonia and severe sepsis

A

Immediate initiation of broad spectrum antibiotics

The best antibiotic should be prescribed first, based on the patient’s risk factors, suspected pathogen and local resistance patterns.

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9
Q

How can the causative organisms be identified preliminarily (2)

A

Gram stain

Rapid antigen detection

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10
Q

What samples are suitable for gram stain (3)

A

CSF
Joint aspirate
Pus

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11
Q

What are some rapid antigen detection methods (2)

A

Immunoflouresence

PCR

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12
Q

What infection site factors will affect the efficacy of the antimicrobial (3)

A

pH of infection site
Lipid-solubility of the drug
Ability to penetrate the BBB

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13
Q

What infections need special considerations when treating (2)

A

Endocarditis

Osteomyelitis

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14
Q

When should IV antibiotics be used

A

Serious (or deep-seated) infection

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15
Q

When should PO antibiotics be avoided

A

Poor GI function or vomiting

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16
Q

When are IM antibiotics not suitable (2)

A

Not an option for long-term use

Avoid if bleeding tendency or drug is locally irritant

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17
Q

What is a problem associated with topical antibiotic use

A

Limited application and may cause local sensitisation

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18
Q

When is IV to PO recommended in hospital antibiotic treatment

A

If the patient has stabilised after 48 hours of IV therapy

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19
Q

What is the goal of therapy for antibiotics that are concentration-dependent at killing the organisms

A

Maximise concentration of antibiotic

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20
Q

What are some antibiotics that are concentration dependent (4)

A

Aminoglycosides
Daptomycin
Fluoroquinolines
Ketolides

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21
Q

What is the goal of therapy in drugs that are time-dependent

A

Maximize duration of therapy

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22
Q

What are some antibiotics that are time dependent (5)

A 
Carbapenems 
Cephalosporins 
Erythromycin 
Linezolid 
Penicillins
23
Q

What are some drugs that are time-dependent with moderate to prolonged persistent effects

A

Maximize amount of drug

24
Q

What are some drugs that are time-dependent with moderate to prolonged persistent effects (5)

A 
Azithromycin 
Clindamycin 
Oxazolidinones 
Tetracyclines 
Vancomycin
25
Q

How long should antibiotics be given for n.meningitidis meningitis

A

7 days

26
Q

How long should antibiotics be given for acute osteomyelitis (adult)

A

6 weeks

27
Q

How long should antibiotics be given for bacterial endocarditis

A

4-6 weeks

28
Q

How long should antibiotics be given for Group A streptococcal pharyngitis

A

10 days

29
Q

How long should antibiotics be given for a simple cystitis (in women)

A

3 days

30
Q

What organisms are most common in skin infections (2)

A

Staph. aureus

Beta-haemolytic streptococci

31
Q

What are the most common skin infections (3)

A

Impetigo
Cellulitis
Wound infections

32
Q

What antibiotic should be used to treat skin infections

A

Flucloxacillin (unless penicillin allergy or MRSA)

33
Q

What is iGAS

A

invasive group a streptococcal infection (Toxic shock syndrome)

34
Q

What is the treatment for iGAS (3)

A

Aggressive and early debridement
Antibiotics - adjunctive use of protein synthesis inhibitors especially, clinidamycin (also has good skin and soft tissue penetration)
Use of IVIg

35
Q

What is the eagle effect

A

Named after Harry Eagle who first described it, originally referred to the paradoxically reduced antibacterial effect of penicillin at high doses, though recent usage generally refers to the relative lack of efficacy of beta-lactam antibacterial drugs on infections having large numbers of bacteria

36
Q

What is the mechanism of the eagle effect

A

Penicillin is a bactericidal antibiotic that works by inhibiting cell wall synthesis but this synthesis only occurs when bacteria are actively replicating (or in the log phase of growth).
In cases of extremely high bacterial burden (such as with Group A Strep), bacteria may be in the stationary phase of growth.
In this instance since no bacteria are actively replicating (presumably due to nutrient restriction) penicillin has no activity.

37
Q

What are some RTIs (3)

A

Pharyngitis
Community acquired pneumonia (mild)
Community acquired pneumonia (severe)

38
Q

What is the treatment for pharyngitis

A

Benzyl penicillin x 10 days

39
Q

What is the treatment for mild community acquired pneumonia

A

Amoxicillin

40
Q

What is the treatment for severe community-acquired pneumonia (2)

A

Co-amoxiclav and clarithromycin

41
Q

What increases the risk of hospital acquired RTIs (2)

A

Tracheal intubation

Mechanical ventilation

42
Q

What is the treatment for hospital acquired RTIs (2)

A

Cephalosporin, ciprofloxacin, piperacillin/tazobactam

If MRSA colonised/risk, consider addition of vancomycin.

43
Q

What are the main causes of bacterial meningitis (3)

A

N. meningitidis
S. pneumoniae
+/- listeria in the very young/elderly/immuno-compromised

44
Q

What is the treatment for bacterial meningitis

A

Ceftriaxone +/- amoxycillin if listeria is likely.

45
Q

What is the treatment of meningitis in a baby less than 3 months (2)

A

Ceftriaxone plus amoxicillin (to cover for listeriosis)

46
Q

Why is ceftriaxone not used in neonates with bacterial meningitis

A

It displaces bilirubin from albumin and because it can cause biliary sludging

47
Q

What is the treatment for neisseria meningitidis

A

Benzylpenicillin (high dose) or ceftriaxone/cefotaxime

48
Q

What is the mechanism of penicillin resistance in neisseria meningitidis

A

The mechanism of relative resistance to penicillin involves, at least in part, the production of altered forms of one of the penicillin-binding proteins.
Although treatment with penicillin is still effective against these relatively resistant strains, there is evidence that low-dose treatment regimens can fail.
Beta-Lactamase production in meningococci is extremely rare but has been reported

49
Q

What is the treatment for simple cystitis (community)

A

Trimethoprim x 3 days

50
Q

What is the treatment for hospital-acquired UTI (commonest type of HAI) (2)

A

Cephalexin or augmentin

51
Q

What must be done in a hospital acquired UTI if there is also a catheter present

A

Change catheter under gentamicin cover

52
Q

How is c.difficile colitis managed (3)

A

STOP offending antibiotic (usually a cephalosporin)
If severe, treat with PO metronidazole
If above fails, use PO vancomycin

53
Q

If antibiotics have not worked in 48 hours, what questions must be asked (6)

A

Does the patient really have a bacterial infection? (Have I collected the relevant cultures?)
Is there a persistent focus present (e.g. an infected vascular or urinary catheter)?
Is there a deep-seated collection (e.g. intra-abdominal) that requires drainage?
Could the patient have bacterial endocarditis?
Am I using the correct dose of the antimicrobial?
Is another infection present (esp consider Candida)?

Kat's Pathology (105 decks)

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