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Pharm > Pharm Abx > Flashcards

Pharm Abx Flashcards

1
Q

what is the prophylactic theory?

A

the pt does not have an infection yet but they are at risk

- a preventative measure

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2
Q

what is empiric therapy?

A

you do NOT know the actual organism causing the infection.

  • what is the likely cause of the infection?
    ex. ) pt has a UTI and you are unsure which organism is causing it.
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3
Q

what is definitive therapy?

A

You know what you’re treating.

You know what the specific baceria causing the pts infection

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4
Q

what is the standard approach to select and modify antimicrobial therapy?

A
  1. confirm the presence of infection
  2. determine the likeliest pathogen
  3. select an empiric therapy
  4. monitor the response
  5. modify or deescalate therapy–> can we narrow the abx to cause less collateral damage
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5
Q

Reasons to avoid abx overuse

A 
resistance 
cost
toxicity
ADR
reduction of normal flora
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6
Q

What are the signs and symptoms of infection?

A
  1. fever –> temp is greater than 38C
  2. leukocytosis–> WBC count is > 10,000
  3. Clinical signs/ symptoms
    - local or systemic
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7
Q

Why is fever not always a reliable sign of infection?

A

It can be

  1. drug-induced
    - b-lactam abx, anticonvulsants,
  2. disease-induced
    - malignancies, autoimmune disorders (collagen-vascular)
  3. Fever may be masked by antipyretic drugs
    - acetaminophen, NSAIDS, aspirin, corticosteroids
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8
Q

What is the relationship between WBC and infection?

A

•Usually associated with increased # of immature neutrophils
- ”left shift” or “bandemia” of > 7%

•WBC may remain normal in some infections
- Low WBC (< 4000 cells/mL) associated with poorer outcomes

•WBC may rise due to non-infectious etiology

  • Myocardial infarction, trauma, leukemia, corticosteroid use
  • Not usually associated with bandemia
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9
Q

How can sign and symptoms help find the source of infection?

A
  1. Superficial or bone.joint infection
    - pain and inflammation
    - swelling, erythema, tenderness, purulent drainage
  2. deep-seated infections
    - pnuemonia, meningitis, endocarditis, UTI
  3. Symtpoms may be referred to an organ
    - cough and sputum production –> pneumonia
    -flank pain–> pyelonephritis
    fever with no other symptoms
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10
Q

What are some ways to determine the most likely pathogen?

A
  • Gram stain
  • Blood cultures
  • culture of infected sites
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11
Q

why should we obtain samples first when determining the most likely pathogen?

A

if we are able to sample from infection and bloodstream before abx, it helps us obtain a better yield.
- Do NOT want to delay abx therapy tho.

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12
Q

How long can we safely wait before giving abx?

A

some infections if you give right away there is a better outcome and the pt does not go into septic shock.
it is ultimately a balancing act

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13
Q

Factors of gram stain

A

gram + or gram -
sharpe –> cocci (sphere) or bacilli (rod)
growth patther –> clusters, chains, or pairs

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14
Q

Gram + cells and their stain pattern

A

gram + organisms have a thick cell wall and will retain the crystal violet color

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15
Q

gram - cells and their stain patter

A

gram - organisms take on the pink/red color or safranin

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16
Q

Gram + and aerobic cells

A

COCCI

  • Streptococci: pneumococcus, viridans strep, group A strep (pairs/chains)
  • Enterococcus (pairs/chains)
  • Staphylococci: S. aureus (coag +), S. epidermidis (coag-, clusters)

BACILLI

  • Corynebacterium
  • Listeria
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17
Q

Gram + and anerobic

A

COCCI
Peptococcus
Peptostreptococcus

BACILLI
Clostridia (C. perfringens, C. tetani, C. difficile)
Propionibacterium acnes

18
Q

Gram - and aerobic and bacilli

A
  • Enterobacteriaceae (E. coli, Klebsiella, Enterobacter, Citrobacter, Proteus, Serratia, Salmonella, Shigella, Morganella, Providencia)
  • Acinetobacter
  • Camphylobacter
  • Pseudomonas
  • Helicobacter
  • Haemophilus
19
Q

Gram - and anerobic

A

BACILLI

- bacteriosides

20
Q

Gram - and aerobic and cocci

A

Moraxella

Neisseria

21
Q

Atypical bacteria

A

•Chlamydia pneumoniae
Ovoid shape (coccobacillus)
Aerobic organism
Intracellular pathogen

•Mycoplasma pneumoniae
Very small aerobic, Gram (-), diplococci
Cannot be seen on typical Gram stain
Difficult to culture

•Legionella pneumophilia
Does not grow on standard culture media
Intracellular, Gram (-)

22
Q

Blood cultures

A

obtain when pt is febrile and pt spikes a fever

obtain two sets

23
Q

Sensitivity results of blood cultures

A

May take 24-72 hours, sometimes longer

•Sensitivity results reported as Susceptible (S), Intermediate (I), or Resistant (R) (not responding to ABX)

SIR

24
Q

Quantitative results

A
  • Culture results may take 12-48 hours, sometimes longer
  • Quantitative results may provide information on bacterial burden
  • Relative quantity (light, moderate, or heavy growth)
  • Actual quantity of colony forming units (CFU)/mL
25
Q

Positive blood cultures do not always confirm infection

A

•Colonization
Bacteria present, but are normal flora and/or not causing symptoms
Example: COPD patients colonized with non-infectious bacteria in lungs

•Contamination
Bacteria present, but likely due to inadequate sampling technique
Example: S. epidermidis present in 1 bottle out of two sets of blood cultures

26
Q

What to consider when choosing and empiric theroy?

A
  • Nosocomial or community-acquired?
  • Mild or severe infection?
  • First or recurrent infection?
  • Infection source removable or not?
27
Q

Resources available for guiding empiric theory

A

Infectious disease society of America
johns Hopkins abx guideline
the Sanford guide to antimicrobial therapy

28
Q

Determine the abx susceptibility or the organism that youre trying to eradicate

A
  • Minimum inhibitory concentration (MIC): the lowest antimicrobial concentration that prevents visible growth of an organism
  • Susceptible (S): In-vitro testing suggests high likelihood of clinical success. Likely to achieve therapeutic concentrations in the patient to treat the infection (MIC < attainable serum levels)
  • Intermediate (I): In-vitro testing suggests questionable likelihood of clinical success. Aggressive dosing may improve chance of clinical success (MIC @ attainable serum levels)

Resistant (R):In-vitro testing suggests high likelihood of therapeutic failure.Unlikely to achieve therapeutic concentrations (MIC > attainable serum levels

29
Q

Patient Factors

A 
organ function
pregnancy
genetics
PMH
Allergies and DRUG interactions
AGE
cost and preference
30
Q

Pharmacokinetic considerations

A

routes of administeration
tissue penetration
drug drug interactions
safety for renal/hepatic pts

31
Q

Pharmacodynamic considerations

A

bactericidal v bacteriostatic
time dependent killers
Concentration dependent killers

32
Q

Will the drug get to the site of infections?

A

•Adequate blood supply?
Abscess, osteomyelitis, or deep cellulitis

•Central nervous system?
Blood brain barrier

•Volume of distribution?
Tigecycline cannot treat blood borne infections (Vd=8L/kg)

•Special circumstances?
Pulmonary surfactant deactivates daptomycin

33
Q

Strategies that may be influenced by how abx exerts its effect: Time-Dependent Killers

A
  • Bactericidal activity maximized if T>MIC is at least 40-50% of dosing interval
  • Continuous or prolonged infusions may help maximize T>MIC
  • Beta-lactams, cephalosporins, carbapenams, vancomycin
34
Q

Strategies that may be influenced by how abx exerts its effect: Concentration Dependent Killers

A
  • The higher the drug concentration, the greater the killing
  • Fluoroquinolones: maximize the AUC:MIC ratio
  • Aminoglycosides: maximize the peak:MIC ratio
35
Q

Combination theray

A

Broadens spectrum of coverage

  • Increase change of therapeutic success
  • increase cost, higher risk of side effects

may yield synergistic effects
- may increase risk of superinfection with more resistant organism

may prevent resistance
- Tb

36
Q

The SELECTIOn and DOSING of the abx can influence therapeutic success

A

the empiric regiment doesn’t cover the infecting organism
-wrong dx, wrong empiric choice, unexpected organism

the concentration of abx is too low at the infected site
- poor absorption or distribution, drug-drug interactions, drug inactivation

37
Q

Host factors may render abx therapy less effective

A

immunosuppression due to disease state
- HIV/ AIDs, Diabetes, COPD, lack of natural defenses (burn)

  • ummunosuppression due to drug therapy
  • chemotherapy
  • chronic corticosteroid use
  • transplant anti rejection meds
  • drugs for autoimmune disorders
38
Q

Types of resistance

A

intrinsic
- naturally occurring

Acquired
-a normally sensitive organism develops resistance through genetic mutation

39
Q

what are the 4 categories of acquired antimicrobial resistance

A
  • alteration in the target site
    binding site altered so abx cant exert pharmacologic
    activity

-reduction in intracellular antimicrobial exposure
pathogen membrane become more difficult for
antimicrobial to penetrate
efflux pump spits out antimicrobial

  • bypass of natural metabolic processes
    antimicrobial inhibits critical pathway but pathogen
    develops new way to survive

-drug inactivation
pathogen secretes enzymes that degrade
antimicrobials

40
Q

pt education on abx

A
  • What allergies do you have?
  • What other medications, including OTC/herbal, do you take?
  • Take the entire duration of antibiotics, even if you feel better
  • For women on oral contraceptives, recommend using backup method for duration and up to 7 days after antibiotic course
  • Report back if you do not feel better or experience adverse events
  • Consider probiotics or yogurt with active cultures to prevent GI intolerance/diarrhea

Pharm (3 decks)

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