Pharm Abx

Question 1

what is the prophylactic theory?

Answer 1

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

- a preventative measure

Question 2

what is empiric therapy?

Answer 2

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.

Question 3

what is definitive therapy?

Answer 3

You know what you’re treating.

You know what the specific baceria causing the pts infection

Question 4

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

Answer 4

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

Question 5

Reasons to avoid abx overuse

Answer 5

resistance 
cost
toxicity
ADR
reduction of normal flora

Question 6

What are the signs and symptoms of infection?

Answer 6

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

Question 7

Why is fever not always a reliable sign of infection?

Answer 7

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

Question 8

What is the relationship between WBC and infection?

Answer 8

•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

Question 9

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

Answer 9

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

Question 10

What are some ways to determine the most likely pathogen?

Answer 10

• Gram stain
• Blood cultures
• culture of infected sites

Question 11

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

Answer 11

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.

Question 12

How long can we safely wait before giving abx?

Answer 12

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

Question 13

Factors of gram stain

Answer 13

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

Question 14

Gram + cells and their stain pattern

Answer 14

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

Question 15

gram - cells and their stain patter

Answer 15

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

Question 16

Gram + and aerobic cells

Answer 16

COCCI

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

BACILLI

• Corynebacterium
• Listeria

Question 17

Gram + and anerobic

Answer 17

COCCI
Peptococcus
Peptostreptococcus

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

Question 18

Gram - and aerobic and bacilli

Answer 18

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

Question 19

Gram - and anerobic

Answer 19

BACILLI

- bacteriosides

Question 20

Gram - and aerobic and cocci

Answer 20

Moraxella

Neisseria

Question 21

Atypical bacteria

Answer 21

•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 (-)

Question 22

Blood cultures

Answer 22

obtain when pt is febrile and pt spikes a fever

obtain two sets

Question 23

Sensitivity results of blood cultures

Answer 23

May take 24-72 hours, sometimes longer

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

SIR

Question 24

Quantitative results

Answer 24

• 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

Question 25

Positive blood cultures do not always confirm infection

Answer 25

•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

Question 26

What to consider when choosing and empiric theroy?

Answer 26

* Nosocomial or community-acquired? * Mild or severe infection? * First or recurrent infection? * Infection source removable or not?

Question 27

Resources available for guiding empiric theory

Answer 27

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

Question 28

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

Answer 28

* 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

Question 29

Patient Factors

Answer 29

``` organ function pregnancy genetics PMH Allergies and DRUG interactions AGE cost and preference ```

Question 30

Pharmacokinetic considerations

Answer 30

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

Question 31

Pharmacodynamic considerations

Answer 31

bactericidal v bacteriostatic time dependent killers Concentration dependent killers

Question 32

Will the drug get to the site of infections?

Answer 32

•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

Question 33

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

Answer 33

* 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

Question 34

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

Answer 34

* The higher the drug concentration, the greater the killing * Fluoroquinolones: maximize the AUC:MIC ratio * Aminoglycosides: maximize the peak:MIC ratio

Question 35

Combination theray

Answer 35

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

Question 36

The SELECTIOn and DOSING of the abx can influence therapeutic success

Answer 36

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

Question 37

Host factors may render abx therapy less effective

Answer 37

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

Question 38

Types of resistance

Answer 38

intrinsic - naturally occurring Acquired -a normally sensitive organism develops resistance through genetic mutation

Question 39

what are the 4 categories of acquired antimicrobial resistance

Answer 39

- 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

Question 40

pt education on abx

Answer 40

* 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