Flashcards in Antimicrobials Deck (106)
What is MIC?
Minimum Inhibitor Concentration
The lowest concentration of antibiotic required to prevent growth
What is MBC?
Minimum Bacterial concentration
Lowest concentration required to kill bacteria
What is the action for bactericidal antimicrobials
Destroys bacterial cell wall
What is the action for bacteriostatic antimicrobials?
Stops bacteria from growing stops DNA synthesis of bacteria and halts production of new bacteria
What is the difference between narrow spectrum and broad spectrum antimicrobials?
Narrow spectrum kills specific types of bacteria
Broad spectrum kills every type of bacteria
Explain concentration dependent killing of bacteria?
Anitibiotic which increase the rate and extent of bacteria killing wih increased concentration
What type of antibiotics are concentration dependent killing antibitics?
Explain time dependent killing of bacteria
Greater concentration do not kill vecteria faster. Clinical efficacy is related to the length of time for which high levels of concentration of the antibiotics are maintained
What types of antibiotics are considered time dependent killing antibiotics?
Macrolides (erythromycin, clindamycin)
T/F: Continuous infusion of antibiotics has shown to be more effective than intermittent boluses
Some antibiotics continue to suppress the growth of bacteria after the antibiotc is no longer detectable. What is this known as?
Post antibiotic effect PAE
What is the post antibiotic leukocyte effect?
After the majority of the bacteria is killed the body can begin to start killing bacteria itself with its own leukocytes
What are the two types of resistance to antimicrobials?
Intrinisic - natural resistance to antimicrobial
Acquired - genetic alteration in the bacteria occurs which causes a once effective antimicrobial ineffective
Describe decreased permeability for resistance
The porins are altered which inhibits the antibiotic from entering the cell causing resistance to the antibiotic
Describe decreased efflux in antibiotic resistance
Cells will actually pump out the antibiotic - importance for macrolides, fluoroquinolones and some beta lactams
Describe inactivation in antibiotic resistance
Bacteria forms its own wnzymes which bust open the beta lactams and inactivates them - the enzyme is betalactamases
Which enzyme inactivates beta lactam antimicrobials?
Beta lactamase busts open the beta lactams an inactivates them causing resistance
What is an example of target modification in antimicrobial resistance?
The bacteria which is suseptable to penicilllin modifies its peniclillin binding proteins which disallow penicillin to bind to its receptors causing resistance to penicillin MRSA is an example
What is a positive reason to use multiple drug therapy?
More then 1 drug may be needed to treat infections. Broad spectrum agents may be able to adequately cover multiple organisms with a single agent
What is a negative outcome of muliple drug therapy
The unintended bacteria is introduced to antimicrobials and begins to produce antibodies against that antimicrobial leading to future resistance
What is an effective way to prevent resistant strains of organisms during mulidrug therapy?
Administer 2 antibiotic with different MOA to prevent resistance
What are the different synergies associated with multidrug therapy
Antagonist 1 +1 = 0.5
Indifferent 1 + 1 =1
Inbetween 1 +1 =1.5
Additive 1+1 = 1.5
Synergistic 1 + 1 = 3
Treatment of an infection with an effective therapeutic course of antimicrobial agents is based on what?
The right concentration of the right antimicrobial reaching the right site of action for a sufficient period of time to kill or inhibit bacterial growth
What is an antibiogram?
Antibiotics are tested against each known bacteria. Antibiograms list the degree of susceptibility and resistnace bacteria has to each antibiotic. Helps to choos the best antibiotic against a specific bacteria
What factos increase a patient risk for a specific type of infection?
Impaired host defenses:
In pregnant women which antibiotic causes acute necrosis of the live, pancreatitis, and possible renal failure and should be avoided?
Which antibitiotic have been deemed safe for pregnancy?
Aminoglycosides if necessary
In regards to nosocomial infections, where do most occur in the body?
Most in the urinary tracct - staph aureus is most common
What devices are highly associated with nosocomial infections
vascular access catheters
A catheter related infections is defined how
At least 1 positive blood culture drawn from both a catheter and a peripheral site
A positive culture drawn through a catheter is nonspecific but a negative culture drawn through a catheter rules out a catheter related infection
What sites of cntral line insertion are associated with the highest rates of infection?
Which antibiotic should first be used to treat catheter related infections?
Vancomycin due to the high prevalence of methicillin reistant Staph aureus. Adjust the therapy when the actual offending organism is properly identified
Which antibiotic is probably the best to use for surgical prophylasxis
1 st generation cepalosporin such as Cefazolin due to it's low cost and broad spectrum and low incidence of allergic reactions
Usually, surgical prophylaxis antibiotics should not be continued for how long after surgery
No more than 24 hours post op
Describe the Class 1 clean wound?
Atraumatic, with no break in sterile technique. The respiratory, GI, and GU tracts are not entered.
No need for prophylactic antibiotic
Describe Class II wound classification
Class II Clean Contaminated
Surgery in areas known to harbor bacteria with no spillage of contents
Describe Class III wound classification
Cass III Contaminated
Major break in sterile technique with a traumatic wound and gross GI spillage, entrance into biliary or GU tract
Describe Class IV would classification
Class IV Dirty infected
Infection exists before surgery. OLd wound with devitalized tissue or perforated viscera
Which wound classification will require at least one dose of antibiotic?
Class II and beyond
Which antibiotic are best for UTI's?
3 rd generation cephalosporins
What is the proper timing of the initation of surgical prophylaxis antibiotics?
Antibiotics should be initiated within 1 hour prior to incision or start of procedure when no incision isrequired
Fluoroquinolone or vancomycin may be initiated 2 hour prior to incision or precedure start
Which antibiotic is most recommended for surgical procedures and which antibiotic may be given as an alternative?
Cafazolin is most commonly given and Clindamycin is the most common alternative
Which antibiotic is more effective against anaerobes and should be given for aspiration pneumonia?
Which bacteria is the leading cause of nosocomial GI infections?
Which form of bacteria can be provoked by the use of antibiotic therapy
Diagnosis of C. Difficile is confirmed by the presence of which toxins?
Either Enterotoxin A or Cytotoxin B
Which antibiotic is the first line of therapy for C. Difficile?
PO Vancomycin may be used in cases not responding to metronidazole
Diicid - new drug
Which antibiotics contain the beta lactam ring and inhibit cell wall synthesis
Beta lactams (PCN)
How do bacteria form resistance to PCN
Bacteria form beta lactamase which is an enzyme that breaks the beta lactam ring and disables the molecule . Bacteria with beta lactamse can resist the effects of beta lactam antibiotics.
What are the beta lactamase inhibitors?
Bacteria with beta lactamase attack these inhibitors leaving the beta lactam ring of the true antibiotic intact
Which beta lactam can produce Jarisch Herxheimer reaction?
A flu like reaction caused by PCN along with GI upset and diarrhea
What is the IV form of PCN?
PCN G = IV/IM
PO form given without food
Amoxicillin is given PO or IV?
-PO without regards to food with or wihout food
Older generations of betalactams (PCN) are better for gram + or gram - bacteria
Older generations are better for gram _ and newer generation are better for gram - bacteria
Which penicillins are poor for PO absorption?
Use of Ticarcillin and piperacillin cause what adverse reactions?
Prolonged bleeding times
neutropenia at high doses
What is the mechanism of action for cephalosporins
Spectrum of action based on generation 1 - 5
Gram + to Gram -
When should first generation Cephalexin and Cefazolin be redosed?
Redose after 2 half lives
(Cefazolin half life is 4 hours)
(Cephalexin half life is 1 hour
Which vephalosporin causes diarrhea and biliary sludging and should not be given to kids?
Which cephalosporin precipitates with calcium in the same IV line?
Which carbapenem has a high risk for seizures?
With cilastatin - inhibits dihydropeptidase which is an enzyme that breaks down imipenem
Which form of Vancomycin is best given for C. Diff?
Highest concentration levels for MIC for vancomycin are for what infections?
Pneumonia, CNS, infection, seer osteomyelitis
What adverse effects are seen with vancomycin?
Red man syndrome
All from rapid infusion
Vancomycin should be infused at what rate
No more than 1 gram / hour
What is a good loading dose for vanomycin?
What is the mechanism of action for vancomycin?
Disrupts cell wall synthesis, vactericidal
Is vancomycin concentration or time dependent?
Which antibiotic causes myelosuppression, anemia leukopenia, pancytopenia, and thrombocytopenia?
Causes accelerated HTN and Fever
Which family of antibiotics causes the most GI upset and toxicity?
Which antibiotic is best for upper and lower respiratory infections?
What effect on the heart may macrolides such as azithromycin have?
Which macrolides are potent inhibitors of CY3A4?
Which macrolids is the 2nd choice for gastroporesis
Whihc family of antibiotics have many drug interaction including NSAIDS, Warfarin, Antacids, Amiodarone?
What CNS effects are seen with fluoroquinolones?
Anxiety altered glucose
T/F: Fluoroquinolones may be given to trauma and orth patients
False Have a higher risk of post op pain
T/F: Fluoroquinolones may be given to children?
Not for children under 12
Could cause joint damage
Which antibiotic is the best drug of choice for GI infections?
Which fluoroquinolone is best for lung infections?
Which antibiotic (Tetracycline) causes permanent tooth discoloration?
At what age should doxycycline not be given to children?
After their adult teeth have come in
Which tetracycline has high incidences of nausea and vomiting?
Which family of anitbiotics prolongs neuromuscular blockade?
Aminoglycosides - interferes with Ca++ and Mg++ cross bridges between cell membranes
Which aminoclycoside has the best gram positive coverage?
2 bacteriostatic antibiotics has the same mechanism of actions?
Which antibiotic is best for dirty surgeries involving the GI tract?
Which antibiotic has the highest risk for C. Diff?
What effect does clindamycin have on neuromuscular blockade?
Prolongs neuromuscular blockade
What effects are seen with metronidazole-coumadin reaction
Coumadin levels increase and PT levels are increased
Which antibiotic is a CYP 450 inducer and shortens the life of medication using th eCYP system?
Rifampin and Rifabutun
What side effects will be seen in all body fluids including tears, saliva, and urine when taking rifampin?
Will see orange red in color
Are beta lactams time dependent or concentration dependent?
Beta lactams are time dependent
Are aminoglycocides time dependent or concentration dependent
Aminoglycosides are concentration dependent
Which antibiotics are of the beta lactam confiuration
Beta lactamase inhibitors
What is the most common form of resistance in antibiotics?
Bacteria cells produce beta lactamase which breaks down the beta lactam ring of the molecule and mades the molecule inactive causeing resistance
When is the best time for administration of PCN?
1-2 hours before a meal with the exception of amoxicillin
Which antimicrobial present the risk of prolonging neuromuscular blockade when paralytics are used?
Particularly when used with non depolarizing neuromuscular blocking agents
Hown may prolonged neuromuscular blockade be treated?
Neostigmine and colcium all increase the presence of acetylcholine at the neuromuscular junction
Which 3rd generation cephalosporin antimicrobial is best for pseudomonas?
Which 3rd generation cephalosporin is best for staph coverage?
Patients with active seizure should not take which antimicrobial?
Which antibiotics are responsible for prolonging QT intervals?
Flurorquinolones - CIPRO , levaquin
Macrolides - erythromycin, azithromycin, clarithromycin
Which antibiotic may have the longest half life
Azithromycin - 68 hours
During pregnancy , which antibiotics should be avoided due to potential for injury to the fetus?