Flashcards in micro poop 2. Deck (50):
1
What factors must be considered in choosing an antimicrobial agent?
identity of infecting organism, information about the susceptibility of the infecting organism, factors specific to the patient
2
What is empiric theory?
the application of knowledge of the organisms most likely to cause infection in a given clinical setting and its most likely susceptibility to an antibiotic
3
Why is knowing the susceptibility of the organism important in choosing an antibiotic?
organisms exhibit intrinsic or innate resistance to certain antibiotics so you won’t consider these, while some are universally susceptible to certain antibiotics
4
What factors to the patient are important to consider when choosing an antibiotic?
history of previous reactions, age (gastric acidity changes with age - important for orally ingested), pregnancy, renal/hepatic function, site of infection
5
pharmacokinetics
encompasses all the ways that the body manipulates a drug, including absorption, distribution, metabolism, and excretion
6
pharmacodynamics
describes the biochemical and physiologic effects of the drug and its metabolism of action on the bacteria
7
bacteriostatic
antimicrobial agents that inhibit the growth and/or reproduction of the infecting agent, but fail to actually kill the agent
8
Why is bacteriostatic typically better than bacteriocidal?
normal defenses typically destroy the microorganism
9
What are examples of bacteriostatic agents?
macrolids (erythromycin), clindamycin, sulfamethoxazole, trimethoprim, tetracyclines, chloramphenicol
10
bacteriocidal
antimicrobial agent that is capable of causing irreversible damage or death to the organism
11
What are examples of bacteriocidals?
b-lactam antibiotics (penicillins and cephalosporins), vancomycin, aminoglycosides, fluoroquinolones
12
What is a factor that can influence if a antimicrobial is bacteriostatic or bacteriocidal?
antimicrobial concentration at the site of action - can be bacteriostatic at low concentrations and bactericidal at high concentrations
13
MIB
Minimal bacteriocidal concentration - the lowest concentration which prevents the organism from multiplying
14
broad spectrum antibiotics
active against wide range - usually both gram positive and gram negative
15
When are broad spectrum typically used?
empirically prior to identifying the causative bacteria (wide differential and potentially serious illness)
16
narrow spectrum antibiotic
active against a select group of bacterial types
17
What are the five mechanisms antibiotics inhibit/kill bacteria?
interfere with cell wall synthesis, protein synthesis, cytoplasmic membrane function, nucleic acid synthesis, metabolic pathway
18
What are antibiotics that interfere with cytoplasmic membrane function tricky?
all organisms have a cytoplasmic membrane
19
What antibiotics interfere with cell wall?
beta lactams (penicillin, cephalosporin, carbapenems, monobactams), vancomycin, bacitracin
20
What antibiotics interfere with cell membrane?
polymyxins
21
What antibiotics interfere with folate synthesis?
sulfonamides, trimethoprim
22
What antibiotics interfere with DNA gyrase?
quinolones
23
What antibiotics interfere with RNA polymerase?
rifampin
24
What antibiotics interfere with ribosome subunits?
macrolides, clindamycin, linezolid, cholamphenicol, streptogramins, tetracyclines, aminoglycosides
25
What is the mechanism of action for inhibitors of cell wall synthesis?
interfere with peptidoglycan sheet synthesis and murrain assembly
26
What are the beta-lactams?
PCCM (P-in, C-in, C-em, M-am) penicillin, cephalosporin, carbapenem, monobactam
27
How do beta lactams work?
bind at the active site of the transpeptidase enzyme that cross-links the peptidoglycan strands, irreversibly inhibiting the enzyme - formation of cell wall is prevented (non toxic to human)
28
What is the general structure of a penicillin? What group does it belong to?
house with an attached garage, beta lactams that block cell wall synthesis
29
How are cephalosporins categorized?
by generation - each generation exhibiting increased spectrum of activity as well as increased resistance to destruction by beta=lactamase enzymes
30
What is the structure of a cephalosporin?
weird house with attached garage
31
What are the third and fourth generation cephalosporins more targeted towards?
gram negative bacteria
32
carbapenems
cell wall inhibition - active against all pathogenic organisms and resistant to destruction by the extended spectrum beta lactamases
33
What is the structure of a carbapenem?
house with both attached and detached garage
34
What is the only antibiotic that works against MRSA?
vancomycin
35
What is the method of action for vancomycin?
blocks residues instead of cleaving like penicillin - prevents crosslinking
36
What bacteria are vancomycin effective against?
gram-positive bacteria (including MRSA) - gram negative resistant due to LPS porons
37
What is used for people who are allergic to penicillin? What is the method of action?
inhibitors of protein synthesis - infere with formation of 30S complex, 70S ribosome, or block elongation process
38
aminoglycosides - method of action and danger of these drugs
inhibit protein synthesis - causes misreading of mRNA —> therapeutic level is high, near toxic level - need to stop and give kidneys a rest
39
linezolid - method of action and when should it be used
inhibit protein synthesis - should only be used against gram + bacteria that are resistant to other antibiotics
40
macrolids
bacteriostatic - block protein synthesis
41
lincosamides
similar to macrolids - inhibit protein synthesis
42
chloramphenicol - method of action and when should it be used
inhibits protein synthesis - VERY TOXIC - should only be used against salmonella
43
tetracyclines
inhibit protein synthesis - static in nature, immune system must be able to clear the bacteria
44
quinolones/fluorquinolones
inhibition of DNA synthesis - esp inhibiting DNA gyrases/topoisomerases required for supercoiling DNA
45
metronidazole
inhibition of DNA synthesis
46
rifampin
inhibition of RNA synthesis
47
bacitracin
inhibition of RNA transcription
48
What is trimethoprim used in combination with?
sulfamethoxazole
49
trimethoprim
prevention of synthesis of folic acid
50