Antibiotics Flashcards
What 3 antibiotics are resistant to ESBL producers?
Cephalosporins
Penicillins
Aztreonams
MIC definition
Lowest concentration of antibiotic that prevents growth
MBC definition
Lowest concentration of antibiotic at which bacterial population killed
MIC testing methods
Broth
E test
Automated systems
Qualitative susceptibility tests
Kirby Bauer
Principle of E test
Plastic strips containing preformed and predefined continuous stable antimicrobial gradient
Mueller Hinton agar
Ellipsis of growth - MIC
What tube is the MIC?
First tube without turbidity
Principle of Kirby Bauer
Single drug concentration diffuses out of disk
Creates a gradient (highest closest to disk)
Measure zone of inhibition
What things can cause an falsely large zone in Kirby Bauer?
Thin media
What can cause a false small zone in Kirby Bauer?
Too much in bacteria
What antibiotics inhibit cell wall synthesis?
Beta lactams (penicillins, cephalosporins, carbapanems, monobactams)
Vancomycin
Daptomycin
Polypeptides
What antibiotics inhibit gyrase?
Topoisomerase
Quinolones
What antibiotics inhibit folate synthesis?
Trimethoprim
Sulfamethoxazole
What antibiotics inhibit free radicals?
Metronidazole
Nitrofuratoin
What antibiotics inhibit the 50S unit?
Macrolides Clindamycin Linezolid Streptogramins Chloramphenicol
What antibiotics inhibit 30S?
Aminoglycosides
Tetracyclines
Tigecycline
what causes:
Tetracycline zone too large
clindamycin zone too small
E. coli or S. aureus controls
pH too low
what causes:
small tetracycline zone
large clindamycin zone
E coli or S aureus controls
pH too high
what causes:
small aminoglycoside zone
P. aeurginosa control
Ca and/or Mg too low
penicillins
methicillin, oxacillin, ampicillin, piperacillin
cephalosporins
cephalexin
cefotoxin
carbapenems
imipenem
monobactams
aztreonam
glycopeptides
vancomycin
macrolides
erythromycin
tetracylcines
tetracycline
doxycycline
aminoglycosides
gentamycin
tobramycin
amikacin
sulfonamides
trimethoprim
quinolones
ciprofloxacin
levofloxacin
major organism natural penicillins
strep
1st gen cephalosporins
cephalothin
cefazolin
cephalexin
cefadroxil
1st gen cephalosporin activity
G+C except enterococcus
enterics
2nd gen cephalosporins
cefoxitin
cefuroxime
cefotetan
cefuroxime
3rd gen cephalosporins
ceftoxamine
ceftriaxone
ceftizoxime
ceftazidine
aztreonam active against
pseudomonas
GNR
beta lactams
penicillins
cephalosporins
monobactam
glycopeptides
miscellaneous beta lactams
imipenem
meropenem
doripenem
vancomycin active against
G+
C diff
bacitracin active against
G+
some G-
topical
polymyxin B and colistin active against
G-
topical
aminoglycosides active against
G+
G-
what is tobramycin particularly useful for
pseudomonas and acinetobacter
tetracyclines active against
G+
G-
intracellular organisms
macrolides active against
intracellular organisms
erythromycin active against
G+ Respiratory infections (M pneumoniae, Legionella, Neisseria, Haemophilus)
clindamycin active against
G+
what G+C is universally susceptible to penicillin
group A, B, C strep
drugs for G- infections
aminoglycosides ES pencillins cephalosporins quinolones imipenem
drugs for pseudomonas
aminoglycosides
ES penicillins
3 gen cephalosporins
imipenem
ANA drugs
ES penicillins B lactams cefoxitin chloramphenicol imipenem metronidazole
nalidixic acid active against
UTI
flroroquinolones active against
complicated UTI
invasive ear infectionsfrom G-
too much Ca and Magnesium in Mueller Hinton affects
decreased activity of aminoglycosides and tetracyclines
increased thymidine in mueller hinton affects
decreased activity of sulfonamides
increased pH affects what
increased activity against aminoglycosides, eryhtromycin, clindamycin
(increased diameter)
decreased activity of tetracycline
agar too thick
smaller zones of inhibition
agar too thin kirby bauer
larger zones of inhibition
drugs for enterobacteriaceae
penicillins cephalosporins aztreonam imipenem aminoglycosides quinolones tigecycline trimethoprim sulfamethoxazole
drugs for staph
penicillins quinolones vanc erythromycin clindamycin trimethoprim tigecycline
drugs for pseudomonas
penicillins cephalosporins aztreonam imipenem aminoglycosides quinolones
drugs for enterococcus
ampicillin gentamycin vancomycin tigecycline linezolid
drugs for strep pneumoniae
pencillin cephalosporins imipenem quinolones vanc erythromycin clindamycin trimethoprim
organisms that most often produce beta lactamase
staph haemophilus influenzae neisseria gonorrhoeae moraxella enterococcus
most sensitive beta lactamse method
chromogenic cephalosporin nitrocefin
3 mechanisms for resistance to beta lactam anitbiotics in staph aureus
production of penicillin binding protein (mecA gene)
hyper beta lactamase production
production of modified PBPs
which type of MRSA is resistant to clindamycin and erythromycin
health care associated infections from MRSA
what gene is responsible for erythromycin resistance
msrA
what gene is responsible for clindamycin resistance
erm
what test is used to detect inducible resistance to clindamycin
D test
organisms that can be ESBL
e coli klebsiella proteus morganella serratia enterobacter pseudomonas
what induces AmpC
cefoxitin
imipenem
ampicillin
organisms with AmpC
providencia aeromonas citrbacter enterobacter morganella pseudomonas
what is AmpC
cephalosporinase
cephalosporin resistance
