AST Flashcards
beta lactams antimicrobial groups
penicillin
cephalosporins
carbapenems
monobactems
beta lactams mechanism of action
affect cell wall synthesis
penicillin
very narrow spectrum of activity
most Enterobacteriaceae and Staph are resistant
beta lactamase inhibitors
combined with beta lactams and help prevent the beta lactamases activity of bacteria
cephalosporins
addition of methyl group to beta lactam ring
1st-5th generation and the later generations have broader range of activity
3rd have greater activity against GNR and greater resistance to beta lactamases
carbapenems
ertapenem, imipenem, meropenem and doripenem
largely resistant to beta lactamases; widest spectrum of activity
IV
monobactems
aztreonam
treats PSA and other GNR
glycopeptide antimicrobial group
IV
interferes w/ cell wall synthesis
vancomycin: very large cannot penetrate GN cell wall; used for methicillin resistant organisms (MRSA)
antibiotics affecting protein synthesis
aminoglycosides
tetracyclines
macrolides
aminoglycosides
bactericidal
bind to 30s ribo preventing attachment to mRNA and translation
treat GN of ab and urinary
aminoglycosides examples
gentamycin
tobramycin
amikacin
aminoglycoside side effects
nephrotoxicity
irreversible ototoxicity (ears)
tetracyclines
bacteriostatic
inhibit by binding 30s ribo and inhibit attach. of tRNA
plasmid mediated resistance is common
tetracycline examples
tetracycline
doxycycline
minocycline
tetracycline treats what bacteria?
Strep
GNB
rickettsiae
mycoplasma
chlamydia
macrolides
bacteriostatic
inhibit prot. syn. by binding 50s ribo inhibit transfer of growing peptide to aa chain
transpeptidation and protein syn. r shut down
macrolide examples
erythromycin
azithromycin
clarithromycin
macrolides are used to treat what bacteria?
staph
strep
some GN
spirochetes
mycoplasma
chlamydia
drug of choice for bordatella pertusis, mycoplasma, legionella
antibiotics affecting nucleic acid synthesis
quinolones
rifamycins
quinolones
bacteriocidal
act on DNA gyrase/ topoisomerases to interfere w/ replication
quinolone examples
ciprofloxacin
levofloxacin
ofloxacin
moxifloxacin
gemifloxacin
quinolones treat what bacteria?
GN (Enteriobacteriacea, Haemophilus, Neisseria, Moraxella catarrhalis
quinolone problems
GI disorder may occur
resistance has been seen
rifamycins
inhibits RNA polymerase which forms mRNA
rifampin (semisynthetic)
for TB
antibiotics affecting metabolic processes
sulfonamides
sulfonamides
folic acid syn. inhibitor
bacteriostatic
used w/ trimethoprim
can cause allergic rxn
mechanisms of resistance
natural (intrinsic)
acquired (mutational)
biofilms
all strains of Klebsiella are naturally resistant to what antimicrobial?
ampicillin
due to gene for penicillin specific beta lactamase
anaerobes are intrinsically resistant to what antibiotic?
aminoglycosides
due to lack of oxidative ET sys.
Staphylococcus saprophyticus is resistant to what antimicrobial?
novobiocin
used for ID
mechanisms of acquired resistance
`chromo mutations:
(target site modification, reduced permeability, bypass inhibited metabolic pathways, activation of efflux systems, prod. of enzymes that modify antibiotic, any combo of above)
bacterial biofilms
prevent phagocytosis
creates environment for exchange of genetic material
MRSA
mecA gene
resistant to all beta lactams, cephalosporins, carbapenems
what is the drug of choice for MRSA?
VANCOMYCIN
what drug is used to test for MRSA?
oxacillin
or cefoxitin
erythromycin resistance is through what gene?
erm gene
D test
erythromycin resistance can trigger clindamycin resistance
tests for this
Mueller Hinton agar
erthyromycin disk and clindamycin disk set close together, if zone of inhibition is a D shape shows inducible clindamycin resistance
VRE
vancomycin resistant Enterococcus
most common vanA and vanB
common antibacterials for UTI
ampicillin
cephalothin
cefazolin
nitrofurantoin
ciprofloxacin
trimethoprim/sulfamethoxazole
gentamicin
treatment of Enterococci
ampicillin
amoxicillin
Enterobacter are intrinsically resistant to what drugs?
ampicillin
1,2, cephalosporins
due to ampC beta lactamase
Serratia are resistant to what drugs?
ampicillin
1 cephalosporins
due to ampC beta lactamase
Citrobacter freundii is resistant to what drugs?
ampicillin
1 cephalosporins
due to ampC beta lactamase
Proteus is resistant to what drugs?
tetracycline and nitrofurantoin
Can instruments detect ampC?
no
Can instruments detect ESBLs?
Only in E. coli and Klebsiella
ESBLs
extended spectrum beta lactamases
inactivate penicillins, cephalosporins
do not hydrolyze cephamycin AB
inhibited by beta lactamase inhibitors
inactive against carbapenems
keyhole phenomenon
test for ESBL
test cefotaxime and ceftazidime alone and w/ clavulanate
If zone size increases 5mm or more w/ clavulanate= ESBL+
when disks are placed close together zones looks like a keyhole
ampC beta lactamases
are cephalosporinases
resistant to beta lactamase inhibitors
hyrdolyze cefamycins
ampC is found in what organisms?
MYSPACE: Morganella morganii
Yersinia enterocolitica
Serratia
Providencia/PSA
Aeromonas
Citrobacter freundii
Enterobacter/Hafnia alvei
