LEC 1 Flashcards
Which bacteria type has a thicker PG layer, Gram + or - ?
+
Gram + bacteria have _ membrane(s); gram - have _ membrane(s)
1, 2
Gram + peptidoglycans contain an ______ residue
L-lysine
Gram - peptidoglycans contain ______
mesodiaminopimelic acid (DAP)
In gram _ bacteria, beta lactamases are confined to the periplasmic space
-
In gram _ bacteria, beta lactamases are excreted through the cell wall to the external enviornment
+
Transpeptidase catalyzes bond formation between 2 ___ residues and one ____
glycine; d-ala
Result of Peptidoglycan cross linking:
peptide-____-_____-_____-peptide
D-ala-glycine-glycine
BL Mechanism: Beta lactams _____ the transpeptidase ___ residue in the enzyme active site
acetylate; serine
BL Mech: acetylation of the serine residue ____ transpeptidase, leading to a defective cell wall, ____ stress, cell lysis and death
inactivates
osmotic
Beta lactams are bacterio____
cidal
Beta lactams are highly reactive due to a highly strained _______
4 membered ring
Mechanisms of resistance to beta-lactams:
____ cellular uptake
mutation of _____ changing the affinity
decreased
PBPs
Mechanisms of resistance to beta lactams:
presence of _____ ____ that pumps AB out
Induction of bacterial ________, catalyzing hydrolysis
efflux pump
beta-lactamases
Penicillin allergy results from the drug acting as a ____ and _____ host protein
hapten;
acylating
Products of penicilling degradation under acidic conditions (ie stomach):
benzylpenicillenic acid; benzylpenillic acid; benzylpenicilloic acid
Electronegative side chains reduce ____, stabilizing penicillin against hydrolysis under _____ conditions, and increasing ____ viability
nucelophillicity; acidic; oral
Penicillin __ is typically administered IV; and penicillin _ is typically oral
G; V
Water soluble penicillins are typically ____ protein bound, while lipophillic penicillins are usually ____ protein bound
less
more
Ampicillin is the ____ protein bound and most water soluble; _____ is the most protein bound and most _____
least;
cloxacillin, lipophillic
More lipophillic side chains = _____ bioavailability and _____ degradation
less; less
Beta lactams are excreted via ____ or ____ routes
renal, biliary
90% of renal excretion is due to tubular _____
secretion
Penicillin are (Cationic or anionic); thus, we use ____ to increase penicillin’s its half-life
anionic;
probenecid
Methicillins (are/are not) sensitive to beta-lactamases. This is due to _____ ____ of the nucelophillic attack on the carbonyl group
are not;
steric hindrance
Methicillins are acid stable or acid labile?
LABILE–>use injection
MRSA is due to a mutation on the ____, causing low affinity for binding of beta lactams. The gene involved is ___, and the protein is ____
PBPs; mecA; PBP2A
Cephalosporins are ___-member rings
6
Cephalexin is _____ active. The _____ group is protonated at physicological pH, making the side chain ____ attracting and decreasing hydrolysis under ____ conditions
orally;
amino;
electron;
acidic
Carbapenems have a ____ group that replaces the _____ ring seen in penicillin, increasing reactivity
methylene; thiazolidine
Imipenem ____ beta-lactamases
inhibits
Imipenem is hydrolyzed by renal _______, so administer it along with _____
dehydropeptidase 1, cilastin
Example of a monobactam:
aztreonam
Aztreonam’s contain a _____ acid group at the ____ position, taking the place of a carboxyl group seen in penicillin
sulfamic; C2
