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Micro Exam 2: Antibiotics (more specific)
Microbiology!
75
Microbiology
Undergraduate 2
11/03/2012

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Cards

Term
What is Gentamicin? 
Definition
most commonly prescribed aminoglycoside
Term
What is Tobramicin?
Definition
an anti-pseudomonal aminoglycoside
Term
What is a common first line antibioitic for uncomplicated UTI's? 
Definition
TMP/SMX
Term
Which drugs require therapeutic drug monitoring?
Definition
drugs with low therapeutic range; aminoglycosides and vancoymycin
Term
Combination therapy may prevent the emergence of resistance of what?
Definition
  • mycobacterium tuberculosis
  • s aureus (fluroquinolone/rifampin)
Term
What are transglycosylases?
Definition
they are a PBP that is takes nascent peptidoglycan to backbone of cell wall 
Term
What are carboxypeptidases and transpeptidases? 
Definition
  • PBPs with a similar function
  • cleave terminal D-ala from pentapeptide 
  • ratio determines extent of cross linking
  • thought to influence cell shape
Term
Beta lactams are contraindicated in what type of patient?
Definition
patient with immediate hypersensitivity reaction history!
Term
if there is a history of skin rash with penicillins, what should you use?
Definition
cephalosporins are almost always safe!
Term
What are types of glycopeptides? What do they act against? 
Definition

They are cell wall active agents; 

vancomycin/teicoplanin

act against gram positive!!

Term
What is the action of glycopeptides? 
Definition
bind to terminal D-ala of nascent cell wall peptides and prevent cross-linking of these peptides to create mature peptidoglycan
Term
What are the 2 types of cell wall active agents?
Definition
  • beta-lactams
  • glycopeptides
Term
S. pneumoniae is responsible for what type of B-lactam resistance?
Definition
altered PBPs
Term
MRSA is responsible for what type of beta-lactam resistance?
Definition
Novel PBPs
Term
What are the 4 types of B-lactam resistance?
Definition
  • B-lactamase (msot common)
  • altered PBPs
  • Novel PBPs
  • altered permeability
Term
Glycopeptide resistanct is a primary concern for which microorganisms?
Definition
enterococcus and S. aureus
Term
Mechanisms of glycopeptide resistance:
Definition
altered target/ substitude D-lac for D-ala and vancomycin can no longer bind
Term
Beta-lactamase inhibitors do not affect which microorganisms? 
Definition
pseudomonas or enterobacter
Term
List 2 beta-lactamase inhibitors and their relative beta-lactam drugs:
Definition
  • clavulanic (amoxicillin and ticarcillin)
  • tazobactam (piperacillin)
Term
List bacteria which can be inhibited by beta-lactamase inhibitors: 
Definition
  • S. aureus
  • H. influenza
  • Niesseria sp. 
  • Bacteriodes fragillis
  • E. Coli
  • Klebsiella
Term
What does MLS stand for and what type of antibiotic are they?
Definition
  • stands for macrolide, licosamides, streptogramins
  • protein synthesis inhibitor
Term
List protein synthesise inhibiting antibioitics:
Definition
  • MLS
  • aminoglycosides
  • tetracyclines
  • linezolid
Term
Most common macrolide and what to look for to decide whether an antibiotic is a macrolide:
Definition
  • Erythromycin
  • look for -mycin
Term
What subunit of ribosome do macrolides bind to?
Definition
50s
Term
Two mechanisms of action of macrolides include:
Definition
  1. block growth of nascent peptide chain by stimulating dissociation of peptidyl-tRNA from ribosome
  2. inhibits assembly of new large ribosomal subunits (leads to depletion in cell)
Term
Macrolide resistance is caused by two (three kind of) mechanisms, what are they? What genes code for them? What phenotype?
Definition
  1. Efflux pump coded by mef(A); M phenotype
  2. Target Site Modification erm(B); MLSB phenotype
  3. rRNA (MLS)
Term
Active Efflux resistance is resistance to which antibiotic only?
Definition
macrolides
Term
is ribosomal modifications of macrolides inducive or constitutive?
Definition
inducive
Term
methylate adenine 2058 of 23s rRNA has to do with what antibiotic and what process?
Definition
macrolides (also MLSphenotype) and process of ribosomal modification resistance (target site modification) erm(B) can be other letters
Term
What are the 4 first choices of macrolide uses?
Definition
  • community acquired pneumoniae
  • pertussis
  • chlamydia trachomatis
  • mycoplasma
Term
What are 2 second choice uses of macrolides?
Definition
pyogenic streptococcal infections and C jejuni gastroentitis
Term
What is different about 2nd generation fluroquinolones? What mechanisms of action and name of drug. 
Definition

ciprofloxacin

- anti-pseudomonal and broader spectrum

Term

What is different about 3rd generation fluroquinolones? What mechanisms of action and name of drug. 

Definition

Moxifloxacin

- enhanced gram positive

+/- anaerobic

Term
what is Qnr resistance?
Definition
protection of topoisomerase in fluroquinolone action
Term
How is acquired resistance to fluroquinolones achieved?
Definition
acquisition of resistance determinants from viridans streptococci
Term
First aminoglycoside and date? Are they natural?
Definition
  • streptomycin (1944)
  • aminoglycosides are natural and semi-synthetic
Term
Aminoglycoside activity against gram positive and negative?
Definition
  • excellent activity against gram negatives (including pseudomonas)
  • good gram positive
Term
When deciding if aminoglycoside or not? 
Definition
  • look for -icin or just -cin
  • ex. gentamicin, tobramicin, amikacin
Term
Do aminoglycosides work in absesses? Why or why not? 
Definition

NO NO NO, do not work in any anaerobic conditions

they gain entry into inner membrane through energy dependent transport system - depend on the electron transport chain where O2 is needed

Term
What step of aminoglycoside action is rate limiting and by what?
Definition
the active transport through inner membrane is rate limiting and binding; blocked by divalent cations and anaerobiosis
Term
Is binding of aminoglycosides reversable or irreversable? What ribosomal subunit do they bind to?
Definition
  • irreversable
  • bind to 30s (like tetracyclines)
Term
What part of protein production does aminoglycosides inhibit?
Definition
proofreading; causes aberrant or truncated proteins
Term
Can aminoglycosides affect mammalian cells?
Definition
yes, at high concentrations it affects proteins (thats why it has a low therapeutic range with vancomycin!!)
Term
What are the three mechanisms of aminoglycoside resistance? 
Definition
  1. altered ribosomal binding site (streptomycin only)
  2. reduced uptake or decreased cell permeability
  3. enzymatic modification (most common)
Term
What is the most common form of aminoglycoside resistance? 
Definition

enzymatic modification!

- >70 enzymes; plasmid mediated, different substrate specificities

Term
What drugs inhibit metabolic pathways?
Definition

trimethoprim and sulfonamides

(TMP AND SMX)

SMX stands for sulfonamethoxazole

Term
TMP/SMX action against gram positive and negative
Definition
good gram negative, some gram positive
Term
sulfonamides act at what part of metabolic inactivation?
Definition
mimic PABA and stop transformation of PABA to dihydrofolic acid by tetrahydropteric acid synthetase
Term
trimethoprimes act at what part of metabolic inactivation
Definition

inhibit dihydrofolate reductase

stops dihydrofolic acid from being tetrahydrofolic acid

Term
TMP/SMX is commonly used for uncomplicated what?
Definition
UTI infections
Term
What is TMP/SMX used against
Definition
  • common uncomplicated UTIs
  • gastrointestinal infunction
  • management of PCP pneumonia
  • very active against anti-staphylococcal agents (CA-MRSA)
Term
Mechanisms of metronidazole action
Definition

short lived toxic intermediates or free radicals that damage DNA and other macromolecules

 

Term
does metronidazole have a high or low bioavailability orally (PO)
Definition
high (>90%)
Term
Does metronidazole have a long or short half life?
Definition
LONG - take bidaily
Term
side effects of metronidazole use
Definition
  • GI intolerance
  • antibuse effect
  • peripheral neuropathy
Term
metronidazole resistance? price?
Definition
  • resistance slow to develope
  • cheap
Term
Uses of metronidazole
Definition
  • anaerobic infections
  • C. Difficile colitis
  • Giardiasis
  • Trichmonas vaginitis and BV
  • H pylori (in combination)
  • parianal disease in IBD
Term
define transglycocylation 
Definition
the process where building blocks of peptidoglycan are added to the peptidoglycan backbone
Term
generations of cephalosporins are divided based on:
Definition
spectrum of activity
Term

second generation cephalosporins are also known as:

3rd generation are:

Definition
  • 2nd gen: respiratory cephalosporins
  • 3rd gen: IV drugs, gram neg activity, little gram pos
  • 5th gen: taken off market
Term
what worries people about VRE and MRSA in hospitals
Definition
VRE is resistant to drug that can be used against MRSA so scared that gene will transfer
Term
What is the best macrolide drug today?
Definition
clarithromycin
Term
what macrolide drug is bad to take - rips gut and you have to take many doses a day?
Definition
erythromycin
Term
In terms of Target Site Modification and Efflux pumps (in macrolides), which gives you low level resistance and which gives you high level resistance?
Definition
efflux = low level; TSM = high level
Term
can you get resistance from down regulation of porin channels?
Definition
NO, if you have efflux AND downregulation you can though (these are acquired genes)
Term
why must mycoplasma be treated with macrolides?
Definition
because mycoplasma doesnt have a cell wall! - it causes lower pneumonia (microlids are used for lower tract infections - upper you use something else)
Term
Are fluroquinolones natural or synthetic?
Definition
completely and totally SYNTHETIC - not found in nature
Term
what were fluroquinolones first designed for?
Definition
malaria
Term
What kind of drug is a respiratory fluroquinolone?
Definition
Moxifloxacin and other 3rd gen ..?
Term
What are the best 2 drugs to treat patients with anaerobic infections?
Definition
metronidazole and clindamicin 
Term
Can you take metronidazole and drink alcohol?
Definition
hell no sir. (violently sick)
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