Antibiotics Flashcards
What is empiric therapy
treatment prior to the identity of the organism
When is empiric therapy indicated
In critically ill patients
What type of treatment is given for empiric therapy
Broad spectrum
What is antibiotic sensitivity consideration based on
Pattern of antibiotic sensitivity
Lab testing
What is MIC
Lowest concentration of a drug that inhibits bacterial growth (minimal inhibitory concentration)
What is MBC
Minimal bactericidal concentration
Lowest concentration of a drug that kills bacteria
How do bacteriostatic antibiotics work
They inhibit bacterial replication but does not kill bacteria
Host defenses required
What are some miscellaneous considerations to include when choosing an antibiotic
Route of administration
Tissue distribution
Route of metabolism/ elimination
Side effects/ toxicity
What are the host specific considerations to have while choosing an antibiotic
Immune status
Anatomy
allergies
Bioavailability
Other drug interactions
age
pregnancy
renal function
Why do you have to consider immune status before giving an antibiotic
Are they neutropenic
Do they have cell mediated defects
What type of antibiotic would you give someone with a compromised immune system
bactericidal
Why do you consider the anatomy before giving an antibiotic
Do they have an abcess, necrotic tissue, foreign material
Need to match the drug bioavailability to the site of infection
What type of drug would you give for an immune protected area
Bactericidal
What are some immune protected areas
CNS
Eye
Bacterial endocarditis
Why is renal function important to consider before administering an antibiotic
Some drugs need to be dose adjusted because the kidney filters them
Why is age important to consider before prescribing antibiotics
You should avoid chloramphenicol and sulfonamides in neonates
avoid tetracyclines in small children
What type of antibiotic would you avoid prescribing during pregnancy
Aminoglycosides
Which antibiotics are poorly absorbed in the GI tract and thus require IV admin instead of oral
Vancomycin and aminoglycosides
What is synergy
When the combined effect of two antibiotics is greater than if they were given alone
What is antagonism
When the combined effect of two antibiotics is worse than if given alone
What is indifference
When the effect of 2 antibiotics equals that of their independent activity
B-lactam combined with aminoglycosides against gram negative bacteria is an example of what type of interaction
Synergistic
Penicillin (Bactericidal against susceptible forms of strep pneumoniae) combined with tetracycline (Bactericidal) would give what type of effect
Antagonistic
What are some examples for antibiotic prophylaxis
prior to surgery
Pre dental extractions
Prevention of TB / meningitis
PJP in HIV infected patients
Recurrent UTI
Which antibiotics require dose adjustment in renal insufficiency
Penicillin
Amoxicillin
Piperacillin/ Tazobactam (Zosyn)
Cephalexin
Cefuroxime
Ciprofloxacin
Levofloxacine
Trimethoprim
Clarithromycin
Where are the common mechanism of action sites
Cell wall synthesis
Folic acid metabolism
Periplasmic space
Cell membrane
Protein synthesis
DNA gyrase
DNA directed RNA polymerase
What are the different types of protein synthesis in which antibiotics can have an effect
tRNA
30s inhibitors
50s inhibitors
What types of drugs are cell wall synthesis inhibitors
Penicillins
Monobactam
carbapenems
Combo agents
Cephalosporins
Glycopeptides
What is the mechanism of action for B-lactam antibiotics
Interfere with cell wall synthesis by binding to penicillin binding proteins.
This compromises the cell wall integrity = cell lysis
Enhances cell breakdown by activating autolytic enzymes
What are penicillin binding proteins
Transpeptidase enzymes that catalyze cross-linking of peptidoglycans
What is penicillin made up of
Thiazolidine
B-lactam ring
Side chain
What does the B lactate ring do
Essential for antibacterial activity
What does the side chain in penicillin do
Determines the antibacterial spectrum and pharmacologic properties of a particular penicillin
What are the classifications of penicillin
Natural
Aminopenicillin
Semi-synthetic
Ureidopenicillin
Beta lactamase inhibitor
What type of penicillin is considered natural
Penicillin G
Penicillin V
Which forms of penicillin are penicillinase sensitive
Natural
Aminopenicillin
What forms of penicillin make up the aminopenicillins
Ampicillin
Amoxicillin
What makes up the semi-synthetic penicillin
Nafcillin
oxacillin
Dicloxacillin
What types of penicillin are penicillinase resistant
Semi synthetic
What makes up ureidopenicillinl
piperacillin
Ticarcillin
How is piperacillin used
Never alone, always needs a b-lactam inhibitor
what type of penicillin treat gram positive cocci
Penicillin G, V
What pathogens are considered gram positive cocci
Strep pneumoniae
Group A strep (S. pyogenes)
Group B strep (S. agalactiae)
Group C,G strep
Viridans strep
What does Strep pneumoniae cause
Sinusitis
otitis media
Pneumonia
meningitis
What does group A strep cause
Bacterial pharyngitis
Cellulitis
toxic shock
Necrotizing fasciitis
What does group C,G strep cause
Cellulitis
Skin/soft tissue infections
What does group B strep cause
Meningitis in newborns
Bacteremia in elderly / diabetics
What pathogen does penicillin G,V not cover
Staph
What is penicillin V typically used for
Generally for group A strep (Strep throat)
Generally in kids or anyone with a doxycycline allergy
Syphillis
What type of gram negative cocci does natural penicillin treat
Neisseria meningitidis (Meningitis and bacteremia)
Why is natural penicillin not useful to treat N. Gonorrhoeae
Because of the widespread presence of penicillinase
What are the pharmokinetics for Penicillin V and G
Penicillin V = oral
Penicillin G = IV/IM
Why is penicillin not a good agent against bactericides fragilis and other bactericides spp?
Because of the presence of beta-lactamase
What is Natural penicillin’s spectrum of activity for spirochetes
Works against
treponema pallidum (Syphilis)
Borrelia burgdorferi (Not typically used to treat Lyme though)
Why does penicillin G require frequent dosing when prescribed
Because of its 1/2hour half life
Which natural penicillin has better oral bioavailability
Penicillin V
If a patient requires an IM penicillin G administration, what is important to remember
That it cannot be given alone when given via IV
What is the most common side effect from Penicillin
Rash
What are the side effects of penicillin
Rash
Seizures
Anaphylaxis
When are patients at a high risk for seizures with penicillin
When a patient has a seizure disorder OR when a high dose of Pen G is given to someone with renal insufficiency
What is a contraindication for natural penicillin
Hypersensitivity to B-lactams antibiotics
Use with caution in patients with asthma or with a hx of multiple allergens
Which organism is penicillin resistant and why
S.aureus
Contains a penicillinase which hydrolyzes the beta lactase ring
If a patient has a suspected S. aureus infection- which antibiotic should NOT be used
Natural penicillin and Aminopenicillin
What is methicillin
The first penicillin developed to resist hydrolysis by staph beta-lactamase
What is methicillin used for
Treatment of infections caused by penicillinase-producing staph
Which type of penicillin is more useful against strep A, Strep B, and strep pneumonia
Penicillin G
What organism is semi-synthetic penicillin not useful against
Gram - activity
What is the IV/IM form of semi-synthetic penicillin
Nafcillin and oxacillin
What is the PO form of semi-synthetic penicillin
Dicloxacillin
Which semi-synthetic penicillin do not require renal or hepatic dosing adjustments
Dicloxacillin
Oxacillin
If a patient comes in with an MSSA infection… what would be the best type of penicillin to treat it with
Oxacillin or nafcillin
If a patient comes in with elevated creatinine, fever, and peripheral eosinophilia, what is their likely diagnosis
Allergic interstitial nephritis
What causes neutropenia with oxacillin/nafcillin dosing and when is it seen
Occurs 3 wks after a high dose therapy and is treated by decreasing the dose
Which antibiotic is 2x more active against enterococci than penicillin
Ampicillin or amoxicillin
If a patient comes in with listeria monocytogenes, what would be the antibiotic used to treat
Ampicillin or amoxicillin
What is the cause of meningitis in immunosuppressed patients, newborns, and individuals over 50
Listeria monocytogenes (Aminopenicillin better to treat than natural penicillin)
What is ampicillin/amoxicillin spectrum of activity against gram positive cocci
Active agent against penicillin-susceptible s. aureus
Not useful for most S.aureus though because of the beta-lactamase ring
What kind of gram - bacteria do ampicillin/amoxicillin treat
H. Influenzae
E. coli
*~40% resistant due to beta-lactamase
What are the common side effects of ampicillin and amoxicillin
Rash (4-8%)
Diarrhea (2-5%)
- worse is ampicillin
If a patient is given amoxicillin when they have infectious mononucleosis, what is the likely reaction going to be
Erythematous rash
What happens to the spectrum of activity if you combine B-lactamase inhibitors
Increase
When is IV ampicillin-sulbactam used (unasyn)
MSSA (gram+)
H. influenza , E.coli, K. Pneumonia (Gram -)
Bacteroides Fragilis (Anaerobe)
When is PO amoxicillin-clavulanate used (Augmentin)
MSSA (gram+)
H. influenza , E.coli, K. Pneumonia (Gram -)
Bacteroides Fragilis (Anaerobe)
What do beta-lactamase inhibitors treat better than ampicillin/amoxicillin
Better gram negative activity
What are the narrow-spectrum b-lactamase susceptible agents
Sreptococci
enterococci
Anaerobes
What are the very narrow spectrum B-lactamase resistant agents
S.Aureus, s epidermidis, streptococci
What type of drug is cephalosporin
Bactericidal
How is cephalosporin different from penicillin
Resistant to hydrolysis by beta-lactamase
R1&R2 side chain substitutions alter antibacterial spectrum and pharmokinetics
How are cephalosporins classified
By generation in order of their development
How does cephalosporin change with each generation
Increase gram negative activity with loss of gram positive activity
Why does cephalosporin have greater resistance to b-lactamases than penicillin
Because cephalosporin has a 6-membered ring (Larger than penicillin)
What are some adverse reactions for cephalosporin
Hypersensitivity
Superinfections
What is the mechanism of action for cephalosporin
Inhibits bacterial cell wall synthesis
How is ceftriaxone administered
IV
Which forms of Cephalosporin is administered via IV therapy
Ceftriaxone
Cefepime
Ceftaroline
Ceftazidime
cafazolin
If a person came in and was diagnosed with MRSA, what could you give as a treatment
Vancomycin
How is aztreonam administered
IV/IM
What class of drug is aztreonam
Monobactam
Broad gram- activity including pseudomonas aeruginosa
What is the mechanism of action for aztreonam
Prevents peptidoglycan cross-linking by binding to PBP3
What can aztreonam be given as an alternative to
Aminoglycosides and 3rd generation cephalosporin
What type of pathogen does aztreonam NOT work against
gram + or anaerobic activity
What type of antibiotic is vancomycin
Non b-lactam
glycopeptide
bactericidal
What is the mechanism of action for vancomycin
Inhibits cell wall synthesis by binding the D-Ala-D-Ala terminal of the forming glycopeptide which prevents cross linking
When is vancomycin used
When there is a drug resistant gram + infection (MRSA and C.Diff)
What type of infection is vancomycin not helpful against
Gram negative activity
What are the side effects of vancomycin
Infusion related flushing (Red man syndrome)
Ototoxicity / nephrotoxicity
What is red man syndrome
Infusion related flushing
When are you more likely to get ototoxicity or nephrotoxicity with vancomycin
At higher doses or in the presence of other toxic drugs
Which type of infection of vancomycin resistant
VRE and VRSA
What is the drug of choice against MRSA
Vancomycin
What type of antibiotic is daptomycin
Lipopeptide
Bactericidal
How is daptomycin administered
IV only
Is daptomycin a broad spectrum or narrow spectrum antibiotic
Narrow
When is daptomycin a useful treatment
With resistant gram positive cocci
-VRE
-MRSA
What is a primary toxicity associated with daptomycin
Myositis (Myopathy, muscle pain)
What are carbapenems
Structure of the b-lactam ring that is highly resistant to B-lactamases
What is one of the broadest spectrum antibacterial agents on the market
carbapenems
What are carbapenems useful against
Gram positive cocci (MSSA, MSSE, S. Pneumonia)
Gram - rod and resistan gram- rods
Anaerobes
An increased expression of AmpC gene is regulated by presence of substrates like what?
3rd generation cephalosporin and other genes
What are the SPACE organisms
Serratia marcescens
Proteus spp
Acinetobacter baumannii
Citrobacter Freundii
Enterobacter spp
What does ESBL stand for
Extended spectrum b-lactamases
What are ESBL organisms
TEM-1
Allow for drug resistance against Beta lactams
Which bacteria are ESBL found on
E.coli and klebsiella
What drug is typically needed against an ESBL
> 3rd generation cephalosporin
What are 3 types of carbapenems
Imipenem
Meropenem
Ertapenem
Which carbapenem is most toxic
Imipenem
What is imipenem inactivated by and what are common side effects
Renal dehydropeptidase
Encephalopathy and seizures
What does imipenem need to be given with to inhibit DHP
cilastatin
What is the difference between imipenem and meropenem
Meropenem is not inactivated by DHP and is less likely to cause seizures
What kind of gram + organisms that can be treated by carbapenems
MSSA
MSSE
What is the spectrum of activity of carbapenems against gram negative organisms
Enterobacteriaceae (Excellent activity against)
Good ESBL
Pseudomonas
What type of drug is fosfomycin
Bactericidal
What is the mechanism of action of fosfomycin
Inhibit the first step of bacterial cell wall synthesis by inhibiting pyruvyl transferase
When is fosfomycin typically used
Treatment of UTIs
particularly those caused by E. coli and enterococcus faecalis
What are the side effect of fosfomycin
Diarrhea
vaginitis
What is the mechanism of action for Daptomycin
It alters the curvature of the cell membrane which leads to holes and leaks, completely disrupting the cell membrane
How is Fosfomycin administered
One time oral dose
