Antibiotics Flashcards
Definition of antibiotic
substance or compound that kills or inhibits growth of bacteria
Endogenous antibiotic
lysozyme from mucus and tears
selective toxicity
ability of antibiotic to cause harm to bacteria without causing damage to the host
Antibiotic potential targets
cell wall synthesis, membrane integrity, folate synthesis, DNA/RNA synthesis, protein synthesis
Bactericidal
kills bacteria, does not rely on immune system for clearance
Bacteriostatic
bacteria “lassoed,” not propagating or proliferating, immune system able to overwhelm bacteria
Spectrum
broad: targets a variety of species
Narrow: targets a very specific species
Antibiotic resistance
bacteria resist actions of frequently used drugs, can mutate
Major cause of abx resistance
over prescription and misuse
Prevention of abx resistance
appropriate abx, use as indicated(!)
Synergy
inhibitory or killing effects of two or more abx in combination are greater than their effects individually
Antagonism
inhibitory or killing effects of two or more abx in combo are less than their effects individually
Cell wall synthesis inhibitors
Beta lactams (penicillins, cephalosporins, carbapenems), monobactams, glycopeptides and lipoglycopeptides
How do glycopeptides and lipogylcopeptides differ from beta lactams?
glyco/lipoglyco peptodes: inhibit cell wall synthesis by binding to D-alanyl-Dalanine terminus
Beta lactams: interact with transpeptidase
Which antibiotic relies on renal dipeptidase inhibitor celastatin?
carbapenems, imipenem
What differentiates second gen cephalosporins from cephamycins?
cover both G+ and G- while cephamycins are active against B. fragilus and some Serratius spp.
What is the general sprectrum of coverage for monobactam aztreonam?
mostly G-, aerobic bacteria
How does resistance to methicillin happen in MRSA?
transpeptidase (penicillin binding protein) mutation prevents methicillin binding
Protein Synthesis Inhibitors
50s: oxazolidinones, macrolides, ketolides, streptogramins
30s: tetracyclines, aminoglycosides, glycylcyclines
What is the difference in MOA between oxazolidinones and streptogramins?
streptogramins: prevent translation by binding to 50s
oxazolidinones: prevent initiation
DNA/RNA synthesis inhibitors
Fluoroquinolones
What proteins do fluoroquinolones inhibit?
Topoisomerase II in G+ bacteria, Topoisomerase IV in G- bacteria
Membrane integrity and folate synthesis inhibitors
membrane integrity: polymyxins
Folate synthesis: sulfonamides and benzylbiyrimidines
Why are sulfonamide and benzylpyrimidines synergistic?
both inhibit folate, sulfonamide inhibits PABA, benzylpyrimidines inhibit dihydrofolate reductase
Are polymyxins active against G+ bacteria?
no, target LPS on G- bacteria
Penicillin MOA
interfere with transpeptidation reaction, inhibiting cell wall synthesis by preventing cross linking of components
Method of penicillin resistance
Beta lactamases break down beta lactam ring; porin and PBP structure alteration; increased efflux
Method of Penicillin G resistance
beta lactamases
Spectrum of Penicillin G activity
G+ coccii (strep spp.), G- coccii (N. meningitidis), T. pallidum, non-B-lactamase anaerobes (C. perfringens)
Penicillin G AE
hypersensitivity reactions (anaphylaxis), N/V/D
Aminopenicillins MOA
cell wall synthesis inhibitors
Aminopenicillins mechanism of resistance
Beta-lactamases
Spectrum of aminopenicillins
G-, G+; E. coli and other enterics; H. influenzae, Klebsiella spp., Proteus spp., B. fragilis
Penicillinase resistant penicillins drugs
methicillin, nafcillin, oxacillin,dicloxacillin
Resistance to penicillinase resistant penicillins
reduced affinity for med in binding pocket of transpeptidase
Spectrum of penicillinase resistant penicillins
staphylococcal spp.
Antipseudomonal penicillins drugs
carboxypenicillins, ureidopenicillins
Mechanism of resistance for antipseudomonal penicillins
beta-lactamase (although should be co-formulated with tazobactam to inhibit beta-lactamase)
Spectrum of antipseudomonal penicillins
P. aeruginosa, G- bacilli, E. coli, H. influenzae, and B fragilis
Cephalosporin MOA
inhibits transpeptidation reaction by binding and inhibiting transpeptidase
Cephalosporin mechanism of resistance
beta-lactamases, altering porins and molecular structure of transpeptidase, efflux pumps
Cephalosporin AE
maculopapular rash, eosionophilia, fever
First generation cephalosporin drugs
cefadroxin, cephalothin, cephradine, cefazolin, cephalexin
Spectrum of first gen cephalosporins
G+ cocci (S. aureus); NOT MRSA, B. fragilis, enterococci, or S. epidermidis; G- bacteria such as M. catarrhalis, K. pneumonie, E. coli, Proteus mirabilis
Second generation cephalosporin drugs
cefuroxime, loracarbef, cefonicid, cefamanadole, cefalcor, cefoxitin
Spectrum of second gen cephalosporins
H. influenzae, N. meningitidis, S. pneumonia, cefoxitin and cefotetan are active against B. fragilis and some Serratia spp.; NO enterobacter spp.
Third generation cephalosporin drugs
cefotaxime, cefixime, cefdinir, ceftibuten, ceftazimide, ceftriaxone
Spectrum of third gen cephalosporins
expansion of G- coverage, slightly less active against G+ like Strep and Staph spp.; work well against Neisseria and Haemophilus spp. (Not Acinetobacter, Serratia, Enterobacter spp.)
Only third gen cephalosporin active against P. aeruginosa
ceftazidime
Cefdinir is active against….
E. coli, S. pyogenes, H. influenzae, P. mirabilis
Ceftriaxone AE
biliary pseudolithiasis, jaundice
Fourth gen cephalosporin drugs
cefepime
Spectrum of cefepime
P. aeruginosa, Enterobacter spp.; Poor activity against B. fragilis
Fifth gen cephalosporin drugs
ceftaroline fosamil, ceftolozane
Spectrum of fifth gen cephalosporins
MRSA, Pseudomonas spp.; Pseudomonas spp.
Carbapenem drugs
ertapenem, meropenem, imipenem
Carbapenems MOA
bind to and inhibit transpeptidase, inhibiting cell wall synthesis
Carbapenem resistance
shrinking of porin channels, upregulation of degradation enzymes
Carbapenem spectrum
gram-negative and positive bacteria
Imipenem spectrum
G+ anaerobes, and most G- rods; P. aeruginosa, Listeria, staphylococci, enterococci, streptococci, Acinetobacter, B. fragilis
Bugs resistant to Imipenem
B. cepacia, C. diff. MRSA, E. faecium
Ertapenem spectrum does not include…
P. aeruginosa, Acinetobacter spp. and enterococcus
AE with imipenem
skin rashes, diarrhea, vomiting, nausea; if the pt is in renal failure imipenem may cause seizures
Monobactam available in the US
Aztreonam
Aztreonam MOA
inhibits G- transpeptidase, preventing cell wall synthesis
Aztreonam spectrum
G- aerobic bacteria, enterobacteriaceae, P. aeruginosa, H. influenzae
Aztreonam AE
pts allergic to ceftazidime will also have a sensitivity; elevations of serum aminotransferases, skin rashes
Glycopeptide drug
vancomycin
Glycopeptide MOA
bind to D-alanyl-Dalanine terminus of cell wall precursor which prevents linking of peptidoglycans
Lipoglycopeptide MOA
dimerize and imbed their structure into the bacterial cell membrane, increasing potency of glycopeptide
Glycopeptide resistance
E. faecium; change in glycopeptide vinding site
Glycopeptide spectrum
G+ bacteria (including drug resistant strep and enterococci, MRSA)
Bacteria resistant to glycopeptides
G- bacilli and mycobacterium, Lactobacillus
Glycopeptide administration
must be thru IV, cannot be absorbed across GI mucosa
Glycopeptide AE
infusion reactions, nephrotoxicity, hypotension, tachycardia and flushing (Red man syndrome)
Beta lactamase inhibitors drugs
not antibiotics; clavulanic acid, sulbactam, tazobactam
Beta lactamase MOA
inhibit beta lactamase
Spectrum of Beta lactamase coverage
dependent on paired antibiotic such as aminopenicillins and piperacillin
Oxazolidinone drugs
linezolid
Oxazolidinone MOA
protein synthesis inhibitor, bind to P site on 50S ribosome
Oxazolidinone restriction
point mutation on 23S rRNA
Oxazolidinone spectrum
G+ bacteria, poor coverage of G-
Oxazolidinone AE
myelosuppression, mitochondrial toxicity, drug-drug interactions
Myelosuppression in oxazolidinone AE
thrombocytopenia
Mitochondrial toxicity in oxazolidinone AE
lactic acidosis, optic neuritis, peripheral neuropathy
Drug-drug interactions in oxazolidinone AE
SSRIs, MAOs–can lead to serotonin syndrome (HA, palpitation, hypertensive crisis)
Macrolides that are clinically used
erythromycin, clarithromycin, azithromycin, fidaxomicin
Macrolides MOA
prevents tRNA translocation from A site to P site, inhibits 50S, and conformational protein change
Macrolide resistance
drug efflux, methylase enzyme production protects ribosome, macrolide degradation, 50S mutations
Erythromycin spectrum
all gram positive bacilli, some gram negatives (Bartonella, T. pallidum, Neisseria); inactive against most aerobic enteric G- bacilli
Azithromycin spectrum
M. catarrhalis, Chalmydia spp., B. burgdorferi, H. pylori, H. influenzae
Clarithromycin spectrum
streptococci, staphylococci, H. influenzae
Fidaxomicin spectrum
C. difficile
Macrolide AE
N/V/D, anorexia, epigastric distress, arrhythmias, hepatotoxicity; skin eruptions, eosinophilia, and fever
Streptogramin drugs
streptogramin A and B
Streptogramin MOA
inhibit protein synthesis by binding 50S, inhibits elongation and induces early termination
Streptogramin resistance
enzymatic inactivation, altered binding sites, drug efflux
Streptogramin spectrum
gram positive cocci, M. pneumoniae, C. pneumoniae, Legionella spp.; NOT G- bacteria, not E. faecium
Streptogramin AE
pain and arthalgia-myalgia syndrome
Tetracycline drugs
minocycline, demeclocycline, doxycycline
Glycylcycline drug
tigecycline
Tetra/glycylcycline MOA
bind 30S ribosome and prevent tRNA from entering A site, inhibiting protein synthesis
Tetra/glycylcycline resistance
decrease influx or increase efflux, upregulation of a protein that dislodges tetracyclines, enzymatic inactivation
Tetracycline spectrum
more active against G+; anaerobes, chlamydiae, mycoplasmas and rickettsiae; MRSA, B. anthracis, L, monocytogenes, V. cholera, Legionella, Plasmodium, T. pallidum
Glycylcycline spectrum
same activity as tetracyclines but greater activity against enterococci, enterobacteriaceae, Acinetobacter spp., B. fragilis
Tetra/Glycylcycline AE
GI irritation, pts at increased risk for C. diff, bind well to developing bones and teeth (will develop a permanent brown stain)
Aminoglycoside drugs
streptomycin, gentamicin, neonmycin, kanamycin
Aminoglycoside MOA
bind to 30S subunit and act as an irreversible inhibitor (inhibit initiation, continuation of translation, introduction of errors in developing protein)
Aminoglycoside resistance
enzymatic inactivation, decreased influx, mutations in 30S subunit prevent binding
Aminoglycoside spectrum
aerobic G- bacteria; Enterobacter spp., E. coli, K. pneumoniae, P. aeruginosa, Serratia spp.
Aminoglycoside AE
nephrotoxic (Gentamicin, neomicin), ototoxic (Gentamicin and streptomycin cause vestibular damage)
Fluoroquinolones drugs
norfloxacin, ciprofloxacin, ofloxacin, gatifloxacin
Fluoroquinolone MOA
inhibit transcription and replication of DNA by binding topoisomerase II
Fluoroquinolone resistance
mutations in binding region on DNA gyrase, active efflux, or upregulation of proteins that shield DNA gyrase
Fluoroquinolone spectrum
active against G+ and G-; Campylobacter spp., Enterobacter spp., Shigella, Proteus, E. coli, Legionella, Chlamydia
Levofloxacin is a good drug for what bacteria
S. pneumon iae
Ciprofloxacin is a good drug for what bacteria
P. aeruginosa
Fluoroquinolone AE
GI side effects, increased C. diff risk, tendon rupture, QT prolongation
Sulfonamide drug
sulfamethoxazole
Benzylpyrimidine drug
trimethoprim
Trimethoprim MOA
inhibits dihydrofolate reductase (cannot make purines)
Sulfamethoxazole MOA
inhibit dihydropteroate synthase, cannot produce folate
Sulfamethoxazole resistance
bacterial overproduction of PABA, reduced binding to enzyme, decrease influx
Trimethoprim resistance
reduced bacterial permeability, upregulation of dihydrofolate reductase, reduced binding affinity to enzyme
Timethoprim monotherapy
can be used to treat UTIs, but combination therapy is more likely
TMP/SMX spectrum
S. epidermidis, S. aureus, S. pyogenes, Viridians, Serratia, shigella, salmonella, enterobacter, P. mirabilis, Nocardia, P. jiroveci, Haemophilus, M. catarrhalis
TMP/SMX AE
anemia, leukopenia, granulocytopenia, N/V, photosensitivity, fever, urticaria, Stevens-Johnson syndrome
Polymyxin MOA
Disrupt G- membrane, bind to and inactivate endotoxin
Polymyxin resistance
rare, only an issue in some Klebsiella and Acinetobacter spp.
Polymyxin spectrum
G- bacteria, aerobes; NOT proteus or serratia, neisseria, burkholderia spp.
Polymyxin AE
nephrotoxicity, slurred speech, vertigo, paresthesia, apnea, muscle weakness