Intro to Antibiotics Flashcards
antibiotic
substance produce by a microorganism that suppresses the growth of another microorganism
bactericidal
kill bacteria
bacteriostatic
inhibit further growth of bacteria
gram positive vs. negative
positive- thick peptidoglycan layer, no outer membrane
negative - outer membrane, thin peptidoglycan layer
empiric therapy
started with a life threatening infection that cannot wait for antibiotic susceptibility testing OR when likely culprits are known
rational therapy
use kirby bauer disc diffusion, minimum inhibitory concentration test and minimum bactericidal concentration test to figure out what antibiotic works on and the correct dosing
superinfection
appearance of a new infection while a patient is being treating with antibiotics for a prior infection. due to the normal microbial flora being eliminitated and pathogenic microorganisms colonize and grow
antibiotic synergism
4X reduction in MIC or MBC when a drug combo is used verses single drugs alone
3 common synergistic pairs
1 blockade of sequential enzymatic steps in a metabolic pathway
- inhibiting enzymatic deactivation of the antibiotic
- enhanced antibiotic uptake by bacteria
antagonism
require more than 50% of MIC of 2 drugs. common with a cidal and static antibiotic used together
beta-lactam antibiotics
penicillins and cephalosporins, bactericidal by inhibiting transpeptidase for crosslinking bacterial cell wall,can cause type 1 hypersensitivity reactions, some bacteria have beta lactamases that cleave the beta-lactam ring to resist the drug, mostly pharmokinetics by kidney and most can have interference when orally absorbed with food
natural penicillins
Representatives - Penicillin G, Penicillin V Potassium and Benzathine (IM)
Activity - gram + and treponema palidum( syphillis)
Uses - strep of pharynx, enterococcal endocarditis
anti-staphylococcal penicillisn
representatives - methicillin, nafcillin, oxacillin, dicloxacillin
activity - better activity against staph. aureus but beware of MRSA
uses - skin infections, ostemyelitis, acute endocarditis
special - mostly eliminated via bile, no dosing adjustments for renal failure
extended spectrum penicillins
representatives - ampicillin, amoxicillin
activity - extended against gram negative
uses - acute otitis media, sinusitis and UTIs
special - food does not interfere with oral absorption of amoxicillin & often given with beta-lactamase inhibitors to prevent breakdown
anti-pseudomonal penicillins
representatives: ticarcillin +clavulanate potassium, piperacillin +tazobactam
activity - extended against gram negatives
uses - septicemia, UTIs, pneumonia, intra-abdominal infections
special - always prescribed with beta-lactamase inhibitor
carbapenems
imipenem+cilastatin, meropenem
activity - extremely broad, reserved for serious infections in hospitalized patients
special - resistant to most beta-lactamases, impinem given with cilastatin due to imipenem break down by dehydropeptidase in kidney
1st Gen cephalosporins
cefazolin, cephalexin
activity - good gram + with moderate gram -
use - minor staphyand strep, UTIs, cefazolin - surgical prophylaxis
2nd Gen cephalosporins
cefoxitin, cefuroxime, cefprozil
activity - incr. against gram - : H influenza, etc
use - acute otisis media and sinusitis
special - cefoxitin - anaerobe b. fragilis as well and used to treat mixed anaerobic infections
3rd Gen cephalosporins
ceftriaxone, cefixime, ceftazidime
activity - gram -
use: powerhouse - UTIs, respiratory, bone/joint, skin/soft tissue, sepsis
special - can cross blood brain barrier
4th gen cephalosporins
cefepime
useful against gram - resistant to 3rd gen
5th gen cephalosporins
ceftralone MRSA activity (only cephalosporin generation)
vancomycin
bactericidal by inhibiting bacterial cell wall synthesis
adverse: ototoxicity and nephrotoxicity
resistance: alteration is cell wall precursors that prevents drug binding
pharmacokinetics - kidneys, no absorbed orally (GI tx only orally)
activity - gram positive
uses - staph infections including MRSA - meningitis, endocarditis, osteomyelitis, skin/soft tissue and pn
macrolide antibiotics
erythromycins, clarithromycin, azithromycin
bacteriostatic by 50S bacterical ribosomal subunit binding
resistance - methylase methylates 50S subunit to prevent drug binding
adversity - stimulates GI mobility and cardiac arrhythmias
pharmacokinetics - azithromcin has 3 day half life due to being concentrated in tissues and slowly released
spectrum - gram positive and m. pneumoniae
use - skin, respiratory tract and chylamydial
special - useful for those allergic to beta-lactams
tetracycline antibiotics
tetracycline, doxycycline, minocycline, tigecycline
bacteriostatic by binding 30S ribosomal subunit
adversity - can be desposited into growing bones, photosensitivity, GI upset
resistance - bacterial efflux pumps
pharmokinetics - multivalent cations decrease oral absorption, kidney except doxycycline
spectrum - atypical bacterial - rickettsia, chlanydiae, m. pneumonie, spirochetes
uses - lyme disease, acne, periodontitis, rickettsial and chylamydial infections
