Chapter 12 Flashcards
goal of antimicrobial therapy
administer a drug to an infected person that destroys the infective agent without harming the host’s cells
Characteristics of Ideal Antimicrobial drug(natural/synthetic)
antibiotics- common metabolic products of aerobic bacteria/fungi
bacteria-streptomyces + bacillus
molds- penicillum + cephalosporium
- selectively toxic to the microbe but nontoxic to host cells
- microbicidal rather than microbistatic
- remans potent long enough to act and is not broken down or excreted prematurely
- is not subject to the development of antimicrobial resistance
- complements or assists the activities of the host’s defenses
- remains active even when diluted in body fluids and tissues
- readily delivered to the site of infection
- reasonably priced
- does not disrupt the host’s health by causing allergies or perdisposing the host to other infections
selective toxicity
-more difficult as characteristics of infectious agent become more similar to the vertebrae host cell, creating more side effects
narrow and broad spectrum
- narrow, penicillin
- broad target most common components of pathogens(ex. ribosomes)
Antimicrobial drugs that affect the bacteria cell wall
- most bacterial cell walls contain peptidoglycan
- penicillins and cephalosporins block synthesis of peptidoglycan
- Active on Young, growing cells, can cross cell walls of gram-negative bacteria
- PENICILLIN
- CEPHALOSPORIN
- VANCOMYCIN
- BACITRACIN
- MONOBACTAMS/CARBAPENEMS
- FOSFOMYCIN
- CYCLOSERINE
- ISONIAZID
Antimicrobial drugs that disrupt cell membrane function
- cells with damaged membranes die from disruption in metabolism or lysis
- these drugs have specificity for a particular microbial group, based on lipid differences in cell membranes
- POLYMYXINS-interact with phospholipids and cause leakage
- amphotericin B + nystatin-form complexes with sterols on fungal membranes which cause leakage
Drugs that affect nucleic acid synthesis(DNA/RNA)
- Block synthesis a nucleotides, inhibit replication, or stop transcription
- CHLOROQUINE-binds and cross-links the double helix
- QUINOLONES- inhibit DNA helicases
- antiviral drugs that are analogs(fakes) of purines and pyrimidines insert in viral nucleic acid, preventing replication
- RIFAMPIN(inhibit RNA polymerase)
Drugs that block protein synthesis
- attack ribosome synthesis, can also damage eukaryotic mitochondria(similar ribosomes features w/prokaryotes)
- AMINOGLYCOSIDES(STREPTOMYCIN/GENTAMYCIN)-insert and cause misreading of mRNA
- TETRACYCLINES-Block attachment of tRNA on the A acceptor site, stopping synthesis
- and LINZOLID, CHLORAMPHENICOL, ERYTHROMYCIN, CLINDAMYCIN, STREPTOGRAMIN
Antimicrobial drugs that affect metabolic pathways (competitive inhibition through metabolic analog)
SULFONAMIDES+ TRIMETHOPRIN-block enzymes required for tetrahydrofolate synthesis needed for DNA/RNA synthesis(can attack mitochondria causing bone marrow issues)
Antibacterial drugs that act on the cell wall(cephalosporins/penicillin)
- beta-lactam group-
- interfere with cell wall synthesis
- most are penicillin and cephalosporins
-Penicillin-can be synthesized in the lab, more economical through microbial fermentation,
CONSISTS OF THREE PARTS
-thiazolidine ring
-beta-lactam ring
-variable side chain dictating microbial actiivity
-G/V most important natural forms
-drug of choice for gram+ cocci(streptococci) + some gram- (meningococcal/syphilis spirochete)
-resistant synthetic penicillin- methicilin, nafcillin, coxacillin
-problems-allergies/resistance
-synthetic penicillin-resistant to penicillinase/more broad spectrum
Cephalosporins
-4 gens, each one more effective against gram-, less side effects/better dosing
Additional Beta-lactams
Carbapenems
-imipenen- broad spectrum drug for infections with aerobic and anaerobic pathogens, low-dose, administered orally with few side effects
Monobactams
-aztreonam- narrow spectrum drug for infections by gram-negative aerobic bacilli, may be used by people allergic to penicillin
Non Beta-lactam Cell Wall Inhibitors
Vancomycin-narrow spectrum, most effective in treatment of staphylococcal infections in cases of P+M resistance,p allergic reaction, toxic/hard to administer
-Bacitracin- narrow spectrum made by a strain of Bacillus Subtitles, topical ointment
-Isoniazoid(INH)- works by interfering with mycolic acid synthesis, used to treat infections w/ M. tuberculosis
-Polymixins- narrow spectrum peptide antibiotics with a unique fatty acid component(treat drug-resistant P. aeruginosa/severe UTI)
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Drugs that Act on DNA or RNA
fluoroquinolones-broad-spectrum effectiveness, bind to DNA gyros, CDC monitoring use to prevent ciproflaxin resistant bacteria
Drugs that interfere with protein synthesis
Aminoglycosides
-broad spectrum, inhibit protein synthesis, useful against aerobic gram-negative rod’s/ Plus certain Graham positive bacteria, streptomycin(plague/TB/tularemia), gentamicin(less toxic, use against gram- rods)
Tetracycline antibiotics
-broad, block protein synthesis by binding to ribosomes
-treat std, lyme, typhus, acne, protozoa, rocky mountain
-chloramphenicol-broad, blocks protein synthesis/peptide formation, chemically synthesized, very toxic, can cause bone marrow damage, used on typhoid/rickettsia/chlamydia/brain abscesses
Macrolides/related antibiotics
-erythromycin- broad, low toxicity, for penicillin resistant, for mycoplasma pneumonia/legionella/chlymadia/pertussis/diptheria/prophylatic before surgery
-newer forms clarithromycin/azithromycin
Drugs that block metabolic pathways
- Most are synthetic
- sulfonamides-1st animicrobic drugs
- Narrow spectrum, block synthesis of folic acid
- sulfisoxazole-shigellosis, UTI, protozoan infections
- silver sulfadiazine- burns/eye infections
- trimethroprim-combo w. sulfamethoxazole-UTI/PCP
