Microbiology Antibiotics

naturally occurring agents produced when cells are infected by virus. IFN-alpha and IFN-beta trigger nonspecific reaction. uninfected cells make antiviral proteins to protect themselves.

viruses

various ones prevent virus by entering host cell

viruses

esample: amatadine prevents uncoating of Influenza A virus

various ones specific for select protease. inhibits proper formation of "working" proteins

viruses

binds to microtubules and prevents spindle apparatus formation

fungi

high penetration into keratin. used for fungal in fects of the skin, nails, ringworm, athletes foot

inhibits DNA gyrase, the enzyme needed for uncoiling bacterial DNA so it can be replicated

broad spectrum

example: ciprofloxacin (Cipro)

binds to the enzyme RNA polymerase which is needed to synthesize RNA

gram positive cocci, tubercle bacilli

mimic the natural occurring nucleosides. mistakenly incorporated into DNA

DNA viruses

virus must be actively replicating

blocks different reaction in folic acid synthesis

synergistic to sulfonamides

competitively inhibits PABA needed for folic acid synthesis so organism cant make nucleic acids

broad spectrum

a strand of nucleic acid complimentary to mRNA, blocks attachment of ribosomal subunits

viruses

binds to 50S ribosome which blocks ribosome movement and prevents reading of mRNA

gram positive organisms (cant penetrate gram negative cell walls)

examples include erythromycin, azithromycin (zithromax) and clarithromycin (biaxin)

block the docking of the tRNA-AA to the A site of the 30S subunit

gram positive, gram negative, rickettsial and clamydial diseases

discoloration off teeth and stunts bone growth in young children

• blocks reading of mRNA by binding to
• 30S subunit of ribosome

gram negative bacteria and mycobacterium

poorly absorbed orally, given IV, narrow therapeutic range, otic and nephrotoxic

prevents peptide bond formation between adjacent amino acids because binds to 50S subunit

gram positive and gram negative, rickettsiae, fungi

in bone marrow prevents incorporation of hemoglobin into RBS=aplastic anemia

change membrane permeability by inhibiting synthesis of ergosterol. blocks the enzyme lanosterol a-demethylase

effective against fungal cells

attaches to ergosterol and changes membrane permeability by creating pores in the membrane

effective against fungal cells

high concetrations can target cholesterol in human cells leading to nephrotoxicity

changes membrane permeability by attaching to phospholipid (phosphatidylethanolamine) in the plasma membrane

gram negative organism especially pseudomonads (pseudomonas aeruginosa)

also targets eukaryotic cells and can use nephrotoxicity used OTC

inhibit synthesis of b-glucan component of cell wall by inhibiting the enzyme 1,3 b-glucan synthase

effective against fungi (candida and pneumocystis)

forms a complex within bacteria that blocks the enzyme, fatty acid synthase. this prevents mycolic acid production

acid fast organisms (mycobacterium)

drug of choice however used with other antimicrobial to prevent rapid resistance

inhibits transport of NAG and NAM to PTG growing points outside of plasma membrane

gram positive organisms (last line against MRSA)

• only used IV
• known as "Mississippi mud"
• otic and nephrotoxicity

inhibits transport of NAM to cell wall by blocking the transporter, bactoprenol

gram positive organisms (staphylococci and streptococci)

renal toxicity restricts use to topical agents (triple antibiotic ointment)

competitively blocks crosslinking of NAG/NAM subunits

gram positive (older agents) gram negative (newer agents)

beacteria developed lactamases that destroy beta-lactam ring