Anti-biotics Flashcards
what is the physical control of microbial growth?
heat sterilisation, radiation sterilisation
what is the chemical control of microbial growth?
antiseptics and disinfectants, natural antimicrobials and synthetic antimicrobials
what are antiseptics
disinfecting agents with sufficiently low toxicity for host cells and can be used on skin
what are sterilants
kill both vegetative cells and spores when applied to materials for appropriate times and temperatures
what are the uses of antiseptics?
treatment of skin infections, prevention of infections in cuts and wounds, cleaning the skin area of surgery, prophylaxis and treatment of infections in mucosal areas, as a scrub for surgeons
what are alcohols used as?
antiseptics and disinfectants to kill vegetative bacteria and fungi by denaturing proteins and disturb the membrane permeability
what is chlorhexidine used as?
an antiseptic
what types of bacteria is chlorhexidine most effective against?
gram+ cocci
give an example of an oxidising agent
hydrogen peroxide
what is the health warning with antiseptics, disinfectants and sterilant users?
they accumulate in the environment or in the patients/caregivers body
what is the definition of an antibiotic?
a chemical substance produced by one organism that is destructive to another
what are the two forms of antibiotics
bacteriostatic and bacteriocidal
what are the cellular targets of antibiotics?
cell wall, cell membrane, nucleic acid, protein synthesis
what are the properties of the ideal antimicrobial agent?
selective toxicity, cidal activity, long plasma half-life, good tissue distribution, low binding to plasma proteins, oral and parenteral preparations, no adverse drug interactions
what are the antimicrobial targets?
inhibition of: cell wall synthesis, protein synthesis, nucleic acid replication and transcription, injury to plasma membrane, inhibition of synthesis of essential metabolites
what molecules prevent cross linking of the cell wall?
beta-lactams e.g., penicillin
how does penicillin inhibit the cell wall synthesis
it binds to penicillin binding proteins
inhibition of cross-linking of cell wall
accumulation of precursor cell wall units
cell lysis
what molecules prevents vertical linking of the peptidoglycan?
glycopeptides e.g., vancomycin
how does vancomycin work?
bind to terminal D-ala residues and prevents incorporation of sub-unit into growing peptidoglycan
how do you inhibit the protein synthesis?
inhibit ribosomal subunits
what are the resistance mechanisms of bacteria?
blocking entry, inactivating enzymes, alteration of target molecule, efflux of antibiotic
give an example of how antibiotic resistance works with penicillin
the B-lactam ring in penicillin is broken by penicillinase
what is the effect of antibiotic resistance on overall antibiotic effectiveness?
originally the effect of antibiotics decrease the number of bacteria by 4 logs but then it increases again so the net loss of bacteria is only 1 log
