BIO205 Topic 6 Chapters 20 & 5

pasteur

high germ theory inspired Lister

Carbolic acid (Phenol)

used by Lister to prevent sound infections; applied to damaged tissues; sterilized instruments & operating environment

sterilizaiton

destroys ALL microbes, endospores, viruses; “sterile item” = free of m., e., & v.

disinfection

eliminates most pathogens; used on inanimate objects/surfaces

sanitation

reduces microbes to safe public-health levels

antiseptic

used on living tissues

bacteriostatic (bacteriostasis)

inhibits but does NOT kill microbes

bactericidal (biocide/germicide [suicide])

irreversibly denatures proteins; kills microbes

pasteurization

brief heating reduces spoilage organisms + destroys pathogens; UHT = shelf-stable; canning destroys C. botulinum endospores

soap - mode of action

mechanical removal of microbes; does NOT kill

nosocomial infections (HAIs)

hospital-acquired; patients more susceptible

resistant group - endospores

Bacillus & Clostridium; extremely resistant

resistant group - pseudomonas

resistant to many disinfectants; can grow in them

resistant group - non-enveloped viruses

resistant due to lack of lipid envelope

resistant group - mycobacterium spp.

waxy cell wall; highly resistant

boiling

100 C for 10 min; kills vegetative cells but NOT endospores

autoclave

121 C, 15 psi, 15 min; kills everything

autoclave indicators

tape turns black; biological indicator = Geobacillus stearothermophilus endospores

hot air oven

200 C for 1.5 hrs; dry heat sterilization

sterilizing inoculating loop

incineration

membrane filtration

removes bacteria from heat-sensitive liquids; HEPA removes >0.3 um

gamma rays

ionizing radiation; destroys DNA; effective against Pseudomonas

most effective against Pseudomonas?

gamma rays

UV radiation - mode of action

causes thymine dimers; poor penetration; used for air, water, & surfaces

alcohols

kill vegetative bacteria + fungi; NOT endospores or non-enveloped viruses; 70% > 100%; damages lipid membranes

quaternary ammonium compounds (Quats)

cationic detergents; kill vegetative bacteria + enveloped viruses; NOT effective on endospores, Mycobacteria, non-enveloped viruses; Pseudomonas can grow in quats

silver nitrate

prevents Neisseria gonnorrhoeae in newborn eyes; silver used in creams/bandages

salvarsan

first chemotherapeutic agent (discovered by Ehrlich)

Chemotherapy

used chemicals to treat disease

sources of antibiotics

microorganisms (fungi, bacteria)

antibiotics

substances produced by microbes that inhibit other microbes

therapeutic index

short wavelength + high TI = safer drug

broad-spectrum

active against many pathogens; risk of dysbiosis

antagonistic

drugs interfere with each other

synergistic

drugs enhance each other

antibiotics targeting peptidoglycan

penicillin, cephalosporins, vancomycin, bacitracin

Beta-lactam rings

presents in penicillin + cephalosporins; inhibits cell wall synthesis

beta-lactamases

enzymes that break B-lactam ring → resistance

protein synthesis inhibitors

aminoglycosides (30S, bactericidal), tetracyclines (30S, bacteriostatic), macrolides (50S), chloramphenicol (50S, last resort)

aminoglycosides

bind 30S; bactericidal

fluoroquinolones

inhibits DNA gyrase

Rifamycin

inhibits RNA polymerase

sulfonamide

competitive inhibitor of PABA (folic acid pathway)

trimethoprim

inhibits later step in folate pathway

isoniazid

inhibits mycolic acid synthesis (Mycobacterium)

MIC (minimum inhibitory concentration)

lowest concentration preventing growth

Kirby-Bauer test

zone of inhibition determines susceptibility

antibiotic resistance - mechanisms

enzymes, altered targets, decreased uptake, efflux pumps

antibiotic resistance - spread

R plasmids via conjugation

antiviral drugs - mode of action

block entry, uncoating, nucleic acid, synthesis, integration, assembly/release

antifungal drugs - mode of action

target ergosterol; echinocandins inhibit cell wall; griseofulvin inhibits cell division; flucytosine inhibits nucleic acid synthesis