chapter 13

Sterilization, disinfection, and antibiotic therapy

Sterilization

destroys all living cells, spores, and viruses

Disinfection

killing or removal from inanimate surfaces

Antisepsis

removing pathogens from surface of living tissues

Sanitization

reducing microbial populations to safe levels

Cidal agents

those that kill microbes (Bactericidal/ Algicidal/ Fungicidal/ Virucidal)

Static agents

those that inhibit or control growth (Bacteriostatic/ Algistatic/ Fungistatic/ Virustatic)

Germicidal

describes an antimicrobial that kills germs (bacterial, fungal, etc)

will -cidial agents sterilize a surface immedately

No not all cells will die instantly

Several factors influence the accumulation of lethal damage

population size + composition/ Agent concentration / exposure time / Presence of organic material

________ agents are commonly used to kill or control the growth of microbes

Physical

Examples of physical agents

Temperature + Pressure (Steam autoclave) / Filtration/ Radiation

is moist heat or dry heat better at killing microbes

Moist heat

Boiling water at ______ kills most vegetative cells (not spores and thermophiles)

100 C

Pasteurization was developed by _______ to save French wine

Louis Pasteur

Pasteurization heats product to a moderately high temperature long enough to kill the pathogen…

Coxiella burnetii

Most pathogens are _____, so they grow slowly (if at all) at refrigeration temperatures

mesophilic

What pathogen still grows in the cold

Lysteria monocytogenes

How is filtration helpful for the sterilization of microbes

solutions can pass through filters with small pores to catch mircobes

what is irradiation

through electromagnetic radiation the water absorbs energy causing causes DNA damage in bacteria and parasites

Minimum Inhibitory Concentration

the lowest concentration of an antimicrobial agent that prevents visible growth of a microorganism (determines drug potency)

Gas Sterilization

done by ethylene oxide for bulk materials (penetrates packing materials) spores/microbes

Antimicrobial Touch Surfaces

like a copper surface releases toxic ions

Bacterial Resistance to Disinfectants

More difficult to develop resistance from chemical disinfectants, triclosan was used at too low a concentration, also biofilms

Antibiotics are produced by microbes to kill other microbes but the ones we take are actually ___ __ which are chemically synthesized or altered antibiotics

chemotherapeutic agents

antibiotics only kill

bacteria

Selective toxicity, a way to only kill the bacteria without harming the host, you can target…

the peptidoglycan (cell wall) because humans dont have it or folic acid synthesis

spectrum of activity

how broad or focused an antibiotic is.

bactericidal vs bacteriostatic

Bactericidal antibiotics kill bacteria. Bacteriostatic antibiotics stop bacteria from growing and multiplying

the time it takes to lower an antibiotic back to the minimum inhibitory concentration happens depends on

kidney secretion and liver

Therapeutic dose of an antibiotic

minimum dose per kg of body weight that stops pathogen growth

Toxic dose of an antibiotic

maximum dose tolerated by a patient

chemotherapeutic index

ratio of toxic dose to therapeutic dose

synergistic drugs

work well when combined

Antagonistic drugs

drugs that interfere with each other and reduce effectiveness

breaks cell wall - penicillin - antibiotic - causes cell to burst

Beta-lactam antibiotics

breaks cell wall - works on penicillin resistant antibiotics - type of modified beta-lactam antibiotics

cephalosporins (blactamase enzyme = ineffective)

what antibiotic disrupts the bacterial membranes polarity

Gramidicin

what antibiotic dissolves the bacterial membrane (only used externally)

Polymyxin

what drug is activated in ANAEROBES by reduction affecting DNA of bacterial cell

Metronidazole

what drug halts the progression of the DNA replication fork targeting the topoisomerases in a DNA molecule

Quinolones

Protein Synthesis Inhibitors

bacteriostatic and selectively toxic

Drugs that target 30S ribosomal subunit

Aminoglycosides / Tetracyclines

Tetracyclines (bacteriostatic)

like doxycycline (they prevent tRNA from entering A site)

Drugs that target 50S ribosomal subunit

Chloramphenicol / Macrolides / Oxazolidinones

what do Chloramphenicol antibacterial agents do (50S subunit)

Blocks activity through peptidyltransferase

what do Macrolides antibacterial agents do (50S subunit)

stop tRNA from moving from A site to P site

what do Oxazolidinones antibacterial agents do (50S subunit LAST RESORT)

Bind to 50S subunit and prevent formation of 70S ribosome

what drugs affect intermediary metabolism in bacteria (Bacteria MUST produce their own folic acid but humans do not – very selectively toxic)

Sulfonamides

Challenges of Antibiotic Resistance

Prevent Entry/ Prevent Binding to Target/ Prevent Accumulation

how does drug resistance develop most commonly

spontaneously via mutations

Fighting Drug Resistance

Dummy compounds perscribed with antibiotics/ modifying antibiotics

Why aren’t there more antiviral agents?

Viruses use host machinery so harder to make it selectively toxic

Fungal infections are difficult to treat due to similarities with human cells so we target their

ergosterol to compromise membrane integrity

Which conditions are used in the pasteurization of milk?

Heat

Penicillin is a …

cell wall synthesis inhibitor

tetracycline…

inhibits protein synthesis

what could be considered antiseptics

Quaternary ammonium compounds/ Alcohols

what couldnt be considered an antiseptic

Chlorine/ Phenylphenol

are disinfectants generally more toxic to living tissues than antiseptics.

yes

The higher the phenol coefficient, the more ______ the disinfectant

effective