Microbial Control

sterilization

removal of all microbial life

commercial sterilization

killing C. botulinum endospores

disinfection

removal of vegetative pathogens

what does it mean if a pathogen is vegetative

it is living, not dormant

antisepsis

removal of pathogens from living tissues

sanitization

lower microbial count

Biocide/germicide

kills microbes

microbiostatic

inhibiting, no killing, microbes, gives immune system time to kill the living ones

List the base types of microbes from least resistant to most resistant

enveloped viruses, most gram positive bacteria, nonenveloped viruses, fungi and fungal spores, most gram negative bacteria, protozoans, mycobacterium, bacterial endospores, prions

Mycobacterium have mycolic acid, which

makes the wall waxy and stronger

Rate of microbial death is _____

constant

list the influences on the effectiveness of a microbial treatment

number of microbes, nature of the microbe, environment, concentration of agent, mode of action of the agent, presence of other material

what are the physical methods of control for microorganisms?

heat, cold and desiccation, radiation, filters, and osmotic pressure

what are the types of heat control

moist heat and dry heat

what is moist heat control

hot water, boiling water, steam/autoclave

what is dry heat control

oven or open flame

what is pasteurization?

example of moist heat, reduces spoilage of organisms and pathogens

what are dry heat examples

heated oven or sterilizing a loop over direct flame

how does cold help control microorganisms

cold will lower the growth rate of many types but it is not a killing effect

how does desiccation help control microorganisms

removes water, resistance varies between species, viruses and endospores are more resistant

how does radiation help control microorganisms

causes enough damage to DNA that microbes are killed, mutations are causes and accumulate, so they can’t reproduce

How do filters help control microorganisms

filters don’t sterilize, but they trap microbes on the filter and liquid passes through

what are filters good for

liquids in which heat would cause problems, like liquids containing needed proteins

how does osmotic pressure help control microorganisms

has high concentration of salts or sugars, causes plasmolysis

what is/are more resistant to high osmotic pressure

molds and yeasts

antibiotic

a substance produced by a microorganism that inhibits another microorgansism

what are the characteristics of an ideal antimicrobial drug

toxic to the microbe but nontoxic to host cells, microbial rather than microbiostatic, soluble in body fluids, remains potent long enough to act and is not broken down or excreted prematurely, slow or no development of antimicrobial resistance, complements or assists the activities of the hosts defenses, remains active in tissues and body fluids, readily delivered to the site of infection, does not disrupt the hosts health by causing allergies or predisposing the host to other infections

Why do bacteria create antibiotics?

because there is competition on where they live, it is something bacteria use to control other bacteria

what is selective toxicity

kills the pathogen without harming the host

T/F: chemotherapy has selective toxicity

false, it is the opposite, destroys the bad and needed cells

Kill vs. Inhibit

microbiocidal vs microbiostatic

antibiotics usually have how many modes of action

one, not mutltiple

Mode of Action: protein synthesis inhibitors acting on ribosomes

blocks initiation of protein synthesis

Mode of Action: folic acid synthesis in the cytoplasm

block pathways and inhibit metabolism

Mode of Action: cell wall inhibitors

block synthesis and repair

Mode of Action: cytoplasmic membrane

cause loss of selective permeability

Mode of Action: DNA/RNA

inhibit replication and transcription, inhibit gyrase, inhibit rna polymerase

Broad spectrum of activity

its good for any or a lot of bacteria types

when are broad spectrum antibiotics used

when you dont really know what is wrong and need to narrow possibilities down

narrow spectrum

bacteria needs specific antibiotics

antibiotic resistance is the idea that

when you use antibiotics against a group, some are susceptible and some are resistant and dont die

When bacteria is naturally more resistant, 

it doesnt die in presence of an antibiotic, so it reproduces and the resistant gene spreads, so now there is a whole population that is resistant

T/F

a microorganism can make itself resistant

false, it either is or isnt

what are the mechanisms of resistance

can inactivate drug via enzymes, reduce the uptake of the drug or not take in enough for damge, drug ejected it/spat out, drug target site is eliminated/inactivated, can shut down entire pathway of drug making it ineffective

Where are resistance genes and how do they spread

often seen on plasmids and can be transferred between bacteria

what are the common misuses of antibiotics

using it for viruses, using it in animal feed, failure to finish prescribed antibiotic regimen, using outdated/weakened antibiotics

What is wrong with using antibiotics for viruses

you introduce it to the natural flora, so you kill them off and only resistant ones will survive, so those genes can be passed onto a dangerous infection

what is the issue with using antibiotics in animal feed

while it does help animals grow bigger quickly, most of the time it it on healthy animals keeps the resistant antibiotic and allows the resistant gene to get passed on and make an infection more dangerous

why should you finish a prescribed antibiotic regimen

if you stop taking them when you feel better, it messes with antibiotic concentration and also leaves the resistant bacteria alive. the regime was meant to target all of the harmful bacteria, which last longer, and if you have a gap in when you take them the lower dosage allows tougher ones to reproduce

what is the problem with using outdated/weakened antibiotics

there is a change in concentration so its not guaranteed to fight the current infection, it can also harm or kill off good bacteria, they can also run out before it actually finishes the job in the case it could fight off the current infection safely

What are some negative responses a host could have to antibiotics

high toxicity to the body, an allergic response, and suppression of normal microbiota of the host

what is an allergic response

when host reacts to medicine in an inappropriate manner, drug causes an immune response in the host

what happens when there is a suppression of normal microbiota of the host

can lead to superinfection by another pathogen that was normally held in check by the normal flora originally

what is the mechanism of action for iodine

penetrates cell walls and interferes with protein function and structure by oxidizing and binding to sulfhydryl groups of amino acids

what group is iodine most effective against

bacteria, fungi, viruses, and protozoa, common as a skin septic

what is iodine less effective against

spores

what is hydrogen’s mechanism of action

produces hydroxyl free radicals that attack membrane lipids, dna, and other essential cell components

what group is hydrogen most effective against

strong oxidizer effective against bacteria, viruses, and fungal spores, sporicidal at high concentrations

what is phenol’s mechanism of action

denatures proteins and disrupts cell membranes and cell walls

what group is phenol most effective against

gram positive bacteria, some gram negatives, fungi, and enveloped viruses. used in some disinfectants and antiseptics

what is bleach’s mechanism of action

released hypochlorous acid which denatures enzymes and damages dna by oxidation

what group is bleach most effective against

it is broad spectrum, so it kills bacteria, fungi, viruses, and spores. it is a common surface disinfectant

what is alcohol’s mechanism of action

denatures proteins and dissolves membrane lipids

what group is alcohol most effective against

vegetative bacteria, fungi, and enveloped viruses, it is not effective against spores or non-enveloped viruses

what is cephalosporin’s mechanism of action

inhibits cell wall synthesis by binding to and blocking penicillin-binding proteins

what group is penicillin most effective against

gram positive cocci and later generations against gram negative rods

what is isoniazid’s mechanism of action and group it is effective against

it is a cell wall inhibitor which blocks synthesis and repair, used to treat mycobacterium tuberculosis but only against growing cells, used in combination with other drugs in active tuberculosis

What is rifampin’s mechanism of action and what is it most effective against

it inhibits rna polymerase, it is limited in spectrum beause it cannot pass through the cell envelope of many gram negative bacilli, mainly used to treat infections caused by gram positive rods and cocci and a few gram negative bacteria. used to treat leprosy and tuberculosis

What is tetracycline’s mechanism of action and what is it most effective against?

it acts as a protein synthesis inhibitor, it is effective against gram positive and gram negative rods and cocci, aerobic and anaerobic bacteria, mycoplasmas, rickettsias, and spirochetes

What is ampicillin’s mechanism of action and what is it most effective against?

has broad spectra of action, are semi-synthetic, works on gram-negative bacilli, disadvantages: can by hydrolyzed by penicillinase, allergies, only fair absorption

substances produced by the natural metabolic processes of some microorganisms that can inhibit or destroy other microorganisms; generally the term is used for drugs targeting bacteria and not other types of microbes

antibiotics

antimicrobials effective against a limited array of microbial types, for example, a drug effective mainly against gram-positive bacteria

narrow spectrum

antimicrobials effective against a wide variety of microbial types, for example, a drug effective against both gram positive and gram negative bacteria

broad spectrum

Sterilization refers to

a. killing all vegetative cells

b. removal of all microbial life

c. removal of pathogens from living tissue

d. lowering microbial count to safe levels

b

Commercial sterilization targets which organism?

clostridium botulinum endospores

Antisepsis means

a. killing all microbes including spores

b. removing microbes from surfaces

c. removing pathogens from living tissue

d. lowering microbial count on utensils

c

Microbiostatic agents:

a. kill microbes instantly

b. are used only on spores

c. inhibit microbial growth but don’t kill directly

d. work only in dry heat environments

c

T/F

Mycobacterium species are harder to kill due to their peptidoglycan cross-links

false, its due to mycolic acid/waxy wall

The rate of microbial death is

constant over time, not immediate

Which of the following does not affect microbial control effectiveness?

a. number of microbes

b. environment

c. microbe color

d. concentration of agent

c

More microbes = _____ control time

longer

Which heat method is best for sterilizing metal instruments (like an inoculating loop)?

dry heat/direct flame

Pasteurization:

a. sterilizes milk completely

b. reduces spoilage organisms and pathogens

c. is a type of dry heat

d. works by deyhdration

b

Cold does what to microbes?

a. kills them instantly

b. slows growth rate, bacteriostatic

c. causes mutations

d. removes spores

b

Desiccation works by

removing water, halting metabolism

Radiation kills microbes by:

a. heating them to death

b. damaging DNA, causing lethal mutations

c. dehydrating the cell

d. increasing oxygen

b

Filters: 

a. trap microbes as liquid passes through

b. are used when heat would damage materials

c. are not sterile methods

d. a and c are correct

e. a, b, and c are correct

e

Osmotic pressure control is least effective against molds and yeasts, why

they tolerate high salt and sugar

Penetrates cell walls, oxidizes and binds to proteins.
→ Broad spectrum; less effective on spores; used as skin antiseptic.

iodine

Produces hydroxyl free radicals that attack membranes and DNA.
→ Strong oxidizer, sporicidal at high concentrations.

hydrogen perozide

Denatures proteins and disrupts cell membranes.
→ Effective vs. Gram+ bacteria, some Gram–, fungi, enveloped viruses.

phenol

Oxidizes enzymes & DNA → broad-spectrum, sporicidal.

bleach

Denatures proteins & dissolves lipids.
→ Kills vegetative cells, not spores.

alcohol

The Kirby Bauer Assay tests:
A) Osmotic pressure tolerance
B) Effectiveness of antibiotics or disinfectants
C) Microbial taxonomy
D) Protein synthesis

b

The zone of inhibition represents

the area where bacterial growth is prevented by the chemical/antibiotic

Antibiotic = substance made by a microorganism that inhibits another microorganism.
True or False?

true

Selective toxicity means

kills pathogen without harming the host

Inhibits cell wall synthesis

cephalosporin

inhibits RNA synthesis

rifampin

Inhibits protein synthesis (ribosomes)

tetracycline