microlab control of microbial growth

describe microbial load

number of infection pathogens on an item

in patient care scenarios, careful cleaning procedures are put into place to

control the spread of infection

process of careful cleaning start out similarly to

cleaning your kitchen surfaces or bathroom

what technique is used to prevent infection transmission from contaminated items to soft tissue of vascular system

sterilization

what is sterilization

a type of decontamination where no microbial load remains on an item

what is the gold standard of steam sterilization

autoclave

describe autoclave

method of inactivating all organic pathogens including spores and prion proteins

what is autoclaving commonly used for

metal tools and heat resistance plastics

describe dry heat

baking objects in an oven

chemical sterilants react with proteins and membranes to destroy

organic pathogens

liquid sterilants can be used to achieve

high level disinfection (HLD)

what is the goal of HLD

kill all but the most resistance of spores

what is intermediate level disinfection (ILD)

level where most bacteria and fungi are inactivated (some spores may remain)

what is low-level disinfection (LLD)

most basic form of disinfection where many bacteria are inactivated and is sometimes referred to as sanitization ; m. tuberculosis may survive and other spores

describe basic cleaning

simple removal of surface oils and debris from an object

what serves as the foundation for all other decontamination processes

simple cleaning

using enzymes during basic cleaning means

a lower temperature can be used during disinfection

ethylene oxide chambers use

toxic ethylene oxide gas to kill organic pathogens

the byproducts of oxide chambers are useful but also harmful in what ways

environmentally damaging, carcinogenic, and explosive

why are oxide chambers used as a last resort for objects

long degassing times and toxicity issues

liquid sterilants require objects to be

completely immersed for a verified period of time to achieve sterilization

examples of liquid sterilants

peracetic acid and glutaraldehyde

why is careful consideration needed before using a liquid sterilant

corrosion of metal and irreversibility

irradiation inactivates microorganisms by

damaging their dna either directly or indirectly

types of irradiation

ultraviolet (UV) light, gamma rays, or X-rays

what type of irradiation is UV

non-ionizing

what type of irradiation is gamma rays/ X-rays

high energy ionizing

UV is only used to sterilize surfaces because

it cant penetrate objects

how is UV light a carcinogen in humans and other animals

any microbes in the direct sightline of UV bulb is inactivated due to DNA damage

skin cell DNA damage by solar UV radiation is linked to

development of skin cancers

indicators to know if sterilization run was successful

biological and chemical

describe biological indicators

small samples of microorganism spores that should be inactivated, a failure to grow is good process

describe chemical indicators

take the form of color-changing compounds that react (ink patches on pouches)

what is antisepsis

process of reducing the microbial load on skin to prevent the spread of infection

example of antisepsis

cleansing of the skin's microbial flora prior to an operation using an iodine solution

what is the spaulding classification scheme

a logical way to determine the disinfection schemes required for items used during patient care

what is the clearest and most concise wat of assessing an object’s infection risk

spaulding classification scheme

why is spaulding classification important

ensures all items receive an appropriate level of decontamination without overburdening an infection control system

an item is split into what 3 categories

critical, semicritical, noncritical

which item poses the highest threat of infection transmission

critical

which item poses the lowest threat of infection transmission

noncritical

describe critical items

objects that are designed to contact normally sterile tissue or enter the vascular system

items deemed critical must be

sterilized using steam methods

examples of critical items

forceps

scalpels

bone saws

describe semicritical items

make contact only with mucous membranes or the skin; do not enter open wounds or penetrate soft tissues

reusable semicritical items should be

steam-sterilized

what is the minimum acceptable process for semicritical items

high-level disinfection

examples of semicritical items

endoscopes and speculums
dental mirrors and other simple hand tools

reusable trays for making tooth impressions

describe non critical items

only ever contact intact skin and do not touch mucous membranes

what level of disinfection is required for noncritical items

low-level

examples of noncritical items

stethoscope

bedpan

walking crutches

what is selective toxicity

idea that a chemical agent or drug can exert toxic effect on a pathogen and leave the infected host organism unharmed

what drugs can exert selective toxicity

penicillin, metronidazole, and chloramphenicol

how could a mutated cell have a survival advantage

if antimicrobial agent is present and actively killing off unmutated competing sister cells at the time

what can lead to antimicrobial resistance

the proliferation of mutant cells

what type of agents contain selectivity toxicity

disinfectant and antiseptic

what type of agent contains selective toxicity

antimicrobial

some disinfect agents can be used in an antiseptic capacity but at what concentration

low concentration

describe antimicrobial agents

antibiotics

how are antibiotics effective

treat bacterial infections

define the term antimicrobial

covers many different compounds that can halt the growth of microbial cells

antimicrobial compounds can be ____ or ___

non-selective or selectivity toxic

efficacy of sterilant

inactivates all living organisms

efficacy of disinfectant

inactivates most organisms, but spores can survive

efficacy of antiseptic

reduces microbial load, varied efficacy

target organism for penicillin

gram + bacteria

target organism for clindamycin

most bacteria

target organism for metronidazole

many bacteria and fungi

target organism for mebendazole

parasitic pinworms

target organism for acyclovir

herpes virus

mechanism for penicillin

inactivates key transpeptidase enzyme in cell wall manufacture

mechanism for clindamycin

interferes with protein translation by binding to ribosome

mechanism for metronidazole

activated only in microbial cells that causes irreparable DNA damage

mechanism for mebendazole

binds key cytoskeletal enzyme preventing worm growth and replication

mechanism for acyclovir

inhibits viral DNA synthesis, preventing replication

how to test if an organism is inactivated by an antimicrobial

agar plate-based and several dilutions

describe disc diffusion assay

filter paper discs are treated with a test antibacterial compound and then placed onto a bacteria inoculated agar plate

in discs test the size of the area around the disc where bacteria can’t grow gives

an indication of the compounds antimicrobial efficacy

describe positive controls

those that are used to demonstrate that an experiment is capable of working

describe negative controls

check those things that shouldn’t affect an experiment dont produce an effect

describe antibiotic multi-susceptibility test ring (AMT)

compares many antibiotics simultaneously; ring comprises many discs each treated with a different test compound

describe epsilometer test

each strip of paper is impregnated with an increasing concentration of a candidate antimicrobial from the bottom to the top

how is the minimum inhibitory concentration (MIC) of a drug required to prevent microbial growth determined

by reading the concentration on the strip where antimicrobial growth is first inhibited

what is a zone of inhibtion

areas where no bacteria can grow around an antibiotic compound

a bacterial “lawn” most often appears as a

light-colored and opaque layer over a darker field of supportive agar jelly

gaps in bacterial lawn represent

where growth has failed

all beta-lactam antibiotics carry a

square-shaped beta-lactam ring at the core of their chemical structure

the square shape ring is highly reactive and responsible for

antimicrobial effects

the transpeptidase enzyme is responsible for

linking together muramic acid side chains of peptidoglycan

mesh-linking in beta-lactam creates a

strong cell wall

penicillin can do what in side chains of peptidoglycan of beta-lactam

mimic a component of side chain and irreversibly bind into the enzyme’s active site, preventing it from carrying out this crosslinking work

penicillin irreversibly can lead to

degradation of the bacterial cell wall

ways that bacteria can become resistant to beta-lactam antibiotics

mutation of the transpeptidase

expression of a lactamase enzyme

altered membrane permeability

active efflux of the drug

describe mutation of the transpeptidase active site

antibiotic can no longer bind to the target enzyme due to a conformational change, the drug can't exert its effect anymore

describe expression of a lactamase enzyme

cleave the all-important square-shaped beta-lactam ring that is the source of this class of antibiotic's effect. By cutting open the ring before the drug has had a chance to interact with its target, the enzyme can prevent any drug-target binding from taking place

describe altered membrane permeability

Changes to the cell wall that prevent or slow down a drug's entry into the cell can confer a degree of resistance. If the drug can't reach the target, it can't have an effect!

describe active efflux of the drug

Efflux pumps are transmembranal proteins that pump compounds out of the cell. if a bacteria begins to express a pump that can remove a drug quickly, the effect of that drug will be hugely reduced.

what are antimicrobial drug targets

components of microbial cells that either not present or are present in a very different form compared to host cells

commonly targeted microbial components

bacterial transpeptidase

DNA gyrase

bacterial ribosome

DNA

RNA polymerase

drug that targets bacterial transpeptidase

beta-lactams (penicillin)