Microbiology exam 2

factors that matter for microbial control

• duration

• concentration

• organic material

• temperature

• types of microbes present

• pH, moisture

static

keep microbes from growing

cidal

get rid of microbes

removal

handwashing; removing not killing

exclusion

keep new microbes from entering

physical

heat, coats, hair nets, etc

chemical

disinfectants, antiseptics, etc

food preservation/safety (physical)

heat, cold, osmotic effects

exponential death

microbial death

does moist or dry heat work better?

moist

thermal death point

temperature heat treatment (10 mins)

decimal reduction time

amount of time heat treatment (reducing by 10%)

thermal death time

amount of death (time took to get rid of 100%)

filtration

• reducing microbes in the air

• HEPA filters will remove almost all microbes from air

radiation

ionizing and non-ionizing radiation work by damaging DNA (cidal)

sterilization (chemical)

gets rid of ALL microbes

disinfection (chemical)

gets rid of most of the microbes

antiseptics

disinfectants that can be used on skin, sometimes mucosa too

chemicals that can achieve steralization

sterilants 

cold sterilization

• uses chemicals at room temp (some instruments would be ruined by heating)

  • aldehydes: Cidex-OPA, glutaraldehyde

gas and plasma autoclaves

• for things that will be damaged by heating or soaking in liquid

• sterrad, steris 

food and toiletry additives

• organic acids (sorbic, benzoic)

• nitrates/nitrites (lunch meats)

• natamycin and nisin (cheeses)

prions control

have to incinerate

endospores control

chemicals and heat

pseudomonas control

chemicals

naked (not enveloped) viruses

chemicals

how viruses are different from cellular organisms

• size

• subcellular structure

• obligate intracellular parasites

growing viruses in the lab

• host cells are needed

• catabolic; most anabolic enzymes are supplied by the host cell

• virus needs only a few genes

viral structure and classification

• viron is extracellular form

  • capsid

  • nucleic acid genes (DNA or RNA)

  • envelope (or naked)

other issues in viral classification

• host range: bacteriophage, e.g. 

• tissue tropism: hepadnaviruses, e.g.

• special enzymes: reverse transcriptase, e.g.

• other: arboviruses = arthropod-bourne

lysogenic

• baceteriophage only

• prophage (provirus)

• lysogen: the cell

• lysogenic conversion can make a baterium more pathogenic

enveloped RNA viruses

lipid layer

retroviruses

reverse transcriptase (RT) (HIV cause of AIDS)

coronavirus

spikes form “crown” on virions” (colds, SARS, MERS, COVID-19)

oncogenic viruses

• viruses promote carcinogenesis

• only increase risk of cancer - not 100%

• Hep B,C,D (not A)

• HPV (4 types, most people have some type)

• Epstein Barr Virus

• HTLV-1 HTLV-2

oncolytic viruses

• viruses destroy cancer cells

• imlygic for advanced melanomas

latent infections

provirus stays inactive in certain cells, no damage or immune stimulation during latency (Chickenpox → Shingles)

persistant viral infection

• slow, progressive, lethal, rare

• measles and subacute sclerosing panencephali

prions

• no genes/nucleic acids

• deformed version of normal brain protein

• induces misfolding of other proteins by “peer pressure”

4 ways of prison transmission

• inherit

• tissue transplant

• meat

• sporadic