Micro MCM unit 1 Flashcards
how genetic changes influence changes in infectious disease
changes in the gene sequence change virulence/pathogenicity, the host they can infect and antibiotic resistance
- syphilis and scarlet fever lose virulence gene
- mutation in flu caused spanish flu pandemic
- AIDS used to infect primates
- staphylococci and others are resistant to penicilin bc of natural selection
- HIV developing resistance to anitvirals
how changes in public health influence changes in infectious disease
clean water, clean air and vaccines make infections more rare
- clean water prevents cholera
- clean air prevents respiratory infections
- vaccines make MMR rare
- in all of these cases the organisms have not changed and will infect if precautions stop being taken
diseases of unknown etiology might be infectious
- recently found stomach ulcers and cervical cancer are infectious
- due to genes and gut microbes
- other possibly infectious conditions include obesity, stroke, heart attack, alzheimers, MS, diabetes
- you can transfer obesity in mice
bacterial structure
- genome made of DNA, no introns
- chromosomes are single, circular
- 70s ribosomes
- peptidoglycan cell wall, optional LPS, LOS envelope
- replicate by binary fission
- genome located in nucleoid
virus structure
- genome of DNA or RNA
- single, segmented chromosomes
- no ribosomes
- protein capsule on outside, optional outer lipid envelope
- replicates by invading bacteria; parasitic
- no particular genome location
eukaryotic structure
- genome made of DNA with introns
- multiple chromosomes
- 80s ribosomes
- replication by mitosis
- genome in the nucleus
bacterial cell size vs. animal cell size
bacterial cells are much smaller so animal cells are able to engulf
possible bacterial morphology under light microscope
cocci
bacilli
vibrio
spirochetes
Neiserria, e coli, pseudomonas, V cholerae, borrelia, treponema shape
Neisseria - diplococci e coli - bacilli pseudenomas - bacilli V cholerae- vibrio borrelia/lyme - spirochetes treponema/syphillus - spirochetes
bacterial structures with pathogenic significance
LPS - part of g- walls, an endotoxin, made of O antigen and lipid A. in g+ techoic acid is similar but less toxic
glycocalyx -
- slime layer - loose coating of polysaccharides that aid in attachment. form biofilms that are more resistant to antibiotics and hygiene tools because more diverse
- capsule - firm enclosure that helps with attachment and makes harder to engulf. can make vaccine targeting capsule (meningococcal capsule gives virulence)
- pili/fimbrae - for attachment. e coli cause UTI this way.
gram stain procedure
- fixation with heat
- crystall violet stain - purple
- iodine - makes crystal violet permanent for g+
- alcohol destain - for g-
- counterstain - safranin
g+ vs g-
- presence of LPS/LOS outside of cell wall in g- and thinner peptidoglycan cell wall
- only g+ make spores
additional bacterial structures for pathogenesis
- flagella - recognized as an antigen in humans
- ribosomes - target for antibiotics
- spores - resistant to antibiotics and genes
importance of exponential growth in pathogenesis and lab diagnosis
lots of nutrients make it very pathogenic
- can grow to take over the world in weeks
- but log phase does not last long
- identify by conditions they grow best in
fermentation vs. O2 based ATP generation
- O2 used electron transport chain, produces a lot of ATP. will be restricted to O2 rich areas of the body
- fermentation produces small amount of ATP. acid from fermentation can be used to identify. leave a lot of energy in waste that can be used by others later. these will grow in sealed cans
- facultative anaerobes can grow in almost anything (e coli)
- aerotolerant if have catalase or dismutase to detoxify O2
quorum sensing
change gene expression based on population density.
- allow conservation of energy and coordinated attack
- low density –> no inducer
- high density–> inducer.
- when theres enough inducer, there is a transcriptional activator that causes density dependent genes to be transcribed/expressed.
- used for making biofilms and virulence factors
dipicolinic acid
calcium chelator in spores
peptidoglycan structure and as drug target
- made of NAG and NAM with peptide cross-links and side chains
- target peptidoglycan because it is essential to bacterial cells but not to human cells.
- penicillin inhibits its synthesis, lysozyme cleaves it
how pathogens spread
- contact - direct, indirect, droplet
- airborne
- respiratory (vehicle and vectors)
chain of infection
- pathogen
- reservoir
- portal of exit
- means of transmission
- portal entry
- new host
strategies to prevent spread of pathogen
- hand hygiene
- PPE
- isolate
- sterilize
- housekeeping
- ventilation
- proper disposal
Airborne precautions
- mask and gloves and private, neg pressure room
- patient mask if leave room
- TB, chicken pox, shingles, measles, pandemic flu
droplet precautions
- coughing, sneezing, talking, procedure
- mask, gown, handwashing
- meningitis, seasonal flu, pertussis, mumps
contact precautions
- microbes spread by direct contact
- gown and alcohol based hand wash
- multi-drug resistant bacteria: MRSA, VRE, acinebacter, ESBL, rotavirus, scabies
contact plus precautions
- serious illness easily transmitted
- soap and water, not alcohol
- disinfect room with bleach
- C dif, diarrhea, norovirus, enteric infections (camp, e coli, shilgella, salmonella, crypto)
reverse isolation
mask, gloves, gown
-protect immunocompromised from other people
sterilization definition
destroy/eliminate all microbes by physical/chemical means
-not for living tissue
disinfection definition
eliminate many pathogens (not spores) on inanimate object
- 3 levels depending on how many microbes destroyed
- 3 levels depending on required strength
antisepsis
reduce microbes on living tissue internally, externally and on surgery tools
-doesnt kill spores and doesnt disinfect
potential for transmitting infectious agents on medical devices
- critical - enter normally sterile area of body. need to sterilize
- semicritical - in contact with mucous membranes or non-intact skin that should be free of microbes other than spores
- use a high level disinfect
- includes respiratory, anesthesia, endoscope, butt, throat - non-critical - for items on intact skin.
- use alc, halogens, phenolics, quants
- bedpans, bp cuff, crutches, computers
physical techniques used for sterilization
- steam/autoclave - effective and quick **most common
- dry heat - for petroleum based substances
- irradiation - single use medical supples
- gas - highly flammable
- plasma - high penetration; excite gases to disrupt metabolism
chemical sterilization techniques
- glutaraldehydes - hospital instruments
- hydrogen peroxide - releases O2 to produce radicals that damage DNA/protein
(6% for equipment, 30% sporicidal) - peracetic acid - mix of acetic and H2O2
- disrupts cell membrane
-clean water tower to prevent biofilm and carcass sanitation
promoter
where, when, what degree a gene is expressed
RNA pol
binds to promoter to initiate transcription and produce mRNA
operon
cluster of genes with related function controlled by 1 promoter
repressor
blocks expression
inducible expression
inducer/substrate binds to repressor to remove it fromo operon and allow expression
negative vs. positive regulation
- positive: usually repressed. need transcription factor to bind at promoter to initiate expression
- negative: product acts as repressor to prevent more of itself from being made
operator
regulates expression of operon and separates gene from promoter
ways to acquire new genes
mutations
- spontaneous
- chemical modifying
- physical agents
these often lead to antibiotic resistance