Foodborne Illnesses

food preservation - refrigeration

slows enzyme activity and metabolism —> slows bacterial growth

food preservation - acidity

low pH disrupts enzymes and cell processes

food preservation - drying

removes water needed for growth

food preservation - salt/preservatives

causes osmotic stress or chemical damage

food preservation - radiation

damages dna

food preservation - heat (pasteurization/canning)

denatures proteins and kills bacteria

food preservation - fermentation

produces acids —> inhibits microbial growth

listeria monocytogenes - food industry threat

can grow in the fridge, has a 20-40% fatality rate, and causes systemic infection

temperature range of growth

determines if bacteria can grow during storage

DRT

time to kill 90% of bacteria at a given temp; longer DRT = more heat resistant

oxygen requirements

facultative anaerobes survive in more environments —> higher risk

sanitization resistance

biofilm-forming bacteria persist on surfaces —> harder to remove

pH tolerance

wider tolerance = can survive in more food types

foodborne intoxication

disease from preformed toxin in food; bacteria may be dead; fast symptoms

foodborne infection

disease from live bacteria growing in host; slower onset

cooking + infection vs intoxication

cooking kills bacteria and prevents infection; heat-stable toxins remain and intoxication still occurs

gene expression adaptation - foodborne

bacteria adjust to gene expression to survive in new environments (food —> host)

SEA (staphylococcal enterotoxin A)

heat stable toxin made in food; superantigen —> inflammation —> intoxication

shiga toxin

AB toxin made in host; inhibits protein synthesis —> cell death —> infection

SEA vs shiga (key difference)

SEA = preformed, heat stable, intoxication

shiga = produced in host, requires live bacteria

ETEC (enterotoxigenic E. coli)

extracellular intestinal pathogen; toxin-mediated diarrhea; usually mild

listeria monocytogenes (pathogenesis)

intracellular systemic pathogen; no toxin; immune response causes damage

listeriolysin O (LLO)

breaks phagosome —> allows listeria to enter cytosol and replicate

intoxication vs infection (data clues)

intoxication = rapid, toxin present, bacteria absent

infection = delayed, bacteria present, growth required

serotype

classification based on surface antigens

serotype vs genotype

serotypes reflect underlying genetic differences

pulsed field gel electrophoresis

separates large dna fragments —> creates band patternd

dna fingerprint

unique band pattern used to match outbreak sources

genome sequencing in outbreaks - foodborne

detects mutations, rearrangements, mobile elements —> identifies strains + tracks spread