Mmg 301 Final Lecture 38

Front 1

Refridgeration

Back 1

lower temperatures=lower microbial growth (some microbes are psychrotolerant and still grow in refrigerators)

Front 2

freezing

Back 2

can prevent growth but may damage some foods

Front 3

acidity

Back 3

acidic pH (less than 5) inhibits the growth of pathogens; can also add salt to food (pickling)

Front 4

drying

Back 4

reducing water contents inhibits growth. partial or complete drying can be used for long-term preservation

Front 5

salt

Back 5

NaCl of >7.5% inhibits most bacteria

Front 6

chemical preservatives

Back 6

sodium benzoate, sodium nitrate, sodium nitrite, sorbic acid, sodium proporionate; act as growth inhibitors and are generally recognized as safe by the FDA

Front 7

radiation

Back 7

pasteurization-short term heating to reduce microbes in food without significant reduction in quality

Front 8

canning

Back 8

heating food in a sealed container (often complete sterility is not achieved due to heat exposure)

Front 9

ultra high pressure processing

Back 9

-"Cold Pasteurization": most, but not all bacteria are kills
-spores are not killed
-also called "Pascalization"
-requires 50,000-100,000 pounds/sq inch

Front 10

what is food poisoning

Back 10

-ingestion of preformed microbial toxins
-microbes that produced the toxins do not need to invade the host
-disease is due to the action of ingested toxin
-most people consider "food poisoning" to be both food poisoning and food infection
-some diseases found to be both food poisoning and food infection

Front 11

3 common bacteria responsible for food poisoning

Back 11

-Staphylococcus aureus
-Clostridium perfringens
-Clostridium botulinum

Front 12

Staphylococcus aureus

Back 12

-commonly found on all humans, especially skin
-found on many common foods
-come strains produce heat-stable toxins
-some strains produce enterotoxins; nausea, vomiting, diarrhea 1-6 hours after exposure

Front 13

Clostridium perfringens

Back 13

-most prevalent food poisoning in US; 248,000 cases/year
-spores germinate and grow in intestines-produce toxins

Front 14

Clostridium botulinum

Back 14

-strict anaerobe commonly found in soil
-spores from soil contaminate in food
-canned foods that are undercooked or low in acid can contain live spores
-after germination in can, botulism toxin is produced

Front 15

food infection

Back 15

-infection arising form ingestion of a pathogen
-disease occurs when organism grows after ingestion
-many pathogens causing food infection also cause waterborne diseases

Front 16

Salmonellosis

Back 16

-infectious agent: caused by various species of Salmonella
-transmission: uncooked or undercooked food containing fecal contamination of food from handlers, food source animals
-illness: strains infect GI tract and produce several enterotoxins; headache, vomiting, diarrhea, can lead to septicemia or typhoid fever

Front 17

Camplyobacteriosis

Back 17

-most prevalent bacterial foodborne pathogen
-campylobacter jejuni; causes > 1 million diarrheal cases each year
-colonizes in the small and large intestine
-some strains produce cholera-like toxin

Front 18

Listeriosis

Back 18

-infectious agent: Listeria monocytogenes bacterium, psychotolerant
-Transmission: mainly an animal pathogen, transmitted to humans through dairy products, also found in many other foods

Front 19

E. Coli 0157:H7

Back 19

-highly pathogenic E.coli, first isolated form contaminated ground beef; found in many other sources
-Infectious agent: E. coli
-transmission: uncooked or undercooked food containing fecal contamination

Front 20

Shiga Toxin producing E. Coli (STEC)

Back 20

-produce Shiga toxin: AB toxin that halts protein synthesis in the host cell
-90% of all STEC are O157:H7
-toxin results in intestinal hemorrhaging and kidney failure

Front 21

Enterotoxogenic E. Coli (ETEC)

Back 21

-colonize intestines and secrete either one or two similar toxins
-toxins difer from the O157:H7 toxins
-toxins cause intestines to excrete excessive fluids

Front 22

Where does Norovirus infect

Back 22

GI tract--> most common cause of gastroenteritis

Front 23

What are symptoms of Norovirus

Back 23

stomach cramps, nausea, vomiting, diarrhea, headaches

Front 24

how is Norovirus transmitted

Back 24

-eating food or drinking liquids that are contaminated with Norovirus
-touching surfaces or objects contaminated with Norovirus, and then placing their hand in their mouth
-having direct contact with another person who is infected and showing symptoms (for example, when caring for someone with illness, or sharing foods or eating utensils with someone who is ill)

Front 25

What is FoodNet and how does it work

Back 25

surveillance database system to watch for foodborne illnesses in a subset of the US population

Front 26

common method of determining the molecular subtype of bacterial food pathogen

Back 26

Pulsed Field Gel Electrophoresis: used to separate large pieces of DNA (30,000-50,000 base pairs); method identifies pathogen by unique "DNA fingerprinting" based on band patterns from gel electrophoresis of restriction enzyme-digested DNA

Front 27

PulseNEt

Back 27

database of PFGE patterns for pathogens; used for investigation and monitoring of outbreaks

Front 28

what happens in primary steps

Back 28

screening/settling-remove solids

Front 29

secondary anoxic and aerobic treatments

Back 29

microbes and protozoans to "eat" organic matter and pathogens

Front 30

tertiary treatment

Back 30

chemical treatment/biological--> disinfect; remove nutrients

Front 31

aerobic process and how it works

Back 31

-treatment of wastewater by aerobic microbes that serve to turn complex carbon-containing compounds to CO2 and CH4
-activated sludge method
-trickling filer method

Front 32

Activated sludge method

Back 32

-uses aerated tanks containing slime-producing bacteria such as Zoogloea as well as other bacteria and protozoans
-the slime produced by Zoogloea results in a flocculent material that serves as a growth stratum form protozoans and other organisms
-the flocs and suspended solids in this process are termed activated sludge

Front 33

trickling filter mehtod

Back 33

-waste water is trickled through bed of small of rocks where protozians and other organisms attach to microbial biofilm on the rock surfaces

Front 34

anaerobic sludge digestion secondary treatment

Back 34

-converts solid organics into gas fermentation products
-an enclosed vessle is used for the anoxic processing-only a small opening for escape of gas
-complex community of anaerobes actively decompose polymers
-final anaerobic metabolites dominate by methane (CH4) and CO2
-the CH4 can be burned or used to power the treatment plant

Front 35

how do we monitor water for pathogens

Back 35

-indicator microorganisms are used for testing water safety
-many bacteria from the intestinal tract become physiologically stressed when introduced into the aquatic environment, and they gradually lose their ability to form colonies on differential and selective media
-various indicator microbes are used to detect fecal wastes in portable and recreational water

Front 36

most common indicator microbe used in water monitoring

Back 36

fecal coliforms (E. coli) and gram negative non-sporulating facultative anaerobic rods from the intestine of warm=blooded; currently the most common method

Front 37

selective growth media are used for detecting fecal coliforms in water samples

Back 37

-a predetermined volume of sample water is filtered through sterile membrane
-membrane is placed onto selective agar medium containing dye indicators
-coliform colonies are colored red