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23 Cards in this Set
- Front
- Back
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Define potable water |
Water free of pathogens, toxins, turbidity, odor, color, and taste |
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Define indicator bacteria |
any easily cultured bacteria that may be found in the intestine and can be used as an index of fecal contamination. |
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Why must water be subjected to microbiological analysis? |
Water easily picks up organisms along it's path to it's destination |
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What are the characteristics of good indicator organisms? Why are they monitored rather than pathogens? |
Gram negative rods called coliforms Indicates fecal contamination They are easier to detect than some other pathogens and are a good indicator of the water's cleanliness |
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What are some indicator species of bacteria, and some pathogens commonly found in drinking water? |
E. coli, Enterobacter, and Citrobacter are all good indicator species Commonly found pathogens include protozoans Giardia and Cryptosporidium, along with bacteria Campylocbacter, Samonella, Shigella, Vibrio, and Mycobacterium |
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What types of water quality analysis is there? |
Coliform Assays Standard Coliform Testing |
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What type of coliform assays are there? |
simple tests like Presence-Abcense broth that detect but not quantify rapid tests that isolate coliform colonies and provide qauntaties rapid tests that identify types of coliforms and their numbers |
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What are the advantages and disadvantages of a standard plate count? |
Advantages: Estimates total viable pop. Disadvantages: Doesn't differentiate coliforms from other species |
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How does membrane filtration work to show presence of E. coli? |
Water sample is filtered through a sterile membrane Membrane is placed on a small petri dish with differential and selective medium (M-FD endo) and incubated Colonies of E. coli are counted after incubation |
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What is the most probable number procedure? |
Also known as MPN, detects coliforms over a series of three tests that require several dozen tubes to be inoculated, incubated and evaluated over three days. The results are subjected to mathematical analysis to determine most likely number of coliforms. Drawbacks: time, expense, doesn't differentiate between fecal and total coliforms. |
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What are the stages of water purification? |
Water is impounded in large resevoir to allow sediment to fall to the bottom, and restrict access .3 ppm copper sulfate added to restric algae growth Pumped to holding tanks where several stages of filtration occur Fluoride, softener, and chlorine are added |
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What are the stages of sewage purification? |
Primary Stage - bulkier material is removed Secondary Stage- Active microbial decomposition, which creates sludge. Water is siphoned off and carried to the Tertiary stage - further filtering and chlorination |
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What is activated sludge? |
Sewage sludge that is stirred and aerated to encourage microbial digestion |
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What does an anaerobic digester do? |
It converts sludge to swamp gas (methane with small amounts of hydrogen), which can be released or used as an energy source |
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What are the two categories of food poisoning? |
Food intoxification food infection |
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Define food intoxification |
The ingestion of an exotoxin secreted by bacterial cells growing in food |
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Define food infection |
The ingestion of live, intact microbial that target the intestine. |
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Name an example of food intoxification |
Botulism (CLostridium botulinum) |
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Name an example of a food infection |
Salmonellosis (Salmonella) |
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Name the ways food borne illness can be prevented |
Preventing the incorporation of microbes into food Preventing the survival/multiplcation of microbes in food Temperature Food additives |
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How are microbes prevented from entering food? |
Asceptic technique in the kitchen Hand washing Avoiding cross contamination |
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What are some ways to prevent the survival/multiplication of microbes in food? |
Heat - by canning, pasteurization, cooking Refridgeration/Freezing Irradiation Preservatives - Salt, acids, nitrites Dessication - unreliable |
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What is the rule of temperature with regard to food safety? |
UNder 4 C, Over 60 C |
