PLSC115: Final Review

Name the four stages of bacterial growth?

- Lag Phase - Log or Exponential Growth Phase - Stationary Phase - Death or logarithmic decline

What types of soil amendments (fertilizers) are available for farmers?

- Manure - Compost - Inorganic Fertilizers

Categorize bacteria by their oxygen requirements

- Obligate Anaerobes - Aerotolerant Anaerobes - Microaerophiles - Facultative Anaerobes - Obligate Aerobes

What the three types of EPI curve distributions?

- Point Source - Continuous Common Source - Propogated Outbreak

What water sources are considered agricultural water by the FDA?

- Surface Water - Ground Water - Municipal Water

What types of water sources are available for farmers?

- Surface Water - Ground Water - Municipal Water - Rain Water

What is the process for using pulse field gel electrophoresis to characterize pathogens in outbreak investigations?

1. You develop a bacterial culture 2. You suspend the cell, which means that you separate it from the sample and place it in nutrient rich environment where you can develop a culture so it can grow on its own 3. You then make agarose plugs 4. Then you lyse the cells 5. You add a restriction enzyme which slices DNA molecules at a specific sequence of bases called the restriction site. 6. Then DNA is put into the gel and has an electric field ran throughout it. - The smaller strands move faster. 7. Scientist would then use the Pulse Net to compare their samples to identify the strain.

What is date of onset interval dependent on?

1/4 of the disease incubation period.

What occurs during the thermophilic phase?

A mixed population of thermophilic bacteria and actinomycetes, and the most heat-tolerant fungi exist and break down proteins, fats, hemicellulose and cellulose.

What is an epi curve?

An epidemic curve is a visual representation that shows how many new cases (the onset of illness) have occurred by contracting a certain foodborne pathogen from a certain food.

Log or Exponential Growth Phase

Bacteria double at an exponential rate The curve increases as long as cells have adequate nutrients and the environment is favorable.

How could climate change impact food safety? Give examples.

Climate Change can impact food safety through flooding because I can cause microbial contamination or chemical contamination because water picks up everything it touches. Another aspect is that since temperatures are increasing the period in which pathogens can live is increased where it would not normally be Drought can affect food safety because farmers will have to use whichever water source is available in order to irrigate crops regardless of water quality. Altered Rainfall Patterns

Psychrophiles

Cold-loving microbes that grow between -10 - 20 degrees Celsius

What information do epi curves provide?

It can tell you the amount of people infected/size of the outbreak in a period of time (the amount of cases) It can show the distribution. It can also give you clues to the outbreak's mode of spread.

Stationary Phase

It is a period of equilibrium; microbial deaths equal the production of new cells ( the growth rate is equal to the death rate).

What are GAPs? Can you name and describe any gaps?

GAPs are good agricultural practices. Some examples are excluding wildlife (both domestic and wild) from the agricultural production process as much as possible and have a plan on dealing with these occurrences. Another example is having proper signage to remind workers of the correct procedures as well as for visitors like on the choose your own production farm. Provide your workers with proper training for each job they will have to do, and provide refreshers, and regular testing to evaluate workers understanding--even if they are friends and family. Providing proper sanitary facilities in a reasonable distance from the fields.

What is the difference between GAPs and the Food Safety Modernization Act's Produce Safety Rule?

GAPs are recommendations and farmers are not required to follow them. The Produce Safety Rule on the other hand is a law and is enforceable.

What is Genome Trackr?

It is the first network of labs to utilize whole genome sequencing for pathogen identification. It consists of public heath (federal and state), university and internationally located labes that collect and share genomic and geographic data from foodborne pathogens.

What is thermophilic composting and how is it achieved?

Its converting plant and animal waste into organic fertilizer using biological processes to treat that waste so that it can be used for agricultural purposes.

Thermophiles

Heat loving organisms that grow between 40 - 70 degrees Celsius.

What are some of the advantages of using Whole Genome Sequencing?

It can determine the complete DNA sequence of an organism's genome. It is inexpensive and easy to use. It can detect more outbreaks. It is more likely to link illnesses to a possible source It can identify unrecognized sources of pathogens. It can stop outbreaks while they are small.

How does antimicrobial resistance affect food safety?

It can lead to the emergence of superbugs which are pathogens that cannot be killed through the use of antibiotics. This affects food safety because if they get on our food and infect us they will be hard to kill. Most times all hospitals can do is assist the body in fighting them off. For those who are vulnerable like children, the elderly, and pregnant women, they are at the most risk because their immune systems are not strong enough to fend them off. In addition, superbugs can infect everyday healthy people.

What are each soil amendments pros and cons?

Manure There is an abundant supply of manure, it is a great source of nutrients, a great way of recycling waste and is great for soil health, but it can harbor human pathogens and needs to be treated before it can be used for agricultural purposes. Compost Since there is an abundant supply of manure and other types of waste the materials to make it are not lacking. It is also a great source of nutrients. It is effective and economical and the pathogens are killed in the composting process. However, composting takes time. Inorganic Fertilizers There is zero chance that you will get a foodborne outbreak from it. You constantly need to replenish it. It is bad for the environment. And you can only use so much of it because state laws limit their use.

What are the three phases of thermophilic composting?

Mesophilic Phase (10 - 40 degrees Celsius) Thermophilic Phase (>40 degrees Celsius) (55-65 degrees Celsius) (130-150 degrees Fahrenheit) Second Mesophilic Phase (10-40 degrees Celsius)

Psychrotrophs

Organisms that grow between 0-30 degrees celsius and are responsible for most food spoilage while in the refrigerator

Mesophiles

Organisms that grow in warm temperatures (10 - 50 degrees C). They like conditions like those in our body.

Obligate anaerobic bacteria

Oxygen is toxic and they can only grow in the absence of oxygen. They use other molecules such as sulfur, nitrate and sulfate in respiration.

Bacteria and Fungi + Waste Moisture Levels between 40% - 60% C:N = 30:1

Produces heat leaving Humus and killing pathogens

How many agricultural uses of water can you name?

Production Water - Irrigation - Mixing and Applying Pesticides - Liquid Fertilizer Application - Frost Protection - Evaporative Cooling - Dust Abatement Post-Harvest Water - Cleaning of contact surfaces - Rinsing/Cooling of produce - By workers for Handwashing

Categorize bacteria by their growth temperature ranges

Pyschrophiles Psychotrophs Mesophiles Thermophiles Hyperthermophiles

Microaerophiles

Require oxygen because they cannot ferment or respire anaerobically, but they cannot tolerate it in high concentrations (atmospheric concentrations).

Obligate Aerobes

Require oxygen for respiration. They cannot ferment or respire anaerobically.

What can a point source outbreak tell you? What does it look like?

That people were exposed to the same source within a short period of time (one event). This graph usually rapidly peaks and falls gradually.

What can a continuous common source tell you? What does it look like?

That the people are exposed to the same source over a long period of time (days or weeks). The number of cases rises gradually and might plateau.

What are the pros and cons of each water source?

Surface Water is easily accessible, but it is of the lowest microbiological quality, it is the highest risk water source, rain fall can increase contamination due to run off, it is not directly usefully (salt water & ocean and seas). Ground water is generally of higher microbiological quality than surface water, but if wells are placed in the wrong area, it is not deep enough or is sealed incorrectly it can be compromised. In addition, the type of aquifer determines how difficult it is to extract the water. Municipal water is of the best microbiological quality, but it can be expensive.

What can a propagated source tell you? What does it look like?

That there is no common source because the outbreak spreads from person to person. This epi curve tends to have larger peaks, each one being one incubation period apart.

How are foodborne outbreak investigations conducted?

The collect epidemiological data. This includes detecting a possible outbreak. Defining and finding cases that fit your definition or definitions. And Generating Hypotheses by conducting interviews Collect trace back data (find a connection to the source) If cases continue you would test the hypotheses by conducting analytic studies and lab testing of samples. Then you would find associations between the food and illness. Then you would find the point of contamination and source of the contaminated food. Following this you would control the outbreak by recalling the products. Removing the source of contamination And Revising the production process so this does not occur again If cases do not fit your definition you would need to come up with new hypotheses and move on from there. If cases stop after controlling the outbreak the you can declared the outbreak to be over. If associations cannot be made and the cases still continue you would also need to come up with new hypotheses and go through the steps again. If you are unable to make associations and the cases stop it is an unsolved mystery and the outbreak would be declared as over.

What occurs during the second mesophilic phase?

The thermophilic bacteria and other heat resistant organisms die off while the temperature decreases and lignin degrades leaving a resistant organic mixture called humus.

What microbiological methods are used to characterize pathogens and link clinical and environmental isolates?

The two big different types of characterization are serotyping and subtyping. Serotyping is a surface antigen based method that uses latex beads that attach to certain surface antigens when present. It is limited to large macromolecules with repeating patterns like microbial capsules, flagella or lipopolysaccharides. Subtyping is a DNA based method that uses DNA to characterize pathogens. The two methods to subtype bacteria include Pulse Field Gel Electrophoresis (PFGE) and Whole Genome Sequencing.

What occurs during the first mesophilic phase?

There is a rapid uptake of soluble sugars and starches which leads to an explosive growth of mesophilic bacteria and fungi.

What occurs during the lag phase?

There is little or no change in the number of cells, but metabolic activity is high because the bacteria are adjusting to the new environment's temperature and breaking down the proteins to be used in cell division.

Hyperthermophiles

They like really hot conditions. They grow between 65 - 110 degrees Celsius.

Aerotolerant anaerobic bacteria

They use fermentation to grow. They cannot use oxygen but they can tolerate it.

Facultative anaerobes

They use oxygen if it is present, but can also convert to anaerobic respiration or fermentation when oxygen is absent.

What is antimicrobial resistance?

When a microbe becomes resistant to an antimicrobial substances like antibiotics due to mutations in their genes. This can result from the use of antibiotics in veterinary medicine to promote growth and to treat humans.

Death or Logarithmic decline phase

When the nutrients are depleted and the death rate is greater than the growth rate.