Bio 261: Chapter 31

Food Preservation: COLD

-*Slows microbial growth rate and delays spoilage* -Psychrotolerant bacteria can grow at refrigerator temperatures -Freezing allows for longer storage, but isn't suitable for all foods The reason we put food in the fridge is so it'll last longer; what happens when you put food in the bacteria is that if there are organisms in the food, their growth will slow down; food will still spoil, but not as fast as at room temp; organisms that can grow in the fridge (4C) are called *psychrotolerant bacteria*; freezing drops the temp down to 0 or below; some organisms would die during freezing, but not all

Food Preservation: PICKLING & ACIDITY

-*pH* is an important factor in microbial growth -Most foods are neutral or acidic -At pH less than 5, most spoilage organisms are inhibited -During the *pickling* process, *acetic acid* is added to a solution with sugar or salt (pickled foods: pickles, fish, peppers, fruits) Remember: bacteria like to grow around a neutral pH; pickling uses vinegar (acetic acid) to decrease the pH and increase salt or sugar concentrations to make a hypertonic solution (greater in one half than the other); the hypertonic solution dehydrates the bacteria and kills them

Naegleria fowleri (Typhoid Fever & Other Waterborne Diseases cont.)

-A *free-living amoeba* found in soil and water runoff, which can also cause amebiasis -Infections usually result from swimming in warm, soil-contaminated water sources (e.g., hot springs, lakes) -*Enters the human body through the nose and burrows directly into the brain, causing extensive hemorrhage and brain damage (meningoencephalitis) -Drug treatment is effective if infections are identified early; deadly if not

Giardia intestinalis (causes Giardiasis)

-A flagellated protist that is usually transmitted to humans in fecally contaminated water -The protist cells produce a resting stage (*cyst*) that is resistant to desiccation and chemical disinfection -Following ingestion, cysts germinate and attach to the intestinal wall, causing symptoms of infection -Many individuals exhibit no symptoms and can act as carriers The cyst is the egg or ova which is spread through contaminated water Ex: Giardial cyst (this is the stage that you would find in the water, which is resistant to chlorination and once ingested germinates into the troph)...then after ingestion you have...the parasite Giarda as a motile trophozoite (this is the stage that would be in the host's intestines)

Entamoeba histolytica (Typhoid Fever & Other Waterborne Diseases cont.)

-A pathogenic protist transmitted to humans primarily through contaminated water and sometimes food -Anaerobic and produces resistant cysts -Infection can be asymptomatic or lead to diarrhea and/or dysentery (diarrhea with blood in it) -If untreated, invasive cells can invade the liver and occasionally the lungs and brain -Amoebicidal drugs are not universally effective Bacillary dysentery is caused by the rod-shaped, gram-negative bacterium Shigella dysenterae; Amoebic dysentery is caused by Entamoeba histolytic, and can be difficult to treat; has a discrete, darkly stained nucleus

Botulism (Clostridial Food Poisoning)

-A severe and often fatal food poisoning -Caused by an exotoxin produced by Clostridium botulinum -*Botulinum toxin is a neurotoxin, but is destroyed by heat* -Average of 150 cases annually -70% of cases are infant; 15% wound; 15% foodborne -Home prepared foods are a common source of illness Botulinum toxin: a neurotoxin that blocks the release of acetylcholine causing a flaccid paralysis which when it occurs in the diaphragm is fatal; a deadly toxin, but is denatured by heat so in order to prevent botulism one can heat their food; remember, this is not the case on staph toxin! the bacterium that causes botulism is found in the soil; infants should not be given honey b/c it may have the C. botulinum spores that can get into child's intestines, germinate, and produce the toxin Remember: babies don't have any normal flora in their intestines when thy are born, & pathogen is able to grow where in older people the normal flora would block the attachment of the pathogen

Clostridial Food Poisoning

-Clostridium prefringens & Clostridium botulinum cause serious food poisoning; produces ensospores that may not be killed during cooking/canning process -C. prefringens is the most commonly reported form of food poisoning, with 248,000 annual causes; large numbers of T cells (>10^8) must be ingested; enterotoxin is produced in the intestinal tract 6-15 hours after consumption The Clostridium are anaerobic, gram-positive rods that produce endospores; they also produce an exotoxin that is associated with food poisoning C. perfringens causes food poisoning and gangrene C. botulinum causes botulism

Foodborne Disease Epidemiology

-Clusters of cases caused by microorganisms in a single source of food -Widespread multiple disease outbreaks caused by processing plant or food distribution center -Spinach and Escherichia coli (O157:H7 ... well studied and quickly traced)

Mushrooms

-Commercially grown mushroom is the basidiomycete Agaricus bisporus (generally cultivated in 'mushroom farms') -Another widely cultured mushroom is the shiitake, Lentinus edulus

Fermented Foods: SOY SAUCE

-Complex fermentation product of soybeans and wheat -Fermentation for 2-4 months in large vats

Fermented Foods: VINEGAR

-Conversion of ethyl alcohol to *acetic acid* -Acetic acid bacteria include *Acetobacter* and Gluconobacter -Processes for production: open vat (Orleans) method, trickle (quick vinegar) method, and bubble method

Food Preservation: IRRADIATION

-Food is irradiated with *ionizing radiation* to reduce bacterial, fungal, and insect contamination -Uses gamma or beta radiation, or X-rays -Irradiated foods must be labeled Ionizing radiation causes breaks in the DNA, which causes mutations and eventually death of organisms; radiation is used to decontaminate fruits, meats, and spices The radura is the international symbol for radiation; packaging of foods treated w/radiation must be labeled with the radura as well as "Treated by irradiation" or "Treated with radiation"

Staphylococcal Food Poisoning

-Food poisoning is often caused by toxins produced by Staphylococcus aureus: S. aureus can grow on common foods, and some strains produce *heat-stable enterotoxins*; *Gastroenteritis occurs within a few hours of consumption* -It is estimated that 185,000 cases of staphylococcal food poisoning occur each year -Enterotoins of S. aureus classified as superantigens produce large T cell responses and an inflammatory response S. aureus produces an enterotoxin that is heat stable which causes severe diarrhea; the fact that the toxin is heat stable means that heating food does not denature the toxin, so if it is present in the food people will get sick; remember, staphylococci are able to grow on salted foods like ham; the organism would from from a carrier touching the food; if left at room temperature, bacteria will grow and make the toxin; when people ingest the toxin, they will develop gastroenteritis within hours; most likely will not kill you; this is a self-limiting illness and supportive therapy is done for patient

Giardiasis and Cryptosporidiosis (Waterborne Microbial Disease)

-Giardia intestinalis causes giardiasis, an acute gastroenteritis (inflammation of stomach & intestines) -Cryptosporidium parvum causes cryptosporidiosis These organisms are found in nearly all surface waters and are *highly resistant to chlorine due to cyst formation* Giardia and Cryptosporidium are protists or parasites that live in the intestines of warm blooded animals (i.e. cows); the larvae and adults live in the host; the eggs or ova are excreted into the feces, which ends up in water supplies; ova are resistant to chlorination and must be filtered out of the water otherwise when people drink the water containing the eggs, once inside the human's intestines the ova develop into larva and adults, causing an infection and disease

Food Preservation: HIGH-PRESSURE PROCESSING (HPP)

-High hydrostatic pressure to kill pathogens and spoilage organisms -Works on fruits, vegetables, ready-to-eat meats, and juices Mechanism: At the top of the vessel there is a piston under pressure; the packaged sits (or floats?) in the water; the vessel is pressure-resistant

Protists (Other Foodborne Infectious Diseases)

-Important foodborne diseases are caused by Giardia intestinalis, Cryptosporidium parvum, & Cyclospora cayetanensis -Can be spread in foods contaminated by fecal matter in water used to wash, irrigate, or spray crops -Fresh fruits are often the source of these infections -Toxoplasma gondii can be spread by raw or undercooked meat

Microbial Sampling for Foodborne Diseases (Foodborne Diseases and Microbial sampling cont.)

-In addition to nonpathogenic microorganisms, pathogenic microorganisms may be present in fresh foods -Rapid detection methods have been developed to look for the presence of some of these pathogens (e.g., E. coli O157:H7) -Tests are molecular and immunology based -In the US, foodborne outbreaks are reported to the CDC -Standard method id isolation of pathogen -Isolation from food (requires treatment of food to suspend microorganisms) -Isolation from diseases patient E. coli O157:H7 is a pathogen that causes hemolytic uremic syndrome; molecular and immunological tests give immediate results as opposed to culturing the bacteria, which will take 24-48 hours, slowing down the production of food; CDC tracks info associated with foodborne outbreaks

Fermented Foods: DAIRY PRODUCTS

-Includes cheese, yogurt, buttermilk, and sour cream -Lactic acid bacteria are added to the milk and the fermentation proceeds for a certain time period -Some products require a second fermentation

Food Infection: LISTERIOSIS

-Listeria monocytogenes is the cause for *listeriosis* -May lead to bacteremia and meningitis -No food product is safe from contamiation -*Psychrotolerant* -L. monocytogenes is an intracellular pathogen; uptake of the pathogen by phagocytes results in the growth and proliferation of the bacterium -Mortality rate of listeriosis is 20% Listeria are gram positive rods that do not make endospores; they are psychrotolerant and are associated with contaminated lunchmeat and food recalls; any time the lunch meat is slimy, the fluid is cloudy and doesn't smell right..DON'T EAT! more than likely has bacteria growing on it

Fermented Foods & Mushrooms

-Many common foods are preserved, produced or enhanced by the actions of microbes (enhanced by fermentation reactions catalyzed by microorganisms) -Fermentation is the anaerobic catabolism of organic compounds (generally carbohydrates) -Important bacteria in the fermented food industry are: *lactic acid bacteria, propionic acid bacteria, and acetic acid bacteria* -*Products of fermentation include yeast bread, cheese, yogurt, buttermilk, sausage, sauerkraut, and soy sauce* Fermentation is actually a method of preserving foods; it is when an organism uses sugar to produces acids, alcohols, and gases; lactic acid bacteria use fermentation to make lactic acid, which reduces the pH of the food

Growth of Organisms in Foods (Food spoilage cont.)

-Microbial growth follows the normal pattern for bacterial growth -Only during the last few population doubling is food spoilage actually observed The bacteria will grow before you see the endproducts of their growth in the form of food spoilage; remember that bacteria reproduce by binary fission and grow exponentially

Food Preservation: DRYING & DEHYDRATION

-Moisture content (*water activity*) is critical for microbial metabolic processes -Sugar and salt reduce the availability of water for microbial growth, and in effect, dehydrating it (Ex: jams, jellies, meats, fish) -*Lyophilization* (freeze-drying) is the physical removal of frozen water under a vacuum (very expensive, but very effective) Removing water causes bacteria to die or at least stop growing; Lyophilization is even a method of culture preservation!

Food Infection: PATHOGENIC ESCHERICHIA COLI

-Most E. coli are nonpathogenic -All pathogenic strains are intestinal parasites, and a few produce potent enterotoxins: -*Shiga toxin*-producing E. coli (STEC), formerly called enterohemorrhagic E.coli (EHEC, i.e., *O157:H7*), produce *verotoxin* -Verotoxin causes bloody diarrhea and kidney failure -Other types of E. coli are enterotoxigenic (ETEC), enteroinvasive (EIEC), and enteropathogenic (EPEC)

Food Preservation: CHEMICAL PRESERVATION

-Over 3,000 compounds are used as food additives -A small number of these are used to control microbial growth; Examples: sodium propionate, sodium benzoate, nitrites (some, such as nitrites, are controversial because studies show they may be harmful to human health) -Significantly extends shelf life of finished foods

Prions (Other Foodborne Infectious Diseases)

-Proteins that adopt novel conformations that inhibit normal protein function and cause degeneration of neural tissue -"New variant *Creutzfeldt-Jakob Disease*", linked to consumption of meat from cattle suffering with bovine spongiform encephalopathy (BSE), a prion disease Prions are infectious proteins that cause mad cow disease or bovine spongiform encephalitis; Creuzfeldt-Jakob disease is a similar disease seen in humans

Cryptosporidium parvum (causes Cryptosporidiosis)

-Protist that lives as a parasite in warm-blooded animals -Produces thick-walled cells (*oocysts*) that are shed in the feces of infected animals -The oocysts are transmitted in fecally contaminated water (they are the eggs found in the water & what gets ingested, starting the infection) -Oocysts are highly resistant to chlorine and UV radiation...thus, sedimentation and filtration methods are most effective at removal -The life cycle for Cryptosporidium is similar to that of Giardia Cryptosporidiosis is usually *self-limiting* mild diarrhea, but can lead to more serious disease in compromised individuals; most people recover from cryptosporidiosis without treatment, unless immunocompromised

Fermented Foods: VEGETABLES & VEGETABLE PRODUCTS

-Sauerkraut (fermented cabbage) -Pickles (fermented cucumbers) -Olives, onions, tomatoes, peppers, and many fruits -Vegetables are often fermented in salt solutions

Fermented Foods: MEAT PRODUCTS

-Sausages are made from pork, beef, and poultry; a blend of meat, salt, and seasonings; lactic acid bacteria are added to the mixture; after fermentation, sausages are smoked and dried -Fish, often mixed with rice, shrimp, and spices

Food Preservation: ASEPTIC FOOD PROCESSING

-Several foods are now processed and packaged aseptically -This food can be stored on shelves for months or longer -Involves flash heating (heating for a short period of time) and packing in sterile containers -Ex: juice boxes and milk substitutes

Viruses (Other Foodborne Infectious Diseases)

-The largest number of annual foodborne infections are thought to be caused by viruses -*Noroviruses are responsible for most infections -Rotavirus, heptitis A virus, and astrovirus are responsible for the rest The norovirus is the virus often associated with cruise ships; individual norovirus particles have an indistinct rough outer edge

Legionellosis (Legionnaires' Disease)

-The prevalence of legionellosis is increasing and infections are often underreported -*Treatment with antibiotics is effective* -Prevention can be accomplished by improving maintenance and design of water-dependent cooling and heating systems and water delivery systems Disinfecting the cooling systems is a method of prevention

Food Preservation: HEATING

-Used to reduce the bacterial load (i.e., *pasteurization*) of a product or to actually sterilize (i.e., canning) -Canning isn't always 100% effective, failure results in swollen cans (DO NOT EAT!) Remember: heat denatures proteins which in turn kills the bacteria; pasteurization is used to reduce the numbers of organisms, esp. pathogens, in heat sensitive foods (like milk); canning can be used for foods that are not effected by boiling temperature; endospores can withstand canning and once an anaerobic environment develops, they germinate and start growing; as they ferment the sugars in the food, they produce acids and gas causing the can to swell; swollen cans are a sign of microbial growth, so DON'T EAT

Typhoid Fever & Other Waterborne Diseases

-Worldwide, the most important pathogenic bacteria transmitted by water are: Salmonella enterica serovar Typhi, a gram-negative rod (causes typhoid fever and has been virtually eliminated in developed countries due to water treatment) & Vibrio cholerae -Viruses can also be transmitted in water and cause human disease (ex: enteroviruses such as poliovirus, norovirus, and hepatitis A are shed into water from feces) -Viruses can survive in water for relatively long periods, but are inactivated by disinfection with chlorine Viruses that infect the intestines are called enteroviruses; we have a vaccine for polio and don't see many cases of it any longer, but before the vaccine people would get infected even in swimming pools; the norovirus is the enterovirus that causes problems on a lot of cruise ships; realize that on a cruise ship, there are a lot of people in close proximity to each other; one carrier can infect many people if sanitary precautions are not taken; Hepatitis A is spread through water and infects the liver

Public Health and Water Quality (cont.)

A commonly used method for performing coliform counts is the IDEXX Colilert test system: -utilizes proprietary substrates -sample with no coliforms remains clear -coliforms turn media yellow -E. coli turns media fluorescent blue

Coliform colonies growing on a membrane filter (Membrane Filter [MF] Test)

A drinking water sample was passed through the filter The filter was then placed on eosin-methylene blue (EMB) medium that is both selective and differential for lactose-fermenting bacteria (coliforms) The dark, shiny appearance of the colonies is characteristic of coliforms Each colony developed from one viable coliform cell present in the original sample

Food Infection: SALMONELLOSIS

A gastrointestinal illness caused by foodborne Salmonella *infection* -Caused by eating food contaminated with Salmonella or handling Salmonella-infected animals -Onset of disease occurs 8-48 hours after ingestion -Disease normally resolves in 2-5 days -Salmonella ingested in food or eater invades phagocytes and grows as an intracellular pathogen Salmonella are gram-negative rods that do not ferment lactose & are pathogens; often associated w/undercooked chicken, pet turtles, & contaminated water; Salmonellosis is typically self-limiting and is due not to a toxin, but an infection

Testing for Coliforms & E.Coli (Public Health and Water Quality)

All tests assay the growth of organisms recovered from the water samples; common methods for enumerating the samples: -Most-probable-number (MPN) procedure -Membrane filter (MF) procedures ...E.Coli can be distinguished from total coliforms with defined substrates (e.g., MUG, IBDG) To know if water is safe to drink or swim in, we do a test called the MPN (most-probable-number) to determine how many coliforms are present; also, Membrane Filter (MF) test; it is easier to test for coliforms than it is for pathogens because they are usually in higher numbers than the pathogens; if the coliforms are present, then there is a possibility that enteric pathogens like Salmonella and Shigella are present

Tertiary Treatment

Any physiochemical or biological process employing bioreactors, precipitation, filtration, or chlorination procedures similar to those used for purification of drinking water; reduces the levels of inorganic nutrients (e.g., phosphate, nitrate, nitrite); most complete method of treating sewage, but not widely adopted due to costs Typically chemical in the form of chlorination to make the water safe to drink; may also be filtered with smaller and smaller pore sized filters; most times, the water will not be chlorinated to be put back into a lake or stream which reduces the cost of the treatment process; chlorination is only required if the water is going to be consumed by humans

Food Infection: CAMPYLOBACTER

Campylobacter spp.: -Common cause of bacterial foodborne infections in the US -More than 2,000,000 cases of bacterial diarrhea per year -Transmitted to humans via contaminated food: poultry, pork, raw shellfish, or in surface waters -Campylobacter replicates in the small intestine -Causes high fever, headache, malaise, nausea, abdominal cramps, and bloody stools Campylobacter is a gram negative curved rod that causes an intestinal infection, leading to diarrhea

Agents and Sources of Waterborne Diseases

Common sources of waterborne disease transmission include: -Potable water used for drinking and cooking (undergoes extensive treatment, including filtration and chlorination) -Recreational water from public ponds, lakes, swimming pools, etc.

Cholera (cont.)

Diagnosis: presence of V. cholerae bacilli in the *"rice water"* stools of patients Prevention: immunization not recommended; public health measures are verrrrry important Treatment: oral rehydration and electrolyte replacement therapy The toxin causes the epithelial cells of the intestines to slough off, resulting in the characteristic 'rice water' stool; the bacteria can be cultured from a stool sample, but the patient will most likely be recovered by the time a positive identification has been made; remember, it takes a day for the stock and another day for the biochemical tests -- a minimum of 48 hours to identify the organism by classical culture methods; symptoms and appearance of the rice water stool is enough to know to keep the patient hydrated

Wastewater treatment processes

Effective water treatment plants use the primary(physical) and secondary(biological) treatment methods; Tertiary treatment to achieve less than 5 BOD units in effluent water is seldom done; if the water is going to be used for drinking, it will undergo a tertiary treatment which is chemical Primary: screening & sedimentation Secondary: Anaerobic digestion --> digested sludge: drying; incineration; use as fertilizer, or burial; -Aerobic Oxidation -->Activated sludge/aeration, Trickling filter; ...leads to Disinfection ---> treated effluent to discharge

Public Health and Drinking Water *Purification*

Effective water treatment practices that reduced the incidence of waterborne disease were not in place until the 20th century; coliform-counting methods were developed and adapted around 1906; water purification started with filtration; about 1913, chlorine came into use as a disinfectant for large water supplies We have water purification plants and regulations about the numbers of coliforms allowed in recreational waters as well as testing to ensure none is in our drinking water; Chlorine is used to disinfect water There was a dramatic reduction in the incidence of typhoid fever after the introduction of both filtration and chlorination

Foodborne Diseases and Microbial Sampling

Food Poisoning (or food intoxication) -Disease that results from ingestion of foods containing preformed microbial toxins -The microorganisms that produce the toxins do not have to grow in the host Food Infection -Microbial infection resulting from the ingestion of pathogen-contaminated food followed by growth pf pathogen in the host Microbes can cause disease by producing toxins or by infection (growth); the same info is true for foodborne diseases

Microbial Growth & Food Spoilage

Food Spoilage: -Any change in appearance, smell, or taste of a food product that makes it unpalatable to the consumer -Food may still be safe to eat, but is regarded as unacceptable -Susceptibility to food spoilage is based in large part on moisture content (*perishable foods have higher moisture content than nonperishable foods*) -Fresh foods are spoiled by both bacteria and fungi: spoilage organisms are those that can gain access to the food and use the available nutrients (Ex: Escherichia coli frequently contaminated meat products because it is found in animals' digestive tracts) The chemical composition of a food determines its susceptibility to microbial spoilage: *perishable, semiperishable, or nonperishable* Microbes can use food to grow on and will spoil it in the process; the amount of water in the food classifies it as perishable, semi, or non Organisms must have water to grow !

Wastewater Treatment facility

Goal is to reduce organic and inorganic materials in wastewater to a level that no longer supports microbial growth and to eliminate other potentially toxic materials; the efficiency of treatment is expressed in terms of a reduction in the *biochemical oxygen demand*: the amount of dissolved oxygen consumed by microbes to completely oxidize all organic and inorganic matter in a water sample Decreasing the BOD is the goal of a wastewater treatment facility, which in turn is directly related to the numbers of microbes present in the water

Wastewater and Sewage Treatment (cont. #2)

In the activated sludge process, wastewater is mixed and aerated in large tanks and slime-forming bacteria (e.g., Zoogloea ramigera) grow and form flocs; most treatment plants chlorinate the effluent after secondary treatment to further reduce the possibility of biological contamination Zoogloea ramigera are the bacteria that float in the water in flocs to remove the organic material and purify the water as it filters through sand traps and on through the treatment facility; the clean water is at the top and flows over into the next area until ultimately it can be clorinated and put back into the environment like a lake to be used as a reservoir for drinking water -Floc formed in the activated sludge process consists of a large number of small, rod-shaped cells of Zoogloea ramigera surrounded by a polysaccharide slime layer, arranged in characteristic fingerlike projections (shown in a negative stain with India ink)

Public Health and Water Quality

It is impractical to screen water for every pathogenic organism; potable and recreational water are routinely tested for specific *indicator organisms*; presence of indicator organism signals potential for disease: coliforms are an indicator organism (not all coliforms are fecal); fecal coliforms are used in water safety testing; Escherichia coli is a key fecal coliform

Legionellosis (Legionnaires' Disease) (Waterborne Microbial Disease)

Legionella pneumophila: -Causes legionellosis -Normally *transmitted in aerosols* -Gram negative bacterium with complex nutritional requirements -Common in terrestrial and aquatic habitats -Relatively resistant to heating and chlorination -Common in cooling towers and evaporative condensers of large air conditioning systems (the pathogen rows in the water and is disseminated in humidified aerosols) -*Infection is not spread from person to person* Legionella pneumophila likes to grow in air conditioning cooling towers and can be aerosol through the A/C ducts where it can be breathed in and cause a lung infection; this disease is not contagious person to person, so you would only get it from the source; this organism will not grow on regular lab media and requires a media called buffered charcoal yeast extract agar to grow

Food Preservation

Methods for slowing spoilage and foodborne disease: -Cold -Pickling and acidity -Drying and dehydration -Heating -Aseptic food processing -Chemical preservation -Irradiation

Sources of Waterborne Infection (Waterborne Microbial Diseases)

Microorganisms transmitted in water generally grow in the intestines and leave the body in feces (*feces then pollute water*); numerous bacterial and protozoan pathogens can be transmitted in drinking water; in the US, the number of disease outbreaks due to drinking or recreational water contamination is low; lack of adequate water treatment facilities and access to clean water contribute to the spread of infectious disease Fecal contamination is typically the reason water may contain pathogens

Changes in sealed tin cans as a result of microbial spoilage (example of canning)

Normal can: the top of the can is pulled slightly in due to the negative pressure (vacuum) inside) Swelling results from minimal gas production; the top of the can bulges slightly Sever swelling due to extensive gas production If you drop a can, the gas pressure exerted results in a violent explosion, tearing the lid apart

Other Foodborne Infectious Diseases

Other bacteria: -Yersinia enterocolitica causes foodborne infections due to contaminated meats and dairy products; can lead to life-threatening enteric fever -Bacillus cereus grows in food that is cooked and left to cool slowly; causes diarrhea and vomiting -Shigella spp. cause nearly 100,000 cases of severe foodborne invasive gastroenteritis each year Yersinia is the same genera that causes plague; this species causes a foodborne infection Bacillus cereus is a gram positive rod that is found in the soil and produces endospores; the food poisoning is self-limiting and is often associated with leaving rice in a rice cooker for extended periods of time; cooking the rice may not kill the spores, and leaving the pot on will allow it to germinate -Shigella can cause gastroenteritis or more severe cases of dysentery

Wastewater Microbiology and Water Purification: Water

Potential common source of infectious diseases; can also be a source for chemically induced intoxications; ensuring water purity is essential for public health; treatment and purification schemes use microorganisms to identify, remove, and degrade pollutants water can be a vehicle to carry pathogenic organisms; if water is contaminated with a toxin or pathogen and a person ingests the contaminated water they can get sick

Drinking Water Purification (cont.)

Purification involves many steps: *Sedimentation* to remove particles *Coagulation and flocculation* form additional aggregates, which settle out *Filtration* *Disinfection* (typically with chlorine gas or UV radiation)

Cholera (Waterborne Microbial Diseases)

Severe diarrhea; caused by Vibrio cholerae; typically transmitted through ingestion of contaminated water; largely restricted to developing countries (Endemic in Africa, Southeast Adia, the Indian subcontinent, and Central&South America); can be controlled by application of water Vibrio cholerae (bacteria that causes cholera) is a gram-negative curved rod that likes to live in brackish water; oysters are filter feeders and if the bacteria is in the water, they take it in; if someone eats a raw oyster that contains the bacteria and its toxin, then the toxin will block the absorption of sodium resulting in diarrhea; the toxin and the bacteria will go on through the person, so it is very important to prevent dehydration; any time we have a drought condition, the concentration of bacteria increases in the water and we will see an increase in cholera

"Rice-water" stool (result of Cholera)

The stool is nearly liquid; the solid material that has settled in a bottom layer is mucus; the stool is essentially isotonic (parts are equal) with blood, containing high amounts of Na+, K+, and HCO3- (bicarbonate) ions, as well as large numbers of Vibrio cholerae cells

Aerobic Secondary Treatment

Uses digestive reactions carried out by microbes under aerobic conditions to treat wastewater with low levels of organic materials; activated sludge and the trickling filter are the most common decomposition processes ; the activated sludge contains the microbes! There are also aerobic bacteria involved in secondary treatment; some of the organisms are in the water and others are attached to rocks & the water trickles over the rocks; the bacteria form a biofilm and break down the organic matter as it trickles over them

Cholera: Pathogenesis

Vibrio cholerae attaches to epithelial cells in the small intestine, where it grows and released cholera toxin; this *enterotoxin* causes severe diarrhea (*can result in dehydration and death unless treated*) Cholera is the result of the cholera toxin blocking the absorption of sodium which causes water to enter the intestines and cause diarrhea; goal: keep the patient alive by hydration!

Primary treatment example

Wastewater is pumped into the reservoir (left) where solids settles As the water level rises, the water spills through the grates to successively lower levels Water at the lowest level, now virtually free of solids, enters the spillway and is pumped to a secondary treatment facility

Drinking Water Purification

Wastewater treated by secondary methods is not yet *potable*, or *safe for human consumption; it requires further treatment to remove pathogens, eliminate taste and odor, reduce chemicals (e.g. iron, manganese), and decrease turbidity; a typical drinking water treatment installation purifies raw (untreated) water Water that is going to be purified for drinking typically would not come from a wastewater treatment facility but would come from an aquifer or reservoir

Wastewater and Sewage Treatment (cont.)

Wastewater treatment is a multistep operation employing both physical and biological processes: -primary, secondary, and sometime tertiary treatments are used -Primary treatment: uses *physical separation* methods to separate solid and particulate organic and inorganic materials from wastewater; AKA initial treatment; a physical process; screens are used to remove large particulates, then sedimentation

Wastewater and Sewage Treatment

Wastewater: domestic sewage or liquid industrial waster Wastewater treatment: relies on industrial-scale use of microbes for bioconversion; following treatment, the discharged treated wastewater (effluent water) is suitable for: -released into surface waters -release to drinking water purification facilities We generate wastewater in every day life, and we have wastewater treatment plants that purify the water and release it into the environment

Anoxic Secondary Treatment

involves a series of digestive and fermentative reactions carried out by various microbes under anoxic conditions; the process is carried out in large, enclosed tanks (sludge digesters or bioreactors) Involves bacteria that use the carbon in the water and break it down to carbon dioxide and water; part of the process involves anaerobic bacteria that are in sludge digesters; they produce methane The major products of anaerobic biodegredation: Methane (CH4) and Carbon Dioxide (CO2)