Unit 3 Exam for Microbiology 3050
Unit 3 Exam for Microbiology 3050 MICRO 3050
Popular in General Microbiology
Popular in Chemistry
This 22 page Study Guide was uploaded by Victoria Hills on Wednesday January 13, 2016. The Study Guide belongs to MICRO 3050 at Clemson University taught by Dr. Rudolph in Spring 2016. Since its upload, it has received 67 views. For similar materials see General Microbiology in Chemistry at Clemson University.
Reviews for Unit 3 Exam for Microbiology 3050
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 01/13/16
UNIT 3 STUDY GUIDE MICR 3050 Chapter 7.1, 7.3 – 7.4, 7.6 – 7.7 1. Describe, in general, microbial growth in natural environments. • Microbial environments: - Are complex - Constantly changing à Seen with different debris in the environment such as a rain drop changing everything - Often low nutrient concentrations (oligotrophic environment) - Think of them literally as microenvironments; ex: one soil particle could have 10 different microenvironments and this often times could have to do with the O l2vels • Microbial growth depends on: - Nutrient supply à Bacteria mainly exist in the famine environment rather than the feast one - Tolerance of environment à O , water, pH, salt, etc. 2 - Inhibitory substances à toxic waste, oxygen (ROS), man-made substances • Most microbes grow attached to surfaces as biofilms - A lot of bacteria don’t live alone because they live better with strength in numbers - Biofilms occur on moist surfaces because of the necessity of water - Bacteria act differently when they are in a biofilm than when they are alone 2. Describe biofilms including their characteristics, growth (formation), advantages (for bacteria), and disadvantages (for humans). • Biofilm formation: - Microbes reversibly attach to conditioned surface and release polysaccharides, proteins, and DNA to form the extracellular polymeric substance - Some bacteria attach to a surface (harder to do so if it has been recently cleaned or is really clean), formation of biofilm occurs and rough up the surface a bit more, and it develops and grows - Pili and capsules, etc. help the bacteria to attach to surfaces - Once enough bacteria have attached, the bacteria send out signals to make EPS (extracellular polymeric substance) for communication with other bacteria and then they act more differently together and continue to build up the polysaccharide matrix (EPS) = negatively charged • Advantages for bacteria: - Location is key with biofilms - Biofilms are a heterogeneous community à Have metabolic difference, location - They provide protection from anti-microbials, cleaners, immune cells (can’t be phagocytized if in a huge chunk) - Microbial interactions à o Metabolic exchange o DNA uptake o Quorum sensing: Cell-cell signal à changes what genes are being expressed; the bacteria secrete a protein when enough bacteria are present (density dependent) - Pure culture biofilm = colony - In the middle, there are slow growers of bacteria due to low O and 2 nutrition - As bacteria perform metabolic processes à waste production, which can be waste for one type of bacteria but be food for another species - Cell-cell signaling can change the physiology of a bacterial cell - Persister cells in the middle of the biofilm have starvation responses and get stronger as they get stickier and therefore more virulent - When cells die in the middle of the biofilm, they die and release DNA (Creates diversity) - Biofilm has channels throughout it for formation, nutrition, etc. • Disadvantages for humans: - Medical: o Form on medical device o Cause disease à ex: dental carries, pneumonia - Industrial: o Interfere with fluids distribution: Biofilm accumulating in water pipes à prevent fluid distribution and concern is pathogen gets into the drinking water o Corrosion potential: Have an object in the water à such as oil rigs, ship hulls, etc. and bacteria create rust - Biofilm on artificial join for ex: would have to be removed because there are too many bacteria/it’s too big to use anti-biotics - Plaque: Bacteria in the middle of the biofilm have no O à 2 fermentation so acid is produced and degrades teeth - Cystic fibrosis: Mucous in lungs and have pseudo. (Soil bacteria) biofilm - Some scientists believe eliminating quorum sensing is key • Ex: Streptococcus pneumonias - Has a capsule and is a pathogen - In high numbers it produces a messenger that tells other bacteria that there is enough of them together so protein changes these cells to become competent, meaning they can take in DNA (transformation) - They produce another protein to be able to kill other bacteria so they can take in their DNA • Ex: Vibrio Fisherie - Halophile in fish and squid in light organ à responsible for their glowing abilities - Produce an auto inducer protein and when it is released it goes with the concentration gradient to the outside of the cell - If in high enough concentrations, can reverse the concentration gradient so it’s higher on the outside so it goes back inside the cell, which triggers the glowing gene to turn on (requires a lot of bacteria for this) - Advantages to glow: Attract prey, help them from predators so when they look up they see a light and think it is the light from the sun Chapter 8.1, 8.3 – 8.4, 8.6 3. Know and describe the methods used to control microbial growth. • Physical Agents: - Heat: o Dry à incineration (Sterilization) vs. dry oven (Sterilization) o Moist à Steam under pressure (Sterilization) vs. boing water, hot water, pasteurization (Disinfection) - Radiation: o Ionizing à X-ray, cathode, gamma (Sterilization) o Non-Ionizing à UV (Disinfection because only sterilizes surfaces) • Chemical Agents: - Gases: o Gases that sterilize o Gases that disinfect - Liquids: o Animate à Chemotherapy and antisepsis o Inanimate à Sterilization and Disinfection • Mechanical Removal Methods: Filtration: - Air: Sterilization - Liquids: Sterilization • Biological Agents: - Predator: Antisepsis - Virus: Antisepsis - Toxin: Sterilization 4. Define the frequently used terms of microbial growth control. • Sterilization: - Destruction or removal of all viable organisms - Includes endospores (Which usually dictate how to sterilize things) - An absolute condition • Disinfection: - Killing, inhibition, or removal of pathogenic organisms - Disinfectants o Agents that are usually chemical that are used for disinfection; ex: Pinesol o Usually used on inanimate objects à Can use H O on l2vi2g tissue (exception), but cannot use bleach on living tissue - Running a dishwasher is disinfecting the dishes because does not kill endospores (Overall microbial load is being reduced and killing pathogens) • Decontaminate: - Removal of pathogenic organisms - Includes water • Sanitization: - Reduction of microbial population to levels deemed safe (based on public health standards) - Considered to be disinfection that is up to public heath standards, but this does not mean that sanitizer is more caustic than a disinfectant (it is possible to have a more concentrated disinfectant) • Antisepsis: - Prevention of infection of living tissue – prevents rotting à means not necessarily killing all the microorganisms - Antiseptics: Chemical agents that kill or inhibit growth of microorganisms when applied to tissue • Chemotherapy: - Use of chemicals to kill or inhibit growth of microorganisms within host tissue - Includes antibiotics, anti-microbials etc. • Antimicrobial Agents: - -Cide: Disinfects o Suffix indicating that the agent kills o Germicide à kills pathogens and many non pathogens but not necessarily endospores; bactericides, fungicides, algicides, and viricides - -Static: “to stop” o Suffix indicating that agent inhibits growth of bacteria or fungi à bacteriostatic and fungistatic o What many antibiotics are – so numbers of prevented from getting too high and the immune system can take care of the rest then 5. Describe the conditions that influence the effectiveness of an antimicrobial agent. • Population size • Population composition à Referring to what species is there—for bacteria, are they in the form of endospores, persister cells, etc.? What about for fungi? • Concentration or intensity of the agent à In general, the more intense, the more microorganisms are killed - Exception: 70 % alcohol kills better than 95 % alcohol because water helps with killing the microorganisms • Duration of exposure à In terms of getting to safe levels—generally, the longer the better the job is done • Temperature: Increasing heat to help antimicrobial agent - Also, with increased temperature, the intensity of the antimicrobial agent may not have to be as high • Local environment - See if the bacteria are in the form of a biofilm - pH à lower temperatures for aiding the antimicrobial agent can be used with acidic pH (more heat is needed with treating basic foods for ex.) - Viscosity - Presence of organic matter à removing this is necessary and is a method to combine with an antimicrobial agent 6. Explain how filters are used and their functions. • Filtration (Mechanical Removal Method) • Reduces microbial population or sterilizes solutions that are heat-sensitive (for solutions that can’t be placed in an autoclave for example) - Membrane filters with defined pore size - Good for antibiotic solutions • Also used for air: - Surgical masks: Disinfect the air - Cotton plugs on culture—depth filter (not going to sterilize usually) - Vessels - High-efficiency particulate air (HEPA filters) - Laminar flow biological safety cabinets à Surfaces are sterilized: Blows sterile air into the cabinets and contaminated air out (don’t have to use a flame here) 7. Describe the physical methods to control microorganisms (moist heat, dry heat, low temperature, UV radiation, ionizing radiation). • Physical methods to control microbes: 1. Heat (moist and dry) à moist is better at lower temperatures 2. Low temperature 3. Radiation: UV, gamma (ionizing radiation) • Moist Heat: - Destroys bacteria, fungi, and viruses - Degrades nucleic acids, denatures proteins, and disrupts membranes – lipid bilayers fall apart - 3 types: a) Boiling: Will not destroy endospores, so does not sterilize b) Autoclaving: Can sterilize, used for lab equipment o Important to be moist o Effective against all types of microbes (Sterilization) o Pressure = 15 psi à not the factor that does the killing o Temperature = 121 degrees C à factor that does the killing o Time = 15-20 min o Validation process: Autoclave, incubate, observe for growth of indicator organisms à can get strips of paper with endospores and put in test tubes after autoclave and if the tubes get cloudy this means that the endospores were activated and germinated instead and the autoclave didn’t really work o With large volumes of liquids, it’s necessary to go longer and have to be careful with lids blowing off it too tight; necessary with having room for boiling o It takes a while for the pressure and temperature to get up to 121 degrees C and then it takes about an hour to cool off c) Pasteurization: Moist heat control method, does not sterilize; First used for wine because wine was turning into vinegar o Controlled heating at temperatures well below boiling in order to not ruin the product à Used for wine, milk, and other beverages o Kills pathogens present and slows spoilage à Reduces the total load of the organisms present (there may still be some bacteria present but not many and won’t grow rapidly) o Process does not sterilize o Ex: Eggs à Put in water baths where they are constantly turned so can get the temperature high enough - Objects that could not be disinfected/sterilized with moist heat: Powders, metals etc. because of rust for metal and can’t be exposed to water • Dry Heat: - Can be with some autoclaves that act like a big oven - Works with objects that cannot be exposed to water - Less effective than moist heat sterilization o Requires higher temperatures and longer exposure times o Items subjected to 160 – 170 degrees C for 2 to 3 hours o Ex: Botulism spores require 2 hours for sterilization vs. 5 min with moist heat - Oxidizes cell constituents and denatures proteins - Dry heat incineration: Flaming loop in lab but doesn’t last long; electric • Low Temperature: - Freezing: < 0 degrees F - ~ -4 degrees F / - 20 degrees C o Stops (static) microbial reproduction due to lack of liquid water o Some microorganisms killed by ice crystal disruption of cell membrane à assume microbes are about the same amount but not growing but will resume once out of the freezer - Refrigeration: ~ 4 degrees C (< 5 degrees C)/ < 40 degrees F o Slows microbial growth and reproduction o Reproduction is not affected by psychotrophs like listeria and with even some mesophiles might be slowly growing • UV Radiation: - Most bactericidal wavelength is 260 nm - Causes thymine dimers in DNA and in cytosine too sometimes; causes DNA to be weak with thymines in between it - Limited to surface sterilization à does not penetrate glass, plastic, dirt, films, etc. = disinfects overall - Water treatment plants use UV light as water comes out - Can damage retinas and skin - Good to sterilize surfaces in an OR for example • Ionizing Radiation: - Agent that penetrates deep into objects - Gamma radiation - Use on things that can’t be around heat or water - Cold sterilization: o Antibiotics o Medical supplies o Food à especially for ground beef for example - With bacteria 60 source under water deep enough so won’t harm people (in a large room) Chapter 9.1 – 9.3, 9.8, 16.9 8. Define antimicrobial, antibiotic, synthetic chemotherapeutic agent, and semi- synthetic chemotherapeutic agent. • Antimicrobial (chemical agent): Used to treat disease by destroying pathogenic microbes or inhibiting their growth within a host - Substances as antimicrobials are not always true chemicals à some are produced by fungi/bacteria for example • Antibiotics: - Microbial products or their derivatives that kill susceptible microbes OR inhibit their growth - This is a true microbial product that is not chemically modified in any way - Ex: Penicillin, streptomycin • Synthetics (chemotherapeutic agent): - Chemicals, dyes poisons - Ex: Sulfa drugs • Semi-synthetic (chemotherapeutic agent): - Where antibiotics are taken and are chemically modified à would want to do this in making sure selectively toxic bacterial resistance mechanisms aren’t in play - Also modified because of how allergic someone might be to the original raw antibiotic - Ex: Ampicillin and amoxicillin are both semi-synthetics of penicillin - Ex: Penicillin is a hapten- not an antigen- allergic individuals have a protein in their blood serum and when it joins the penicillin, it causes an immune resposne because together the protein and penicillin produce an antigen 9. Know and describe the general characteristics of antimicrobial drugs including the terms used to describe their action, spectrum of activity, and their effectiveness. • Selective Toxicity: - Targets only the microbe/pathogen o Bacteria have peptidoglycan in their cell walls, while human cells do not, so use a drug that attacks the peptidoglycan for example—the ribosomes between the human cells and bacterial cells are different enough so the drug will go after the bacteria - Ability of the drug to kill or inhibit pathogen while damaging the • Therapeutic Dose (Effective Dose- ED): - Drug level required for clinical treatment - The amount of drug that has to be taken to treat the illness - Take the effective dose for 50 % of the hosts (ED ) a50 compare to the toxic 50 % (TD ) 50ere 50 of the test subjects get side effects • Toxic Dose: - Drug level at which the drug becomes too toxic for patients (produces side effects) • Therapeutic Index: - Ratio of toxic dose to therapeutic dose - The larger the therapeutic index, the better - When making drugs: TD / ED 50 50 à Want the toxic dose (TD) to be higher – X:1 ration for side effects - Ex: Morphine: 70:1 - Ex: Cocaine: 10:1 à very toxic • Narrow-Spectrum Drugs: - Attack only a few different pathogens - Ex: Drug that goes after gram-positive bacteria • Broad-Spectrum Drugs: - Attack many different pathogens (can go across many different types of organisms) - Make semi-synthetics from antibiotics to make these broad-spectrum drugs in order to be able to kill more microbes • Cidal agents: - Kills microbes • Static agents: - Inhibits growth of microbes • Side effects: - Undesirable effects of drugs on host cells • To determine whether or not an antimicrobial is static or cidal, look at growth curve: - Bacteriostatic: o Both the viable cell count and total cell count would go from exponential growth to leveling off - Bacteriocidal: o The viable cell count would go from exponential to sharp decrease in number o Total cell count would go from exponential and level off and shows that the agent is cidal but didn’t lyse the cells - Bacteriolytic: o Both the viable cell count and total cell count decrease rapidly and no leveling off occurs since the cells are lysed o Some agents are both cidal and lytic 10. Explain how antimicrobials are classified. • Classification: - Molecular Structure: Look at the chemical formula; ex: Penicillin and having beta lactam ring à beta lactam classified - Mechanism of Action - Spectrum of Antimicrobial Activity: Narrow or broad + what type of organism is targeted; what part of bacteria cell wall that’s affected, cidal or static? • Categories: - Synthetic - Semi-synthetic - Antibiotics 11. Know the mode of action, effect (static or cidal), and spectrum of activity for the following antimicrobials: penicillin, erythromycin (Z-pack), ciprofloxacin, and sulfonamide. • Penicillin: - Doesn’t let peptidoglycan link with the peptides so the peptidoglycan falls out during bacterial growth - Cidal - Narrow Spectrum in natural form à Targets gram-positive bacteria because of the exposed peptidoglycan - Broad Spectrum in semi-synthetic form à When penicillin is modified to be able to work against some gram-negative bacteria too • Ciproflaxoacin: - Works against DNA girase because it prevents replication in bacteria - Cidal (Due to the DNA being damaged enough) - Narrow Spectrum: Targets a few types of gram-negative bacteria - Used for UTI infections (E. coliform colin (?)” à urethra à bladder) • Erythromycin (Z-pack): Macrolides - Goes after the 50s subunit of ribosomes à messes up protein synthesis - Static - Broad Spectrum - Semi-synthetic: Z-Pack à made to make a broader spectrum • Sulfonamide: - Chemicals (synthetics) à used because of antibiotic resistance - Goes after the folic acid metabolism—messes up DNA repair mechanism à competes with paba (a metabolite that is needed by the bacterial cell) - Static - Broad Spectrum 12. Define minimum inhibitory concentration and minimum lethal concentration and explain how they are related. • Minimal Inhibitory Concentration: - Lowest concentration of drug that inhibits growth of pathogen - Used to find the ED (therapeutic dose) - This has to be exceeded in order for the drug to be effective • Minimal Lethal Concentration: - Lowest concentration that kills pathogen - Handy if working with cidal drug to kill a pathogen • Depending on the MIC and MLC, they will determine whether or not a drug is cidal or static • Cidal: Can be used to determine the MIC and get an idea of what the MLC is because its usually 2-4 x the MIC = lethal • For some static drugs: If the concentration is increased enough, could be cidal (and same with cidal drugs if the concentration is decreased enough à static) 13. Describe the factors that influence the effectiveness of antimicrobial drugs (Consider when determining the best drug to use). • Ability of a drug to reach the site of infection - Might need a shot vs. oral pill for example in order for the drug to reach the site of infection better • Mode of administration • Susceptibility of pathogen to drug: - Also have to consider what has happened in the body - Ex: With biofilms, bacteria are protected • Ability of drug to reach concentrations in body that exceed the MIC (Minimal Inhibitor Concentration) - If figured out the MIC to inhibit pathogen (static), going to have to exceed a little bit for effectiveness - Same with MLC (if want the drug to be cidal) • Determining the level of antimicrobial activity: - Dilution Susceptibility Test: o Smallest mount of agent needed to inhibit the growth of a test organism = MIC o Broth from which microbes can’t be recovered = MLC o Clear Tube: No growth occurring, but doesn’t mean the bacteria are necessarily killed o With last two tubes that cube be MLC, have to take some out and put on a plate to see if any growth occurs and if it doesn’t then that’s MLC - Disk Diffusion Tests: o Certain concentrations in disk that’s diffusing out à close = higher the concentration and the further out = lower the concentration o The MIC = lower concentration and edge of the zone of inhibition (Can visually see it but don’t know what the concentration is) - Kirby-Bauer Method: o Used to determine the effectiveness of certain antimicrobials through discs with antibiotics in the disk o Sensitivity and resistance determined using tables that relate zone diameters to degree of microbial resistance o Larger the zone of inhibition = the better the antibiotic (Sub- category of anti-microbial which is a natural product of bacteria and fugi) is working 14. Explain the emergence of antimicrobial (drug) resistant bacteria, the mechanisms of bacterial resistance, the origin and transmission of drug resistance, and ways to prevent it. • The serious threat of drug resistance: • Drug resistance has to do with the ability to where bacteria is not susceptible to a particular drug when it should be - The Problem: o Once resistance originates in a bacterial population it can be transmitted to other bacteria through horizontal gene transfer o A particular type of resistance mechanism is not confined to a single class of drugs o Erroneous practices select for the growth of resistance bacteria à putting pressure on microbial to grow through creating natural selection process - The “Superbug” is here! o Methicillin-resistant Staphylococcus aureus (MRSA) that is also resistant Vancomycin (VRSA) – Probably because vancomycin was the only drug for a while that was used to treat MRSA/VRSA o Staphylococcus aureus is an opportunistic pathogen; sources: locker rooms, sports equipment, grows on our skin o A lot of people carry MRSA and don’t have problem with it à if someone gets it once, it’s more likely for the person to get it again o MRSA: causes boils with puss—can get deep o If a microbe has penicillin resistance, this means that it has the B-lactamase enzyme and is therefore resistant to all “cillin” drugs à B-lactamase breaks B lactam ring so penicillin won’t have an effect o Tuberculosis also has a lot of resistance too • Appearance of Antimicrobial Drug Resistance: - Almost every pathogen has resistance out there • Mechanisms of Bacterial Resistance: - Preventing entrance via enzymes that degrade the antimicrobial on the outside of the cell - Efflux pumps: Transport enzyme (a translocase) that transports things (antimicrobials) out à if a cell has one, it will take out a ton of different types of antimicrobials - Inactivation: Via enzymes that inactivate the antimicrobial inside the cell - Target modification: o Drug target o Slightly modified target à ex: Ribosome slightly mutated so drug can’t bind to it o Some sort of mutation has occurred - Alternate Pathway: Antimicrobial still has an effect but the cell compensates for the effect through another biochemical pathway that fixes the problem • Origin and Transmission of Drug Resistance: - Origin: o Natural immunity genes: Protect cells from own antibiotics o Spontaneous mutation: Ex: DNA replication errors o Location of resistance genes: § Chromosome: Very stable and not as easily transferred to other bacteria § Plasmids: AKA R factors à Easily transported to other bacteria § Transpons: DNA sequence that can hop to plasmid from the chromosome and vice versa § Gene casettes and integrons à hopping elements with resistance genes § Target modification usually results with this à doesn’t have to do with exposure to the antimicrobial since the resistance is already there (1 in million to 10 million microbes are resistant) - Transmission: o Horizontal gene transfer à Transformation, Conjugation (Ex: pilus: donor à recipient), Transduction (Viruses) - Have found other bacteria that are already resistant - When we expose bacteria to antimicrobials, we are simply allowing the resistant bacteria to grow - Bacteria make their own antibiotics to kill other bacteria because of competition of space etc. à If a bacteria produces an antibiotic it has to make sure that it doesn’t kill itself (Have natural immunity genes such as efflux pumps) - The DNA of resistant genes has to get onto the chromosome to work • Sources of Antibiotic Resistance: - Inappropriately prescribing practices: Antibiotics do not work on viruses and sometimes they are given anyway; 1/5 of prescriptions are for actual virus infections when 98 % of the time it’s a viral infection - Unregulated sale of antibiotics - Failure to complete courses of antibiotics: It’s important to complete the course of antibiotics because want to kill all the bacteria quickly and immune system can take care of the few bacteria with mutants because other bacteria protect the mutants - Use of antibiotics as animal growth enhancers (Illegal): Problem because could contaminate the environment and if get resistant bacteria on body not good o 80 % of the antimicrobials in the US go to livestock • Preventing Emergence of Drug Resistance: - Give drug in high concentrations to destroy susceptible + want high enough levels of the drug so that it stays in the body long enough - Give two or more drugs at the same time à can be a little questionable because if there is selection for resistant mutants, don’t want multiple resistance resulting with multiple antimicrobials - Use antimicrobials only when necessary à wait to see if viral first - Use narrow spectrum antimicrobials à broad spectrum usually is what is given so you will get better immediately, but should culture the bacteria to choose a narrow spectrum antimicrobial; broad spectrum drugs also kill good bacteria too so can get yeast infections for ex. (Can produce bad symptoms) - Possible future solutions: o Continued development for new antimicrobials à many have been soil bacteria o Use of bacteriophages to treat bacterial disease – these are viruses that infect bacteria and bind to LPS or peptidoglycan etc.; used a disinfectant on surfaces in Europe Chapter 41.1 – 41.3, 41.5 – 41.6 15. Describe the intrinsic and extrinsic factors that control the growth of microorganisms in food. • 2 Purposes of Use of Microbial Growth in Food: a) Enhance/preserve food b) Bacteria to grow = spoilage • Intrinsic Factors: Food composition and structure - Quality of food à structure, grounded, liquefied, solid, considers how much oxygen is present, pH • Extrinsic Factors: - Environmental in terms of how the food is stored, prepared, what preservatives are added etc. • Microbial growth in food may result in spoilage: - Alters food rendering it unsuitable for consumption à smell, excess liquid around it, color, slimy - Different foods undergo different types of spoilage processes - Spoilage effects won’t show up until late exponential phase - If eat a spoiled food à depends on if get sick if pathogens are present - Food borne illness = pathogens grown to high enough levels or enough toxin is produced to cause illness - Think about what bacteria will growing foods due to intrinsic factors - Protein deamination = smell, H S 2ay be produced, carbohydrate fermentation à sour/acidifed - Can usually figure out what spoils food because of where it grows à ex: Lactic acid bacteria in milk and pseudomonas = soil bacteria in fruits, vegetables, maybe meat 16. Describe food spoilage and how foods can be preserved. • Food composition and spoilage: - Carbohydrates: o Mold predominates o Degrades food by hydrolysis o Little odor (By fungi) o Ergotism: Disease caused by Claviceps purpurea toxins à can grow on moldy grain (moist place) which makes a toxin that causes hallucinogenic alkaloid; can cause involuntary muscle contractions, vertigo, tingling in the extremities, abortion - Proteins or fats: o Bacterial growth predominates o Putrefaction = rotting à due to anaerobic breakdown of proteins and creates foul-smelling amine compounds o Rotting tissue (like on an open wound) • Intrinsic Factors: - pH: Low pH favors yeast and mold à most bacteria like a pH of ~ 7 (acidity can preserve food against bacteria) - Presence and availability of water: In general, lower water activity inhibits microbial growth à dry foods can absorb water though if they are in a humid environment - Oxidation-reduction potential: Lower redox (less oxygen)—favors growth of anaerobic bacteria - Grinding and mixing promotes microbial growth à taking bacteria in from the outside to make oxygen more available in the inside - Antimicrobial substances: Coumarins (F/V), lysozyme (Found in tears/saliva + some foods have lysozyme naturally), allicin (product by garlic) • Extrinsic Factors: (Environmental ways to store food for preservation) - Temperature: o Lower temperatures retard microbial growth à refrigeration slows down, freezer can stop but won’t kill all bacteria - Relative humidity: o Higher levels promote microbial growth - Atmostphere: o Oxygen promotes growth à mixing/grinding brings more oxygen inside the food o Modified atmosphere packaging (MAP) à use of shrink wrap and vacuum technologies to package food in controlled atmospheres (increases shelf-life of food by 2-5 x’s because oxygen is removed) • Food Preservation: - Removal of microbes à filtration (Filters can sterilize depending on their pore size) - Low temperature: o Refrigeration at < or = 5 degrees C (Generally aim for 4 degrees C) o Freezing at < or = to -18 degrees C - High temperature: o Cooking and holding at high temperature à raising temperature enough to kill microbes and after refrigeration or keep at heat at high enough temperature à usually > 140 degrees F (Use of lamps, steaming, water baths) o Pasteurization o Canning - Danger Zone = 5 – 60 degrees C (41- 140 degrees F) à don’t want food at these temperatures for too long • High Temperature: Canning - Food heated to 115 degrees C for 25-100 min (Like with an autoclave) - Kills spoilage microbes + endospores - Spoilage of commercially canned foods is rare - Clostridium botulinum requires anoxic conditions, sometimes heating actvates endospores à if have a swollen can do not buy – because of the gas production of the bacteria - Dented cans aren’t necessarily a problem - Even if cans are not heated to 121 degrees C, can still sterilize the cans if heat for a long time - pH of <4.6 means don’t have to heat up as high of a temperature à acidic = prevents germination in endospores, so don’t have to worry about fruit • Pasteurization: Not sterilization - Kills pathogens and substantially reduces number of spoilage organisms via heating the food up - Different pasteurization procedures heats for different lengths of timeà shorter heating times result in improved flavor - 2 Main Types: a) Low Temperature Holding: (LTH) à 63 degrees C for 30 min o Like with milk, but 30 min. = long time at high temperature b) High Temperature Short Time (HTST) à 72 deegrees C for 15 seconds then rapid cooling o Can get better quality milk c) Method for sterilization: Ultrahigh-Temperature (UHT) processing à 138 degrees C for 2 seconds o For organic milk and milk that doesn’t have to be refrigerated + creamers, juice boxes etc.; 75 days shelf-life o Even though sterilized at the plant, it won’t stay sterilized but will increase the shelf-life • Reduction in Water Availability: - Dehydration - Adding solutes à salt, sugar etc. • Chemical-Based Preservation: - GRAS (Chemical Agents “Generally Recognized as Safe”) à These can only be used to preserve foods - Ex. of concerning chemicals used for food preservation: o Sodium nitrate: Potential carcinogens; Is put in meats to make them look better o Ethylene/propylene oxides: Used to fumigate but considered to be a carcinogen o Niacin: Natural antibiotics produced by bacteria • Gamma Radiation: - Safe and don’t have to use a lot of chemicals as a result for food preservation - Very good for ground beef due to its penetrating power - Used to try to prevent insects from coming into country with imports - Cobalt 60 source required - Can sterilize depending on the dose of radiation and the time 17. Compare and contrast food infection and food intoxication. Be able to categorize the disease causing food-borne microorganisms that were discussed into the appropriate category. • Food-Borne Disease: - About 48 million cases per year in the US where 18 % are attributed to known pathogens and at least 3,000 deaths per year occur in the US - Most cases are due to dehydration problems and the most susceptible are the very old, very young, and immunocompromised - Transmission: Could be due to breakdown in hygiene, fecal-oral route (even transmitted when viral), fomites (epidemiological term: Inanimate object that can transmit disease – ex: food, door knob etc.) • Food Infection: - Infection resulting from the ingestion of pathogens in food - Ingestion of pathogen, followed by growth, tissue invasion, and/or release of toxins à Ex: Salmonella - Can take a while to have symptoms here - In general, food infections are caused by gram-negative bacteria, viruses, or protozoa - Have to consume a certain number (Infectious dose levels)—this is usually more than 1 million bacteria - Toxins may or may not be released - Viral food infections can be pretty short • Food Intoxication: - Ingestion of preformed microbial toxins in foods - Symptoms shortly occur after the food is consumed - Growth of disease-causing microorganisms is NOT required (The bacteria could still be present but could be dead for example) - Generally caused by gram-negative bacteria - Organism doesn’t have to colonize in the body à It’s not the bacteria that makes you sick, it is the toxins from the bacteria that make you sick (Ex: Sometimes cooking doesn’t help, as seen with Staph) • Annual Estimates of Food Borne Disease for the US: - Bacteria: 4,177,500 - Protozoa: 359,000 o Fecal contaminants too - Viruses: 9,282,000 à Shows viruses are more likely to be the cause for food borne disease than bacteria o Most common: Nora-Virus • Overall: Food infection results from the ingestion of foodborne pathogens, while food intoxication results from the ingestion of microbial toxins (Here, even if food is reheated, still can get sick with foodborne intoxication) 18. Be able to identify the causative organism of a food-borne illness based on the general characteristics of the microbe, its sources, how it causes disease (toxins, etc.), the characteristic symptoms of the disease, the individuals that are susceptible, the foods involved, and/or the mishandling of the food that lead to the illness. • Listeria monocytogenes: Causes a food infection - Gram-positive (An exception to food infection bacteria being usually due to gram-negative), facultative aerobe (Grows best with oxygen but can grow without oxygen too via fermentation), coccobacillus - Psychotroph, acid-tolerant (Not as sensitive to stomach acid when ingested), salt-tolerant - Sources: Soil, water, fecal material, vegetation, silage - Foods: Uncooked meat and vegetables (Raw), fruits, processed foods (Cold cuts, sandwich meats, hot dogs), unpasteurized milk and milk products (Soft cheeses) - Invasive pathogen (proliferation in phagocytes of GI tract, where the L.monocytogenes is not killed and takes over the phagocyte and reproduces inside so it bursts the phagocyte and more bacteria is released into the body) - Infectious dose: ~ 1000 bacteria à very low - Most individuals can be exposed to L. monocytogenes and be fine except for the very young/old and immunocompromised - Listeriosis: Food Infection o Symptoms: a) Onset: Few days to 2 months (> 12 hours for GI symptoms) b) Fever, muscle aches, nausea, diarrhea, headache, stiff neck (Can lead to bacterial meningitis), loss of balance, miscarriage c) Duration: Usually 5-10 days o High concern for pregnant women, the young and old, and immunocompromised individuals most vulnerable o Responsible for the largest meat recall in US (2002) à Recall was for deli meats, hotdogs (27.4 million pounds) o Cantaloupe (2011) à Spray was not on the rind o At-risk people should not eat soft cheeses, refrigerated smoked meats, deli meats, and undercooked hotdogs (Because L. monocytogenes is salt tolerant) • Salmonella: Causes food infection - Gram-negative bacillus, facultative aerobe - Sources: Sewage (GI tract of birds and other animals + pets such reptiles = turtles, lizards, birds) - Foods: Poultry, beef, pork, fruits, vegetables, eggs, (Custards, cakes, pigs, egg nog), dairy products à Any meat, F/V, problem with unpasteurized eggs - All salmonella species we know are pathogens, but different case with naming these bacteria with Serobar = a variant of Salmonella with a different antigen so have a different antibody reaction - Salmonellosis (Food Infection)—aka gastroenteritis o Servovar Typhimorium is the most common agent of salmonellosis (Gastroenteritis = Stomach + intestines + inflammation) à Cells multiply and colonize in the GI tract; cell-associated endotoxins (Means the toxin is specifically part of the cell = lipid A portion of LPS on the outer membrane of gram-negative bacteria) are r7spo9sible for symptoms o Infectious Dose: Usually 10 -10 viable cells à Very contaminated food, not been heated again before eat it; Salmonella has to get through stomach to intestines to get sick- it does this by embedding itself in fat (Requires consumption of fatty foods to do this) which is used to proteict the bacteria from the acid in stomach o Cooked or canned food becomes infected bya food handler and not reheated to kill bacteria o Symptoms: a) Onset: 8-48 hours b) Diarrhea*, abdominal cramps, low-grade fever, nausea, sometimes vomiting c) Duration: Usually 2-5 days d) 10-20% of victims become carriers for 4-8 weeks à Can be found in feces of people too and transported to food o In order to make person sick, occurs only when the Salmonella cells die when blood stream absorbs the endotoxin o Taking antimicrobials to treat Salmonellosis can be a problem because more endotoxin can be released and there is a concern with anti-biotic resistance - >1.4 million cases of Salmonellosis occur each year, as estimated by the CDC - 2007 Peter Pan peanut butter recall – caused by leaky roof where birds nested • Pathogenic Escherichia coli: Causes food infection - Gram-negative, facultative aerobe, coccobacillus - Sources: Sewage (GI tract of animals)—fecal contaminant - 6 total Categories: 1. Enterophathogenic infantile diarrhea: In the intestines, infants can get diarrhea because don’t have developed microflora to outcompete the E. Coli pathogenic flora 2. Enteroinvasive Shigella-like dysentery: E. Coli gets into phagocytes and reproduce there à watery + some bloody diarrhea (Shigella- like dysentery) 3. Enterotoxigenic “traveler’s diarrhea”: Production of exotoxin and endotoxin = one of the causes of traveler’s diarrhea and can be from drinking water in other less developed countries (Watch out for F/V because contaminated water can get into tissues) 4. Enterohemorrhagic: Bloody diarrhea - Foods: o ETEC (Enterotoxigenic) Contaminated drinking water o EHEC (Enterohemorrhagic) Undercooked ground beef, unpasteurized dairy products and fruit juices, spinach, water - Enterohemmorrhagic E. Coli (0157:H7): Food infection (NOT an intoxication because it has to grow and produces more exotoxin to make symptoms worse) o Carried by cattle, deer, pigs etc.; can live on surfaces and compost, this shows that food doesn’t have to be in the danger zone o Leading cause of kidney failure in children due to the production of an exotoxin à E. Coli (O157:H7) can attach to the renal epithelial cells so have autoimmune response); for the elderly, kidney failure can also be experienced and this group only has a 50% survival rate at this point o Infectious Dose: Unknown and may be as little as 10 bacteria (Acid-tolerant, therefore stomach has little affect on destroying bacteria) o Produces toxins à hemorrhagic colitis (Bleeding of the intestines) and Hemolytic Uremic Syndrome; because these exotoxins are produced, Have cells that are lysed by anti- biotics that release more exotoxins o Bacteria destroyed by proper heat treatment – cooking food well enough o Symptoms: a) Onset: 3-5 days b) Bloody stools, intense abdominal pain, fever and vomiting is rare, kidney failure, brain damage, death c) Duration: 5-10 days d) Estimated 73,000 cases per year in the US resulting in 60 deaths • Staphyloccocus aureus: Causes food intoxication - Gram-positive, coccus, facultative aerobe - Can thrive in high-salt (~10%) and low a hwbitats (grows on dry skin) - Sources: Human nasal cavity, skin, skin sores à mucous contamination - Enterotoxins producer (An exotoxin that affects intestines) à The toxin is extremely heat stable, so if food is reheated it won’t be protected - Foods: Cream-filled baked goods, poultry, meat, gravies, egg and meat salads, puddings, vegetables (+ Food left out in the danger zone way too long - Carried on skin so it can easily contaminate food - Opportunistic pathogen so if it gets in the wrong place in the body it can cause an infection; ex: If have a cut à MRSA, which is harder to treat - Has a super antigen: Illicits more T-cell activity than a normal antigen (Gets a more severe immune response) - Overall, eating S. aureus won’t be a problem, but if it has time to grow then it will produce an exotoxin (enterotoxin specifically) = a super antigen and can be due to leaving foods out in the danger zone - Staphylococcoal Food Intoxication: o Foods usually contaminated during food preparation o Contaminated foods are kept for several hours at room temperature or outdoors (which supports rapid growth) à But if food is chilled or heated up enough before sitting in this danger zone for long, not enough toxin will be produced to make people sick o Symptoms: Severe dehydration as result; septic shock like symptoms a) Rapid onset (1-8 hours) b) Nausea, explosive vomiting, abdominal pain, diarrhea, headache, weakness, no fever (usually subnormal body temperature) c) Duration: 1-2 days d) Antibiotics won’t help because a preformed toxin is what is produced à IV given and anti-nausea treatment • Clostridium botulinum: Causes food intoxication - Gram-Postive, spore-former, strict anaerobe (Requires anoxic conditions) - Sources: Soil and water à contamination of F/V in fields - Can be implicated in wound (Similar to tetanis—seen with illicit drug use with dirty needles), infant, and food-borne botulism - Produces a heat labile proteinaceous neurotoxin (An exotoxin) à Cooking is protective and denatures C. botulinum - Toxin is produced best in high protein, low acid foods (needs to be > pH of 4.6)—why canned fruit that is acidic doesn’t have issues - Toxins are destroyed by high heat (80 degrees C for 10 min) - Foods: Non-acid, home-canned vegetables like corn and beans, smoked and fresh fish; ex: Beans are low-acid, and have high protein - Botulism (Food Intoxication): o Endospores may contaminate raw foods before harvest or slaughter o Most foodborne cases occur form eating foods that are not cooked after processing o Home-canned foods implicated in > 72 % of foodborne outbreaks (It’s necessary to use the pressure canner correctly), < 10 % from commercially processed o Infant botulism usually occurs in infants up to 2 months old due to raw honey à Can be contaminated with C. botulinum spores where they don’t germinate in the honey but can in the intestines in anoxic conditions vs. developed microflora of adults that could handle the bacteria a little better o Symptoms: a) Onset: 18-24 hours b) Blurred vision, dizziness, cramps, sometimes vomiting, no fever, nausea, constipation, heart paralysis, difficulty in swallowing, speaking, and breathing (Will be put on iron lung if get to hospital; anti-toxin can be given can be given to get the toxin out of the system—antibiotics wouldn’t work because neurotoxin would be produced even more) c) Duration: 1-10 days to life à Because neurotoxin damages the nervous system d) Mortality: 21 % due to not being diagnosed fast enough e) Treatment: Anti-toxin o Cases: 1. Sauteed onions where sat in mound and created anoxic conditions at the center 2. Baked potatoes: Activates endospores when wrapped in aluminum foil and were left for 18 hours and made cold dip 19. Describe other food-borne infectious diseases that are not caused by bacteria. • Most foodborne infections are through to be caused by viruses • Symptoms: Gastroenteritis (Inflammation of the stomach and intestines) characterized by diarrhea, nausea, and vomiting • Recovery is spontaneous and rapid (Usually within 24-48 hours) à Has to build up in body (Takes 1-2 days) • Noro-viruses are responsible for most mild foodborne infections in the US (9 million of the 13 million) • Rotavirus (Diarrhea virus), astrovirus, and hepatitis A (Comes from contaminated shellfish—ex: raw oysters) collectively causes 100,000 cases • Ovearll most other foodborne infectious diseases are fecal contaminants because that’s where they are found in the highest numbers • Foodborne Protozoan Diseases: - Giardia lamblia, Cryptosporidium parvum, and Cyclospora cayetanensis can be spread via food (contaminated by fecal matter in untreated water used to wash, irrigate, or spray crops), and via drinking water - Giardia lamblia: Picked up from wilderness area à not disinfecting water properly; explosive diarrhea; lose a lot of weight; can recur if it’s not cured - Cryptosporidium parvum: Beaver fever à Causes problems in animals too, makes little cysts that are resistant to cholorine - Foods involved: Fresh foods such as fruit, often imported from other countries (From bad water source) - Taxoplasma gondii: A protozoan spread through cat feces or undercooked meat (Part of this virus’s lifecycle needs to be in a cat’s intestines) and humans can get it from changing litter boxes • Prion Disease: - Prion-infecting agent made out of proteins that cause disruption in neural tissue - Infectious protein and it’s thought that they are misfolded and when they get into the body they cause neural tissue to misfold which causes plaques and holes in the brain tissue - Symptoms: Depression, loss of motor coordination, dementia, death - nvCJD (Creutzfeldt-Jakob disease =degenerative, invariably fatal brain disorder) linked to consumption of meat products from cattle afflicted with BSE (bovine spongiform encephalopathy -“Mad Cow Disease”) - If consume BSE/Mad cow disease there is a slight chance of getting nvCJD (V= means when a contaminated food is eaten) - Rapid onset for vCJD à For young adults/children, they have higher and short incubation times so the symptoms show up faster than from other sources; once the symptoms show, can die within a year; for others = 20 years before symptoms show up - Ban on feeding cattle meat and bone meal have appeared to stop the development of new cases of BSE in Europe à It was realized that this caused is what was caused the BSE/mad cow disease to spread - Papua New Guinea: Cannibals that ate their dead relatives à nvCJD (Called “Coo roo” 20. Distinguish between safe and unsafe food practices. • Clean: Wash hands and surfaces often, wash raw F/V • Separate: Don’t cross-contaminate • Cook: Cook to proper temperatures • Chill: Refrigerate promptly (Smallerc containers used are better—there is a problem with bulky foods) • Always refrigerate perishable food within 2 hours à only if the temperature is < 90 degrees F/< 32 degrees C • When the temperature is > 90 degrees F/32 degrees C, then have to store within 1 hour • Use cooked leftovers within 4 days—if they are stored properly in the refrigerator 21. Understand the role of fermentation in food production, and be able to recognize various fermented foods. • Catabolism of glucose à pyruvate (pyruvate dervatives) à Take electrons from NADH à fermentation products (Whole point = recycle NAD+) • Fermentation products affect taste, decrease the pH to make acids that can also affect flavor, consistency, and preservation of food • In some cases fermentation can spoil food • Using microbes to make/spoil food à Usually due to a succession of microbes (1 microbe ferments first and then the next one comes in and continues fermenting, etc.) = self-limiting process because fermentation products can be inhibitory; there also may be several types of fermentation processes going on • Dairy products • Meat products • Vegetables and vegetable products • Yeast bread • Chocolate: Have coco seeds and open the pods to release them and they are put into boxes in groups and covered with banana leaves (Sweat boxes) à This is where the fermentation occurs (No addition of bacteria is added) - First the yeast ferment the seeds and the pulp à CO +2alcohol, and when the alcohol gets to high enough levels then the lactic acid
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'