microbiology food part2

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microbiology food part2
2010-12-17 12:43:08


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  1. Microbial food spoilage:“first come – first serve”
  2. Odor:
    due to production of volatile endcompounds
  3. Color:
    pigment production or oxidation
  4. Texture
    softening due to the breakdown ofpectin in vegetables or the tissues byproteinases
  5. Accumulation of gas
    CO2, H2 or H2S2
  6. Slime formation
    due to the production ofdextrans and/or amount of microorganisms
  7. Foodborne diseases
    Food poisoning-
    Caused by preformedtoxin in the food; organism may or may notbe alive and growing; Clostridium botulinumand Staphylococcus aureus
  8. Food infection
    Live cells delivered bycontaminated food; organism multiply oncefood is ingested; Salmonella
  9. Staphylococcus aureu
    Gr+, non-motile,asporogenous cocci• “grape-like” clusters• enterotoxin• effective at 1ug/kg• protein of 239 aminoacids• serological types: A, B, C,D, F
  10. Staphylococcus aureusFOOD POISONING SYNDROME
    • onset: 0.5 to 6 hours• recovery: 24 to 72 hrs• major symptoms: vomiting, diarrhea• other symptoms: nausea, salivation,cramps, retching,prostration
  11. Infant botulism:
    consumption of honey that iscontaminated by spores (0 - 2 months)• Treatment: antitoxin and ventilation
  12. Botulism and Temperature Abused Pot Pie
    Patient: 56 year old diabetic woman• Symptoms: diplopia, weakness, difficultybreathing, chest pain, respiratory arrest.• Scenario: Son prepared pot pie for mother.Father brought home take-out hamburgers.Mother left pot pie out on shelf (in California, inAugust), and ate it two and one-half days laterwithout reheating.• Illness: next day. Type A botulinum toxin wasisolated from the left-over food and patient'sserum.
  13. C. perfringens
    C. perfringens produces cpe gene productas paracrystalline inclusionbody released during sporulation. Alsomakes beta-toxin (necrotic).
  14. Salmonellosis
    Gram negative enteric bacterium; all strains arepathogenic; transmission is from sources (eggs, meats)and by food handlers
  15. Salmonellosis Enterocolitis
    (most commonly by S. typhimurium): 105 - 108viable cells; disease onset within 8 - 48 hrs; headaches, chills,vomiting, diarrhea and fever (2-3 days); continuous shading oforganism for months/years; treatment - non
  16. Salmonellosis Typhoid fever
    (Salmonella enterica serovar Typhi ): Septicemialeading to high fever that can last for several weeks; mortality is15% if untreated; antibiotics
  17. Escherichia coli
    Gram-negative rod• non-sporeformer• Flagellated• facultative anaerobe• generally harmless,• pH: 6.0-8.0• Temp.:37oC• Aw: 0.94-0.97
  18. Pathogenic E. coli
    Some strains of E. coli; diarrhea and urinary tractinfection; classification of pathogens is based on toxinand diseases
  19. Enterohemorrhagic
    colonization of thesmall intestine and verotxin production -> hemorrhagicdiarrhea and kidney infection; uncooked andundercooked ground meat; occasional epidemics
  20. Enterotoxigenic
    Travelers diarrhea) - heat labile toxin;water and produce in developing countries; immunity
  21. Enteropathogenic
    diarrhea that afflicts young children
  22. Enteroinvasive
    • invasive colon infection; bloodydiarrhea; survival in phagosomes; in developing countries
    • Treatment and prevention: diseases are self-containedbut antibiotics help.
  23. Campylobacter jejuni Characteristics
    High morbidity, low mortality– Sensitive to freezing– Survives in refrigerated foods– will not grow at <30◦C– Microaerophilic– Fragile organism, sensitive to drying,heat, acidic conditions, and disinfectants-
  24. Campylobacter jejuni
    Disease–Onset 48-82 h followingingestion–Profuse diarrhea– Invasive–Survives phagocytosis
  25. Listeria monocytogenes
    Gram+, small, non-sporeforming rod
  26. L. monocytogenes- disease symptomes
    Low grade "flu-like" infection - not serious, except inpregnant woman (who abort
  27. What is a Prion?
    Prions are proteins that are unique in theirability to reproduce on their own andbecome infectious
  28. Composition of Prions
    Prions are composed largely, if not entirely, of aprotein designated as the scrapie isoform of the prionprotein, PrPSc.
  29. Spongiform disease
    Diseases caused by prions are called spongiform disease– Brain tissue in those infected has a sponge-like appearance
  30. What are Normal Prions?
    – Neuronal membrane glycoprotein (PrPC
  31. What is their Function? normal prions
    Unknown• Resistance?
  32. abnormal prions
    Isoforms of normal brain proteins• Cause brain damage
  33. Howdo they replicate?
    Abnormal prions interact with normal prions• Act as templates to change conformation• Cascade mechanism
  34. how do they inflict brain damage?
    Allows self-replication• Causes insolubility– Aggregate as amyloid fibrils– Causes neuron apoptosis– Make holes in brain
  35. You can’t kill what isn’t alive Control and Prevention
    Prions cannot be destroyed by boiling, alcohol, acid, standard autoclavingmethods, or radiation
  36. Resistant or partially inactivated
    UV and ionizing radiation– Nonionic and nondenaturing anionic detergents
  37. Moderately inactivated
    – Acetone– Ether– Ethylene oxide
  38. Effectively inactivated
    Proteases– Denaturing detergents (SDS)– Urea– Harsh organic solvents (phenols)– Strong oxidizing agents
  39. fire walls aganist the spread of bse 1st Firewall
    UK ban on the import of live ruminant animals and most productsderived from them
  40. 2nd Firewall
    Surveillance of the U.S. cattle population for the presence of BSE– Food Safety and Inspection Service (FSIS)
  41. 3rd Firewall
    FDA u.s. food and drug adminstration 1997 animal feed ban– Prohibits the feeding of most mammalian protein to ruminant animals,including cattle
  42. 4th Firewall
    No bovine tissues known to be at high risk for carrying the agent of BSEenter the human food supply regulated by USDA
  43. 5th Firewall
    Effective response planning
  44. Regulations Effective StartingJan 2004 Product Holding
    FSIS inspectors no longer mark cattle tested for BSE as "inspected andpassed" until confirmation is received
  45. Advanced Meat Recovery
    FSIS expanded a prior prohibition on spinal cord from being allowed inproduct– Prohibits dorsal root ganglia, clusters of nerve cells connected to the spinalcord
  46. Air-Injection Stunning
    FSIS banned the practice of air-injection stunning
  47. Specified Risk Material
    Skull, brain, trigeminal ganglia, eyes, vertebral column, spinal cord and dorsalroot ganglia– 30 months of age or older and the small intestine of all cattle are specified riskmaterials that are prohibited in the human food supply.– Tonsils from all cattle are also not allowed in the human food supply.
  48. Additional Bans and Regulations Downer Cattle
    Banned from human food chain– A hidden camera investigation by the Humane Society at the Hallmark/Westland MeatPacking company in Chino, California– Recall involved 143 million pounds of raw and frozen meat
  49. Dead Cattle
    Banned from human food chain
  50. Specific changes in FDA’s present animal feed rule
    Mammalian blood and blood products to be fed to other ruminants as a protein source.– Use of “poultry litter” as a feed ingredient for ruminant animals• Bedding, spilled feed, feathers, and fecal matter that are collected from living quarters wherepoultry is raised.– Plate waste as a feed ingredient for ruminants– Requires equipment, facilities or production lines to be dedicated to non-ruminant animalfeeds if they use protein that is prohibited in ruminant feed
  51. Why do "new" pathogens emerge?
    CHANGES IN EATING HABITS: fresh, organic• CHANGES IN AWARENESS: computer databases• CHANGES IN DEMOGRAPHICS: larger sensitivepopulations• CHANGES IN PRIMARY FOOD PRODUCTION: scaleof operation, global production• CHANGES IN FOOD PROCESSING TECHNOLOGY:chill, vacuum packaging• CHANGES IN HANDLING AND PREPARATION:homerefrigeration, microwave• CHANGES IN THE MICROORGANISMS:plasmid
    “Any chemical that when added to food, tends toprevent or retard deterioration, but does not(A)include common salt, sugars, vinegars, spices,or oils extracted from spices, substances addedto food by direct exposure to wood smoke, orchemicals applied for their insecticidal orherbicidal properties.”
  53. Bacteriocins
    Bacteriocins are defined as ribosomally-producedproteinaceous substances of bacterial origin thatexhibit antimicrobial activity.They kill sensitive cells by formingpores in the membrane causingthe leakage of cellular materials,and the depletion oftransmembrane potential(Δψ) and/or the pH gradient.
  54. Bacteriocins are
    NOT antibiotics!