microbiology food part2

•Bacteria•Yeast•Molds

due to production of volatile endcompounds

pigment production or oxidation

softening due to the breakdown ofpectin in vegetables or the tissues byproteinases

CO2, H2 or H2S2

due to the production ofdextrans and/or amount of microorganisms

Caused by preformedtoxin in the food; organism may or may notbe alive and growing; Clostridium botulinumand Staphylococcus aureus

Live cells delivered bycontaminated food; organism multiply oncefood is ingested; Salmonella

Gr+, non-motile,asporogenous cocci• “grape-like” clusters• enterotoxin• effective at 1ug/kg• protein of 239 aminoacids• serological types: A, B, C,D, F

• onset: 0.5 to 6 hours• recovery: 24 to 72 hrs• major symptoms: vomiting, diarrhea• other symptoms: nausea, salivation,cramps, retching,prostration

consumption of honey that iscontaminated by spores (0 - 2 months)• Treatment: antitoxin and ventilation

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.

C. perfringens produces cpe gene productas paracrystalline inclusionbody released during sporulation. Alsomakes beta-toxin (necrotic).

Gram negative enteric bacterium; all strains arepathogenic; transmission is from sources (eggs, meats)and by food handlers

(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

(Salmonella enterica serovar Typhi ): Septicemialeading to high fever that can last for several weeks; mortality is15% if untreated; antibiotics

Gram-negative rod• non-sporeformer• Flagellated• facultative anaerobe• generally harmless,• pH: 6.0-8.0• Temp.:37oC• Aw: 0.94-0.97

Some strains of E. coli; diarrhea and urinary tractinfection; classification of pathogens is based on toxinand diseases

colonization of thesmall intestine and verotxin production -> hemorrhagicdiarrhea and kidney infection; uncooked andundercooked ground meat; occasional epidemics

Travelers diarrhea) - heat labile toxin;water and produce in developing countries; immunity

diarrhea that afflicts young children

• invasive colon infection; bloodydiarrhea; survival in phagosomes; in developing countries
• Treatment and prevention: diseases are self-containedbut antibiotics help.

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-

Disease–Onset 48-82 h followingingestion–Profuse diarrhea– Invasive–Survives phagocytosis

Gram+, small, non-sporeforming rod

Low grade "flu-like" infection - not serious, except inpregnant woman (who abort

Prions are proteins that are unique in theirability to reproduce on their own andbecome infectious

Prions are composed largely, if not entirely, of aprotein designated as the scrapie isoform of the prionprotein, PrPSc.

Diseases caused by prions are called spongiform disease– Brain tissue in those infected has a sponge-like appearance

– Neuronal membrane glycoprotein (PrPC

Unknown• Resistance?

Isoforms of normal brain proteins• Cause brain damage

Abnormal prions interact with normal prions• Act as templates to change conformation• Cascade mechanism

Allows self-replication• Causes insolubility– Aggregate as amyloid fibrils– Causes neuron apoptosis– Make holes in brain

Prions cannot be destroyed by boiling, alcohol, acid, standard autoclavingmethods, or radiation

UV and ionizing radiation– Nonionic and nondenaturing anionic detergents

– Acetone– Ether– Ethylene oxide

Proteases– Denaturing detergents (SDS)– Urea– Harsh organic solvents (phenols)– Strong oxidizing agents

UK ban on the import of live ruminant animals and most productsderived from them

Surveillance of the U.S. cattle population for the presence of BSE– Food Safety and Inspection Service (FSIS)

FDA u.s. food and drug adminstration 1997 animal feed ban– Prohibits the feeding of most mammalian protein to ruminant animals,including cattle

No bovine tissues known to be at high risk for carrying the agent of BSEenter the human food supply regulated by USDA

Effective response planning

FSIS inspectors no longer mark cattle tested for BSE as "inspected andpassed" until confirmation is received

FSIS expanded a prior prohibition on spinal cord from being allowed inproduct– Prohibits dorsal root ganglia, clusters of nerve cells connected to the spinalcord

FSIS banned the practice of air-injection stunning

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.

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

Banned from human food chain

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

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.”

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.

NOT antibiotics!