food microbiology lects 6-10

salmonella carriers?

humans -asymptomatic carrierrs are potentially dangerous when unnoticed ~ 5% of patients clinically cured from typhoid remain carriers for months or even years -antibiotics are usually inefective on carriage

Foodborne diseases and Death..... three pathogens greatly associated with them:

• Three pathogens: Salmonella Listeria Toxoplasma

Gram-Negative Pathogens Associated with food

• Vibrio • Aeromonas • Shigella • Salmonella • Escherichia coli • Yersinia • Campylobacter

what are viruses

bundle of genetic material that work as pathogen. either DS or SS Virus units are call virions not cells in terms of virus (bacteriophages) it has two cycles either: -lytic cycle where it lyses (kills the bacteria) or - Lysogenic where it incorporates its DNA inside the bacteria's dna

Generation time? and common PREDOMINANT microorganisms

generation time is important and it means the time it takes for microorganisms to reproduce. Predominant microorganisms: 1- pseudomonas spp 1% 2- Acinetobacter and morexella - 11% 3- Brochothrix thermosphacta - 13% 4- Other - 75% ALSO Same conditions (12d incubation at 2°C) but anaerobically: then Prevalence of Lactobacillus and/or Leuconostoc

Calicivirus

***Pathogenesis ‐ the viruses infect and kill cells of the small intestinal mucosa*** -ex of calicivirus: Norovirus and Sapovirus • Norwalk‐like virus (NLV) • Sapporo‐like virus (SLV) -Infectious dose as low as 10‐100 virus particles -1-3day incubation period -they r small non-enveloped spherical viruses -SS RNA -first gastrointestinal virus reported to be foodborne (emerged as main foodborne virus) -SYMPTOMES: low grade fever, diarrhea, headache vomiting. [symptomes last 2-3days] -illness mild and self-limiting - Highly contagious! - High rate of transmission to contacts - Mode of transmission: INDERECTLY BY CONTAMINATED FOOD, WATER, OR ENVIRONMENT

Prion pathogenesis?

***• All pathological features are confined to the central nervous system*** • The prion protein accumulates selectively and abnormally in CNS nerve cells during the course of the disease. • the pathology does NOT include any signs of inflammation or fever. ***- immune system does not respond to the prion protein*** Human Prion diseases include both **inherited as well as transmissible** neurodegenerative disorders. • All diseases known to be of prion etiology, in animals and humans, are neurodegenerative diseases. In the human this includes: - Creutzfeldt‐Jakob disease (CJD) - Fatal Familial Insomnia - Gerstmann‐Straussler syndrome - Kuru The most common form of Prion disease in animals is [Scrapie], a disease of sheep and goats

HEPATITIS A (picornavirus SS positive RNA)

- ***PICORNAVIRUS SS POSITIVE RNA*** -SMALL NON ENVELOPED SPHERICAL VIRUS -INCUBATION: 15-50 DAYS -Non‐specific symptoms including fever, headache, fatigue, nausea, abdominal discomfort, followed by symptoms of hepatitis 1‐2 weeks later -Illness generally self‐limited, lasting up to several months -Peak virus shedding of HAV Infeces occurs during the 2 weeks before the onset of jaundice or liver enzyme elevation -Outbreaks r not common because bcuz infectious usually occur among children and are generally ASYMPTOMATIC HIGH RISK FOODS: **MOLUSCAN SHELL FISH**[Shellfish collect thevirus from the water subjected to fecal pollution but they themselves dont become infected.], DESSERTS, FRUITS, VEGETABLES, SALADS

Viruses that cause gastroenteritis?

- Rotavirus -Enteric adenovirus -Astrovirus -- Two genera of enteric calicivirus: • Norwalk‐like virus (NLV) • Sapporo‐like virus (SLV)

Picornavirus

- SS virus -enterovirus, Hepatitis A, Poliovirus

salmonella spp.

- causes disease -effective does is as few as 15-20 cells and it depends upon age and health of host -strain differences among the members of the genus

prion disease symptoms:

- dementia initially characterized by loss of memory -progressive insomnia -diminish intellect and poor judgement Transmission: horizontal transmission transmission from one person to another, either directly or by fomites or by ingestion of contaminated meat.

common sources for spread of a salmonella infection?

- eggs and poultry -contaminated water, milk, milk products, beef, fruit, vegetables and dairy products -for infants: exposure to reptiles, riding in shopping cart next to poultry, or consuming liquid infant formula Fecal-oral transmission from person to person in areas with poor sanitation and contaminated or non chlorinated water is the route for enteric or typhoid fever

Enteric typhoid fever. What caused it and what are the steps?

- it is caused by S. Typhi (humans r the only reservoir) steps: 1- enter the human digestive tract 2-penetrate intestinal mucosa 3-Viable bacteria and LPS (endotoxin) is released into blood stream 4- septicemia is caused (remember septic shock)

important facts of prion

- prions are infectious self replicating protein that dont have either DNA OR RNA -Prions replicate by reshaping the normal protein PrP(c) [33-35] into PrP(sc) [27-30]

pathogenicity and virulence factors? have to overcome what before it happens?

- the non specific barriers which are the first line of defense - non specific second line of defense such as phagocytes and inflamatory response, - the immune response (which can be specific or non specific)

Microbial food spoilage - favorable conditions (for it to happen)

- transfer the microorganisms into the food -optimal environment for microorganisms: A(w), Nutrients, atmosphere -proper (abuse of temperature) - jeopardy in Sufficient time of storage

how to prevent salmonella?

--->>well best way to prevent salmonella is to thoroughly cook everything <<< - Separate raw meat, poultry, and seafood from other foods in your refrigerator -refrigerate promptly - Wash Hands and Surfaces Often - Wash your hands, cutting boards, dishes etc with hot soapy water before handling food

spoilage: Low-heat-processed cured meat - aerobic conditions

--Lactobacillus spp.: production of H2O2 and browning --Enterococcus casseliflavus: brown and yellow spots

Fecal‐orally transmitted hepatitis viruses

-Hepatitis A virus (HAV) : *VACCINE AVAILABLE* -Hepatitis E virus (HEV)

Factors Contributing to Outbreaks

-Improper warm holding -Cross-contamination Inadequate thawing -Contaminated canned food Undercooking -Contaminated processed food -Inadequate re-heating - Inadequate cooling -Storage at ambient temperature -Preparation too far in advance (long time before hand)

Changes in Food Quality

-Odor: due to production of volatile end-compounds -Color: pigment production or oxidation -Texture: softening due to the breakdown of pectin in vegetables or the tissues by proteinases -Accumulation of gas: CO2, H2 or H2S2 -Slime formation: due to the production of dextrans and/or amount of microorganisms

How can Salmonella infection be treated ?

-Rehydration, intravenous fluids. • Ampicillin, gentamycin, trimethoprim/sulfamethoxazole or ciproflaxin. Some are resistant to antibiotics. • Consequences of Salmonella: Reiter's syndrome. Pain in joints, irritation of eyes and painful urination.

shigella

-Shigella is gram negative rod - NON MOTILE (unlike salmonella) -Facultative anaerobe Frequently found in : - in water polluted with human feces - raw vegetables - milk and dairy products - Salads (potato, tuna, shrimp, macaroni, and chicken) - poultry and Contamination of these foods is usually through the fecal-oral route.

Non-invasive Microorganisms

-Vibrio cholerae -Cryptosporidium - Giardia - Enterotoxigenic E. coli.

difference between food spoilage and food poisoning.

-food spoilage is the actual food that has become spoiled and it usually does not cause illness because consumer rejects it. - Food poisoning happens when the consumer ingested enough pathogens or toxins for him to become sick. In many cases food poisoning is caused by food that smells, taste, and looks NORMAL.

enteric typhoid fever

-incubation time: 5-21 days - transmission from contaminated water, or animal products, or contact with infected person/carrier A stepwise increase in temperature that plateaus in the second week at 39-40°C -symptoms: septicemia, high fever, headache, constipation, vomiting and diarrhea It may disseminate to lungs ,gallbladder ,kidneys,or CNS ****Untreated patients experience either complications or resolution**** by - Intestinal perforation occurs in 3-10% of patients - Other complications include endocarditis, pericarditis, pneumonitis, orchitis, and focal abscess the fourth wee

Prion disease characteristics?

-long incubation (years) -attacks CNS (central nervous system) -causes cavities in Neurons -Causes sponge like changes in gray matter -always Fatal (no known treatment) -causes amyloid plaquetes -Symptomes: Loss of muscle coordination Dementia characterized initially by loss of memory, diminished intellect and poor judgement.

Rotavirus

-non enveloped DS RNA ViRUS - found in contaminated food in water -Fever, vomiting, watery diarrhea -One third of hospitalized children below age 5 with diarrhea are positive for rotavirus.

Normal cells in prions? and abnormal?

-normal neural cells have PrP(c) soluble 33-35 --> PrP(c) is protease sensitive and helix rich - ABNORMAL cells have PrP(sc) insoluble 27-30 --->PrP(sc) is protease resistant and pleated rich

foodborne viruses

-strict intracellular (inside cell) -cannot replicate in food or water -the most common source of food source of viral gastroenteritis are due to viruses -foodborne viruses are transmitted interically (fecal -oral route)

how to detect foodborne viruses? How do we prevent it?

-to detect it we isolate virus from food with methods such as Electronmicroscopy(EM), immunoassay, PCR - probes/primers to specific portions of genome Prevention? Preventing contamination - Preventing human fecal contamination - Monitoring shell‐fish harvest waters - Good hygiene - High standards of food protection and sanitation procedures - Vaccination against Hepatitis A

BACTERIMIA

-typically occurs in immunocompromised patients -bacteria enter and circulate thru bloodstream -Generally associated w/ a localized infection (may be a part of a mixed salmonella infection) -symptomes: prolonged or recurred fevers -Infants and immuno-compromised patients are at risk of developing serious complication such as MENINGITIS, SEPSIS.

which organisms appear faster in food ... for food spoilage?

1- bacteria 2-yeast 3- Molds

3 main syndromes of salmonellosis?

1- gastroenteritis 2-enteric fever 3-Bacteremia

Spoilage of Fresh and Ready-to-Eat Meat Products

1-Pseudomonas spp.: use glucose, amino acids - produce malodorous methyl sulfides, esters and acids 2- Acinetobacter and Morexella: use amino acids - produce odors

Shigella - Disease

Bacillary dysentery • Symptoms : - Abdominal pain; cramps; diarrhea, fever; vomiting; blood, pus, or mucus in stools; tenesmus. -onset: 12-50hours ***Infective dose -- As few as 10 cells** The disease is caused when virulent Shigella organisms attach to, and penetrate, epithelial cells of the intestinal mucosa. After invasion, they multiply intracellularly, and spread to contiguous epithelial cells resulting in tissue destruction. Some strains produce enterotoxin and Shiga toxin

Intoxication

Disease caused by ingestion of a pre- formed toxic chemical that is neither mediated immunologically (allergy) Eg: botulinum toxin, S.aureus enterotoxins, aflatoxins, histamine, mycotoxins. Non-microbial: Mercury, lead, DDT, solanine (potato).

where are prions found?

Found in neural cell membrane (brains) extra notes: - resistant to acids - highly resistant to UV and boiling - nuclease resistant - sensitive to proteases

Adenoviruses

Human adenoviruses types 1 ‐ 33

Infection

Ingestion of viable organisms that multiply in the gastrointestinal tract or another body organs

Types of intestinal infections: invasive

Invasive: Attachment and invasion of epithelium of the colon( Shigella) or illeum (Salmonella) followed by exotoxin production which induces diarrhea.

Types of intestinal infections: systemic

Systemic: Attachment and penetration of small intestine epithelium followed by invasion of subepithelial tissue. Eg: S. typhi

spolilage: Post-cooking contamination of low-heat- processed UNCURED meat

Lactobacillus and Leuconostoc spp.: accumulation of CO2 and liquid without changes of color, texture and odor Clostridium spp.: gas production, odor, color changing from brown to pink to red (4 wks)

Spoilage of Fresh Meat Vacuum-Packaged Meat

Lactobacillus curvatus and Lactobacillus sake-->metabolize glucose to acetic acid and acetoin, and leucine and valine to isovaleric and isobutyric acids. They also utilize cysteine to produce H2S Leuconostoc carnosum and Leuconostoc gelidum->>produce CO2 and lactic acid, causing accumulation of gas and liquid in the package Sherwanella putrefacience -->metabolizes amino acids to produce methylsulfides and H2S H2S oxidizes myoglobin to a form of metmyoglobin (green discoloration)

spoilage: Low-heat-processed cured meat - anaerobic conditions

Lactobacillus sake, Lactobacillus curvatus, Lactobacillus viridescens, Leuconostoc carnosum, Leuconostoc gelidum, Leuconostoc mesenteroides. [Cloudy appearance, accumulation of CO2, slime due to dextran formation by Leuconostoc spp. and acidic flavor]

Spoilage of Raw Milk Non-refrigerated condition - growth of mesophiles

Lactococcus Lactobacillus Enterococcus Micrococcus Bacillus Clostridium Pseudomonas Proteus

what type of genetic code do foodborne viruses are mainly?

Mainly RNA viruses -smaller viruses SS viruses (picornavirus, calicivirus) -LArger viruses DS virus (ROTAvirus) ***hepatitis A is the only reportable virus in the US**

Spoilage of Fish by Gram-Negative Rods

Oxidation of non-protein nitrogenous compounds: NH3 NCH3 (trimethylamine) Histamine Putrescine Cadaverine Indoles H2S Mercaptans Dimethyl sulfide Acetic acid Isobutyric acid Isovaleric acid

spoilage of raw milk

Pseudomonas (Lac-): •bitter, fruity or unclean taste due to proteolysis •rancid flavor due to production of lipases Lac+ coliforms: •lactic acid •acetic acid formic acid •CO2 and H2 •curdling, foaming and souring of milk

Spoilage of Fish

Pseudomonas spp. Acinetobacter Moraxella Flavobacterium Shewanella Alcaligenes Vibrio

- type of shigella that is.... • endemic in developing countries • most frequently isolated species worldwide (60%)

S. flexneri

Super PAthogen

SALMONELLA b/c of --Adhesins --Invasion --Toxins --Disarming host

invasive microorganisms

Salmonella, Camplobacter, Listeria, E.coli 0157:H7, Hepatitis A

Spoilage of Pasteurized Milk

Thermoduric bacteria: Micrococcus Enterococcus *Lactobacillus *Streptococcus *Corynebacterium (* means, some species) spores: Bacillus Clostridium

Post-Pasteurization contamination of milk

UHT-treated (151°C few sec) milk is an essentially commercially sterile product that can only contain viable spores of some thermophilic bacteria Bacillus cereus: produces lecithinase, which hydrolyzes phospholipids causing aggregation of fat globules and their adherence to the container surface - "bitty" defect "Sweet curdling": due to production of rennin-like enzymes causing curdling at higher pH than required for "acid curdling"

Gastroenteritis

incubation period: 8-48 hours symptomes: acute onset of fever and chills, nausea, vomiting, diarrhea, abdominal cramping - fever generally subsidizes in 72h -diarrhea 3-7 days and it can be bloody -fever 38 - 39C -Dehydration

salmonellosis?

is an infection caused by salmonella bacteria

salmonella growth temperature and pH

salmonella can growth from 7-48C but most optimum below 10C and the pH for growth of salmonella is 4-9

Prions

some transmissible spongiform encephalopathies (TSEs) are caused by an infectious agent consisting solely of proteins **Infectious agent termed prion, specific protein named PrP (protease resistant protein)** -Proteinaceous infectious particles -Lack of nucleic acids -Product of human gene PrP,found in chromosome 20

Inactivation of viruses in foods?

such as - thermal processing - Depuration or relaying of shellfish - Oxidizing agents, UV -HACCP

Spoilage in ready to eat meat products due to temperature?

thermophilic spores, will not germinated unless the product is temperature abused

vCJD and BSE

types of prion disease vCJD: • rare and fatal human neurodegenerative condition • Transmissible Spongiform Encephalopathy (TSE) prevention of these 2? statutory ban on the feeding of protein derived from ruminants (e.g. cattle, sheep and goats) to any ruminant

Shigella - epidemiology

• Common and causes recurrent problems in settings of poor hygiene - maysweepthroughentirecommunities endemic throughout worldwide - 164.7millioncases • InUS: - 300,000cases - number attributable to food is unknown, but given the low infectious dose, it is probably substantial ****• Children at high risk**** - toddlers aged 2to4 - total of 69% of all episodes and 61% children <5 years of age - spread in child-care settings

Pathogenecity & Virulence factors of shigella

• Entry into epithelial cells: - invasion plasmid antigens (Ipa) - surface presentation antigens (Spa) - membrane excretion proteins (Mxi) - virulence proteins (Vir) • Intracellular and intercellular spread - virulence proteins (Vir) • shiga toxin (Stx) • Neuroaminidase (produced by Shigella dysenteriae). It degrades neuraminic acid (also called sialic acid), an intracellular cement of the epithelial cells of the intestinal mucosa

Normal Flora Vs Pathogens

• Human body is well-provided with bacteria • Contains more bacterial cells than human cells. Large intestine 10 % bacteria by weight, 10 11 cells per gram. Skin, mucosal membranes, gingival cervices have their own rich population of cells. • Normal flora: Does not cause diseases • Pathogens: colonizing the body and produce diseases.

Allergy

• Immunolgically based hypersensitivity due to exposure to a chemical (typically proteins). • Eg: milk, eggs, peanuts, soybeans, crustaceans. • Metabolic disorders: Genetically based disorder from the inability to metabolize a chemical that is toxic to certain individuals. • Eg: Lactose intolerance. Favism

how are prions come to be?

• In "infected" cells, PrP 27‐30 is produced from PrP 33‐35 • PrP 27‐30 triggers a series of reactions that produce more PrP 27‐30, i.e. PrP 27‐30 induces its own synthesis.......both PrP different in one single a.a residue "Asp 178" • This conformational change has three effects: 1. Induces the same permanent conformation change in PrP 33‐35 2. β‐sheet‐forming peptides aggregate to form amyloid fibrils 3. ***The amyloid fibrils kill thalamus neurons through apoptosis***

Opportunists Microorganism

• Lack specific genes necessary for colonization • Cannot produce diseases in healthy human • If general health declines- cause diseases. • If host defenses are compromised- cause infection.

Diseases transmitted by foods

• More than 200 known diseases • Causes include viruses, bacteria, parasites, toxins, metals and prions. • Symptoms range from mild gastroenteritis to life- threatening neurologic, hepatic and renal syndromes. • Many pathogens of greatest concern are E.coli 0157:H7, Listeria monocytogenes, Camplobacter jejuni and Cyclospora cayetanesis.

Drug-resistant Salmonella

• Multidrug-resistant (MDR) strains have increased • emerge in response to antimicrobial usage in food animals - Selective pressure - other factors

Types of intestinal infections: non invasive

• Non-invasive: attachment to epithelium of small intestine followed by enterotoxin production and diarrhea. Eg: Enterotoxigenic E. coli and Cholera

Host defense:

• Phagocytes: neutrophils, monocytes and macrophages attracted to invading bacteria by chemotaxis. • Intracellular killing: phagosome containing the engulfed bacteria fuses to a new vacule producing lysosome (Phagolysosome). • Non-resistance bacteria killed by hydrolytic enzymes (lysozyme, phospholipase and proteases). Superoxide and Hydrogen peroxide.

shiga toxin

• Produced by S. dysenteriae (a type of shigella) • 68 kDa multi-subunit protein • One A subunit (32 kDa) • Five B subunits (7.7 kDa) • Toxin is a protein that has enterotoxic, neurotoxic and cytotoxic activities. • ***Inhibits protein synthesis***** • Acts on lining of blood vessels • B subunits bind to Gb3 to enter cell • A subunit interacts with ribosomes to inactivate them

Site of infection for shigella

• Terminal ileum and colon • Penetrates the epithelium and multiplies within the epithelial cells, then the organisms spread laterally to adjacent cells, producing necrosis and death of parches of cells. This leads to ulcers which exude blood that is present in diarrheal stools.