Food Microbiology

Food and beverages are a

source of nutrients for humans and microorganisms

Sources of contamination

soil, food handling, improper food storage, globalization

Soil

where plant-based food is grown, and where animal products live

True/False: Soil organisms in food are usually not pathogens, but can cause spoilage

True

Food Handling

harvest/slaughter

food handlers

unsanitary working conditions

Improper food storage

improper refrigeration

What is the major cause of food-related illness

improper refrigerations P

Perishable

easily supports growth

Semi-perishable

spoils less quicklyN

Non-perishable

edible for a long time

Spoilage likelihood related to

extrinsic factor and intrinsic factor

Extrinsic factor

Factors that are directly related to storage/external factors

Intrinsic factors

Factors directly related to food

Water activity (a_w)

The amount of water and its accessibility to microorganisms ranging from 0-1

Methods of controlling food spoilages include

reduce A_w, control temperature, and pasteurization

Control of food spoilage: Reduce a_w

drying (sun/oven), freeze drying (frozen then dried under vacuum

Control of food spoilage: Control of temp

Refrigeration (4oC-effective for all except psychotolerants); high cooking temperatures

Control of food spoilage: Pasteurization methods

controlled heating below boiling

flash pasteurization

ultra high temp (UHT) sterilization

Flash pasteurization

high temperature short term (HTHS)

quick controlled heat to 72 for 15 second followed by rapid cooling

Ultra High Temp sterilization

Heat liquid to >135 °C for 2-5 sec, then cool; no refrigeration needed, and can stay at room temp for 3 months

Gastroenteritis

Inflammation of the stomach and intestinal lining can be caused by a variety of microorganisms from contaminated food or water

Bacteria enterotoxins

acts on the small intestinal lining, causing a massive fluid secretion into the intestinal lumen

Worldwide diarrheal disease

leading cause of childhood death and 2nd only to respiratory adult death

The two primary types of food related diseases

Foodborne infection and foodborne intoxication

Foodborne infection

ingestion of the pathogen followed by growth in the host, tissue invasion, and release of toxins

Cholera

Vibrio cholerae; fecal-oral transmission

Cholera secretes ___ which is a ___

coleragen; AB exotoxin

Choleragen

binds to epithelial cells of the SI, causing the PM to become highly permeable to water, damaging the lining and causing rice water stool

Mucolytic enzymes

penetrate intestinal mucus

Fimbriae

attachment to the cell surface where choleragen is produced

Sequence Choleragen (CT) mechanism of action

l. rapid fluid loss from intestine

ll. G protein activation leads to adenylate cyclase activation

lll. Increase cAMP production

lV. A subunit enters and dissociates

V. secretion of H₂O and ions into lumen

Vl. efflux o,f Cl^- out of the cell causing an osmotic imbalance

Vll. B subunits bind to the receptor

Vlll. A1 ADP-ribosylates G proteins

lX. Activated CFTR chloride channels

Vll > lV > Vlll > ll > lll > lX > Vl > V > l

Profuse diarrhea

loss of 10-15 intestinal fluid and electrolyte imbalance and water loss

An increased concentration of blood proteins can result in

circulatory shock and collapse (Loss of BP, deminished blood circulation and inadequate blood flow to tissues) and death

Treatments for Cholera

fluid and electrolyte replacementS

Salmonellosis is mainly (organism name)

S. typhimurium and S. enteritidis

Salmonellosis can be contracted from

meats, poultry, fish, eggs, and dairy products

Salmonellosis effect

invades the intestinal lining to damage tissue, causing diarrhea and abdominal pain

Salmonellosis is a gram ___ and ___

negative; endotoxic

Escherichia Coli

from contaminated food and water, causing rapidly dehydrating conditions

Traveler’s diarrhea

from E. coli as pathogens are usually absent from new environments

Enterotoxigenic E. coli (ETEC)

bind to intestinal epithelial cells and produce enterotoxins to secrete electrolytes and water into lumen (diarrhea)

Enteroinvasive E. coli (EIEC)

invade cells and produce enterotoxins secrete electrolytes and water into lumen (diarrhea)

Enteropathogenic E. coli (EPEC)

binds to cells to cause lesions and damage microvilli secrete electrolytes and water into lumen (diarrhea)

Enterohemmorrhigaic E.coli (EHEC)

Toxins that kill vascular endothelial cells secrete electrolytes and water into the lumen (diarrhea)W

Which type of E. coli is responsible for most of E. coli outbreaks in the US

EHEC

Foodborne intoxication

pathogen secretes a toxin, contaminates food, and is ingested

True/False: The presence of a living organism is NOT required in foodborne intoxication

True

In foodborne intoxication symptoms produce

shortly after food is consumed, because there is no need for the growth of the organism

Clostridium botulinum

Obligate anaerobe endospore-forming found in soil and aquatic sediments

The most common source of infection for Clostridium botulinum is

home-canned food not heated sufficiently to kill endospores

Endospore germination

produced toxins during the vegetative state; can be eaten if food is not cooked properly, resulting in toxins remaining active

Botulinum toxin is a

neurotoxin

Botulinum toxin pathway

l. prevents exocytosis and the release of acetylcholine

ll. Binds to synapses of motor neurons

lll. Cleaves synaptobrevin (synaptic vesicle membrane protein)

lV. Flaccid (limp) paralysis results

V. no contractions in response to motor neuron activity

ll > lll > l > V > lV

Symptoms of Botulinum toxin

occurs within 18-24 hours of ingestion

blurred vision, difficulty swallowing and speaking, muscle weakness, nausea, vomiting

If Botulinum toxin is left without treatment

1/3 of patients dead in a few days by cardiac or resp failure

Infant Botulinum

Ingestion of endospores naturally found in honey and house dust that germinate in the intestine to multiply and produce toxins, resulting in death by respiratory failure