Chapter 36 Food and Foodborne Microbial Diseases

Food Classification

Food Preservation Methods 1.Cold..refrigeration (4 o C), freezing (-20 to -80 o C) 2.Pickling – Acidity….weak acids (pHs <5) 3.Drying – Dehydration….reduces water activity 4.Heating – pasteurization, boiling, autoclaving

a is Ok, something wrong b to d

Food Preservation Methods 1.Cold..refrigeration (4 o C), freezing (-20 to -80 o C) 2.Pickling – Acidity….weak acids (pHs <5) 3.Drying – Dehydration….reduces water activity 4.Heating – pasteurization, boiling, autoclaving 5.High Pressure Processing..up to 100,000 lb/in 2 6.Chemical Preservatives. 7.Irradiation.

International Symbol for Radiated Foods Clicker Question:

Staphylococcal Food Poisoning Clicker Question:

Staphylococcus aureus Toxins TOXINACTION Hemolytic toxinsAnimal cell lysis HyaluronidaseBreakdown of hyaluronic acid CoagulaseFibrin Formation StaphylokinaseFibrin Breakdown LeukocidinKills WBC’s. Epidermolytic toxinExfolation Enterotoxins–A,B,C,D,E,F.Emetic Response

Enterotoxins Small: kD Heat Stable – can resist boiling (unlike the bacterium!!) Toxic Dose: as low as 1ng, usual is 1-5 μg (cells >10 5 /g) Emetic Response Mechanism 1. Direct on vagus nerve and sympathetic system. 2. Super Antigen (IL-2 mimics this response). 3. Both. Diarrhea Mechanism – unknown, no c-AMP involvement

Incubation Period to Emesis Classic Staph Food Poisoning: Cafeteria of a College Dormitory…to the College Clinic (69 cases)

Foods Involved + Symptoms

Botulism : Clostridium botulinum

Review of Endospore Location Clostridium botulinum Bacillus pasteuri Bacillus cereus Terminal Spore Subterminal Spore Central Spore

Clostridium Fermentations – From Glucose

What Can’t Clostridium spp Ferment?

In what types of Foods can C. botulinum grow? Clicker Question:

Botulism Toxin : Flaccid Paralysis

Botulism Toxin Effect on Motor Neurons

Infant Botulism: Floppy Baby Syndrome

Wound Botulism

Food Infection : Salmonella enterica Peak in 1985 due to pasteurized milk mixed with raw (unprocessed) milk in Illinois.

Salmonella enterica : over 1,400 Serovars Salmonella enterica serovar Typhi is usually abbreviated: Salmonella Typhi or S. Typhi. Typhoid Fever has a very low incidence in USA, only in people acquiring the disease outside USA. However, all the other strains (servoars) cause the data in the preceding figure: salmonellosis.

Reservoirs

Salmonella Taxonomy – Part 1 Gram Negative rods, facultative, catalase pos, oxidase neg Closely related to Escherichia coli Serogroups: 1941 – 100 serogropus of S. enterica 1964 – 900 serogroups now - > 2,400 serogroups. -based on H and O antigens. IMViC -+-+, Lactose neg, all H 2 S pos.

H 2 S Production on TSI Triple Sugar Iron Agar 1% sucrose 1% lactose 0.1% glucose Na-thiosulfate ferrous sulfate Tryptone, Peptone Yeast Extract agar Phenol red pH 7.3 Left to Right: Control (uninoculated); Pseudomonas aeruginosa; Escherichia coli; Salmonella Typhimurium; Shigella flexneri Clicker Question:

H 2 S Production on TSI Triple Sugar Iron Agar 1% sucrose 1% lactose 0.1% glucose Na-thiosulfate ferrous sulfate Tryptone, Peptone Yeast Extract agar Phenol red pH 7.3 Left to Right: Control (uninoculated); Pseudomonas aeruginosa; Escherichia coli; Salmonella Typhimurium; Shigella flexneri Clicker Question:

Salmonella colonies XLT4 agar

Clicker Question:

Enteritis (Salmonellosis) Disease Characteristics 1.Incubation Period – mostly 6hrs to 2 days. ID 50 = 10 to 10 6 cells 2.Symptoms: diarrhea, abdominal cramps, mild fever, nausea, vomit, chills headache --- duration 2 – 3 days. 3.Therapy – non needed, antibiotic treatment gives no benefit. Eat yoghurt! 4.Carrier state for a few months from bacteria in ileum and colon. Adherence – mannose binding pili Receptor mediated endocytosis  multiply intra-cellularly and released to lamina propera  involvement of inflammatory cells and release of prostaglandins  increase in c-AMP and diarrhea (usually not toxin associated like cholera, but a few have enterotoxins).

Salmonella World Wide Clicker Question:

Infective Dose

Diagnosis, Treatment, Prevention Diagnosis: Symptoms, culture organisms from fecal sample.. and suspected food. Isolates sent to other labs (Food Net and Pulse Net) that use molecular methods of ID such as pulse- field gel electrophoresis of DNA fragments… pin points the source of the outbreak. Treatment: used to shorten course of disease and reduce the carrier state…but multiple drug resistant Salmonella is a significant clinical problem. Prevention: cook your food. Infected individuals are banned (in some states) from work as food handlers until their feces are negative for Salmonella on three separate cultures.

E. coli can be both non-pathogenic and pathogenic. Normal human feces has 10 7 E. coli / gram Feces have ~ bacteria / gram Is E. coli dominant ? How have some E. coli become pathogenic? There are several major types of E. coli pathogens =>

This is STEC in your Text.