Microbes and Food 4/18/14

Transcription

1 Ques%on(about(the(E.#coli#data.( Group(Projects(and(the(proposal:( Laboratory(Reports((wri%ng(project(#1)( Tuesday:( Start(microbes(in(food(experiment( Begin(phase(contrast(Microscopy( Thursday:( Analysis(and(observa%on(for(microbes(in(food(exercise.( Complete(phase(contrast(microscopy(observa%ons( Microbes and Food 1

2 4/18/14 Lab: microbiological analysis of food Goal:(inves%gate(the(presence(of(microbes(in(food.( Methods:( Collect(food(samples( Process(known(amount(of(food(in(a(blender( Pour(plate(dilu%ons(in(Tryp%case(soy(agar(and(MacConkey( agar( Count(colonies( Work(with(your(group(to(choose/process(food(item( Uncooked,(raw(foods:(vegetables(and(fruit( Don t(pick(a(items(with(a(thick(skin:(e.g.(apples,(pears,( lemons,(tomatoes( Trypticase Soy Agar MacConkey Agar 2

3 Two types of growth media d: MacConkey Agar (Per liter): Peptone 17 g Proteose Peptone 3 g Lactose 10 g. Bile Salts 1.5 g. Sodium Chloride 5 g Neutral Red 0.03 g Agar 13.5 g MacConkey: selective for Gram negative bacteria Also indicates colonies that ferment lactose TSB agar (Per Liter): 15 g Pancreatic Digest of Casein 5 g Papaic Digest of Soybean 5 g Sodium Chloride 2.5 g Dipotassium Phosphate 2.5 g Dextrose 15 g agar Trypticase Soy Agar: non-selective medium undefined similar to LB Has glucose Buffered by phosphate Why study microbes and food? Spoilage( results(from(growth(of(microbes(in(food( alters(food(visibly(and(in(other(ways,(rendering(it( unsuitable(for(consump%on( involves(predictable(succession(of(microbes( different(foods(undergo(different(types(of(spoilage( processes( toxins(are(some%mes(produced( 6( 3

4 Food-Borne Diseases Food$borne)infec-ons) Inges%on(of(microbes,( followed(by(growth,(%ssue( invasion,(and/or(release(of( toxins( Raw(foods((e.g.,(sprouts,( raspberries,(and(seafood)( are(important(sources( Salmonella#food(poisoning.( Food)intoxica-ons) Inges%on(of(toxins(in(foods( in(which(microbes(have( grown( include(staphylococcal(food( poisoning,(botulism,( Clostridium#perfringens( food(poisoning,(and(bacillus# cereus(food(poisoning( Copyright( (The(McGrawSHill( Companies.(Permission(required(for( reproduc%on(or(display.( 7( Bacteria on broccoli International journal of food microbiology (2000) volume: 60 issue: 1 page: Broccoli picture from Wikipedia 4

5 International journal of food microbiology (2000) volume: 60 issue: 1 page: Table 1. Produce varieties and sample numbers. 5

6 Figure)2.)Rela-onships)between)bacterial)communi-es)on)each)produce)type)and)rela-ve)abundances)of) bacterial)families.) Leff JW, Fierer N (2013) Bacterial Communities Associated with the Surfaces of Fresh Fruits and Vegetables. PLoS ONE 8(3): e doi: /journal.pone Table)3.)Bacterial)OTUs)represen-ng)large) propor-ons)(>5%))of)their)bacterial) community)on)a)given)produce)type.) Leff JW, Fierer N (2013) Bacterial Communities Associated with the Surfaces of Fresh Fruits and Vegetables. PLoS ONE 8(3): e doi: /journal.pone

7 Food spoilage Intrinsic and Extrinsic Factors affecting spoilage: 13( Figure 34.1 Table 34.1 putrefac%on( proteolysis(and(anaerobic(breakdown(of( proteins,(yielding(foulssmelling(amine( compounds,(such(as(cadaverine(and(putrescine( ph(impacts(composi%on(of(microbial( community(and(therefore(types(of(chemical( reac%ons(that(occur(when(microbes(grow( in(food( 14( 7

8 Intrinsic Factors food(composi%on( ph( presence(and(availability(of(water( oxida%onsreduc%on(poten%al( altered(by(cooking( physical(structure( presence(of(an%microbial(substances( 15( Physical Structure grinding(and(mixing(increase(surface(area(and( distribute(microbes( promotes(microbial(growth( outer(skin(of(vegetables(and(fruits(slows( microbial(growth( 16( 8

9 Extrinsic Factors Temperature( lower(temperatures(retard(microbial(growth( rela%ve(humidity( higher(levels(promote(microbial(growth( atmosphere( oxygen(promotes(growth( modified(atmosphere(packaging((map)( use(of(shrink(wrap(and(vacuum(technologies(to(package(food( in(controlled(atmospheres( Water(ac%vity,(a w.(1(=(pure(water( 7.5%(NaCl(inhibits(bacterial(growth((a w (0.957)( Sugar(can(also(be(inhibitory.( 17( Pathogens and food Enteric pathogen using a type 3 secretion system to stick to the host cells 9

10 Needle complex of S. typhimurium type III secretion system 100 nm 100 nm Type III Secretion Machines: Bacterial Devices for Protein Delivery into Host Cells Science 21 May 1999: vol. 284 no Some food-borne pathogens Organism) E.#coli#(EPEC)( ENTEROPATHOGENIC( E.#coli#(ETEC)( ENTEROTOXIGENIC( Staphylococcus# aureus# Incuba-o n)period) Vomi-ng) Diarrhea) Fever) Clinical)features) 3S5(days( +/S( ++( +/S( Necrosis(of(colon(epithelial(cells;( deadly(bloody(diarrhea.( E.#coli#O157:H7( 24S72(hr( +/S( ++( +/S( Traveler s(diarrhea,(caused(by( heat(labile((lt)(and(heat(stable( (ST)(toxins;(selfSlimi%ng( 1S8(days( +++( +( S( Enterotoxin(causes(intense( vomi%ng;(selfslimi%ng;(toxins(are( produced(in(contaminated(meat,( dairy,(bakery(products( Bacillus#cereus# 2S16(hr( +++( ++( S( Enterotoxins(formed(in(the(food(or( the(gut(by(the(growing(organism( Salmonella#spp.# (gastroenteri:s)# 10 5 #cells#dose# 8S48(hr( +/S( ++( +( Grows(in(gut;(gradual(onset(of( diarrhea(and(fever;(nausea;( headache(muscle(aches;( prolonged(carriage;(meats,( poultry,(eggs( 10

11 Other food borne infections Campylobacter#jejuni# transmijed(by(uncooked(or(poorly(cooked(poultry( products,(or(raw(milk( listeriosis( pregnant(women,(the(young(and(old(and(immunos compromised(individuals(most(vulnerable( responsible(for(the(largest(meat(recall(in(2002,(u.s,(27.4( million(pounds!(( at(risk(people(should(not(eat(sol(cheeses,(refrigerated( smoked(meats,(deli(meats(and(undercooked(hot(dogs( Intracellular(mo%lity(video:( hjp:// 21( Food Borne Infections Escherichia#coli# diarrhea(caused(by(enteropathogenic,( enteroinvasive(and(enterotoxigenic(types( E.#coli(0157:H7(is(thought(to(have(acquired( enterohemorrhagic(genes(from(shigella,( including(genes(for(the(shigaslike(toxin( 22( 11

12 Detection of Food-Borne Pathogens Slow (culture(techniques( tradi%onal(biochemical( profiles,(selec%ve(media(cultures(the(pathogen.( Rapid(tests:( Immunological(techniques( ELISA s(can(be(very(sensi%ve( Detects(an%gen(directly( Molecular/DNASbased(techniques:( PCR(to(detect(toxin(genes(or(the(pathogen(itself( Probes(used(to(detect(specific(DNA(or(RNA(by(hybridiza%on( Pro:(Sensi%ve(and(specific( Con:(Detec%on(limit(issues( The(rapid(tests(are(presump%ve(and(require(follow(up( culturing( 24( 12