MICROBIOLOGY OF FOODS
MICROBIOLOGY OF FOODS FSTC 606
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This 19 page Class Notes was uploaded by Pietro Buckridge on Wednesday October 21, 2015. The Class Notes belongs to FSTC 606 at Texas A&M University taught by A. Castillo in Fall. Since its upload, it has received 26 views. For similar materials see /class/225845/fstc-606-texas-a-m-university in Food Science & Technology at Texas A&M University.
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Date Created: 10/21/15
Microorganisms Causing Foodborne Disease Grampositive sporeformers Costrdium perfrhgens Costrdium bowlhum Costridium botuinum Strictly anaerobic Grampositive Sporeformer Causes botulism Severe intoxication Flaccid paralysis caused by a neu rotogtltin 8 toxins described A B C C1 C2 D E F G 0 C2 is not a neurotoxin o Thse toxins are hat labile 80 C for 5 min C botuInum Botulism 0 1st outbreak described in 1793 in Germany Associated with sausage Latin botlIIIS sausage 0 There are 3 categories of botulism Food poisoning Associamd with homemade canned foods or preserves 7 intoxication Wound botulism Associa d with handling conmminated materials when being Infant bomlism Associamd with bee honey in lacbams 7 Toxiirifectiori C botuinum Food poisoning o Incubation period of 12 to 36 hours 0 Begins with gastrointestinal problems Nausea Vomiting Diarrhea May not be caused by the toxin because not present in other illnesses When typical botulism signs develop constipation 0 First indicators of botulism Fatigue Muscular weaknss C botuinum o Followed by ocular effects eyei s r sluggish response ofpupils no light 7 Blurred and double vision 0 Mouth effects a Dryness 7 Dif culty in speech and swallowing o Musculatures controlling limbs and respiration become progressively paralyze o Dath within 3 to 5 days respiratory failure 0 Complete recovery may require several months C bowmum oEpidemiology oMost cases are caused by types A B or E 0C botuI39num Type A most frequent in the US Associated with fruits and vegetables 0C botuI39num Type E is a psychrotroph Associated with smoked sh 0C botuI39num Type B more frequent in Europe Associated with homecanned ham or baked foods oCommerciaIIy canned foods have only been associated with few outbreaks oSausage has not been associated with botulism in decades Methods for isolation Needs anaerobic environment to grow Food suspension is heated to eliminate nonsporeformers Enrichment in cooked meat broth at 30 C for 7 days Plate on horse blood or egg yolk agar Select typical colonies Conduct toxin identification C pen rhgens o Gram positive 0 Sporeforming rod 0 Strictly anaerobic Wi survive and occasionally grow in the presence of 02 o Encapsulated o Nonmotile C pen rngens Formerly C WeclrI39 Associated with gas gangrene One of the most common causes ofdiarrhm worldwide 5 types based on toxin production B C D E r Toxins B and C per ingerstype A is responsible for food poisoning and gas gangrene 7 Only produces toxin s This toxin also has lecilhinase activity Phospholipase o C per ingerstype C r Produces and p tox39ns 7 Cause of enteritis necroticans 7 Severe but rare condition associamd with pork in Papua New Guinea during festivities C pen rhgens Growth cha racteristics vegetative cells Temperatu re o 12 0 Optimum 43 47 C Generation time of 71 min at 41 C 0 Minimum 50 0 Optimum 60 75 Min aw 095 097 Resistance spores D100 031 38 min C pen rhgens o Incubation period 824 h o Necessary to ingest large numbers of vegetative cells 106 108 cells 0 Syndrome Explosive diarrhea Sever abdominal pain Nausea lss common Fever and vomiting unusual Dath uncommon unless underlying illness Symptoms subside in 12 to 24 h C pen rhgens 0 Found in most raw animal products 7 Raw meaE Raw poultry e Dehydrated soups and sauces o 339 o n In on In In 0 g 3 g n i o c n E m m a 7 High prevalence 7 High nutrient content protein 7 cooking creams reduced environment suitable for growth C pen rhgens o Outbreaks frequently occurring at foodservice establishments 0 Temperature abuse 0 Spores need to germinate and grow to high numbers to cause infection 0 Once the intestine is colonized vegetative cells sporulate o Toxin is released at sproulation C pen rhgens Control and Prevention 0 FDA Food Code Rapid uniform cooling of food gtgtTo 21 C within 2 h and gtgt from 21 C to 5 C within 4 h Rehmt to internal temperature of 74 C Hold cooked dishs 260 C or g5 C o Impossible to eliminate from foods 0 Prevent by proper food preparation and storage techniques C pen rhgens o Outbreaks frequently occurring at foodservice establishments 0 Temperature abuse 0 Spores need to germinate and grow to high numbers to cause infection 0 Once the intestine is colonized vegetative cells sporulate o Toxin is released at sproulation C pefrngens Methods for analysis 0 Dilutions and plating onto twptose sulfite cycloserin TSC agar 0 Incubate under anaerobic conditions 0 Select typical colonies for further identi cation Lactose fermentative Liquefies gelatin 0 MPN is also used when low numbers are expected Rapid Methods for Microbiological Analyses of Foods BY Alejandro Castillo Food Science and Technology Texas AampM University Testing is a part of the sampling plan in a microbiological criterion Components of a microbiological criterion lldentity of the food or ingredient Agent of concern This approach J Analytical method isgqodror Equot39nquot t rrquotquot quot u Sampling plan may lMicrobiological limits Applicability of rapid testing methods in a HACCP program Principle Rapid methods applicable Hazard analysis Yes Identi cation of CCP No Establishing critical limits YESN0 Monitoring YesNo Corrective action Yesquot Record keeping No Verification Yes Rapid methods can help speed the decision making process Relative interest of microbiologist on rapid methods 10 a Medlcal Mlcroblologlsts 5 6 o 2 4 E o n 2 0 1965 1975 1985 1995 2000 Year Advantages of rapid testing methods Same or greater sensitivity accuracy and speci city as conventional methods Savings of space and materials Reduction in human errors and labor cost when automated methods are used The microbiologist can judge data organize activities and repeat tests if necessary Rapid Methods Microbiological methods that produce results in 24 h or less In the practice results are not always obtained within 24 h Ex ELISA for Salmonella ID 6 h 9Preenrichment 18h M broth 18 h ELISA 6 h 918186 42 h Time for conventional method 45 days Specific characters can be used to develop rapid tests Examples V97 E coli produce Dglucuronidase Methyl umbelliferyl glucuronide MUG test E coli PetrifilmTM gt90 S aureus produce TNase Lachica TNase test Application of rapid tests Microbial enumeration V Quantification of microbial toxins Vldentification of microorganisms and their toxins Verification of sanitizing procedures in food plants Microbial Enumeration Various systems for estimation of microbial numbers Automated Microbiological System MalthusAT ThermalActivityMonitor Microcalorimetry Changes in CO2 DEFT Res pirom eter Other systems for microbial enumeration Redigel lsogrid Petrifilm Spiral plater Sperman correlation coefficient of different me ads for simpli ed bacterial count I I quotI n I I quotI m I I ns R w I I D5 nz I I n v v a a AFC Redigel Pelri lm Spiral lsnglid cmm warm11991 What is Petrifilm Petrifilm xSimple method xLittle space used xMinimizes time for anal sis Material preparation lnocuation time Coony countingtime Petrifilm Aernhlc mane cnunl Cnll39nms mm 5 can no helpsmmzllllnu wanum Mums dmuuvlms mm mm m a m Veass md mums Iaan Nu m m lemmenun Counts of different heatstressed indicators in cow methods Pathogen Detection Most common methods Immunoassays Hmmunofluorescence Hmmunomohilization 39mmunoassays ELISA DNA hybridization Filter hyh zation Liquid rI Ization Polymerase chain reaction PCR lmm unoassays Sandwich enzymeJinked immunosorbent assay ELISA lmmunoassays Sandwich ELISA Immunoassay lmmunoimmobilization Salmonella 1 2 BioControl Systems Inc For flagellated bacteria only DNA hybridization HID5PM 39 panama lnr vimu wlu39 u a Polymerase Chain Reaction PCR 39 of a DNA sequence in a sample fMultiple chains of the same DNA sequence are more easily detected by hybridization High specificity and sensitivity gtDetects as little as 50 ng DNA Combined methods lmmunomagnetic separation W 9 y Dynabeads Combined methods E conthM Listeria Salmonella Clearviewm MicroScreen Bacterial Identification Automated systems Minikits Automated systems VITEK Automated colorimeter Most common mInlklts JMiniaturized multiple tests Enterotube ll 9Roche Diagnostics for Entembacteriaceae API abioM rieux Kits for specific microorganisms MicroID aorganon Teknika Kits for specific microorganisms Methods to assess plant sanitation ATP bioluminiscence JATP Adenosin triphosphate Venergyrich compound JMost important energy carrier in metabolic processes JPresent in all living cells Animals Plants Microorganisms bacteria yeasts molds ATP bioluminiscence technique Total ATP measured M icroorganisms Food residues Free ATP bioluminiscence technique Mgquot ATP luciferin luciferase Oxyluciferin C0Z ATP Bioluminiscence Rapid results M Sensitive Aows for immediate corrective action Conclusions Different products more choices Rapid testing will not modify 39 of microbiological testing Positive results by rapid methods have to be confirmed by conventional methods