Food Microbiology

RomaniaJuly 2007

Joe Blair, D.V.M.Senior Vice President

BASICINTRODUCTION

Bacteriology - Introduction Single cell - protoplasm covered with membrane Membrane called cell wall Covered with Jelly-like material (slime) Gram stain - positive/negative

Bacteriology - Introduction Size - microscopic - measured in microns One micron = 1/10,000 cm (1/25,000 inch) 0.3 to 5.0 microns Reproduce by binary fission May occur very rapidly with ideal conditions (can be less than 20 minutes)

Bacterial Growth Curve(at a constant favorable temperature)A. Lag Phase or Phase of AdjustmentB. Log Growth PhaseC. Stationary (or resting) PhaseD. Death PhaseE. Phase of ReadjustmentBacterial Growth Curve

Environment FactorsOxygen Requirements Aerobes - require free oxygen Anaerobes - grow without free oxygen Facultative anaerobes - either with or without O2

Environment FactorspH - Degree of acidity or alkalinity

Moisture - expressed as water activity (Aw) - pure water Aw = 1.0 Salt Tolerance varies with different organisms

Environmental Factors Temperature Psychrophiles - thrive below 20oC/68oF (Seafood) Psychrotrophs - multiply in refrigeration temps 5-7oC/32-45oF (grows faster >7oC/45oF .) Includes most meat spoilage organisms Mesophiles - Prefer warmer temps 20-44oC/70- 110oF Body temperature ideal Pathogens, foodborne illness

Environmental FactorsTemperature continued:Thermophiles - Prefer Higher Temps 49-60oC/120-140oF Plague canning industry Commercially sterile OK at usual storage temps

Time/Temperature - VERY important relationship

Clostridium perfringens

Bacillus cereus

E.coli O157:H7

Staphylococcus aureus

Listeria monocytogenes

Listeria monocytogenes

Salmonella

Salmonella with Flagella

Shigella

FOODBORNE ILLNESS

DEFINITIONS OF A FOODBORNE OUTBREAKTwo or more persons with similar illness/common food

Epidemiological analysis implicates food sourceUse of Genetic Fingerprint very accurate & becoming more common

ILLNESS DEPENDS UPON:Pathogen/toxin presentPathogen growsThreshold of susceptibility in consumer exceeded

FOODBORNE ILLNESS STATISTICSCollecting statistics on foodborne illness is an inexact scienceSymptoms are often similar to other illnesses.The vast majority of foodborne illnesses are not reported.For every reported case of salmonellosis. 30-100 go unreported.

FOODBORNE ILLNESSData Sources:Foodborne Diseases Active Surveillance Network (FoodNet)National Notifiable Disease Surveillance SystemFoodborne Disease Outbreak Surveillance SystemOther Sources (Incl. DNA)

FOODBORNE ILLNESSApprox. 76 Million Cases per Year325,000 Hospitalizations5,000 Deaths

FOODBORNE ILLNESSKnown Pathogens14 Million Illnesses60,000 Hospitalizations1,800 Deaths

FOODBORNE ILLNESSKnown Pathogens:Salmonella, Listeria and Toxoplasma responsible for 1,500 Deaths and Represent 75% of Known Pathogens

FOODBORNE ILLNESSUnknown Agents:62 Million Illnesses265,000 Hospitalizations3,200 Deaths

FOODBORNE ILLNESSPreliminary 2004 Surveillance Data15,807 Lab-Confirmed Cases (US)6,464 Salmonellosis5,665 Campylobacteriosis2,231 Shigellosis401 E. coli O15H:7120 Listeriosis

FOODBORNE ILLNESS 2004 Surveillance Data Continued:

613 Cryptosporidiosis124 Vibrio Infections15 Cyclosporiasis

http://www.cdc.gov/mmwR/

FOODBORNE ILLNESS Comparison of 2004 Data with 1996-1998 8% < Salmonella 31% < Campylobacter 42% < E. coli O157:H7 40% < Listeria 45% < Yersinia No Change - Shigella 45% > Vibrio

IN HACCP TERMS THEY AREBIOLOGICAL HAZARDS

BIOLOGICAL HAZARDSDisease producing (Pathogens) organisms that can infect or intoxicate humans (and animals) and cause foodborne illness.

TYPES OF FOODBORNE DISEASEFoodborne Infection A disease that results from eating food containing living harmful pathogens. Examples:SalmonellaListeria monocytogenes

TYPES OF FOODBORNE ILLNESSFoodborne Intoxication A pathological condition that results when the toxins or poisons from pathogens are present in ingested food. Examples:Staphylococcus enterotoxinClostridium botulinum toxin

BACTERIA ASSOCIATED WITH FOODBORNE ILLNESSEscherichia coli O157:H7SalmonellaCampylobacter jejuniClostridium perfringensShigella

BACTERIA ASSOCIATED WITH FOODBORNE ILLNESSListeria monocytogenesClostridium botulinumStaphylococcus aureusYersinia enterocoliticaVibrio vulnificus

VIURUSES AND PARASITES ASSOCIATED WITH FOODBORNE ILLNESSHepatitis A Norwalk VirusesTrichinella spiralisCryptosporidium parvumGiardia lamblia

FACTORS AFFECTING GROWTH OF PATHOGENSWarm TemperatureNeutral pH(pH7)High Water ActivityAppropriate TimePlentiful Supply of NutrientsFree of PreservativesPresence or Absence of Oxygen

CHARACTERISTICS OFFOODBORNE PATHOGENS

Bacillius cereusSource:Intestinal tract of humans, cereal dishes with corn/corn starch, mashed potatoes, vegetables, pudding, sauces and soupsDisease:B. cereus food poisoningTransmission:Ingestion of organism

Bacillius cereusSurvives normal cookingFacultative AerobepH 4.9 - 9.3 promotes growthOptimal temperature for growth 10 - 50C

Bacillius cereusControl:Proper heatingProper coolingMaintain appropriate time and temperature

Campylobacter jejuniSource:Intestinal tract: 30-100% poultry, 40-60% cattle, 60-80% swine, and milkDisease:CampylobacteriosisTransmission:ingestion of organism

Campylobacter jejuniHeat sensitive >60CSensitive to oxygen (anaerobic)Sensitive to dryingSensitive to room temperature storageSensitive to acidic conditionsSensitive to disinfectantsOptimal temperature for growth 5 - 42CpH 6.5 - 7.5 promotes growth

Campylobacter jejuniControl:Proper heat treatmentAvoid cross-contaminationFreezing

Clostridium perfringensSource:Soil, air, water, sewage, and intestinal tract of animals and humansDisease:Perfringens food poisoningTransmission:Ingestion of organism

Clostridium perfringensSurvives normal cooking, including boilingAnaerobic reduced oxygenGrowth temperature: 12 - 50COptimal temperature for growth 43 - 45CSlow cooling/non-refrigerated storage promotes growth> 60C prevents growth

Clostridium perfringensControl:Proper heatingProper re-heatingProper cooling

E. coli O157:H7 The Pathogen

E. coli O157:H7

Facultative (can grow in limited amounts of oxygen), gram-negative rod

Minimum growth temperature (7C - 8C)

Optimum growth temperature (35C - 40C)

Escherichia coli O157:H7Sensitive to heat >60CpH 4.4 9.0 (Survives at low pH)Moist, low-acid foods at > 7C promote growthAw 0.93 - 0.97 ( has occurred in some dry sausages)Low infectious dose

E. coli O157:H7

Large numbers of generic E. coli are found in the intestines of all animals and humans and E. coli O157H7 is a rare but very pathogenic variety.

Produces a very potent toxin (verotoxin shiga-like toxin closely related to Shigella dysenteriae)

Causes severe damage to the lining of the intestines

Escherichia coli O157:H7Source:Intestinal tract of cattle and humans

Disease:Hemorrhagic colitis (bloody diarrhea), hemolytic uremic syndrome (HUS), thrombotic thrombocytopenic purpura (TTP)

E. coli O157:H7

Transmission Ingestion of organismsPerson to person contact

Infectious dose

E. coli O157:H7

First recognized as a human pathogen in 1982 (2 outbreaks in Oregon and Michigan)

CDC 1999 Estimated 62,000 cases of symptomatic E. coli O157:H7; 1,800 hospitalizations; 52 deaths

E.coli O157:H7

3000 cases may develop hemolytic uremic syndrome (HUS) kidney failure

Highest incidence in children under 5 years old

E.coli O157:H7

Sources include:Ground beefUnpasteurized milk and juicesSprouts, Lettuce, Spinach, CeleryContaminated lakes, pools, inadequately chlorinated drinking waterManure as fertilizer or close proximity to livestockContaminated irrigation waterImproper hygiene of farm workers

E. coli O157:H7 TestingBasic Tenants Microorganisms are NOT randomly distributed in productOccur as individual cells or clumpsSingle samples do not give meaningful information (composite)No sampling plan can ensure the safety of the final product100% assurance is NOT possible`

E. coli O157:H7 TestingBasic Tenants

Is this the best we can do without a kill step?

Can we live with the plan we develop?

Escherichia coli O157:H7Control:Proper cooking and re-heatingAvoid recontaminationProper refrigeration (

Salmonella spp.Source: Intestinal tract of humans and animalsDisease:SalmonellosisTransmission:Ingestion of organism

Salmonella spp.Heat sensitive >60CAerobic and anaerobic growthpH 4.6 prevents growthOptimal pH for growth 6.5 - 7.55 - 47C growth rangeOptimal temperature for growth 35 - 37C

Salmonella spp.Control:Proper cookingAvoid recontaminationLow pHEmployee hygiene

Listeria monocytogenesSource:Infected animals, soil, waterDisease:ListeriosisTransmission:Ingestion of organism

Listeria monocytogenesKilled by pasteurization time/temperatureAerobic and anaerobic growthpH

Listeria monocytogenesControl:Proper heatingAvoid recontaminationLow pHLow water activityDevelop sanitation monitoring program to eliminate or minimize environmental contamination

Staphylococcus aureusSource:Humans nasal passages and skinDisease:Staphylococcal food poisoningTransmission:Ingestion of Staphylococcal enterotoxin

Staphylococcus aureusHeat sensitive to >60CEnterotoxins very heat stable, withstands boilingAerobic or anaerobicCan grow between 6.7 - 45.4COptimal temperature for growth 37 - 40CpH 4.5 - 9.3 growth rangeToxin not produced below pH 5.2Resistant to high salt (up to 15%)

Staphylococcus aureusControl:Proper hygieneProper refrigeration 60CExclusion of food handlers with boils, sores, abscesses

Clostridium botulinumSource:Soil, marine sediment, intestinal tract of animals and fish, vegetables and grainsDisease:BotulismTransmission:ingestion of toxin

Clostridium botulinumExtremely heat resistantControlled retort processing necessaryToxin destroyed by heat (boil 5 min)Anaerobic or reduced O2 growthNon-proteolytic grow to 3CProteolytic grow to 10CSpores germinate and grow in most low acid foods under anaerobic conditions

Clostridium botulinumControl:Retort product to destroy sporesLow pH

Yersinia enterocoliticaSource:Meat, pork, lamb, fish, raw milk, porcine wasteDisease:YersiniosisTransmission:Ingestion of organism

Yersinia enterocoliticaGrows well in refrigeration 2 - 45CSensitive to heat 50CSalt (5%) prevents growthpH 4.6 prevents growth

Yersinia enterocoliticaControl:Proper heat treatmentAvoid cross-contamination with pork and porcine waste

CONTROL OF BIOLOGICAL HAZARDS Prevent Pathogen Contamination Good Personnel Hygiene Avoid Cross-Contamination Sanitation of Work Surfaces

CONTROL OF BIOLOGICAL HAZARDSDestroy Pathogens Introduced into the FoodProper Cooking Time and TemperatureFreezing (for parasites)Irradiation

CONTROL OF BIOLOGICAL HAZARDSPrevent Growth of Pathogens to Harmful Levels Refrigeration or Freezing Avoid DANGER ZONE (4-60C/40-140F) Decrease pH and/or Water Activity Hold Food at Elevated Temperature (>60C/140F)

CONTROL OF BIOLOGICAL HAZARDSReduce Pathogens to Acceptable Levels Lactic acid rinses Trisodium phosphate Acidified sodium chlorite (Sanova) Chlorine

BIOLOGICAL HAZARDSMost Food Poisoning is the Result of Improper Handling and Cooking

BASIC HANDLING RULES FOR PREVENTION OF BIOLOGICAL HAZARDSKeep meat cold or hotThaw frozen meat in refrigerator or microwaveClean and sanitize food contact surfacesCook to proper temperaturesPrevent cross contamination/recontamination.

Produce: A Pathogen Vehicle of Increasing Public Health Significance

Outbreaks and Associated Cases in U.S., 1990-2003More than 3,500 reported foodborne disease outbreaks in the United States between 1990-2003 with food as the vehicle

CommodityNo. of outbreaksNo. of casesSeafood723 8,071Multi-ingredient foods60118,006Produce43225,823Poultry 35411,894Beef 34310,872Eggs30910,750Produce was vehicle of outbreaks having the highest average number of reported cases CSPIs Outbreak Alert

Increased Consumption of Fresh Fruits and Vegetables

Examples of Recent Produce-Associated Outbreaks

Salmonella Newport Outbreak in UKMore than 360 cases of S. Newport infection in England, Scotland, Northern Ireland and Isle of Man between Sept 9 and Oct 7, 2004

Vehicle Iceberg lettuce purchased at fast food/take away restaurants

Multistate Hepatitis A Outbreak Associated with Green OnionsThree outbreaks of hepatitis A infection during Sept. Oct. 2003OCharleys, Knoxville, TN (70 cases)One Atlanta and two central Georgia restaurants (230 cases)Chi-Chis, Monaca, PA (> 550 cases)

CDC, Morbid. Mortal. Weekly Report. 52:1155-1157 (2003)

Multistate Hepatitis A Outbreak Associated with Green OnionsGreen onions imported from Baja California, Mexico, were vehicleAt restaurant, onions were prepared by rinsing intact bundles, cutting off the roots, and removing the rubber bandsOnions were chopped and held refrigerated for up to 3 days & periodically added to 40 to 80-qt. (35-76 liter) batches of salsa

CDC, Morbid. Mortal. Weekly Report. 52:1155-1157 (2003)

Hepatitis A Outbreak Associated with Raw BlueberriesSharp increase in cases of hepatitis A in first four months of 2002 in Auckland, New Zealand (81 lab-confirmed cases between 1/1-5/31/02)High % cases were from higher socio-economic areas, people had not traveled outside New ZealandThis suggested a seasonal food that was more expensive and not widely consumedCase-control study revealed vehicle was blueberries

Hepatitis A Outbreak Associated with Raw BlueberriesSite investigation of orchard revealed a 9-year-old child who was present during the harvest - developed hepatitis A symptomsAudit revealed multiple opportunities for an infected worker to contaminate product fecally during picking and packing -Orchard had 3 pit latrines - one was in the middle of blueberry plants and two were 30 m from the plants

Cyclosporasis Outbreak Associated with Snow Peas

In May - July 2004, 96 cases of Cyclospora cayetanensis infection associated with a residential facility in PennsylvaniaAssociated with pasta salad containing raw snow peas imported from GuatemalaSnow peas were the vehicle of CyclosporaCDC Morbid. Mortal. Weekly Report 53(37):876 (2004)

Outbreaks of Yersinia pseudotuberculosis Infection from Grated Carrots103 cases Y. pseudotuberculosis O:1 infection among school children in Kotka City in Finland in May 2003

Case study identified grated carrots as vehicle - traced back to a farm where the organism was isolated from 5 of 13 samples taken from a peeling machine

E. Coli O157H7 2006-2007Numerous US cases associated with California produced produce:Bagged spinach and other salad greensCelery, etc Exact source of organism not definitively determined. Suspect contaminated water and/or domestic & feral animals

A common feature of many recent produce-associated outbreaks

Failings in good agricultural practices (GAPs)

Need effective antimicrobial treatments for produce that have been validated for killing enteric pathogens and retaining fresh-like characteristics of treated products irradiation a possibility??

Food Ingredients - Concerns Melamine added to wheat gluten other ingredients?Millions of Kgs. of pet food recalledImported ingredients very widespread use in foods (almost 100% of ascorbic acid used in the US is imported)

International Distributions of Foods & Ingredients: A Growing Public Health Concern