10/18/2017 Learning Objectives Food 1.Use basic biochemical characteristics to identify Microbiology Listeria monocytogenes 2.Understand what conditions in foods favor the Chapter 13 AN INTRODUCTION growth of L.monocytogenes 3.Recognize,from symptoms and time of onset,a case of foodborne illness caused by L.monocytogenes Listeria 4.Choose appropriate interventions to prevent L. monocytogenes monocytogenes growth 5.Identify environmental sources of L.monocytogenes 6.Understand the role of L.monocytogenes toxin(s) and virulence factor(s)in causing foodborne illness Outbreak Outbreak 1998-1999 Sporadic outbreaks 1998-1999 ·Spring summer1998 ·November1998 hot dog plant had unusually high numbers -a 31-yr-old camp counselor died in Ohio of Listeria genetic fingerprints of the strains were identical ·July1998 so they must have eaten a similar food -air conditioning unit thought to be the ·Early December1998 source of Listeria was removed -hot dogs were statistically implicated as the cause ·October1998 ·Mid December1998 -CDC investigated 4 listeriosis cases from hot dogs from Sara Lee's Bil Mar Foods Plant were implicated Tennessee -4 people dead -a 74-yr old woman who loved hot dogs died plant stopped shipping the hot dogs additional cases came in from other states
10/18/2017 1 Chapter 13 Listeria monocytogenes Learning Objectives 1. Use basic biochemical characteristics to identify Listeria monocytogenes 2. Understand what conditions in foods favor the growth of L. monocytogenes 3. Recognize, from symptoms and time of onset, a case of foodborne illness caused by L. monocytogenes 4. Choose appropriate interventions to prevent L. monocytogenes growth 5. Identify environmental sources of L. monocytogenes 6. Understand the role of L. monocytogenes toxin(s) and virulence factor(s) in causing foodborne illness Outbreak 1998-1999 Sporadic outbreaks • Spring summer 1998 – hot dog plant had unusually high numbers of Listeria • July 1998 – air conditioning unit thought to be the source of Listeria was removed • October 1998 – CDC investigated 4 listeriosis cases from Tennessee - a 74-yr old woman who loved hot dogs died - additional cases came in from other states Outbreak 1998-1999 • November 1998 - a 31-yr-old camp counselor died in Ohio - genetic fingerprints of the strains were identical so they must have eaten a similar food • Early December 1998 - hot dogs were statistically implicated as the cause • Mid December 1998 - hot dogs from Sara Lee’s Bil Mar Foods Plant were implicated - 4 people dead - plant stopped shipping the hot dogs
10/18/2017 Outbreak Outbreak 1998-1999 1998-1999 ·22 December1998 ·January1999 -Sara Lee announce the recall of all meat -USDA issued its first press release on the processed at the Bil Mar plant recall ·23 December1998 Did not help a 27-yr-old pregnant woman who outbreak strain of Listeria monocytogenes gave birth to stillborn twins was isolated from an opened package of Bil Listeria monocytogenes was isolated from the Mar hot dogs placenta This meets USDA criterion for a recall ·May1999 ·25 December1998 USDA advises immunocompromised not to eat -another victim dies in New york hot dogs unless they are thoroughly heated Outbreak Listeriosis In the past 25 years,listeriosis has become a USDA typically issues 30 recalls for L. major foodborne disease monocytogenes contamination each year Primarily foodborne and not waterborne The number of recalls is increasing Outbreaks have been linked to coleslaw, Food safety is a critical component of cheeses,lunch meats,milk,chicken nuggets,and fish food-testing processes for many companies ·1600 cases per year ·266 deaths each year Items are recalled as a precaution or reaction to specific tests .3rd leading cause of death from food poisoning Lunch meat contamination cost the US about 1.1 billion dollars each year
10/18/2017 2 Outbreak 1998-1999 • 22 December 1998 - Sara Lee announce the recall of all meat processed at the Bil Mar plant • 23 December 1998 - outbreak strain of Listeria monocytogenes was isolated from an opened package of Bil Mar hot dogs - This meets USDA criterion for a recall • 25 December 1998 - another victim dies in New York Outbreak 1998-1999 • January 1999 - USDA issued its first press release on the recall - Did not help a 27-yr-old pregnant woman who gave birth to stillborn twins - Listeria monocytogenes was isolated from the placenta • May 1999 - USDA advises immunocompromised not to eat hot dogs unless they are thoroughly heated Outbreak • USDA typically issues 30 recalls for L. monocytogenes contamination each year • The number of recalls is increasing • Food safety is a critical component of food-testing processes for many companies • Items are recalled as a precaution or reaction to specific tests Listeriosis • In the past 25 years, listeriosis has become a major foodborne disease • Primarily foodborne and not waterborne • Outbreaks have been linked to coleslaw, cheeses, lunch meats, milk, chicken nuggets, and fish • 1600 cases per year • 266 deaths each year • 3rd leading cause of death from food poisoning • Lunch meat contamination cost the US about 1.1 billion dollars each year
10/18/2017 Primary factors contributing to Primary factors contributing to listeriosis listeriosis 1.Listeria 4C 2.Changing population: monocytogenes more at risk people such thrives in the cold as elderly or where it immunocompromised. 90% outcompetes other L.m.is an opportunistics p bacteria that 20c pathogen. normally outcompete poisoning are in L.m.at warmer groups. Learn more temperatures Weeks of storage Primary factors contributing to listeriosis Listeriosis 3.Changing food production practices Sporadic and rare and severe 4.Increased use of refrigeration to Causes meningitis,septicemia,and preserve food-L.m.grows better in abortion the cold than other organisms 5.Changing eating habits-greater .15.9%of people who get listeriosis die demand for fresh,unprocessed food from it without preservatives Long lag from consuming the food to 6.Changing awareness and ability to illness detect outbreaks
10/18/2017 3 Primary factors contributing to listeriosis 1. Listeria monocytogenes thrives in the cold where it outcompetes other bacteria that normally outcompete L. m. at warmer temperatures Primary factors contributing to listeriosis 2. Changing population: more at risk people such as elderly or immunocompromised. L. m. is an opportunistic pathogen. Primary factors contributing to listeriosis 3. Changing food production practices 4. Increased use of refrigeration to preserve food – L.m. grows better in the cold than other organisms 5. Changing eating habits – greater demand for fresh, unprocessed food without preservatives 6. Changing awareness and ability to detect outbreaks Listeriosis • Sporadic and rare and severe • Causes meningitis, septicemia, and abortion • 15.9% of people who get listeriosis die from it • Long lag from consuming the food to illness
10/18/2017 Characteristics of Listeria Listeria monocytogenes Joseph Lister invented Differs from most other pathogens medical disinfection and Widely distributed in nature had a mouthwash and Genus Resistant to adverse environmental named after him conditions Nonpathogenic species are isolated from the same foods and environments as L. Psychotrophic and grows in human monocytogenes macrophages Thirteen serotypes of L.monocytogenes Survives for a long time in or on food, Three serotypes predominate in listeriosis soil,plants,surfaces patients Unclear:the illness is severe but making PulseNet established by the CDC helps all food Listeria free is unrealistic identify strains by DNA fingerprints Susceptibility to physical and Susceptibility to physical and chemical agents chemical agents ·Listeria monocytogenes grows from O°C Survives but does not grow at a pH to 45C but grows slowly at cold below 4.3 temperature Organic acids,such as acetic,citric and Freezing does not reduce the numbers lactic acids,inhibit growth Killed at temps greater than 50C Grows best at water activity of greater Temperature (C)Doubling time than 0.97 and survives at water activity growth (hours) of0.83 4 43 10 6.6 Heat resistance increases as the water 37 activity decreases
10/18/2017 4 Listeria monocytogenes • Differs from most other pathogens • Widely distributed in nature • Resistant to adverse environmental conditions • Psychotrophic and grows in human macrophages • Survives for a long time in or on food, soil, plants, surfaces • Unclear: the illness is severe but making all food Listeria free is unrealistic Characteristics of Listeria • Joseph Lister invented medical disinfection and had a mouthwash and Genus named after him • Nonpathogenic species are isolated from the same foods and environments as L. monocytogenes • Thirteen serotypes of L. monocytogenes • Three serotypes predominate in listeriosis patients • PulseNet established by the CDC helps identify strains by DNA fingerprints Susceptibility to physical and chemical agents • Listeria monocytogenes grows from 0oC to 45oC but grows slowly at cold temperature • Freezing does not reduce the numbers • Killed at temps greater than 50oC Temperature (oC ) Doubling time – growth (hours) 4 43 10 6.6 37 1.1 Susceptibility to physical and chemical agents • Survives but does not grow at a pH below 4.3 • Organic acids, such as acetic, citric and lactic acids, inhibit growth • Grows best at water activity of greater than 0.97 and survives at water activity of 0.83 • Heat resistance increases as the water activity decreases
10/18/2017 Susceptibility to physical and Listeriosis and foods chemical agents Ready-to-eat foods What foods are risky? Grows well and survives in 6.5%salt Pose a high listeriosis risk Lowering temperature increases survival for susceptible populations in high salt .20%of refrigerators have temperatures greater than Control of Listeria is best achieved by 50F multiple hurdles and environmental Refrigeration cannot ensure the safety of monitoring ready-to-eat foods Refrigeration is an environment where Listeria can outcompete mesophilic pathogens Listeriosis and foods Listeriosis and foods Milk Cheeses Raw milk is a source of L.monocytogenes L.monocytogenes survives cheese Pasteurization reduces the numbers of manufacturing and ripening Lm Temperature hardy,grows in the cold and Post-process milk contamination is a salt tolerant concern as Listeria grows faster in Soft cheeses are a risk factor for pasteurized milk than in raw milk due to listeriosis fewer competitors
10/18/2017 5 Susceptibility to physical and chemical agents • Grows well and survives in 6.5% salt • Lowering temperature increases survival in high salt • Control of Listeria is best achieved by multiple hurdles and environmental monitoring Listeriosis and foods Ready-to-eat foods • Pose a high listeriosis risk for susceptible populations • 20% of refrigerators have temperatures greater than 50oF • Refrigeration cannot ensure the safety of ready-to-eat foods • Refrigeration is an environment where Listeria can outcompete mesophilic pathogens Listeriosis and foods Milk • Raw milk is a source of L. monocytogenes • Pasteurization reduces the numbers of Lm • Post-process milk contamination is a concern as Listeria grows faster in pasteurized milk than in raw milk due to fewer competitors Listeriosis and foods Cheeses • L. monocytogenes survives cheese manufacturing and ripening • Temperature hardy, grows in the cold and salt tolerant • Soft cheeses are a risk factor for listeriosis