Food Microbiology

Karl R. Matthews, is Professor of Microbial Food Safety at Rutgers University. He received a Ph.D. from the University of Kentucky in 1988. Dr. Matthews has earned an international reputation for his work on the interaction of foodborne pathogens with fresh fruits and vegetables. This includes demonstrating the internal localization of bacteria during growth of leafy greens. He further showed that the internalization process is a passive event by demonstrating the internalization of fluorescent polystyrene beads. Dr. Matthews has also been active in research on antimicrobial resistance of foodborne bacteria and development of novel antimicrobial agents. Kalmia E. Kniel is Professor of Microbial Food Safety in the Department of Animal and Food Sciences at the University of Delaware. She received her Ph.D. from Virginia Tech in Food Science and Technology in 2002. Her doctoral work focused on protozoan parasites. After that, she was a postdoctoral microbiologist at the USDA Agricultural Research Service's Animal Parasitic Diseases Laboratory. She is now nationally recognized as a leading expert in transmission of viruses, protozoa, and bacteria in the preharvest environment. Dr. Kniel has been active in researching the mechanisms behind the survival and inactivation of norovirus, hepatitis A virus, and other enteric viruses prevalent in our water and foods. She is an active advocate for teaching food safety at all levels and has been involved with elementary and secondary education. At the University of Delaware, she teaches courses on foodborne outbreak investigations and the basics of food science and food safety from farm to fork. Thomas J. Montville is Distinguished Professor Emeritus at Rutgers University, where he received his B.S. in 1975. Dr. Montville received his Ph.D. from the Massachusetts Institute of Technology (MIT) and then worked at the U.S. Department of Agriculture (USDA) as a research microbiologist before returning to Rutgers as a professor. He has published over 100 research papers on Clostridium botulinum, Listeria monocytogenes, antimicrobial peptides, and Bacillus anthracis. Dr. Montville is a fellow of the American Academy of Microbiology and a fellow of the Institute of Food Technologists.

Preface

About the Authors

SECTION I Basics of Food Microbiology

1 The Trajectory of Food Microbiology
Introduction
Who's on First?
Food Microbiology, Past and Present
To the Future and Beyond
Summary
Suggested reading
Questions for critical thought

2 Microbial Growth, Survival, and Death in Foods
Introduction
Food Ecosystems, Homeostasis, and Hurdle Technology
Foods as Ecosystems
Classical Microbiology and Its Limitations
Limitations of Detection and Enumeration Methods
Plate Counts
Selective, or Differential, Media
Most-Probable-Number Methods
Enrichment Techniques
Physiological States of Bacteria
Introduction
Injury
Viable but Nonculturable
Quorum Sensing and Signal Transduction
Biofilms
Factors That Influence Microbial Growth
Intrinsic Factors
Extrinsic Factors
Homeostasis and Hurdle Technology
Growth Kinetics
Microbial Physiology and Metabolism
Carbon Flow and Substrate-Level Phosphorylation
The TCA Cycle Links Glycolysis to Aerobic Respiration
Conclusion
Summary
Suggested reading
Questions for critical thought

3 Spores and Their Significance
Introduction
Spores in the Food Industry
Low-Acid Canned Foods
Bacteriology of Sporeformers of Public Health Significance
Heat Resistance of C. botulinum Spores
Spoilage of Acid and Low-Acid Canned and Vacuum-Packaged Foods by Sporeformers
Spore Biology
Structure
Macromolecules
Small Molecules
Dormancy
Resistance
Freezing and Desiccation Resistance
Pressure Resistance
gamma-Radiation Resistance
UV Radiation Resistance
Chemical Resistance
Heat Resistance
The Cycle of Sporulation and Germination
Sporulation
Activation
Germination
Outgrowth
Summary
Suggested reading
Questions for critical thought

4 Detection and Enumeration of Microbes in Food
Introduction
Sample Collection and Processing
Analysis
Metabolism-Based Methods
Surface Testing
Summary
Suggested reading
Questions for critical thought

5 Rapid and Automated Microbial Methods
Introduction
Sample Processing
Requirements and Validation of Rapid Methods
Rapid Methods Based on Traditional Methods
Immunologically Based Methods
Molecular Methods
A Potpourri of Rapid Methods
Summary
Suggested reading
Questions for critical thought

6 Indicator Microorganisms and Microbiological Criteria
Introduction
The Purpose of Microbiological Criteria
The Need To Establish Microbiological Criteria
Definitions
Who Establishes Microbiological Criteria?
Sampling Plans
Types of Sampling Plans
Establishing Limits
Indicators of Microbiological Quality
Indicator Microorganisms
Metabolic Products
Indicators of Foodborne Pathogens and Toxins
Indicator Organisms
Fecal Coliforms and E. coli
Metabolic Products
Application and Specific Proposals for Microbiological Criteria for Food and Food Ingredients
Current Status
Summary
Suggested reading
Questions for critical thought
SECTION II Foodborne Pathogenic Bacteria

7 Regulatory Issues
Introduction
U.S. Agencies Involved in Food Regulation
The USDA
The FDA
The CDC
Surveillance
When an Outbreak Occurs
Agroterrorism
What's Next?
Global Perspective
"It Takes a Village" and Maybe More
Summary
Suggested reading
Questions for critical thought

8 Bacillus cereus
Outbreak
Introduction
Characteristics of the Organism
Environmental Sources
Foodborne Outbreaks
Characteristics of Disease
Dose
Virulence Factors and Mechanisms of Pathogenicity
The Emetic Toxin
Enterotoxins
B. cereus as a Medical Pathogen
The Spore
Summary
Suggested reading
Questions for critical thought

9 Campylobacter Species
Outbreak
Introduction
Characteristics of the Organism
Environmental Susceptibility
Reservoirs and Foodborne Outbreaks
Characteristics of Disease
C. jejuni and C. coli
Other Campylobacter Species
Epidemiological Subtyping Systems Useful for Investigating Foodborne Illnesses
Infective Dose and Susceptible Populations
Virulence Factors and Mechanisms of Pathogenicity
Cell Association and Invasion
Flagella and Motility
Toxins
Other Factors
Autoimmune Diseases
Immunity
Summary
Suggested reading
Questions for critical thought

10 Clostridium botulinum
Introduction
Four Faces of Botulism
Characteristics of the Disease
Toxic Doses
Characteristics of C. botulinum
Classification
Tolerance to Preservation Methods
Sources of C. botulinum
Occurrence of C. botulinum in the Environment
Occurrence of C. botulinum in Foods
Virulence Factors and Mechanisms of Pathogenicity
Structure of the Neurotoxins
Genetic Regulation of the Neurotoxins
Mode of Action of the Neurotoxins
Summary
Suggested reading
Questions for critical thought

11 Clostridium perfringens
The Foodborne Illness
A Spore's-Eye View of Clostridium perfringens Toxicoinfections
Cruel and Unusual Punishment
Incidence
Vehicles for C. perfringens Foodborne Illness
Factors Contributing to C. perfringens Type A Foodborne Illness
Preventing C. perfringens Type A Foodborne Illness
Identification of C. perfringens Type A Foodborne Illness Outbreaks
Characteristics of C. perfringens Type A Foodborne Illness
Infectious Dose for C. perfringens Type A Foodborne Illness
The Organism
Overview
Classification: Toxin Typing of C. perfringens
Control of C. perfringens
Reservoirs for C. perfringens Type A
Virulence Factors Contributing to C. perfringens Type A Foodborne Illness
Heat Resistance
C. perfringens Enterotoxin
Summary
Suggested reading
Questions for critical thought

12 Enterohemorrhagic Escherichia coli
Outbreak
Introduction
Categories of E. coli
Characteristics of E. coli O157:H7 and Non-O157 EHEC
Acid Tolerance
Antibiotic Resistance
Inactivation by Heat and Irradiation
Reservoirs of E. coli O157:H7
Detection of E. coli O157:H7 and Other EHEC Strains on Farms
Factors Associated with Bovine Carriage of E. coli O157:H7
Cattle Model for Infection by E. coli O157:H7
Domestic Animals and Wildlife
Humans
Disease Outbreaks
Geographic Distribution
Seasonality of E. coli O157:H7 Infection
Age of Patients
Transmission of E. coli O157:H7
Examples of Foodborne and Waterborne Outbreaks
Characteristics of Disease
Infectious Dose
Mechanisms of Pathogenicity
Attaching and Effacing
The Locus of Enterocyte Effacement
The 60-MDa Plasmid (pO157)
Stxs
Conclusion
Summary
Suggested reading
Questions for critical thought

13 Listeria monocytogenes
Outbreak
Introduction
Characteristics of the Organism
Classification
Susceptibility to Physical and Chemical Agents
Listeriosis and Specific Foods
Ready-to-Eat Foods
Milk Products
Cheeses
Meat and Poultry Products
Seafoods
Other Foods
Environmental Sources of L. monocytogenes
Food-Processing Plants
Prevalence and the Regulatory Status of L. monocytogenes
Human Carriers
Foodborne Outbreaks
Characteristics of Disease
Infectious Dose
Virulence Factors and Mechanisms of Pathogenicity
Pathogenicity of L. monocytogenes
Specific Genes Mediate Pathogenicity
Summary
Suggested reading
Questions for critical thought
More questions than answers

14 Salmonella Species
Outbreak
Introduction
Characteristics of the Organism
Biochemical Identification
Taxonomy and Nomenclature
Serological Identification
Physiology
Reservoirs
Characteristics of Disease
Symptoms and Treatment
Preventative Measures
Antibiotic Resistance
Infectious Dose
Pathogenicity and Virulence Factors
Specific and Nonspecific Human Responses
Attachment and Invasion
Growth and Survival within Host Cells
Virulence Plasmids
Other Virulence Factors
Summary
Suggested reading
Questions for critical thought

15 Shigella Species
Outbreak
Introduction
Classification and Biochemical Characteristics
Shigella in Foods
Survival and Growth in Foods
Characteristics of Disease
Foodborne Outbreaks
Virulence Factors
Genetic Regulation
Conclusions
Summary
Suggested reading
Questions for critical thought

16 Staphylococcus aureus
Outbreak
Characteristics of the Organism
Historical Aspects and General Considerations
Sources of Staphylococcal Food Contamination
Resistance to Adverse Environmental Conditions
Foodborne Outbreaks
Incidence of Staphylococcal Food Poisoning
A Typical Large Staphylococcal Food Poisoning Outbreak
Characteristics of Disease
Toxic Dose
Toxin Dose Required
Microbiology, Toxins, and Pathogenicity
Nomenclature, Characteristics, and Distribution of Enterotoxin-Producing Staphylococci
Introduction to and Nomenclature of the Staphylococcal Enterotoxins
Staphylococcal Regulation of Staphylococcal Enterotoxin Expression
Summary
Suggested reading
Questions for critical thought

17 Vibrio Species
Outbreak
Introduction
Characteristics of the Organism
Epidemiology
Characteristics of Disease
Susceptibility to Physical and Chemical Treatments
V. cholerae
V. mimicus
V. parahaemolyticus
V. vulnificus
V. fluvialis, V. furnissii, V. hollisae, and V. alginolyticus
Summary
Suggested reading
Questions for critical thought

18 Yersinia enterocolitica
Outbreak
Introduction
Characteristics of the Organism
Classification
Susceptibility and Tolerance
Characteristics of Infection
Reservoirs
Foodborne Outbreaks
Mechanisms of Pathogenicity
Pathological Changes
Virulence Determinants
Chromosomal Determinants of Virulence
Other Virulence Determinants
Pathogenesis of Yersinia-Induced Autoimmunity
Summary
Suggested reading
Questions for critical thought
SECTION III Other Microbes Important in Food

19 Lactic Acid Bacteria and Their Fermentation Products
Introduction
The Biochemical Foundation of Food Fermentation
Catabolic Pathways
Genetics of Lactic Acid Bacteria
Dairy Fermentations
Starter Cultures
Production of Aroma Compounds
Vegetable Fermentations
Ingredients and Additives Used during Fermentations
Sauerkraut Fermentation
Pickle Fermentation
Meat Fermentations
Summary
Suggested reading
Questions for critical thought

20 Yeast-Based and Other Fermentations
Introduction
Fermentations That Use Yeast
Bread
Beer
Wine
Vinegar Fermentation
Cocoa and Coffee Fermentations
Cocoa
Coffee
Fermented Foods of Non-Western Societies
Summary
Suggested reading
Questions for critical thought

21 Spoilage Organisms
Introduction
Meat, Poultry, and Seafood Products
Origin of the Microflora in Meat
Origin of the Microflora in Poultry
Origins of Microfloras in Finfish
Origins of Microfloras in Shellfish
Bacterial Attachment to Food Surfaces
Microbial Progression during Storage
Muscle Tissue as a Growth Medium
Factors Influencing Spoilage
Control of Spoilage of Muscle Foods
Milk and Dairy Products
Milk and Dairy Products as Growth Media
Psychrotrophic Spoilage
Spoilage by Fermentative Nonsporeformers
Spore-Forming Bacteria
Yeasts and Molds
Spoilage of Produce and Grains
Types of Spoilage
Mechanisms of Spoilage
Influence of Physiological State
Microbiological Spoilage of Vegetables
Microbiological Spoilage of Fruits
Microbiological Spoilage of Grains and Grain Products
Summary
Suggested reading
Questions for critical thought

22 Molds
Introduction
Isolation, Enumeration, and Identification
Aspergillus Species
A. flavus and A. parasiticus
Other Toxigenic Aspergilli
Penicillium Species
Significant Penicillium Mycotoxins
Fusaria and Toxigenic Molds Other than Aspergilli and Penicillia
Toxigenic Fusarium Species
Other Toxic Molds
Summary
Suggested reading
Questions for critical thought

23 Parasites
Outbreak
Introduction
Protozoa
Cryptosporidium spp.
Cyclospora cayetanensis
Toxoplasma gondii
Giardia intestinalis
Other Protozoa of Interest
Helminths
Roundworms (Nematodes)
Tapeworms (Cestodes)
Flukes (Trematodes)
Detection
Preventative Measures
Summary
Suggested reading
Questions for critical thought

24 Viruses and Prions
Introduction
Viruses
Elementary Virology
Viruses as Agents of Foodborne Illness
Bacteriophages in the Dairy Industry
Beneficial Uses of Viruses
Prions
A Short History of the Prion
Prion Biology
Summary
Suggested reading
Questions for critical thought
SECTION IV Control of Microorganisms in Food

25 Chemical Antimicrobials
Introduction
Factors That Affect Antimicrobial Activity
Organic Acids
Parabenzoic Acids
Nitrites
Phosphates
Sodium Chloride
Water Activity
Disinfectants
Sulfites
Chlorine
Quaternary Ammonium Compounds
Peroxides
Ozone
Naturally Occurring Antimicrobials
Lysozyme
Lactoferrin and Other Iron-Binding Proteins
Avidin
Spices and Their Essential Oils
Onions and Garlic
Isothiocyanates
Phenolic Compounds
Summary
Suggested reading
Questions for critical thought

26 Biologically Based Preservation and Probiotic Bacteria
Introduction
Biopreservation by Controlled Acidification
Bacteriocins
General Characteristics
Bacteriocin Applications in Foods
Probiotic Bacteria
The Human GI Tract Is a Microbial Ecosystem
Summary
Suggested reading
Questions for critical thought

27 Physical Methods of Food Preservation
Introduction
Physical Dehydration Processes
Drying
Freeze-Drying
Cool Storage
Controlled-Atmosphere Storage
Modified-Atmosphere Packaging
Freezing and Frozen Storage
Preservation by Heat Treatments
Technological Fundamentals
Thermobacteriology
Calculating Heat Processes for Foods
Summary
Suggested reading
Questions for critical thought

28 Nonthermal Processing
Introduction
Acceptance
High-Pressure Processing
Ozone
Ultraviolet Light
Pulsed Electric Fields and Pulsed Light
Oscillating Magnetic Fields
Ultrasound
Conclusions
Summary
Suggested reading
Questions for critical thought

29 Sanitation and Related Practices
Introduction
Food Safety Objectives
Good Manufacturing Practices
General Provisions (Subpart A)
Buildings and Facilities (Subpart B)
Equipment (Subpart C)
Production and Process Controls (Subpart E)
DALs (Subpart G)
Sanitation
SSOPs
HACCP
Conclusions
Summary
Suggested reading
Questions for critical thought
Critical Thinking Skills

Useful Websites for Food Safety Information

Glossary
Answers to Crossword Puzzles
Answers to Selected Questions for Critical Thought
Index