Salmonella

Rufus K. Guthrie

• Publisher: CRC Press
• Year: 2018
• Print ISBN: 9781315897424
• eBook ISBN: 9781351093422
• Topic: Technology & Engineering
• Subtopic: Food Science
• Index: Technology & Engineering

Salmonella deals with the common infectious disease, Salmonellosis, which is commonly foodborne and is easily spread in any kitchen. The source of the pathogenic organisms is frequently poultry and the organism is often spread in the kitchen from poultry to other foods. This book describes the organisms, paths of transmission, infection and its treatment, and the control of the spread of the disease. The book is written so that food handlers at all levels can readily understand the material included. The book will also be easily understood by the lay person who could find it useful in any kitchen. Salmonella is excellent as a text or supplementary reading for food technology classes and sanitation classes.

Chapter 1

THE SALMONELLA

“Salmonella in eggs! Botulism from garlic-in-oil! Listeria in cheese! It seems that every day newspapers are shouting headlines about outbreaks of foodbome illnesses. Just within the past year, for example, eggs contaminated with Salmonella bacteria have sickened scores of consumers in the northeastern U.S., airline food tainted with Shigella bacteria brought down members of the Minnesota Vikings football team, and three residents of New York state were hospitalized with botulism after they ate an unrefrigerated garlic-in-oil mix. In fact, the Food and Drug Administration scientists estimate that tens of millions of cases of foodborne disease occur every year in this country.” So begins an article by Catherine Carey writing for the FDA Consumer in June 1989.¹

Infections other than salmonellosis are involved in the statement by Catherine Carey, but this statement serves to emphasize the importance of foodborne disease. That importance is similar to the importance of salmonellosis. According to numbers of cases reported and in the opinion of many in the public health professions, salmonellosis is one of the most common (if not the most common) infectious diseases transmitted by contaminated foods. The most feared infection caused by bacteria in this genus is typhoid fever, an infection caused by Salmonella typhi; most feared because it is by far the most severe of the salmonellosis infections in terms of symptoms and outcomes.² Although most feared, the incidence of typhoid fever is not nearly so great as the incidence of other infections caused by other Salmonella serovars which are called salmonellosis. It has also become true in more recent years that those cases of typhoid fever which do occur, in this and other developed countries, are most likely to be foodborne rather than waterborne as in the past.² Changes in the pattern of incidence of salmonellosis have been noted in both the U.S. and U.K. since the days of World War II in the 1940s. Black et al.³ suggest that the actual incidence of salmonellosis in this country is not truly measured by the system which has been in place since the 1940s. He gives as an example the fact that in the years 1953 to 1955, the reports of outbreaks of infection in England and Wales were 28 times as high as were reports in the U.S. One of the reasons given for the belief that our reports were too low was the fact that in Great Britain, a cause of their high incidence of salmonellosis was believed to be the importation of powdered eggs from this country. Those authors also express the belief that an increased use of mass food processing and distribution was a factor in the increase in incidence of salmonellosis, as were advances or changes in surgical and medical procedures which made the risk of infection by Salmonella higher and with the increased risk. There were also increased economic costs to the public in general.

TABLE 1.1
Ten Most Important Infectious Disease Groups According to the National Foundation for Infectious Diseases — Ranked as Priorities for Research

Top Ten Infectious Diseases, 1988

AIDS

Hospital-acquired infections

Hepatitis

Diarrheal diseases

Meningitis and encephalitis

Respiratory infections

Sexually-transmitted diseases

Infections in cancer and transplantation

Urinary tract infections

Tropical and parasitic diseases

From National Foundation for Infectious Diseases, The Double Helix, 3(3), 3–5,1988. With permission.

The National Foundation for Infectious Diseases^{4, 5} recently revised the rankings of the top ten infectious diseases in order to set priorities for research funding, training, and the need for preventive education (Table 1.1). This ranking is not in order of numbers of cases, but is in general arranged according to the impact expected on public health in order to set research funding priorities. Fourth among these diseases was the general classification of “diarrheal diseases”. This includes many infectious diseases, among them many of which are transmitted by contaminated foods, and certainly includes salmonellosis.

Black et al.³ from Massachusetts General Hospital reviewed unusual aspects of the cases of salmonellosis over a period of 6 years. They concluded that salmonellosis can be divided into four different clinical syndromes: gastroenteritis, bacteremia with or without extraintestinal localization, enteric fever (typhoid-like syndrome), and the carrier state (either temporary or permanent). Of these, their findings indicated that gastroenteritis was the syndrome appearing in approximately 70% of the cases, and that salmonellosis most often occurred following consumption of contaminated food–regardless of the clinical syndrome which appeared. In these cases, S. typhi always caused an enteric fever type of disease, and the unusual infections were always caused by some other serovar or strain of Salmonella. On the other hand, the carrier condition rarely occurred other than in those patients infected with S. typhi. The temporary carrier condition (convalescent carrier) occurred in other infections, but very rarely became permanent. The investigators made a point of the fact that symptomless carriers are an important source of the organisms when these persons are occupied as handlers of foods. At least a number of such carriers probably acquired the condition while employed as handlers of uncooked meats and carcasses of animals to be used for foods. Their findings were that of 500 outbreaks in the U.S., the Caribbean area, and South America, 56% of the outbreaks were traced to symptomless carriers employed as food handlers.³

It is generally believed that only a very small portion of the cases which do occur are ever recognized, and it has been said that as few as 1 % of the clinical cases of salmonellosis are reported to the proper authorities.⁶ Todd⁷ calculated that for Canadian and U.S. data, the numbers of reported cases need to be multiplied by a factor of 350 to approach what is likely to be the actual number of cases occurring. There is general agreement that salmonellosis, or salmonella gastroenteritis occurs frequently in small outbreaks as foodborne infections, and that children and the elderly are the most likely targets for this infection. Larger outbreaks are likely to occur in hospitals, other institutions, restaurants, or nursing homes. Hospital outbreaks are likely to last for some considerable period of time since the organisms tend to survive in the environment, and are cross-transmitted by personnel who handle contaminated food, clothing, or instruments.⁶ It has been estimated that there may be 2 to 3 million cases of salmonellosis in the U.S. each year, with only a small proportion of these appearing as a part of the statistics of the disease.

Reporting outbreaks of salmonellosis and other foodborne infections helps keep the public aware of the constant danger of this type of infectious disease. Although the fatality rate from most of these infections is comparatively low, the fact that there are deaths occurring, and that there are consistent increases in numbers of cases reported, continue to remind that these infections are important factors in the total picture of public health and infectious diseases in this country, and indeed worldwide. The incidence and the fatality rates of these infections remain higher in the underdeveloped than in the developed nations of the world. The poor reporting in this country, and the less efficient reporting of such infections in other parts of the world, may lead to a false sense of security in all countries, but we need to be reminded on occasion that these diseases do still exist worldwide, and that the death rates from these infections are higher in other countries than in the U.S. As long as the diseases exist anywhere in the world, they can be transported, and transmitted to persons in any country by populations as mobile as now exist.

Although reporting of infectious disease occurrence in this country is likely to be more accurate than in many others, it is apparent from our history that our reports are not, and never have been accurate. In 1893 an Act of Congress authorized collection of information on the occurrence of infectious diseases from state and municipal offices on a weekly basis. Since that time, a gradual increase has occurred in the number of reports received by the Public Health Service, but not all states began to report regularly until 1925. The Communicable Disease Center was responsible for the reporting of venereal disease in 1957, for tuberculosis in 1960, and, finally, for nationally reported diseases in 1961. Changes in the characteristics and occurrence of diseases over the years have required that the reporting system be frequently modified, and that new diseases be periodically added.

Examination of the economic effects of outbreaks of salmonellosis in the human reveals that this impact may be considerable. A recent report⁸ indicates that in developing countries with economies which are marginal, the impact of foodborne diseases such as salmonellosis may be devastating. Another expert committee⁹ analyzed the different factors which go into calculations of the costs of outbreaks of foodborne diseases. That report concluded that patients must include payment for hospitalization, physician services, nurse services, medications, work time lost, pay lost, microbiological testing, and follow-up costs. The outbreak also incurs expenses for workers compensation, food industry costs to locate the problem and correct it (this may involve lay-off time for workers and rearrangement of work schedules), and all aspects of investigation into the source and nature of the infection spread.

Todd^7,10 has written two excellent summaries of the numbers of cases of infections (including resulting deaths) and the costs of foodborne diseases in the U.S. and Cana...

Table of contents

• Cover
• Title Page
• Copyright Page
• Dedication
• Table of Contents
• Chapter 1 The Salmonella
• Chapter 2 Taxonomy and Grouping of the Salmonella
• Chapter 3 Salmonellosis — The Infection
• Chapter 4 Control of Salmonella Spread
• Chapter 5 Antibiotic Sensitivity of Salmonella
• Chapter 6 Preventing the Contamination of Foods by Salmonella
• Chapter 7 Salmonella enteritidis in Eggs
• Chapter 8 Microbiological Methods for Detection of Salmonella Contamination
• Appendix A Culture Media Used for Salmonella Isolation, Culture, and Identification
• Appendix B Antigenic Schema for Salmonella
• Appendix C Reagents Useful in Microbiological Study
• Glossary
• Index