Douglas L. Archer

Incidence and cost of foodborne diarrheal disease in the United States

An estimated 68.7 to 275 million cases of diarrheal disease episodes from all causes occur annually in the United States, representing an average of 0.29 to 1.1 cases per person per year. The total number of cases of foodborne origin and subsequent person-to-person transfer was estimated to be at least 24 million and perhaps as many as 81 million or more cases per year. Updating previously published patient cost estimates, including lost wages as well as direct medical costs, the average estimate-based value for food-associated illness is in the billions of dollars per year. Scientifically established chronic sequellae to diarrheal disease further increase the total economic burden but cannot be estimated from available data. Other associated clinical problems that are likely to be related to acute diarrheal episodes would further increase costs.

Preservation microbiology and safety: Evidence that stress enhances virulence and triggers adaptive mutations

Abstract Bacteria present in food systems are frequently subjected to stresses that are purposefully placed in the food systems as barriers to their growth. Studies using modern genetic tools are pointing to the fact that while such barriers play a vital role in preventing the outgrowth of pathogenic bacteria, in certain cases, the virulence of the stressed pathogens may increase. In short, the bacteriums environment may ‘arm’ that bacterium to survive similar stresses encountered in the human host. In this Viewpoint article, I wish to focus on the ability of environmental stress to modulate bacterial virulence, and also to act as a potential driving force promoting adaptive mutations that may serve to select strains that are even more virulent.

Freezing: an underutilized food safety technology?

Freezing is an ancient technology for preserving foods. Freezing halts the activities of spoilage microorganisms in and on foods and can preserve some microorganisms for long periods of time. Frozen foods have an excellent overall safety record. The few outbreaks of food-borne illness associated with frozen foods indicate that some, but not all human pathogens are killed by commercial freezing processes. Freezing kills microorganisms by physical and chemical effects and possibly through induced genetic changes. Research is needed to better understand the physical and chemical interactions of various food matrices with the microbial cell during freezing and holding at frozen temperatures. The literature suggests that many pathogenic microorganisms may be sublethally injured by freezing, so research should be done to determine how to prevent injured cells from resuscitating and becoming infectious. Studies on the genetics of microbial stress suggest that the induction of resistance to specific stresses may be counteracted by, for example, simple chemicals. Research is needed to better understand how resistance to the lethal effect of freezing is induced in human pathogens and means by which it can be counteracted in specific foods. Through research, it seems possible that freezing may in the future be used to reliably reduce populations of food-borne pathogens as well as to preserve foods.

Evidence that Ingested Nitrate and Nitrite Are Beneficial to Health

The literature was reviewed to determine whether ingested nitrate or nitrite may be detrimental or beneficial to human health. Nitrate is ingested when vegetables are consumed. Nitrite, nitrates metabolite, has a long history of use as a food additive, particularly in cured meat products. Nitrite has been a valuable antibotulinal agent in cured meats and may offer some protection from other pathogens in these products as well. Nitrites use in food has been clouded by suspicions that nitrite could react with amines in the gastric acid and form carcinogenic nitrosamines, leading to various cancers. Nitrates safety has also been questioned, particularly with regard to several cancers. Recently, and for related reasons, nitrite became a suspected developmental toxicant. A substantial body of epidemiological evidence and evidence from chronic feeding studies conducted by the National Toxicology Program refute the suspicions of detrimental effects. Recent studies demonstrate that nitrite, upon its ingestion and mixture with gastric acid, is a potent bacteriostatic and/or bactericidal agent and that ingested nitrate is responsible for much of the ingested nitrite. Acidified nitrite has been shown to be bactericidal for gastrointestinal, oral, and skin pathogenic bacteria. Although these are in vitro studies, the possibility is raised that nitrite, in synergy with acid in the stomach, mouth, or skin, may be an element of innate immunity.

Diarrheal Episodes and Diarrheal Disease: Acute Disease with Chronic Implications

Diarrheal episodes and diarrheal disease are often considered to be acute events of limited duration; a review of current literature indicates that this is not true. Diarrheal episodes caused by many bacteria, viruses, protozoans and other parasites cause alteration of intestinal structure and function. Consequences of such diarrhea-associated gut alterations include loss of normal defense mechanisms against secondary opportunistic pathogens and the ability to exclude macromolecules from systemic circulation. Additionally, loss of endogenous nutrients and malabsorption of essential nutrients result from diarrheal episodes; the consequences of such losses, even of a single essential nutrient, is compromised immune function, which predisposes to further infection. The net result of such events in some persons is long-term debilitating disease(s) such as allergy, autoimmune disorders and neoplasia.

Enteric Microorganisms in Rheumatoid Diseases: Causative Agents and Possible Mechanisms

The role of foodborne enteric pathogens in the development of three seronegative spondarthropathies (ankylosing spondylitis, Reiters disease and reactive arthritis) is discussed. Although the prevalence of the HLA-B27 antigen in blood-related individuals suggests a genetic predisposition to these diseases, exogenous environmental factors are also indicated. A clinical profile is given to clarify certain relationships of the seronegative arthropathies. Evidence of the involvement of enteric pathogens in the onset of these conditions following gastrointestinal illness is considered along with the interactions of general and molecular mechanisms of the disease processes and the immune response.

Foodborne Gram-Negative Bacteria and Atherosclerosis: Is There a Connection?

There is some evidence that endotoxin-containing bacteria may contribute to atherogenesis. The degree to which bacterial insults contribute to the total body burden of atherosclerotic lesions cannot be determined at this time. It is important to realize that there are other potential sources of injury to the vascular endothelium, mechanical, chemical, immunologic and biological, which may initiate formation of an atherosclerotic plaque. It must also be remembered that the process of atherogenesis is extremely complex and involves many factors other than the initial injury to endothelium. The suggested role for endotoxin, particularly endotoxin from degrading bacteria in macrophages, in concert with the inflammatory factors induced by endotoxin from endothelium and vascular smooth muscle cells, is an attractive hypothesis for several reasons. First, dampening of inflammatory responses by effects of N-3 polyunsaturated fatty acids (omega-3s) is explained, particularly their direct influence on monocyte functions. Second, the hypothesis provides a model system in which the first step in atherogenesis may be studied prospectively, while other factors may be varied to determine their influences on later stages in the process of plaque formation. Recombinant DNA techniques and sophisticated immunologic tools are available to study the entire process, as are animal models in which to conduct studies with relevance to the human. Although at present, the link between foodborne gram-negative bacterial pathogens and atherosclerosis is largely unproven, the possible role of such organisms warrants more research. Additionally, should the link be firmly established, it would further underscore the importance of food safety in the biological sense.

Identification and Characterization of Cefotaxime Resistant Bacteria in Beef Cattle

Third-generation cephalosporins are an important class of antibiotics that are widely used in treatment of serious Gram-negative bacterial infections. In this study, we report the isolation of bacteria resistant to the third-generation cephalosporin cefotaxime from cattle with no previous cefotaxime antibiotic exposure. The prevalence of cefotaxime-resistant bacteria was examined by a combination of culture based and molecular typing methods in beef cattle (n = 1341) from 8 herds located in North Central Florida. The overall prevalence of cefotaxime-resistant bacteria was 15.8% (95% CI: 13.9, 17.8), varied between farms, and ranged from 5.2% to 100%. A subset of isolates (n = 23) was further characterized for the cefotaxime minimum inhibitory concentration (MIC) and antibiotic susceptibility against 10 different antibiotics, sequencing of nine β- lactamase genes, and species identification by 16S rRNA sequencing. Most of the bacterial isolates were resistant to cefotaxime (concentrations, > 64 μg/mL) and showed high levels of multi-drug resistance. Full length 16S rRNA sequences (~1300 bp) revealed that most of the isolates were not primary human or animal pathogens; rather were more typical of commensal, soil, or other environmental origin. Six extended spectrum β-lactamase (ESBL) genes identical to those in clinical human isolates were identified. Our study highlights the potential for carriage of cefotaxime resistance (including “human” ESBL genes) by the bacterial flora of food animals with no history of cefotaxime antibiotic exposure. A better understanding of the origin and transmission of resistance genes in these pre-harvest settings will be critical to development of strategies to prevent the spread of antimicrobial resistant microorganisms to hospitals and communities.