Correspondence

Escherichia coli O157:H7

N Engl J Med 1995; 333:1711-1712December 21, 1995

Article

To the Editor:

There is a growing need for an honest analysis of what we do and do not know about emerging infections such as enterohemorrhagic Escherichia coli and for cost-effective incentives to produce a safe food supply. Despite impressive progress in some areas (such as reductions in salmonella and listeria infections since the late 1980s1,2), the report by Boyce et al. on enterohemorrhagic E. coli infections (Aug. 10 issue),3 which are estimated to account for over 20,000 infections and 250 deaths each year in the United States, raises the question of how best to prevent the potentially serious threat to health posed by contaminated food (especially meat).

At a recent conference sponsored by the U.S. Department of Agriculture (USDA) (“An Evaluation of the Role of Microbiological Criteria in Establishing Food Safety Performance Standards in Meat and Poultry Products”), the consensus emerged that although salmonella may be the best marker organism for contamination of poultry, E. coli is a better indicator of contamination of meats other than poultry. The organism is readily quantifiable, best reflects fecal contamination (at present), and is probably better than specific pathogens such as E. coli O157 that are more difficult to test for and present in much smaller numbers and that testing for may cause other important enteric pathogens to be missed. Despite the frequent presence of moderate numbers of E. coli in contaminated food, however, the information currently available simply does not permit definitive standards.

Perhaps the best solution, when one does not have all the answers, is simple honesty. Instead of pretending to know how many of which organism represents a threat, perhaps we could provide information about the “microbiologic quality” of a product (from either current or recent lots), just as the food industry provides exhaustive data on the numbers of calories and grams of fat, cholesterol, sodium, vitamins, and so forth. In product information collected by the USDA, this information could be expressed as a USDA microbiologic-quality grade based on the mean E. coli counts. The industry could then advertise Grade A as being within 1 SD of the USDA mean, Grade AA as more than 1 SD below the USDA mean, and Grade AAA as more than 2 SD (or z scores) below the USDA mean for the previous year. Grades B, C, and D could be assigned for z scores above the mean.

Such a grading system would provide incentives for companies with products of the highest microbiologic quality to use this information in marketing the products, with the recognition that at present we do not know the absolute quantities of organisms that should be allowed. In addition, this grading system would allow consumers to make informed choices when buying food. This approach might also allow us to learn about levels of microbiologic quality that are readily achievable and levels at which health risks arise. Such an approach may be acceptable to parties with opposing political viewpoints and may actually help provide a safer food supply.

Richard L. Guerrant, M.D.
University of Virginia School of Medicine, Charlottesville, VA 22908

David M. Theno, Ph.D.
Jack-in-the-Box Restaurants, San Diego, CA 92123

3 References

1
National Salmonella surveillance summary, 1994. Atlanta: Centers for Disease Control and Prevention, 1994.

2
Tappero JW, Schuchat A, Deaver KA, Mascola L, Wenger JD. Reduction in the incidence of human listeriosis in the United States: effectiveness of preventive efforts? JAMA 1995;273:1118-1122
CrossRef | Web of Science | Medline

3
Boyce TG, Swerdlow DL, Griffin PM. Escherichia coli O157:H7 and the hemolytic-uremic syndrome. N Engl J Med 1995;333:364-368
Full Text | Web of Science | Medline

To the Editor:

Boyce and colleagues provide a comprehensive review of E. coli O157:H7 and the hemolytic–uremic syndrome in North America. In England and Wales, E. coli O157:H7 is also an emerging problem, with laboratory isolations having risen from 6 (0.01 per 100,000 residents) in 1983 to 411 (0.8 per 100,000 residents) in 1994.

Between 1992 and 1994, 1266 laboratory isolations were reported, the majority of cases being sporadic. During this period, 159 persons were infected in 18 outbreaks; 40 percent of those infected persons were admitted to the hospital, 18 percent had the hemolytic–uremic syndrome, and 2.5 percent died — all much higher percentages than those reported by Boyce et al. for the United States. Of the 18 outbreaks, 9 were transmitted through the consumption of contaminated food, 4 through both the consumption of contaminated food and person-to-person contact, 2 through contact with cattle, 1 through person-to-person contact, and 2 by unknown routes.

E. coli O157 is the most common verocytotoxin-producing E. coli in England and Wales.1 Many laboratories test fecal specimens for E. coli O157 only if the patient has bloody diarrhea, but about half the patients who are infected do not have blood in their stools.2 A government working group has recently issued recommendations for the surveillance of infections in humans and farm animals, improvement of subtyping methods, evaluation of procedures for testing food and environmental samples, and implementation of a monitoring system (Hazard Analysis and Critical Control Points) for the storage, handling, and heat treatment of raw foodstuffs.1

E. coli O157 infection has become an important public health problem in recent years. The organism can cause serious morbidity and mortality among those affected, particularly children, with long-term residual impairment in renal function reported in a substantial proportion of childhood survivors of the hemolytic–uremic syndrome.3 The introduction of effective prevention and control measures is essential.

Michael J. Ryan, M.B., M.P.H.
Patrick G. Wall, M.B., M.V.B.
Thomas Cheasty, B.Sc.
Public Health Laboratory Service Board, London NW9 5DF, United Kingdom

3 References

1
A Working Group of the Advisory Committee on the Microbiological Safety of Food. Report on Vero cytotoxin producing Escherichia coli. London: Her Majesty's Stationery Office, 1995.

2
5Vero cytotoxin producing Escherichia coli: which specimens should be tested? Commun Dis Rep CDR Wkly 1995;5:147-147
Medline

3
Fitzpatrick MM, Shah V, Trompeter RS, Dillon MJ, Barratt TM. Long term renal outcome of childhood haemolytic uraemic syndrome. BMJ 1991;303:489-492
CrossRef | Web of Science | Medline

Author/Editor Response

The authors reply:

To the Editor: Ryan and colleagues report an increase in the rate of laboratory isolation of E. coli O157:H7 in England and Wales from 1983 to 1994, which may reflect a true increase in the incidence of E. coli O157:H7 infections, as well as greater awareness on the part of physicians and more thorough laboratory screening and reporting. The rates given for hospitalization, death, and development of the hemolytic–uremic syndrome among 159 persons affected in 18 outbreaks in England and Wales are all higher than the rates reported among 1557 persons affected in 19 outbreaks in the United States.1,2 Differences in case definitions and in the thoroughness of case finding may make these rates difficult to compare. For example, if the case definition included a culture-confirmed infection or if case finding focused on patients with bloody diarrhea, only severe cases would be likely to be detected, which would result in higher rates of hospitalization, death, and development of the hemolytic–uremic syndrome.

Ryan and colleagues note that a government working group in England and Wales has made specific recommendations concerning surveillance of E. coli O157:H7 infections. Recently, a consensus panel on E. coli O157:H7 infections in the United States issued a similar statement,3 including the recommendation that all diarrheal stools submitted for the examination of bacterial enteric pathogens also be cultured for E. coli O157:H7.

Drs. Guerrant and Theno's suggestion that meat be graded for microbiologic quality is intriguing and might allow market forces to improve the processing of meat in order to decrease contamination levels. Performance-based grading,4 a similar approach that has been proposed, would rate processing plants on the basis of compliance with industry standards for processing, as well as past and current microbiologic testing for products. The USDA recently proposed a regulation that would modify the current system of meat and poultry inspection, which is based on physical inspection, supplementing it with the science-based monitoring system called Hazard Analysis and Critical Control Points, which would include microbiologic testing at critical steps during processing. Implementation of such a system would be an important step toward improving the safety of meat in the United States. Decreasing the number of infections due to E. coli O157:H7 and other foodborne pathogens will require safer methods of production, slaughter, processing, storage, and distribution of meat to reduce contamination, as well as education about the need to cook ground beef thoroughly.

Thomas G. Boyce, M.D.
David L. Swerdlow, M.D.
Patricia M. Griffin, M.D.
Centers for Disease Control and Prevention, Atlanta, GA 30333

4 References

1
Boyce TG, Swerdlow DL, Griffin PM. Escherichia coli O157:H7 and the hemolytic-uremic syndrome. N Engl J Med 1995;333:364-368
Full Text | Web of Science | Medline

2
Griffin PM. Escherichia coli O157:H7 and other enterohemorrhagic Escherichia coli. In: Blaser MJ, Smith PD, Ravdin JI, Greenberg HB, Guerrant RL, eds. Infections of the gastrointestinal tract. New York: Raven Press, 1995:739-61.

3
Brotman M, Giannella RA, Alm PF, et al. Consensus conference statement: Escherichia coli O157:H7 infections -- an emerging national health crisis, July 11-13, 1994. Gastroenterology 1995;108:1923-1934
CrossRef | Web of Science | Medline