Journal

of Hospital

Infection

(1992) 21, 163-167

LEADING

Conventional

ARTICLE

screening

Escherichia

for

enteropathogenic Is it appropriate

coli in the UK.

or

necessary? K. J. Morris

Department

of Microbiology, North

and

G. Gopal

Rao

North Tyneside General Hospital, Shields NE29 8NH, UK

Accepted fey publication

13 April

Rake Lane,

1992

Summarv: Entcropathogenic Escherichia coli (EPEC) is a well-recognized cause of infantile d:arrhoea in the developing countries. In the developed countries. however. the incidence of EPEC associated outbreaks has dramatically declined. The’last major outbreak in the UK was reported in 1980. This paper reviews the recent advances in the field of pathogenesis of diarrhoea caused by EPEC and questions the need to screen routinely for EPEC by conventional serological methods used in clinical microbiology laboratories in the UK. Keywords: screening.

Enteropathogenic;

Escherichia

coli;

epidemiology;

pathogenesis;

Introduction

Enteropathogenic Escherichia coli (EPEC) has been responsible for many serious outbreaks of infantile diarrhoea throughout the world.‘m7 While continuing to be a major cause of diarrhoeal disease in the developing world, in the past decade there has been a dramatic decline in the incidence of outbreaks of EPEC-associated diarrhoea in the developed world. The last outbreak of this infection in the UK was reported in 1980.’ In this paper we briefly review the recent advances in the field of pathogenesis of diarrhoea caused by EPEC, discuss the implications of changing epidemiology and the advances in the understanding of pathogenesis on the detection of these infections in clinical microbiology laboratories in the UK. Changing

epidemiology

of EPEC in the UK

Outbreaks of childhood diarrhoea with high mortality rates were reported in London as long ago as the 17th century. Descriptions of these outbreaks Correspondence

to: Dr G. Gopal Rae.

0195-6701/92/070163

+OS

503.00/O

CC 1992

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The

Hospital

Infection

Society

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K. J. Morris

and

G. Gopal

Rao

record the fact that they were most common in the summer months and that the diarrhoea occurred during the first 2 years of life, often at the age of weaning.’ During the 1930s and ’40s many outbreaks of infantile diarrhoea occurred predominantly in childrens’ wards and hospital and community nurseries both in Europe and the USA.‘,2,8 In the early 1940s Bray and Beaven concluded that certain strains of E. coli (later named enteropathogenic E. coli by Neter in 1950) were responsible for these outbreaks of diarrhoea.3,6 Further studies in various parts of the world incriminated a series of different strains of E. coZi.8 Using Kauffman’s serogrouping scheme, at least 17 serogroups of E. cob were recognized to be capable of causing infantile diarrhoea.3 The outbreaks of EPEC-associated diarrhoea continued to occur in hospitals in the UK and in Europe in the 1950s and ’60s and in the early 1970~.~ For reasons not entirely clear, however, these outbreaks have become increasingly uncommon, with the last outbreak of infantile diarrhoea in the UK reported in 1980.’ Many theories have been put forward to explain this decline, such as better hygiene, hospital control of infection programmes and general awareness.3’4 In a recent review, Cooke commented on the decreasing importance of EPEC in the UK; about 1300 faecal isolates in children under 3 years old were reported in England and Wales.’ This may not, however, reflect the true incidence of the infection for two reasons. Firstly, many laboratories have discontinued detecting EPEC in sporadic cases and secondly, the serogrouping tests which are almost universally used by those laboratories that continue to detect the organism, grossly overestimate the number of truly pathogenic organisms. Pathogenesis

of EPEC-associated

diarrhoea

The pathogenic mechanisms involved in EPEC-induced diarrhoea have only been unravelled in recent years. It has been suggested that intestinal adhesion and subsequent colonization are the key initial steps by which pathogenic E. coli establishes infection within the gut and induces diarrhoea.” The adhesins of EPEC are distinct from those of enterotoxigenic E. coli (ETEC) in that EPEC adhesins are not of fimbrial and they adhere specifically to tissue culture cell lines such as origin” HEp-2 and HeLa cells. l2 This ability has been linked to the possession of a plasmid encoding the EPEC adherence factor or EAF.13 EPEC adherence to human intestines is a two-stage mechanism, firstly the initial attachment of the bacteria to the mucosa, promoted by these plasmid-encoded adhesins and, secondly, the effacing of microvilli and intimate EPEC attachment which may occur in the absence of the first stage.14 It has been proposed that the intimate attachment of EPEC to the intestinal mucosa could disturb the function of the microvillous border and bring about diarrhoea.” When

Screening

for E. coli.

Appropriate

or necessary?

165

EPEC adhere to intestinal mucosae they produce a characteristic ‘attaching and effacing’ (AE) lesion in the brush border. l6 The lesion is characterized by destruction of the microvilli and intimate attachment of bacteria to cup-like projections of the apical enterocyte membrane, with which dense condensations of microfilaments are associated.‘4t’7 Early studies of the toxic activities of EPEC showed that the strains cause accumulation of fluid in the rabbit ligated ileal loop test.* Further studies, using a perfused rat jejunum assay, showed some strains of EPEC were able to elaborate a potent heat-labile (LT) and a heat-stable (ST) enterotoxin causing fluid secretion distinct from the LT and ST of enterotoxigenic E. coli.” Other studies have shown that EPEC elaborate a toxin similar to the cytotoxin of Shigella dysenteriae serotype 1 .19 Thus, the virulence of EPEC strains is multifactorial and a great deal has yet to be learnt.20 Detection

of EPEC in faeces

In many laboratories in the UK it is conventional to screen for EPEC in the stools of children under 3 years of age with diarrhoea. This consists of preliminary slide agglutination tests followed by confirmatory tube agglutination tests using pooled and individual antisera against a limited range of the commoner EPEC serotypes. All positive isolates are then biochemically identified. These tests do not necessarily identify pathogenic isolates while overestimating the incidence of EPEC. A new diagnostic test, the FAS test (Filamentous Actin Stain) based on fluorescent microscopical identification of the ‘attaching and effacing’ lesion produced in tissue culture cells infected with EPEC has been proposed.*’ However, the FAS test does not differentiate between AE (attaching and effacing) EPEC strains and AE verotoxigenic E. coli strains. Thus, FAS testing in combination with verstoxin testing has been proposed as a more accurate method for detecting EPEC than ‘0’ serogrouping.22 Other methods for identifying EPEC include the use of DNA probes to detect the presence of EAF (effacing and attaching factor), but a possible disadvantage of these is that they may detect strains that have the required gene sequence, but which do not express the property.23 To confuse the situation further, it has been reported that many serogroups of EPEC may not possess EAF but could still cause diarrhoeal symptoms.22 The

need

to screen

for EPEC

The serogrouping methods used currently are time consuming, expensive and fail to detect the EPEC strains accurately. The FAS test, whilst being more accurate, requires tissue culture facilities to which many diagnostic laboratories do not have access and DNA probes are not available for routine use. In our laboratory approximately 1600 specimens have been screened for

166

K. J. Morris

and G. Gopal Rao

EPEC in the past 7 years of which only 30 have been positive. If, as overestimates the incidence of suggested by Knutton et a1.,23 serogrouping EPEC by a factor of 7, then approximately four cases of true EPEC infection were identified in the 7 years and none of these resulted in outbreaks (unpublished observations). In the light of our experience and the dramatic decline of the incidence of EPEC-associated outbreaks nationally, we propose that screening for EPEC need not be performed routinely in diagnostic laboratories. In the event of an outbreak of diarrhoea, specimens could be referred to laboratories with tissue culture facilities where the EPEC could be identified more accurately using the FAS test. However, in developing countries where EPEC is a major cause of infantile diarrhoea, screening routinely for EPEC is both necessary and appropriate. 23-29There is still a need, however, to use tests that will detect EPEC accurately and further research directed to developing convenient and reliable tests for routine use is needed. The authors would like to thank Dr U. Wariyar, Consultant Mrs C. Chicken for secretarial assistance in the preparation

Paediatrician, for his advice and of the manuscript.

References on enteropathogenic Escherichia coli. 1. Edelman R, Levine MM. Summary of a workshop r Infect Dis 1983; 147: 11081118. 2. Gross RJ. Escherichia coli diarrhoea. J Infect 1983; 7: 177-192. R. Enteropathogenic Escherichia coli of classic serotypes MM, Edelman 3. Levine associated with infant diarrhea: epidemiology and pathogenesis. Epidem Rev 1984; 6: 31-51. coli 0142.H6; a drug-resistant RJ, Rowe B, Threlfall EJ. E SCh erichia 4. Gross enteropathogenic clone? J Hyg Camb 1985; 94: 181-191. M, Rahman KM. Enteropathogenic Escherichia coli diarrhea in 5. Moyenuddin hospitalized children in Bangladesh. r Clin Microbial 1985; 22: 838-840. MM. Escherichia coli that cause diarrhea: enterotoxigenic. enteropathogenic. 6. Levine enteroinvasive, enterohemorrhagic and enter0adherent.J InfectDis i987; 155: 377-389: RM. Traditional enterouathoeenic Escherichia coli of infantile diarrhea. 7. Robins-Browne I I Rev Infect Dis 1987; 9: 28-53. E. coli of classic serotypes associated with 8. Levine MM, Edelman R. Enteropathogenic infant diarrhea: epidemiology and pathogenesis. Epidemiol Rev 1984; 6: 3 1-51. of foodborne illness. Lancet 1990; 336: 790-793. 9. Cooke EM. Epidemiology JP, Old DC. Adhesive properties of Enterobacteriaceae. In Beachey EH, Ed. 10. Duguid Bacterial adherence. Receptors and Recognition, Series B, VoZ. 6 London: Chapman and Hall Ltd 1980; 185-217. 11. Scotland SM, Richmond JE, Rowe B. Adhesion of enteropathogenic strains of Escherichia coli (EPEC) to HEp-2 cells is not dependent on the presence of fimbriae. FEMS Microbial Lett 1983; 20: 191-195. A, Gross RJ, Scotland SM, Rowe B. An adhesive factor found in strains of 12. Cravioto Escherichia coli belonging to the traditional infantile enteropathogenic serotypes. Curr Microbial 1979; 3: 95-99. 13. Levine MM, Nataro JP, Karch H et al. The diarrhea1 response of humans to some classic serotypes of enteropathogenic Escherichia coli is dependent on plasmid encoding an enteroadhesiveness factor. J Infect Dis 1985; 152: 550-559. S, Lloyd DR, McNeish AS. Adhesion of enteropathogenic Escherichia coli to 14. Knutton human intestinal enterocytes and cultured human intestinal mucosa. Infect Immunol 1987; 55: 69-77.

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or necessary?

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15. Moon HW, Whipp SC, Argenzio RA, Levine MM, Gianella RA. Attaching and effacing activities of rabbits and human enteropathogenic Escherichia coli in pig and rabbitintestines. Infect Immunol 1983; 41: 1340-1351. 16. Knutton S, Baldwin T, Williams PH, McNeish AS. New diagnostic test for enteropathogenic Escherichia colk. Lancet 1988; 1: 1337. 17. Ulshen MH, Rollo JL. Pathogenesis of Escherichia coli gastroenteritis in man-another mechanism. N Engl J Med 1980; 302: 99-l 01. 18. Klipstein FA, Rowe B, Engert RF, Short HB, Gross RJ. Enterotoxigenicity of enteropathogenic serotypes of Escherichia coli isolated from infants with epidemic diarrhea. Inf Immunol 1978; 21: 171-178. 19. O’Brien AD, LaVeck GD, Thompson MR, Formal SB. Production of Shigella dysenteriae type-l like cytotoxin by Escherichia coli. J Infect Dis 1982; 146: 763-769. 20. Law D. Virulence factors of enteropathogenic Escherichia coli. J Med Microbial 1988; 26: l-10. 21. Knutton S, Baldwin T, Williams PH, McNeish AS. Actin accumulation at sites of bacterial adhesion to tissue culture cells; the basis of a new diagnostic test for enteropathogenic and enterohemorrhagic Escherichia coli. Infect Immunol 1989; 57, 1290-1298. 22. Smith HR, Scotland SM, Stokes N, Rowe B. Examination of strains belonging to enteropathogenic Escherichia coli serogroups for genes encoding EPEC adherence factor and vero cytotoxins. J Med Microbial 1990; 31: 235-240. 23. Knutton S, Shaw R, McNeish AS, Philips A, Price E, Watson P. Diagnosis of enteropathogenic Escherichia cola’. Lancet 1989; 2: 218. 24. Cravioto A, Reyes R, Ortega G, Fernandez G, Hernandez R, Lopez G. Prospective study of diarrboeal disease in a cohort of rural Mexican children: incidence and isolated pathogens during the first two years of life. Epidemiol Infect 1988; 101: 123-134. 25. McConnell MM, Chart H, Scotland SM, Smith HR, Willshaw GA, Rowe B. Properties of adherence factor plasmids of enteropathogenic Escherichia co/i and the effect of host strain on expression of adherence to HEp-2 cells. r Gen Micvobioll989; 135: 1123-I 134. 26. Nataro JP, Kaper JB, Robins-Browne R, Prado V, Vial P, Levine M. Patterns of adherence of diarrheagenic Escherichia coli to HEp-2 cells. Pediatr Infect Dis J 1987; 6: 829-83 1. 27. Toledo MRF, Carmo M, Alvariza B, Murahovischi J, Ramos SRTS, Trabulsi LR. Enteropathogenic Escherichia coli serotypes and endemic diarrhea in infants. Infect Immunol 1983; 39: 586-589. 28. Da Silva MLM, Mortara RA, Barros HC, De Souza W, Trabulsi LR. Aggregation of membrane-associated actin filaments following localized adherence of enteropathogenic Escherichia coli to HeLa cells. J Cell Sci 1989; 93: 439446. 29. Mechanisms in enteropathogenic Escherichia coli diarrhoea. Lancet 1983; 1: 125+1253.

Conventional screening for enteropathogenic Escherichia coli in the UK. Is it appropriate or necessary?

Enteropathogenic Escherichia coli (EPEC) is a well-recognized cause of infantile diarrhoea in the developing countries. In the developed countries, ho...
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