925 SEROTYPING OF ENTEROPATHOGENIC ESCHERICHIA COLI
Fig. 3- G.F.R. in 3 patients who deteriorated despite combined suppression and anticoagulation.
glomerulonephritis with glomerular deposits, and some (not represented here) have circulating anti-glomerular-basementmembrane antibody and Goodpasture’s syndrome. It is equally clear that the presence of diffuse crescent formation is a reliable marker of poor prognosis in the majority of patients affected in this way, irrespective of the glomerular changes or the presence or absence of systemic vasculitis. It is difficult to believe that the data shown in the figures represent the natural history of patients with rapid decline in renal function and diffuse crescent formation, and they certainly do not correspond to our own findings in 32 patients studied before 1971. Evidence for spontaneous recovery in this group of patients is restricted to occasional anecdotes, and if patients satisfying strict criteria for severe disease of this type have recovered, then they deserve note in the literature.3 We observed recovery of function in only 2 patients before 1971; both were treated with prednisone and an immunosuppressant (azathioprine in 1 and cyclophosphamide in the other); 1 had Henoch-Schönlein purpura and the other post-streptococcal nephritis. Others. have also recorded recovery on immunosuppressive treatment but with greater frequency than has been our experience. Kincaid-SmithS has reported recovery of anuric patients treated with combined immunosuppression and anticoagulation, although we’ did not see this. We remain convinced that some aspect of this treatment has modified the course of the disease in these patients, who are at risk from early and permanent renal failure. An effect of earlier patient referral or a shift in the subgroups of extracapillary glomerulonephritis cannot be excluded in improving results over the past 4 years, but if treatment is to be effective it seems as though it must be started before anuria, at least in the majority of patients. Despite the obvious short-term and longterm risks and inconveniences of the treatment, we continue to use it in these carefully selected patients. Whether it has a role in less serious forms of glomerulonephritis is even more contentious, and a decision must await the results of controlled trials now in progress. J. S. CAMERON D. GILL -
Departments of Medicine, Pædiatrics, and Pathology, Guy’s Hospital, London, SE1 9RT.
D. R. TURNER C. CHANTLER C. S. OGG G. VOSNIDES D. G. WILLIAMS
3 Møller, B. B., Jans, H. Lancet, 1975, i, 231. 4. Jensen, H., Ølgaard, K., Faarup, P. Acta med. scand. 1974, 196, 383. 5 Kincaid-Smith, P. Abstracts, 6th Meeting of the International Society Nephrology, Florence, June, 1975.
SIR,—Enteropathogenic Escherichia coli have an important role in infantile enteritis and travellers’ diarrhoea. As a result of their study of travellers’ diarrhoea. Sack and his colleagues’ support the concept that enteropathogenicityof E. coli is not a function of serotype but may depend on the plasmid-determined ability to produce enterotoxin. There have been suggestions that in the investigation of acute diarrhoea serotyping of E. coli is of little or no help and that to recognise the ability to produce enterotoxin may be all that is required.2 We are concerned that these implications may cause confusion amongst those responsible for the laboratory investigation of infantile enteritis. Infantile enteritis has many similarities to E. coli enteritis in piglets, and in the latter disease it has been shown that strains which produce enterotoxin may not cause diarrhoea when fed to experimental animals.’ In piglet enteritis other factors are important-e.g., the possession of the K88 antigen, which so far has been found in strains of only a few "0" serogroups. Similar factors may be important in infantile enteritis. Enterotoxin production should not be equated with enteropathogenicity ; nor should it be assumed that serotyping is no longer of value in the understanding of the epidemiology of infantile enteritis. For almost thirty years epidemiological studies of infantile enteritis have depended on serotyping E. coli. These studies have shown that a small number of E. coli serogroups have been repeatedly responsible for epidemics throughout the world,4whereas other serogroups have been consistently related to healthy subjects. The recent discovery that the enterotoxin of E. coli may be plasmid-controlled does not detract from the value of these classical observations. The plasmid-mediated transfer of enterotoxigenicity has been achieved in the laboratory, and it has been suggested that the ingestion of a few enterotoxigenic E. coli might lead to the transfer of the plasmid to the resident E. coli in the bowel. The implication here is that any strain of E. coli might acquire the plasmid and produce enterotoxin ; but it seems likely that this transfer does not occur all that frequently in vivo. Strains which cause epidemics may have some special ability to acquire this plasmid and this ability may be related to serotype. So far plasmidcontrolled transfer of enterotoxin production has been demonstrated in only a few strains from human sources and it is possible that in some of the classical infantile enteropathogenic serogroups the enterotoxin may have chromosomal determinants as in Vibrio choleræ.5 Although the concept of serotype-related enteropathogenicity is not perfect it has proved useful in the recognition and control of many outbreaks of infantile enteritis.4 Serotyping of E. coli has not been extensively used in the investigation of travellers’ diarrhoea and we are aware ofonly one field study of travellers’ diarrhoea in which a large number of cases were involved and where the E. coli were serotvped.6 In this study in Arabia an epidemic serogroup (0148.H28) was discovered, and subsequently was’ found in cases of travellers’ diarrhoea in Vietnam’ and in epidemics in Japan.8 Strains of this serogroup from all three areas have been shown to produce an enterotoxin. Further studies of travellers’ diarrhoea may show that, as in infantile enteritis, only a few serogroups are involved, although these serogroups seem to be different from those traditionally associated with epidemics of infantile enteritis. Sack, D. A., Merson, M. H., Wells, J. G., Sack, R. B., Morris, G. K. Lancet, 1975, i, 928. 2. J. Am. med. Ass. 1972, 222, 896. 3. Smith, H. W., Linggood, M. A. J. med Microbiol. 1971, 4, 467. 4. Taylor, J. J. appl. Bact. 1961, 24, 316. 5. Vasil, M. L., Holmes, R. K., Finkelstein, R A. Science, 1975, 187, 849. 6. Rowe, B., Taylor, J., Bettelheim, K. A. Lancet, 1970, i, 1. 7. Du Pont, H. L., Formal, S. B, Hornick, R B., Snyder, M. J., Libonati, J P., Sheahan, D. G., La Brec, E. H., Kalas, J. P. New Engl. J. Med. 1971, 285, 1. 8. Sakazaki, R. Personal communication. 1.
926 There have been many studies of enterotoxin production by E. coli strains from travellers’ diarrhoea although it is unfortunate that in most of the studies the serotypes have been incompletely reported and often completely omitted.9-11 Conversely, enterotoxin tests have been rarely used in studies of enteropathogenic E. coli from epidemics of infantile enteritis. We have used the infant mouse test9 for heat-stable enterotoxin (s.T.) and the Chinese hamster ovary-cell test’2 for heat labile enterotoxin (L.T.), in the study of epidemic strains of E. coli from well-documented outbreaks of infantile enteritis in the British Isles. There is little doubt that these strains were the causative organism of these outbreaks and yet we were unable to show enterotoxin production using either of these tests although control strains consistently behaved correctly. In Western Europe infantile enteritis remains the main problem associated with enteropathogenic E. coli, and at the present time clinical laboratories have no alternative to serotyping in their investigations of outbreaks. We recommend that serotyping of E. coli should continue and suggest that there is a need for extensive evaluation of the relationship between serotype, enterotoxin production, and enteropathogenicity. Conclusions resulting from the study of the travellers’ diarrhcea situation should not be extrapolated without qualification to the infantile-enteritis problem. Salmonella and Shigella Reference Laboratory, Central Public Health Laboratory, Colindale Avenue, London NW9 5HT.
B. ROWE R. J. GROSS SYLVIA M. SCOTLAND
CURABILITY OF BREAST CANCER
SIR,—Dr Brinkley and Dr Haybittle (July 19. p.95) point the limitations involved in defining "cure" in terms of general population mortality, since they found a rather high
death rate due to breast cancer in the cancer group followed for 25 years. They comment: "the probability of dying from cancer of the breast in this [cancer] group is still greater than that [probability] in the normal population, and one would therefore hesitate to say that they are cured." What Brinkley and Haybittle have shown is not so much a problem with defining "cure" in terms of general-population mortality, but rather a lack of knowledge on our part-in this case, about breast cancer. Without fairly extensive knowledge of causal mechanisms and initiating circumstances, there is little to rely on in applying the term "cure", except perhaps general-population mortality. The paradigm kind of cure is probably surgical removal of an offending organ or destruction of bacteria, where the destruction can be confirmed. In these instances, flare-ups can usually be distinguished from new cases, certainly an important factor in applying the term "cured." But cancer of the breast does not yet sit nicely near these paradigmatic cures. Brinkley and Haybittle’s conclusion that "one would hesitate to say they [the breast-cancer group] are cured" might better be expressed as an inability to say which members of the breast-cancer group are cured-in a sense of "cured" independent from general-population mortality. But it does not follow-nor, I realise, did they mean to imply that it didthat sorne members aren’t indeed cured. Hershey Medical Center, Pennsylvania State University, Hershey, Pennsylvania 17033, U.S.A.
Ching, Y.-C., Williams, R. G., Harden, L. B. J. infect. Dis. 1972, 125, 407. 10. Evans, D. G., Evans, D. J., Gorbach, S. L. Infect. Immun. 1973, 8., 731. 11. Gorbach, S. L., Kean, B. H., Evans, D. G., Evans, D. J., Bessudo, D. New Engl.J Med. 1975, 292, 933. 12. Guerrant, R. L., Brunton, L. L., Schnaitman, T. C., Rebhurn, L. I., Gilman, A. G Infect Immun. 1974, 10, 320. 9. Dean, E G.,
SIR,—Dr Richens and Mr Dunlop (Aug. 9, p. 247) propose rational approach to the monitoring of serum total-dilantin concentration based on the application of Michaelis Menten kinetics to the metabolism of dilantin which does not follow first-order kinetics.’-3 The use of their nomogram, which enables one to predict serum total-dilantin concentrations in a patient on various dosages of dilantin, has two major pitfalls for the unwary. Firstly, there is great inter and intra individual variation in both of the factors Vmax and Km (in the authors’ study of the order 100-1000 mg/day and 2.5-25 mg/l respectively). These can vary with age, sex, height, weight;° genetic differences;s duration of dilantin intake;6 competition from the major metabolite of dilantin;7 other drug intake;! and different disease states.s Secondly, while serum-protein-binding may have little effect on the metabolism of dilantin, since its volume of distribution is high,9 it does have a great effect on the serum concentration of free active drug present for a given serum total-dilantin concentration. 10 Protein binding of dilantin is affected by the serum-protein concentration and by the affinity of the protein for dilantin, and there are inter-individual differences for both."Serum-protein concentration can vary in the same individual with posture,12 venous stasis,different disease states, and possibly with age-" and affinity is affected by competition from the major metabolite of dilantin,7 other drugs," disease states,9 15 temperature," and other phy siological constituents (e.g., bilirubin and free fatty acids 16). Patients given a dose of dilantin predicted by the nomogram of Richens and Dunlop, or taking a constant dose of dilantin, could develop widely varying serum total-dilantin concentrations under certain conditions. These problems could be overcome by being aware of the inter and intra individual variation of Km and Vmax, giving small increments of dosage, and monitoring serum total-dilantin concentrations at appropriate intervals. If one could measure serum-free dilantin concentration one could overcome the problem of protein-binding. Although the free concentration can be estimated by ultrafiltration or possibly by a tourniquet test similar to that described for calcium,17 these methods are unfortunately not routinely available. Such measurements would be of great value in those patients in whom the serum-protein concentration or affinity might be significantly abnormal (e.g., in cases of hypoproteinaemia or in patients taking another drug which affects dilantin binding). a
Division of Clinical Chemistry, Institute of Medical and
Veterinary Science, Box 14, Rundle Street Post Office, Adelaide, South Australia.
P. J. PHILLIPS R. W. PAIN B. MCL. DUNCAN
Ashley, J. J., Levy, G. Res. Commun. chem Path. Pharmac. 1972, 4, 297 Gerber, N., Wagner, G. J. ibid. 1972, 3, 455. 3. Bochner, F., Hooper, W. D., Tyrer, J. H., Eadie, M. J. Neurol. Neurosurg Psychiat. 1972, 35, 873. 4. Houghton, G. W., Richens, A., Leighton, M. Br. J clin. Pharmac 1975, 2, 251. 5. Kult, H. Ann. N. Y. Acad. Sci. 1971, 179, 704. 6. Bochner, F., Hooper, W., Tyrer, J., Eadie, M. Proc Aust Ass Neurol 1973, 7.
9, 171. Litteri, J. M., Mellk, H., Louis, S., Kutt, H., Durante, P., Glasko. A New
Engl. J. Med. 1971, 285, 648. Kutt, H. in Antiepileptic Drugs, (edited by D. Woodbury), J K. Penry and R.P. Schmidt); chapt. 12. New York, 1972. 9. Odar Cederlöf, I., Borgå, O. Enr. J. clin. Path. 1974, 7, 31. 10. Hayes, M. J., Langman, M. J. S., Short, A. H. Br. J. clin. Pharmac 1975. 2, 73. 11. Lunde, K. M., Rane, A., Yaffe, S. J., Lund, L., Sjoqvist, F Clin Pharmac Ther. 1970, 11, 849. 12. Statland, B. E., Bokelund, H., Winkel, P. Clin. Chem. 1974, 20, 1513 13. Christiansen, C., Naestoft, J., Hvidberg, E. F., Larsen, N. E, Peterten, B Clinica. chim Acta, 1975, 62, 65. 14. Woodford-Williams, E., Alvarez, A. S., Webster, D., Landless, B., Divon, M P. Gerontologia, 1964, 10, 86. 15 Lund, L., Lunde, P. K., Rane, A., Borgå, O Sjoqvist, F Ann N YAcad Sci. 1971, 179, 723. 16. Fredholm, B. B. Rane, A., Persson, B. Pediat. Res 1975, 9, 26 17. Pain, R. W., Rowland, K. R., Phillips, P. J., Duncan, B McL Br med J (in the press). 8.