1205

pale and cold hands with sweating and mild tremor probably due to peripheral vasoconstriction (without alteration in blood-pressure). This started 15-20 min after the injection of insulin and lasted for about 20 min. In 2 patients who developed frank hypoglycaemia, peripheral vasoconstriction and sweating continued for more than 2 h. Hence CBF and blood-pressure were maintained despite concomitant alterations in peripheral vascular tone. Our observations agree with those of Kety et al. who .showed that CBF in hypoglycaemic patients remained unchanged in spite of a significant fall in oxygen consumption associated with a low blood-glucose concentration. The fact that intravenous insulin induces hypotension and syncope in diabetic patients with autonomic neuropathy2.3 and the fact that it reduces the vasoconstrictive response of the isolated rat tail vein to noradrenaline in vitro9 suggest a direct non-neuronal effect of insulin on the cardiovascular system, particularly the blood vessels. Intravenous injections of insulin in patients with autonomic neuropathy can also induce faint without a significant fall in blood-pressure, which suggests that insulin may reduce CBF independently of its other cardiovascular effects. The absence of this effect of insulin on our patients is thus probably due to intact neuralreflex mechanisms which prevent a fall in CBF. Therefore it seems that the variability in basal CBF and the altered reactivity of CBF to CO2 depend on undefined metabolic factors that alter the sensitivity of CO2 receptors in cerebral vasculature. There may also be a change in local vascular mechanisms involving the balance between the secretions of thromboxane, a vasoconstrictor of platelet origin, and prostacyclin, a vasodilator of endothelial origin. A recent study suggests that the veins in diabetic patients produce less prostaI cyclin than those in the controls. 11 Whatever the mechanism underlying the instability of CBF in insulin-dependent diabetics, the clinical relevance of this phenomenon is clear. Firstly, sudden falls in CBF would make diabetic patients with marginal cerebral-blood perfusion more vulnerable to cerebral anoxia and would compound the effect of a negative response to CO2 as described before.’ Secondly, unexpected falls in CBF would cause the symptom of an impending faint, so often mistaken for hypoglycwmia by both the patient and the clinician. This emphasises the need to make glucose measurements in insulin-dependent diabetic patients with hypoglycoemia before glucose is administered or long-term insulin therapy is altered. This applies especially to patients with atypical hypoglycxmic sensations that are not associated with sweating, for in our experience it is often these episodes that are not due to true

hypoglycaemia.

Requests for reprints should be addressed

to

P.D.

REFERENCES 1. Dandona

P, James IM, Newbury PA, Woollard ML, Beckett AG. Cerebral

blood flow in diabetes mellitus: evidence of abnormal cerebrovascular

reactivity. Br Med J 1978; ii: 325-26. 2. Miles DW, Hayter CJ. The effect of intravenous insulin on the circulatory responses to tilting in normal and diabetic subjects with specific reference to baroreceptor reflex block and atypical hypoglycæmic reactions. Clin Sci 3.

1968; 34: 413-30. Watkins PJ. Provocation of postural hypotension by insulin. Diabetes 1975; 25: 90-95.

Page M,

EMERGENCE OF

TRIMETHOPRIM-RESISTANT ENTEROBACTERIA IN PATIENTS RECEIVING LONG-TERM CO-TRIMOXAZOLE FOR THE CONTROL OF INTRACTABLE URINARY-TRACT INFECTION K. J. TOWNER N. J. PEARSON ANNE M. MCSHERRY W. R. CATTELL F. O’GRADY

Department of Microbiology, University of Nottingham, and Department of Nephrology, St. Bartholomew’s Hospital, London EC1

patients with previously intractable urinary-tract infection treated with lowco-trimoxazole for 6-58 (mean 32·7) months, the

Summary dose

In

percentage of infected urines fell from 41·4 before

treat-

6·3 during treatment. Only 6 episodes of infection were due to trimethoprim-resistant bacteria. Results in a small group of patients in whom treatment was continued with trimethoprim alone were similar. Under the conditions of this study, long-term control of urinarytract infection was not materially compromised by breakthrough infections due to trimethoprim-resistant ment to

organisms. Introduction TEN years ago we first reported our successful use of long-term low-dose co-trimoxazole for the control of intractable urinary-tract infection. The safety and efficacy of such a regimen has been widely accepted both in adults2 and in children3 but long-term therapy is always threatened by the possible emergence of bacterial resistance.

Bacterial resistance to co-trimoxazole is of particular interest for two reasons: the complexity of resistance to the trimethoprim component and the interaction between resistance to each component, trimethoprim and sulphamethoxazole. It has generally been assumed that the presence of sulphonamide in the commercially available mixture significantly controls the emergence of trimethoprim resistance, but the prevalence of sulphonamide-resistant enterobacteria and the possibility of plasmid transfer of resistance to both components makes it

Lennox GA, Rowan JO. Two minute slope inhalation technique for cerebral blood flow measurement in man. J Neurol, Neurosurg Psychiat 1976; 39: 145-46. 5. Mallett BL, Veall N. The measurement of regional cerebral clearance rates in man using 133Xe inhalation and extracranial recording. Clin Sci 1965; 29: 179-91. 6. Obrist WD, Thompson HK, King CH, Wang HS. Determination of regional cerebral blood flow by inhalation of 133Xe. CircRes 1967; 20: 124-35. 7. Paulson OB, Cronquist S, Risberg J. Regional cerebral blood flow: a comparison of 8-detector and 16-detector instrumentation J Nucl Med 1969; 10: 164-73. 8. Kety SS, Woodford RB, Harmel MH, Freyhan FA, Appel KE, Schmidt CF. Cerebral blood flow in schizophrenia. The effect of barbiturate semi-narcosis, insulin coma and electroshock. Am J Psychiat 1948; 104: 765-69. 9. Alexander WD, Oake RJ. E ffect of insulin on vascular reactivity to norepinephrine. Diabetes 1977; 26: 611-14. 10. Gunderson HJ, Christiansen NJ. Intravenous insulin causing loss of intravascular water and albumin and increased adrenergic nervous activity in diabetes. Diabetes 1977; 26: 551-57. 11. Silberbauer KF, Schernthaner G, Sinzinger H, Piza-Katzer H, Winter M. Decreased vascular prostacyclin in juvenile-onset diabetes. New Engl J Med 1979, 300: 366-67. 4.

Wyper DJ,

1206 to assess how valuable the protective effect of sulphonamide is likely to be. With the release of trimethoprim for use alone-the case for this having been argued for some years’*’—it is important to establish as far as possible the likely effect of separating the components on the prevalence of trimethoprim resistance.

difficult

Patients treated with low doses of an antibacterial agent for long periods generally offer a particular opportunity to observe the extent to which treatment is compromised by emergence of resistance. We report here observations on patients treated over some years with

low-dose co-trimoxazole, trimethoprim,

or

nitrofuran-

toin.

Treatment Patients with significant bacteriuria in two successive samples were treated initially for two weeks, usually with ampicillin but in a few cases with other agents. Those who relapsed were then treated for a further two weeks with an appropriate agent selected after in-vitro sensitivity tests. Patients who again relapsed or who had frequent reinfection (two or more episodes in six months) were examined radiologically for surgically remediable lesions. In the absence of such lesions they were treated with diminishing-dose co-trimoxazole. Initially conventional therapeutic dosage (two tablets b.d.) was given for two weeks. If the urine was then sterile, the dosage was reduced to one tablet at night for a further two weeks and, if the urine remained sterile, to one tablet on alternate nights. Some patients who were intolerant of sulphonamide were transferred to long-term treatment with trimethoprim alone (minimum maintenance dose 100 mg on alternate nights) and some, because of intolerance to co-trimoxazole or for other reasons, were treated with long-term nitrofurantoin (minimum maintenance dose 100 mg nightly). Long-term low-dosage therapy was stopped at intervals (the practice eventually adopted being to continue therapy for six months in the first instance) and reinstituted if relapse or early reinfection occurred. Patients who became infected while receiving longterm therapy were treated with an appropriate agent, as indicated by in-vitro sensitivity tests in conventional dosage or as necessary to eradicate infection while low-dose therapy was continued. This sequential system of management yielded five groups of patients: (1) those who responded to initial therapy; (2) those treated with long-term co-trimoxazole; (3) those treated with long-term trimethoprim alone; (4) those treated with long-term nitrofurantoin; and (5) those referred to the clinic with a diagnosis of chronic urinary infection who had no episodes during the period of observation.

-e.g., enterococci-were noted. All enterobacteria isolated were identified according to Cowan and Steele,8 and their sensitivity to trimethoprim and sulphamethoxazole was determined on Oxoid DST agar plus 5% lysed horse blood in which the drugs were incorporated as described by Greenwood et at.9 Isolates with a level of resistance to trimethoprim of 8 mg/l or to sulphamethoxazole of 32 mg/1 were tested for their ability to transfer their resistance to genetically marked strains of Escherichia coli by methods described elsewhere. 10

Results

There is a fundamental difficulty in avoiding bias in presenting results of the present kind, particularly when the three sites (faeces, introitus, and urine) were not sampled at similar intervals or frequency or for the same total period in all patients. In many patients what was believed to be the same organism was recovered from all three sites on more than one occasion, and the inclusion of all these strains would plainly weight the proportion of resistance recorded. Conversely, among the ten colonies examined from a single specimen it was common to find that the clones differed considerably in their degree of resistance to sulphonamide and trimethoprim. We have generally concerned ourselves, therefore, not with the number of strains found to be resistant but with the number of patients who harboured, and particularly those who acquired, resistant strains and with the influence of this acquisition on the patients’ response to treatment.

Distribution of

Resistance

2877 strains were examined. Minimum inhibitory concentrations (MICs) of trimethoprim for strains isolated before, during, and after long-term co-trimoxazole are shown in fig. 1 and the distribution of resistant strains among the three sampling sites from the five groups of patients is shown in table i. The numbers in most of the groups are small, but the prevalence of sulphonamide resistance was 60-80% in patients who had received some form of antibacterial therapy and 40% in those who had received none. Trimethoprim resistance was observed only in patients who had received trimethoprim either alone or combined with sulphamethoxazole, the prevalence being similar although the group receiving trimethoprim alone contained only 5 patients and they had in any case previously received co-trimoxazole.

Specimens Midstream urine samples were obtained at each clinic attendance. Patients were also taught to examine their own urine at regular intervals with the filter-paper-strip method6 and later in the study the dip-slide method. At each clinic attendance periurethral swabs were taken and patients were taught to sample the periurethral area between clinic attendances by means of a tampon as previously described.’ Faecal samples were obtained at intervals from all the patients.

Bacteriology The number, identity, and significance of urinary isolates assessed by standard methods. Periurethral and faecal specimens were inoculated onto either CLED agar (Oxoid CM301) or McConkey agar (Oxoid CM7). Enterobacteria were counted and whenever possible ten individual colonies were selected for further study. Other organisms seen incidentally

were

Fig. I-Distribution of resistance to trimethoprim in strains isolated from urine, introitus, and faeces before, during, and after treatment with long-term low-dose co-trimoxazole.

1207 TABLE

I-DISTRIBUTION

OF RESISTANCE TO SULPHAMETHOXAZOLE AND TRIMETHOPRIM

The 29 patients who received long-term co-trimoxazole were treated for 6 to 58 months (mean 32.7 months), during which time 1163 samples of urine were examined. Their overall response to long-term co-trimoxazole is shown in fig. 2. There was no obvious differ20

r

BEFORE TREATMENT

in the response of

patients with or without radioabnormalities the of logical urinary tract. Discrepancies between the numbers on sections of fig. 2 occur because not all patients were sampled both before and after treatment. The proportion of infected urines fell from 41-4% before treatment to 6-3% during treatment and rose to 36-7% after treatment. ence

Breakthrough Infection 11 patients had nineteen episodes of infection while receiving long-term therapy. The causative organisms in 8 of them tients (no.

listed in table n. 1 of the remaining pa11) had a single episode of infection with Streptococcus facalis, and another (no. 7) had a single episode of infection with Pseudomonas ceruginosa. From the third (no. 1) strains of Proteus mirabilis isolated on 8 occasions during a single episode of infection were unfortunately lost before they were further examined, as was an organism isolated during one of three episodes of infection in patient 4, in whom another episode was due are

Candida. Resistance to trimethoprim and sulphamethoxazole was thus measured in 8 patients who had fourteen episodes of infection due to enterobacteria. The MICs of both drugs for the strains is given in table n, which shows that four strains were resistant to sulphonamide alone and six to both sulphonamide and trimethoprim. to

TABLE II-ENTEROBACTERIA CAUSING EPISODES OF

URINARY-TRACT INFECTION DURING LONG-TERM CO-TRIMOXAZOLE

Fig. 2-Proportion

of infected urines recovered before, during, and after treatment with long-term low-dose co-trimoxazole in patients whose intravenous pyelogram showed 0 no abnormality, x calculus disease, . hydrokinetic abnormalities (e.g. dilated and distorted’upper tracts; large residual bladder volume), other disorders.

1208 TABLE III-DISTRIBUTION OF TRIMETHOPRIM RESISTANCE AMONG STRAINS ISOLATED FROM THE CO-TRIMOXAZOLE

The four remaining strains were fully sensitive. There were no strains resistant to trimethoprim alone. The distribution of resistance in strains recovered from faeces, introitus, and urine of the patients treated With long-term co-trimoxazole is shown in table ill. Of the strains listed, E. coli accounted for 74% before treatment, 61% during treatment, and 70.5% after treatment. When resistance to trimethoprim was transferable the MIC was always > 1024 mg/1. Discussion These results confirm the efficacy of long-term lowdose co-trimoxazole in the control’ of intractable urinary-tract infection. Even over a long period of therapy, failure due to superinfection or breakthrough infection with resistant species or strains was rare. Of the 29 patients, 2 had single episodes of infection with Strep. fcECalis or Ps. ceruginosa and 1 an episode of doubtful significance due to Candida. Infection with trimethoprim-resistant strains of natively susceptible species was also uncommon. There were only six such episodes, two (both in 1 patient) due to strains carrying plasmids conferring resistance to both sulphonamide and trimethoprim and four to strains with low-level trimethoprim resistance presumably due to chromosomal mutation. In 1 other patient, from whom strains in the stool were found to carry plasmid-mediated trimethoprim ’resistance, similar organism caused urinary infection shortly after long-term co-trimoxazole. The remaining episodes were due to trimethoprim-susceptible strains, four being also susceptible to sulphonamide. It appears, therefore, not only that breakthrough infections were uncommon but also that among those that occurred, other reasons for failure (including, presumably, non-compliance) were more important numerically than was the emergence of resistance. Is it likely that the results would have been worse had the patients been treated with trimethoprim alone? There is no doubt that trimethoprim exerted selective pressure, for organisms resistant to it were found only in those patients who had received the drug, either alone or in combination. However, the distribution of resistant strains among the small number of patients who received trimethoprim alone was virtually identical to that observed in the larger group treated with co-trimoxazole, so that trimethoprim without sulphonamide did not appear to have a dramatically enhanced capacity to select for resistance. Unfortunately the contribution made to the debate by the findings in these few patients is weakened by the fact that they had previously received co-trimoxazole and before that ampicillin, which could itself select for plasmids conferring sul-

29

PATIENTS ON LONG-TERM

phonamide resistance. This, at least in Escherichia, could have an important bearing on trimethoprim resistance. Sulphonamide resistance was common in patients without known exposure but trimethoprim resistance was found only in those who had received the drug. Among E. coli strains low-level’ (presumably chromosomal) resistance to trimethoprim was not observed in the absence of a plasmid conferring resistance to sulphonamide. In one strain in which low-level trimethoprim resistance was found alone it was thought probable that a sulphonamide plasmid had been lost on storage, because both before and after the recovery of the strain apparently identical strains bearing a sulphonamide plasmid were recovered on several occasions from this

patient. It remains to be established whether this indicates that the acquisition of plasmid-mediated sulphonamide resistance facilitates the development of chromosomal resistance to trimethoprim or is simply the result of the selective pressure exerted by the particular sequential regimen adopted, in which patients first received ampicillin and subsequently co-trimoxazole. In support of the possibility that plasmid and chromosomal resistance may be linked, Aymes and Smith" have shown that the expression of moderate levels of trimethoprim resistance may be controlled by both plasmid and chromosomal genes. In this group of patients those treated with trimethoprim fared no worse than those treated with co-trimoxazole in terms of superinfection with trimethoprim-resistant strains, and it is possible that without previous exposure to drugs selecting for plasmid-mediated sulphonamide-resistance they might have fared better. In mounting any comparative trial of trimethoprim versus co-trimoxazole for the long-term control of urinary-tract infection it is evidently important that the nature and genetic basis of resistance in any emergent strains should be established and that patients should be clearly defined in relation to their prior exposure to agents that may affect the selection of strains which could possibly be "primed" to the development of trimethoprim resistance.

Requests for reprints should be addressed to N.J.P., Department of Microbiology, University Hospital, Queen’s Medical Centre, Nottingham NG7 2UH. REFERENCES

1. O’Grady F, Chamberlain DA, Stark JE, et al. Long-term, low-dosage, trimethoprim-sulphamethoxazole in the control of chronic bacteriuria. Postgrad Med J 1969; 45: suppl. November, 61-64. 2. Stamey TA, Condy M, Mihara G. Prophylactic efficacy of nitrofurantoin macrocrystals and trimethoprim-sulphamethoxazole m urinary infections. N Eng J Med 1977; 296: 780-83. 3. Smellie JM, Katz G, Grüneberg RN. Controlled trial of prophylactic treatment in childhood urinary-tract infection. Lancet 1978; ii: 175-78.

1209

ORAL REHYDRATION OF NEONATES WITH DEHYDRATING DIARRHŒAS GLORIA POSADA DANIEL PIZARRO DAVID NALIN LEONARDO MATA EDGAR MOHS Carlos Saenz Herrera National Children’s Hospital, San Jose, Costa Rica; Department of Social Security, Government of Costa Rica; Faculty of Medicine and Institute for Health Research, University of Costa Rica; and Center for Vaccine

Development, University of Maryland, U.S.A.

Thirty-nine of forty neonates with mean dehydration equivalent to 6·7% of bodywere weight orally rehydrated with a glucose/electrolyte solution. Only one patient required any intravenous fluids for rehydration. Hypernatræmia and acidosis

Summary

at admission were corrected within a few hours without complications. It seems that oral rehydration, is suitable for neonates as well as for children and adults.

present

Introduction ACUTE diarrhoeal dehydration in neonates is usually treated with intravenous fluids.1 Oral rehydration, based on knowledge of glucose-enhanced sodium and water absorption, was first used in 19682 in adults and older children with cholera.2,3 Later studies included infants over 3 months old with non-cholera diarrhoea, and a few aged 1 to 2 months,4-8 but oral therapy of neonates has not yet been reported.

Patients and Methods

Forty patients (twenty female) with dehydration due

to

watery diarrhoea were orally rehydrated after parents gave informed consent. Mean age was 20-3±1-1 days (± SEM) (range 7-30 days). Mean preadmission duration of diarrhoea was 2-6±0.3 days (range 1-8 days), with an average of 7.3±1.8 stools reported during the 24 h before admission. The oral solution was based on the World Health Organisation formula,9 but had a slightly higher potassium concentration, and contained (g/1): sodium chloride, 3.5; sodium bicarbonate, 2.5; potassium chloride, 2.25; and glucose, 20-0. Composition was chemically confirmed. The solution as prepared contained acute

(mmol/1): glucose, 110; Na+, 90; K+, 30; HCO,, 30; Cl-, 90. Patients had one or more signs of dehydration, including sunken eyes, sunken anterior fontanelle, and diminished skin elasticity and turgor. Mean dehydration was 6.7%±0.6%. 53% had more than 5% dehydration, including 13% with 10% dehydration, confirmed by weight-gain after rehydration. 28% had fever and 10% had hypothermia. Exclusive breast-feeding was reported in 15% of neonates and exclu-

dry mouth,

4.

Anderson JD, Lewis EL, Gillespie WA. Comparative efficacy of sulphonamide and co-trimoxazole. Lancet 1973; ii: 509-11. 5. O’Grady F. Trimethoprim-sulphamethoxazole: a reappraisal. Can Med Ass J 1975; 112: 5-7. 6. Leigh DR, Williams JD. Method for the detection of significant bacteriuria in large groups of patients. J Clin Pathol 1964; 17: 498-503. 7. Cattell WR, McSherry MA, Brooks HL, O’Grady F. The carriage of Escherichia coli on the peri-urethral area and in the faeces in patients on longterm low-dose cotrimoxazole therapy. Clin Nephrol 1976; 6: 506-08. 8. Cowan ST, Steel KJ. Manual for the identification of medical bacteria. Cambridge: Cambridge University Press, 1974. 9. Greenwood D, Pearson NJ, O’Grady F. Cefuroxime: a new cephalosporin antibiotic with enhanced stability to enterobacterial &bgr;-lactamases. J Anti-

Lacey RW,

microb Chemocher 1976; 2: 337-43. 10. Towner KJ, Pearson NJ, Cattell WR, O’Grady F. Trimethoprim R-plasmids isolated during long-term treatment of urinary tract infection with cotrimoxazole. J Antimicrob Chemother 1979; 5: 45-52. 11. Aymes SGB, Smith JT. Trimethoprim resistance controlled by a combination of plasmid and chromosomal genes. Genet Res 1977; 29: 35-45.

sive bottle feeding in 28%; the rest received both breast and bottle feeds. After brief history and physical examination at admission, patients were weighed and in 22 cases a venous blood-sample was taken. Treatment was explained to the mothers, who administered the oral fluids (37°C) in baby bottles, (50 or 100 ml bottles, depending on infant’s size). They gave 2 bottles of oral solution followed by 1 of plain water and repeated this 2:11 regimen until staff judged rehydration to be complete. Nasogastric tubes were used in 3 cases in which oral intake was poor. The amount of fluid (including oral solution plus plain water) needed for complete rehydration was estimated as the product of percentage dehydration (based on clinical signs) multiplied by double the admission weight (in kg), to allow for deficits and continuing losses correction of both during the rehydration period. After receiving this amount, patients were re-examined, including body-weight, and the regimen was continued if rehydration was not yet complete as judged by clinical signs, including skin elasticity. After rehydration a second blood-sample was drawn and patients were offered breast milk or half-strength milk formula (0-4 kcal/ml, or 1.6 J/ml, 50-100 ml every 3-4 h). We gave instructions and oral-therapy ingredients to mothers when infants were discharged, so that they could continue maintenance therapy at home.lO Mothers were told to return to clinic the next day, or earlier, if difficulties developed. Infants were discharged when their faeces ceased to be completely watery and breast milk or half-strength formula feedings were being tolerated. Sodium and potassium were determined by flame photometry ; bicarbonate and pH by Instrument Labs Model 213 blood gas analyser; and osmolality by Osmette freezing-point-depression osmometer. Faeces from twenty-two of the patients were cultured on ’Tergitol’ (Bacto Labs) with triphenyl tetrazolium chloride and on MacConkey’s agar media, and twenty-one were also preserved frozen in brain-heart medium with 0.5% bovine serum albumin, penicillin and streptomycin for later testing by enzyme-linked immunosorbent assay (ELISA) for rotavirus." Suspected salmonella, shigella, and enteropathogenic Escherichia coli (EPEC) were identified by biochemical tests and by seroagglutination with appropriate antisera after subculture on lysine-iron and triple-sugar-iron media. The presence of EPEC was confirmed by titration of 0 antigen in boiled cultures. 1’,13

preadmission

Results Oral

in the emergency

room succeeded in rehydration thirty-nine of the forty patients, and oral maintenance was also successful in thirty-four of the patients who, after rehydration was complete, were given maintenance therapy by their mothers at home. Mean total oral fluid intake was 385±40 ml for oral solution and 13 5 ± i 2 ml for other fluids (water plus milk). Preadmission vomiting was reported in 58%, and 33% and 10% vomited once or twice during therapy, respectively. These infrequent episodes did not interfere significantly with the progress of rehydration. Two patients vomited four times, including the patient who required intravenous fluids. Mean rehydration time was 8-2±0-8 h (range, 2-25 h), and was