INFANT SALMONELLA CARRIERS

940 5-minute intervals. When three samples had been taken the was removed and three further specimens were collected. Radio-assay showed that after the removal of the clip the concentration of dibromoprocaine in the right auricle rose

SURVEYS

OF

CHILDREN UNDER THE AGE

OF 2 YEARS

clip

appreciably : 0-3-0-3-0-4-clip off 0-5-0.5-0-6 Vglml. in spite of the fact that the azygos concentration after the last sample, thirty minutes after administration, was only 0-6 g./ml. The experiments also showed that the clamp upon the azygos vein did not deny the drug circulation.

access

to the

CONCLUSION

We conclude that in the cat the venous channels are a direct route of drainage from the spinal subarachnoid space. Of the veins examined, the azygos vein carries the highest concentration of substances introduced into the

spinal theca.

We are grateful to Prof. A. D. Macdonald and Prof. G. A. G. Mitchell for facilities and criticism. The expenses were defrayed by the Medical Research Council to whom thanks are due. REFERENCES

Best, C. H., Taylor, N. B. (1945) Physiologica Basis of Medical Practice.

London.

Cathelin, F. (1912) cited by Weed (1922). Cotugno, D. (1770) cited by Elman (1923). Dandy, W. E., Blackfan, K. D. (1913). J.

Amer. med. Ass.

61,

2216.

Elman, R. (1923) Bull. Johns Hopk. Hosp. 34, 99. Flexner, S., Amoss, H. L. (1914) J. exp. Med. 20, 249. Goldberg, A., Koster, H., Warshaw, R. (1943) Arch. Surg., 46, 49. Hill, L. (1896) Physiology and Pathology of the Cerebral Circulation. London.

Horbatsky, S. (1916) cited by Labat (1923). Howarth, F. (1948) Nature, Lond. 161, 857. Howe, H. S. (1929) Proc. of Assoc. for Research in Nervous and Mental Disease. Baltimore ; vol. VIII., chap. II. Hunter, A. R. (1946) Lancet, i, 380. 11, 78. Johnston, J. F. A., Henderson, V. E. (1932) Anesth. & Analges. Johnston, T. B., Whillis, J. (1946) Gray’s Anatomy. London. Key, A., Retzius, G. (1876) Studien in der Anatomic des Nervensystems und des Bindegewebes. Stockholm. Labat, G. (1923) Regional Anesthesia. Philadelphia. Levinson, A. (1919) Cerebrospinal Fluid in Health and Disease. London.

Mettler, F. A. (1948) Neuroanatomy. London. Mott, F. W. (1910) Lancet, ii, 1, 79. Quincke, H. (1872) cited by Weed (1922). Reiner, M., Schnitzler, J. (1894) cited by Weed (1922). Stout, R. B. (1929) Amer. J. Surg. 7, 57. Walker, A. E., Johnson, H. C. (1946) Penicillin in Neurology. Springfield, Ill. Weed, L. H. (1914-15) J. med. Res. 26, 51. (1922) Physiol. Rev. 2, 171. Weigeldt, W. (1921) Münch, med. Wschr. 68, 838. Ziegler, P. (1896) Arch. klin. Chir. 53, 75. —

INFANT SALMONELLA CARRIERS I. M. MACKERRAS V. M. PASK B.Sc. M.B., Sydney From the Queensland Institute of Medical Research, Brisbane MILD or unappa,rent salmonella infections in infants have sometimes been recorded-e.g., by Angrist and Mollov (1946)-but they seem to have attracted little attention, and the general impression gained from published reports is that these organisms are highly pathogenic to the very young. Evidence which we have obtained recently in Brisbane, however, points to a striking contrast in the behaviour of epidemic and ’

endemic infections. In the epidemic series (Mackerras and Mackerras 1949a) all the children under the age of 2 years from whom Salmonella bovis-mzorbificans was isolated, had had at some

stage

an

active, usually

gastro-enteritis, faeces during the

severe,

and the organism was found in their incubation period, throughout the clinical illness, and up to six months after clinical recovery. About 40% retained their infections for less than a month, 25% for one to two months, and 35% for more than two months. Infections in older children and adults were mild or

unapparent and generally transitory. Other species of salmonella were not infrequent in _

the.

same

age-groups at the

same

time.

They

were

In addition, 6 S. bovis-morbificans were found in a ward survey of children under the age of 2 years admitted to hospital for conditions other than gastro-enteritis during the epidemic, 2 S. typhimurium in 27 children examined in a similar ward survey since the epidemic, and 2 S. muenchen in week-old infants in a maternity

hospital.

-

scattered sporadically in the community, sometimes associated with gastro-enteritis in infants, but usually with little or no clinical indication of their presence at any age. As a rule, these infections were relatively transient, though they persisted longer in infants than in older persons. It is with the endemic infections in young children that we are concerned here. Some of the observations have been used incidentally in discussing the mode of spread of the epidemic (Mackerras and Mackerras 1949a), but they are felt to be of sufficient general interest to justify a separate account here. RESULTS

OF SURVEYS

All the specimens were plated on’Difco SS ’ agar a.nd inoculated into tetrathionate broth, which in turn was plated on SS agar next day. Our findings are set out in the accompanying table. The first three groups shown in the table were studied in connexion with the epidemic, but directed our attention to the problem ; the fourth was examined specifically to define it. Dr. H. C. Murphy, director of maternal and child welfare, arranged for specimens of faeces to be submitted to us from a continuous series of infants admitted to the clinics under his control. These children were mostly " feeding problems " but were completely unselected as regards " bowel upsets " ; some had a past history of diarrhcea, some had loose motions while under observation, and most had normal stools ; none was ill enough to be sent to hospital. In Dr. Murphy’s opinion they were a representative sample of that part of the infant population which is admitted to the clinics. The survey reported here lasted from March 10, 1948, to May 4, 1949. Sixteen strains of salmonella were isolated from 14 infants in this series, 1 infant having a S. typhi-muriuna infection followed by infection with S. adelaide and later by another with S. typh,i-,nturium four months after the first. The over-all incidence was 3-5%. Infections were scattered irregularly throughout the year, with most of them in the hotter months : January, 3 ;

February, 1 ; March, 2 ; April, 1 ; May, 1 ; June, 2 ; September, 1 ; October, 1 ; November, 1 ; December, 3.

They to

are

too few to have statistical

meaning

in relation

season.

The following brief analysis, by species of salmonella, is based on all the infections recorded in the table and beneath it : S. paratyphi-B. (1).-The child had had mild diarrhaea a fortnight previously, but had not been put to bed, and was normal when examined. It was still infected and still well when lost sight of eight weeks later. S. typhi-murium (9).-One child had had clinical gastroenteritis five weeks previously, 5 had had intermittent mild

941 no clinical signs. Only 3 were followed until the duration of known infection being nine weeks, less than two weeks, and probably less than a week. S. derby (3).-One child had had two earlier attacks of diarrhoea and vomiting, but was normal when examined ; the others had had no gastro-intestinal upsets. The duration of infection was not followed. S. chester (1).-The child had no clinical signs ; the organism was isolated only once in five examinations, the infection being apparently transient. S. bovis-rzorbifccan,s (8).-Seven children belonged to the epidemic series and had had gastro-enteritis either before or after examination. The eighth child was from the clinic series in the postepidemic period ; he had no clinical signs and remained infected for four weeks. S. muenchen (2).-Both cases were neonatal and both unapparent ; their infections lasted three and more than five weeks. S. bareilly (1).-The child had had three attacks of mild diarrhoea in the two months before examination but was gaining weight normally. The duration of infection was not

diarrhoea, and 3

negative,

followed. S. pullorum (1).-This infection was completely unapparent, and the organism was found only once-at the second of five examinations. S. adelaide (5).-One child had had mild diarrhoea ; the other cases were unapparent and with negative histories. Four cases were followed through, the infections lasting ten, more than three, two, and two weeks from the first examination. ORIGIN

OF INFECTIONS

We lack information to suggest how most of these babies became infected. They came from widely scattered parts of Brisbane, with no association between infections except possibly in some of the institutional cases. Three sets of records are, however, of interest : A baby received her infection with S. wM6M.c6M from her mother at or soon after birth, and it was transmitted, presumably by the staff, to another baby in the same nursery (Mackerras and Mackerras 1949b). A baby, aged 3 months, was infected with S. adelaide. The parents were clear (3 negative specimens from each) ; the household was clean, and no positive cultures were obtained from food, utensils, dust, &c. ; rats entered the house from a colony infesting uncleared ground nearby, and one of them was found to be infected with S. adelaide. These examinations were made late in the child’s infection. A baby, aged 21/2 months, was found infected with S. adelaide on Oct. 7. Its mother and its sister were negative. Three weeks later all 3 were found to be infected. The baby may have been infected from an unknown source and have passed the infection to the others.

Apart from these indications we can only note that (1) except for the first neonatal S. mzcenche7zinfection, all the infected babies were either artificially fed or received some supplemental feeding ; and (2) there were sufficient salmonella carriers (3%) in the adult human population and in rats (1-5%) for either to have served as sources of the babies’ infections (Mackerras and Mackerras 1949a), though no direct associations were found other than those noted. DISCUSSION

The chief point of interest in these observations is the extremely low pathogenicity of all species of salmonella in Brisbane at present. There were 19,000 children under the age of 2 years in the metropolitan area at the end of 1948 (Mr. S. E. Solomon, Government statistician, personal communication). If our clinic records approximate to a random sample, there would have been upwards of 600 salmonella infections scattered through this section of the population during the period of the survey ; yet only 33 cases of salmonella gastro-enteritis were treated in hospital. Even S. p7M-tK/M"MMH,, which can undoubtedly cause severe illness, seems to have done so only in a, minority of recent infections. We do not know why this is so ; but we suspect that relative benignity is the normal state of the organisms, and that pathogenicity is associated either with dosage of infection

with selection by passage of virulent The conditions under which epidemics arise certainly favour the latter hypothesis. Benignity of most endemic salmonella infections is not confined to Queensland. Rubbo (1948) doubted the capacity of the Melbourne strain of S. derby to kill, unless it was associated with some concurrent severe illness, and Dr. John Perry (personal communication) has also encountered many unapparent infections in a recent The phenomenon is hospital survey in Melbourne. probably general, and it is of considerable epidemiological significance, because infection may be widespread in a community but completely unsuspected and therefore not attacked. There is, in fact, a permanent potential epidemic risk, and it is easy to understand how epidemics often arise when children are crowded together under conditions which favour spread from child to child or, more

probably,

mutants.

(Brehme 1948). We feel that this infant carrier-rate of salmonella infections is just as important in the community as typhoid and dysentery carrier-rates in older persons. It certainly should receive close consideration in any plan of prevention. SUMMARY

A salmonella carrier-rate of about 3-5% in children under the age of 2 years in Brisbane is recorded. Though the organisms seem normally to be benign, they constitute a permanent epidemic risk. Our thanks are due to Miss Mary McCaffrey for much help in the laboratory work, and to Miss Nancy Atkinson, of the Institute of Medical and Veterinary Science, Adelaide, for identifying the strains of salmonella isolated. REFERENCES

Angrist, A., Mollov, M. (1946) Amer. J. med. Sci. 212, 336. Brehme, T. (1948) Lancet, ii, 604. Mackerras, I. M., Mackerras, M. J. (1949a) J. Hyg., Camb. 47, 166. Mackerras, M. J., Mackerras, I. M. (1949b) Aust. J. exp. Biol. med. Sci. 27, 163. Rubbo, S. D. (1948) J. Hyg., Camb. 46, 158.

EFFECT OF THE HEAD-DOWN POSITION ON THE CIRCULATION IN HYPOTENSIVE STATES A. J. P. GRAHAM M.B. Lond., F.R.C.S.

READER

IN SURGERY

FOR DENTAL

STUDENTS

D. M. DOUGLAS M.B.E., Ch.M. St. And., F.R.C.S. LECTURER IN EXPERIMENTAL SURGERY

UNIVERSITY OF EDINBURGH

IN the treatment of traumatic shock the clinical improvement which sometimes follows elevation of the foot of the patient’s bed is generally assumed to be the result of increased blood-flow to the brain and of acceleration of the venous return from the lower part of the body. Until recently it has been customary to express these changes in terms of pulse-rate and of arterial bloodpressure, and clinical experience suggests that in most cases this is a reliable method. However it is possible that blood-pressure records do not always truly indicate the blood-flow when the bloodpressure is low. Under high spinal anaesthesia, very low, or even unrecordable blood-pressures have been associated with apparently good oxygenation of the tissues, and recovery without obvious ill effects has followed (Griffiths and Gillies 1948). The present study was undertaken to measure the effect of the 18° head-down position on the cardiac output and blood-pressure of animals in a hypotensive state. Cardiac Output.-Fick in 1870 first pointed out how the cardiac

output could be calculated from the gaseous exchange of