1. The review of the laboratory evidence published since the introduction, ten years ago, of the alcohol-treated typhoid vaccine furnishes additional support for abandoning the old method of making typhoid vaccine. The alcohol-treated vaccine has advantages in regard to both the Vi-antibody response and the degree of systemic reactions produced.

2. The technique of the preparation of alcohol-killed and alcohol-preserved typhoid-paratyphoid vaccine has remained as originally described. The methods of selecting the vaccine strains and routinely examining the cultures have also remained unchanged.

3. The necessity of testing typhoid vaccines not only by active-immunity tests in mice but also for their antibody-stimulating properties is again stresssed. These tests consist of immunization of rabbits, estimation of their Vi- and O-agglutinin titres and passive-immunity tests in mice.

4. The most important sources of error in mouse-protection tests are:

(a) the use of a test culture of less than the maximum degree of mouse-virulence;

(b) the use of the mucin technique;

(c) immunization by intraperitoneal injections when the challenge dose also is given by this route.

Much of the experimental work on typhoid vaccine has been invalidated by these three pitfalls.

5. It is suggested that the mucin technique be abandoned in the assay of typhoid vaccine.

6. A source of error in the rabbit test is the presence of pre-formed Vi agglutinins. These are found in rabbits harbouring coliform organisms which possess the typhoid Vi antigen. Such rabbits do not respond to injections of typhoid Viantigen.

7. Standardization of the potency of typhoid vaccine has now become possible. Either an alcohol-preserved or a dried vaccine can serve as ‘standard vaccine’, to be used in combination with the ‘Provisional Standard Anti-typhoid Serum’. Both of these vaccines remain stable for a number of years.

8. Suggestions are briefly outlined for:

(a) the routine examination in the course of preparation of the vaccine;

(b) the official control of the potency of typhoid vaccine.

9.The paratyphoid components of T.A.B.C. vaccine can be standardized in an analogous manner.

1. Alcohol-killed and alcohol-preserved typhoid vaccine retains its power of stimulating Vi- and O-antibody formation unimpaired during storage at 1–2° C. for at least 10 years.

2. The Vi antibody induced by immunization with the 10-year-old vaccine possesses full ‘functional efficacy’ in passive-immunity tests in mice.

3. The expiry date of this type of vaccine can be extended to a period of 10 years, provided the vaccine is kept in cold storage.

4. Alcoholized vaccine can serve as ‘standard vaccine’ in any future attempt at standardization of the potency of typhoid vaccine.

1. A double enteric infection is defined as the simultaneous infection of an individual or group of individuals with two organisms of the enteric group. The literature of the previously recorded cases and epidemics, in which the diagnosis of double enteric infection has been established by cultural methods, is reviewed.

2. An account is given of a double enteric outbreak of seventy–six cases which occurred amongst British troops and police at Acre, Palestine, in 1948. The infection is thought to have been due to contamination of the water supply with sewage during the civil disturbances. The diagnosis was established bacteriologi–cally in seventy-four cases (93.3%);Salm. typhi was isolated in forty–three cases, Salm. paratyphi B in three, and both Salm. typhi and Salm. paratyphi B from twenty–eight cases. There were three fatal cases in the epidemic (mortality rate = 3·94%).

3. The morbidity rate from enteric fever among the infantry unit was 60%, and among the Palestine police, 17%. The possible reasons for this difference is discussed, and the conclusion drawn that it was probably due to the Palestine policemen being older men, with longer overseas service and more 'seasoned' to life in subtropical conditions.

4. Thirteen cases were treated with polymyxin B (15 mg. 4-hourly for 4-day periods); with this small dose no beneficial therapeutic effects were observed, and ten cases showed evidence of renal damage while under treatment.

5. The bacteriology, epidemiology and clinical aspects of double enteric infections are discussed. The diagnosis of a double enteric infection may be established with the greatest certainty by blood culture. Such infections are usually water-borne or milk-borne, and tend to occur when there has been a severe breach of hygiene, e.g. in the contamination of a water supply by sewage. The claim that the prognosis in instances of double enteric infection is worse than with single infections is not supported by the experiences at Acre where the three fatal cases occurred in cases infected with Salm. typhi alone.

1. The results of 192 blood cultures in an epidemic of enteric fever are analysed. The epidemic was caused by a double enteric infection with Salm. typhi (Vi-phage type T) and Salm. paratyphi B (Vi-phage type ‘Dundee’).

2. All of sixty –five cultures between 102 and 104∘ F. were positive, and a significant number of positive cultures at lower body temperatures were obtained. Three out of four cultures, taken when the temperature was subnormal, were positive. In seventy–one out of seventy–six cases (93·4%) a positive blood culture was obtained.

3. The highest percentage of positive isolations was obtained in the second week of disease. In the severe cases the highest percentage occurred in the third week. The reasons for this, and the findings of previous studies, are discussed.

4. No difficulty was encountered in obtaining positive blood cultures in previously inoculated individuals.

5. The average period of incubation of the cultures, required to produce a positive result, was 4–5 days, and 17% did not become positive until the ninth to eleventh day of incubation.

6. The discovery of ehloramphenicol has emphasized the need for the early diagnosis of enteric fever. This can most readily be achieved by the method of blood culture.

1. An epidemic of typhoid fever involving 135 persons in a semi-closed community of. 742 persons is described.

2. There were nineteen symptomless excreters (14·1%).

3. Among the 116 clinical cases there were seven deaths, giving a case fatality of 6.03%. If the case fatality were calculated on the total persons involved (including symptomless excreters), the figure would be 5·2%.

4. The origin of the outbreak was not discovered, but there was strong cricumstantial evidence in favour of a milk-borne infection.

1. An account is given of the finding of 19 symptomless excreters of Salm. typhi and of 15 incubating cases (‘precocious carriers’) in the course of repeated examination of the faeces of 435 staff and patients at the hospital.

2. In a comparison of the frequency of isolation of Salm. typhi from the faeces it was found that the the selenite F enrichment method was more efficient than enrichement in Kauffmann 's tetrathionate broth, and that both methods were superior to direct plating on desoxycholate citrate agar.

3. Examination of sera from cases of typhoid fever showed that, in some cases, H- and O-agglutinin titres which would normally be regarded as ‘diagnostic’ may be reached well within the first week of illness.

4. Measures are described which were taken to exclude connexion between this outbreak and (a) a chronic carrier found during investigation of the hospital milk supply, and (b) the incidence of typhoid fever at another hospital.

5. A case of typhoid fever at Shrewsbury is described which was probably infected by an abortive missed case. Attempts to make a retrospective bacteriological or serological diagnosis of the latter were unsuccessful.

6. An account is given of the use of the sewage-pad method in an attempt to trace the source of infection in the case of a sewer worker who developed typhoid fever 14 months after the main epidemic and was probably infected by an intermittent carrier at the hospital.

1. The low Vi-antigen content and low mouse virulence of freshly isolated cultures of the Oswestry strain of Salm. typhi reflected its low virulence for man. This is additional evidence of the association between the degree of virulence of Salm. typhi and its Vi-antigen content.

2. The prediction that the epidemic caused by this typhoid strain of low mouse virulence would resemble a paratyphoid-B outbreak more closely than an average typhoid outbreak proved to be correct.

3. Sera from convalescent patients in this typhoid outbreak showed significant Vi-agglutinin titres in spite of the low Vi-antigen content of freshly isolated cultures.

4. The nutritional requirements of the Oswestry strain were unusual, and its sensitivity to the specific Vi-typing phages was variable. This caused considerable difficulty in the typing of the cultures.

5. Additional tests of identity had to be employed in order to distinguish the epidemic strain from other strains of the same Vi-phage type isolated in the vicinity. Colony size, colonial morphology, biochemical reactions and sensitivity to anti-O bacteriophage served as useful ancillary criteria.