1. Faeces from apparently healthy Bantu children from schools in Soweto township near Johannesburg were examined eight times at fairly regular intervals over a period of 1 year.2. Only fifty-five children were present for all eight investigations and, of these, 36·4% yielded salmonellae and 9·1% shigellae. Taking the group as a whole, 26·2% of the children had salmonella infections and 6·2% shigella infections.3. Parasites were shown to be present in sixty-four of the 130 children during the period of the investigation.4. As in other surveys, there were more isolations in summer than in winter.5.S. labadiandS. typhimuriumwere most frequently isolated, with the group B–E constituting 75% of the total isolations.S. typhi, S. paratyphi A, BandCwere not found.6. Water supplied to each house by the Johannesburg municipality was of good quality, yet it did not affect the incidence of salmonellosis and shigellosis.7. In spite of better socio-economic conditions the incidence of salmonellosis is comparable to the two previously mentioned surveys. These findings indicate a lack of instruction on personal hygiene and the importance of public health measures.
1. Faeces from apparently healthy Bantu school children of a periurban district of Johannesburg were examined eight times at regular intervals over a period of 1 year.2. Of 75 children, 29·3 % experienced at least one salmonella infection and 2·7 % one shigella infection. It is suggested that over a year nearly all children will have one, and many of them several, infections with these pathogens. The infections occurred at a low rate throughout the year.3. In most cases the infections were asymptomatic. A few of the children showed evidence of being salmonella carriers of long standing.4. Eighteen different salmonella types were recovered. Salmonella typhi, S. paratyphi B and S. paratyphi C were absent. The organisms were highly resistant to penicillin, erythromycin and novobiocin and a few strains were also resistant to chloramphenicol and tetracycline.5. The drinking water was of poor quality and may well be implicated in the transmission of the infections.Our thanks are due to the Director of this Institute, Dr J. H. S. Gear, for permission to publish this paper; to Mr R. G. Robinson for assessing the microorganisms'sensitivity to antibiotics; and to the South African Council of Scientific and Industrial Research, Pretoria, for a grant enabling us to meet the transport expenses.
be used. After 24 hours of incubation, the white lines can easily be seen with the naked eye. RESULTS One hundred routinely isolated strains of C. diphtheriae were tested in parallel for toxigenicity by using, 1, the standard Elek test, 2, the modified test, and 3, the intradermal method in the guinea-pig. The results are shown in Table I.The gel-precipitation method for the determination of the toxigenicity of Corynebacterium diphtheriae, as described by Elek (1948), has been in use in this laboratory as a routine procedure since 1949. In view of the difficulty often experienced in reading weakly positive results, the technique was modified as described below. METHODPrepare the basic medium as described by Elek, and distribute 10 ml. amounts into sterile 9 cm. petri dishes. These should be stored at 4°C. until required. Before carrying out a test, allow the surface of the medium to dry in an incubator for 20 to 30 minutes.Saturate a sterile 6 mm. disc of Ford's 428 mill filter paper with diphtheria antitoxin containing approximately 2,000 units per ml. Place the disc on the medium and inoculate the culture at a distance of 6 mm. from the edge of the disc, over an area roughly the size of the disc. For this purpose it is convenient to place the petri dish on a white card marked with two concentric circles, 6 mm. and 18 mm. in diameter respectively. The disc can then be centred over the smaller circle, and the cultures inoculated in such a way that the nearest point of the inoculum is 6 mm. from the disc.Four cultures may be tested around each disc. As four discs can be accommodated on each plate, a total of 15 tests and a positive control (Park-Williams 8) can be carried out on one petri dish. Incubate at 37°C. and examine after 24 hours. A positive result is indicated by the appearance of fine white lines of precipitation tangentially between the disc and the test cultures. It is possible to read the plates after an incubation period of six hours, when a hand lens should
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