Salmonellae and shigellae in a group of periurban South African Bantu school children

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.

MECHANISMS OF ENDOTOXIN TOLERANCE. II. RELATIONSHIP BETWEEN ENDOTOXIN TOLERANCE AND RETICULOENDOTHELIAL SYSTEM PHAGOCYTIC ACTIVITY IN MAN

Healthy male volunteers were rendered tolerant to the pyrogenic and toxic activities of bacterial endotoxin by daily intravenous injections. Five subjects were given 0.5 microg Salmonella typhosa endotoxin for 7 days; four subjects were given Pseudomonas endotoxin, increasing over a period of 30 days from 25 to 250 microg. Reticuloendothelial system (RES) phagocytic activity was assessed by serial measurements of the clearance of I(131)-labeled aggregated human serum albumin. In no subject was an increase in RES phagocytic activity detectable. Such negative findings could not be attributed to decreased RES blood flow.-Additional studies on the pyrogenic responses of man to various schedules of endotoxin administration revealed: (a) Hyperreactivity of some subjects to a second injection of endotoxin administered 24 hours after the initial dose; (b) prevention of such hyperreactivity by plasma from donors tolerant to a heterologous endotoxin, but not from normal donors; (c) reduced reactivity to a second injection of endotoxin given 7 days after the initial dose; (d) reversal of induced tolerance by administration of half the dose of endotoxin followed 2 hours later by the second half; (e) reversal of induced tolerance 24 hours after administration of a heterologous endotoxin; (f) enhanced dermal reactivity to endotoxin induced inflammation during tolerance. The observations are consistent with the hypothesis that tolerance to the pyrogenic activity of endotoxin in man is not based upon generalized enhancement of RES phagocytic activity or exhaustion of host reactivity but rather involves the participation of specific antibody which assists the RES in the clearance and inactivation of the endotoxin molecule.

EXPERIMENTAL SALMONELLOSIS. III. NEW TOXIC FRACTION (L) OBTAINED FROM SALMONELLA ENTERITIDIS AND ITS IMMUNOLOGICAL PROPERTIES

Kawakami, Masaya (Gunma University, Maebashi, Japan), Nobutaka Osawa, and Susumu Mitsuhashi. Experimental salmonellosis. III. New toxic fraction (L) obtained from Salmonella enteritidis and its immunological properties. J. Bacteriol. 86:872-879. 1963.-A method is described for the purification of the heat-labile toxins of a fully virulent strain, 116-54, of Salmonella enteritidis by ion-exchange chromatography. One component of the heat-labile toxin (L) was homogeneous, as evidenced by the results of the ultracentrifugal analysis and agar gel diffusion test. The mouse ld(50) was 1.3 mug, and chemical studies indicated that this toxin was a simple protein in nature. It was also evidenced by chemical and immunological tests that this toxin differs from the O antigen (lipopolysaccharide-protein complex).

ALTERATIONS IN THE MOUSE VIRULENCE OF SALMONELLA TYPHIMURIUM BY GENETIC RECOMBINATION

Krishnapillai, V. (Walter Reed Army Institute of Research, Washington, D.C.), and L. S. Baron. Alterations in the mouse virulence of Salmonella typhimurium by genetic recombination. J. Bacteriol. 87:598-605. 1964.-The genetic basis of mouse virulence was investigated with an avirulent strain of Salmonella abony as chromosomal donor and a virulent strain of S. typhimurium as recipient in recombination experiments. In these genetic crosses, the transfer of partial avirulence was found to segregate among the hybrids that were examined. At least two determinants controlling avirulence were depicted to account for the partial avirulence of the hybrids. One of these determinants is indicated as being in the region of the locus for streptomycin sensitivity or resistance, and the other was adjacent to the locus for inositol utilization. Moreover, both determinants were essential for the phenotypic expression of complete avirulence in a hybrid. This was established by the results of experiments in which an initial, partially avirulent hybrid was backcrossed with the S. abony donor so that it further received the additional determinant.

OPPORTUNISTIC INFECTIONS. THE CONCEPT OF 'OPPORTUNISTIC INFECTIONS'

Images