How long should patients with Salmonella typhi or Salmonella paratyphi be followed-up? A comparison of published guidelines.

Records were examined for 242 individuals infected with Salmonella typhi or S. paratyphi identified in Birmingham between 1981 and 1988, with a total of 335 person years of follow-up. Of these cases 77 and 78 per cent respectively were followed beyond the point at which surveillance would have ceased under guidelines published by the American Public Health Association and by the Public Health Laboratory Service for England and Wales. Under these two sets of guidelines only seven (3.8 per cent) and eight (4.3 per cent) cases respectively had subsequent positive faecal or urine cultures over a median of 335 and 295 days of additional follow-up. After 0, 1, 2, 3, 4 and 5 prior consecutive negative sets of cultures obtained at weekly intervals the likelihood of the next set of cultures being positive was 26, 9, 5, 2.2, 2.4 and 0 per cent respectively. Only 38 (1.7 per cent) of 2184 follow-up urine cultures were positive; these results did not influence duration of follow-up. Only 26 (2.6 per cent) of 1002 contacts were infected; the yields of the first, second and third sets of cultures were 1.5, 0.6 and 0.5 per cent respectively.

Infective conjunctivitis and corneal scarring in three brothers with sex linked hypogammaglobulinaemia (Bruton's disease).

The ocular findings in three brothers with Bruton's disease are reported. All three boys had purulent conjunctivitis, but the two older brothers also developed marked corneal scarring with visual impairment. Haemophilus influenzae was cultured from conjunctival swabs; it was resistant to neomycin but sensitive to chloramphenicol. Tear analysis showed that the three subjects had normal levels of lysozyme but no detectable IgA.

Homogeneity of envelope proteins of Escherichia coli separated by gel electrophoresis in sodium dodecyl sulfate.

Some envelope proteins of Escherichia coli show variable behavior in acrylamide gel electrophoresis in 1% sodium dodecyl sulfate, depending upon the conditions of the solubilization. When solubilized in 1% sodium dodecyl sulfate at 70 C for 20 min, three distinct peaks (peaks 4, 6, and 7) are seen at molecular weights of 57,800, 44,300, and 38,400, respectively. However, when the envelope fractions are solubilized in 1% sodium dodecyl sulfate at 100 C for 5 min, or when they are treated with N, N-dimethylformamide at acidic pH before solubilization by our method, only a single peak at 48,000 molecular weight is observed in the molecular weight range mentioned above. That is, peaks 4 and 7 disappear and a new peak appears at the position overlapping with peak 6. Proteins isolated from peaks 4 and 7 show the similar molecular weight shifts to the new peak by the treatment at 100 C. No other peaks show any change by the heat treatment. The increase at the new peak is completely accounted for by the decrease at peaks 4 and 7, indicating that the new peak is composed of proteins from peaks 4, 6, and 7. However, it is concluded that these three peaks consist of distinctly different proteins for the following reasons: (i) they have different amino acid compositions, (ii) they show different solubilities in the nonionic detergent, Nonidet P-40, and as shown previously, (iii) peak 6 (protein Y) is related to deoxyribonucleic acid synthesis, and (iv) proteins in peaks 4, 6, and 7 have different resistance to proteolytic enzymes. Although the reasons for the anomalous molecular weight shifts of these peaks are not well understood at present, it is important to solubilize the E. coli envelope proteins by the standard method in order to investigate their properties and functions of the envelope proteins.

Specific removal of proteins from the envelope of Escherichia coli by protease treatments.

When the envelope fraction of Escherichia coli was treated by trypsin, about 40% of total envelope proteins were removed from the fraction without changing its phospholipid content. Analysis of envelope proteins by acrylamide gel electrophoresis in 0.5% sodium dodecyl sulfate revealed that trypsin treatment was very specific; one of the major proteins (molecular weight, 38,000) and all proteins of molecular weight greater than 70,000 were completely removed by the treatment. On the other hand, three other major proteins were found to be resistant to the treatment, including protein Y, which was previously shown to be related to deoxyribonucleic acid replication. The trypsin treatment of the envelope fractions composed of a five electron-dense layered structure formed vesicles with a triple-layered membrane (two electron-dense layers). Pronase treatment of the envelope fraction removed about 60% of the envelope proteins without changing its phospholipid content. A major protein of molecular weight of 58,000 was found to be the only protein resistant to the Pronase treatment. Application of these treatments is useful for purification and structural studies of envelope proteins.