SUMMARYDuring a period of five years 1192 water samples from swimming pools were examined for staphylococci and 338 for coliform organisms only. Eighty-nine different pools were sampled.Numbers of staphylococci, estimated by the membrane filtration technique did not bear any significant relation to either bathing load or concentration of free chlorine.Wide variation in the staphylococcal count was observed when different parts of a pool were sampled on the same occasion.The only practicable standard for pool samples in relation to staphylococci would appear to be that these organisms should be absent from 100 ml. water when the pool has been out of use during at least ten hours before sampling if filtration and chlorination are adequate.
SUMMARYSalmonella infection on two pig farms and its relation to infection in pigs at slaughter was studied. On the first farm feed ingredients were mixed on the farm, and these included fish meal which was found to be contaminated with salmonellas. The feed was pumped to pigs in liquid form. There was a high salmonella isolation rate at slaughter when the contaminated fish meal was fed in liquid feed, but it was significantly lower when no fish meal was fed to the pigs examined at slaughter. In some instances the same serotypes were found in fish meal and pig excreta on the farm and in caecal contents of the pigs at slaughter. No serotype was repeatedly isolated from any source and it appeared that the serotypes were not able to establish themselves in the pigs. It is concluded that infection found at slaughter originated on the farm where fish meal introduced and maintained infection. There was an opportunity for salmonellas to have multiplied in the liquid feed for several hours each day.On a second farm environmental conditions were similar, but feed was given in the form of ready-made pellets and nuts. Salmonellas were not isolated from the feed. At slaughter there was a significantly lower isolation rate than on the first farm.
SummaryAn investigation into the classification of strains of Shigella sonneiby the method of phage-typing (using unadapted bacteriophages) is described.829 strains, obtained during 3 years from twelve regions in England (including Monmouthshire) were examined by a standard technique. There were fifty-two outbreaks (involving 587 strains) from which two or more strains were isolated.Results confirmed the finding by Hammarström in Sweden that such classification was possible, strains falling into twenty phage-types of which thirteen were found more than once. All strains were typable, 74% belonging to the same type. In forty-seven outbreaks the phage-type was uniform, the commonest type occurring in thirty-eight of these. In five outbreaks the phage-type was not uniform.It is concluded that this method of phage-typing, because of evidence of type instability and because the majority of strains belong to the same phage-type, has little practical value as a routine procedure in the control of Sonne dysentery in this country.
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