IN the preceding paper Pattison et al. (1955) gave the results of a study of the type classification by Lancefield's precipitin method of 66 human and 170 bovine strains of group-B Streptococci isolated in Britain. It was then recorded that 43 of the strains, all bovine, could not be included in Lancefield's classification because they apparently lacked type polysaccharide. The present paper reports the results of a further examination of these strains, and reviews the whole question of the type classification of group-B streptococci.The materials and methods employed were similar to those already described by Pattison et al.
RESULTS
Attempts to denurnstrate type polysaccharideThe various methods tried were as follows :-(a) Methods of extraction. These were carried out on one or more strains. Details are given in table I. All tests were made with group-absorbed sera, and all extracts were tested before and after trypsinisation and before and after pepsinisation. No type-precipitating antigen retistant to the action of pepsin w w identified.It was thought possible that minimal amounts of type polysaccharide might be detected if a sufficiently large volume of cells was extracted, but extraction with N/5 HCl at 50" C. for two hours of the cells from one-litre amounts of Todd-Hewitt broth culture incubated at 37" C. overnight failed to reveal type polysaccharide.(c) Examination of culture supernatant and cell washings. To test the possibility that type polysaccharide in these strains might be very loosely atbched to the cells, examination waa made of the supernatant of 18-hour Todd-Hewitt broth cultures incubated at 37OC. overnight, and alao of saline washings of the cells centrifuged from these cultures. Results were negative.(d) Extraction of cultures in different p h e s of growth. Extraction at 5OOC. for two hours with N / 5 HCI of the ceUs centrifuged from 2-, 4-, 6-, 8-, 10-and 12-hour cultures in Todd-Hewitt broth and in glucose broth failed to reveal type polysaccharide.(b) Extraction of cells from one litre of culture.
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