O antigen loss by semi-rough E. coli causing recurrent urinary infections, analysed by gel column filtration and gas-liquid chromatography.

The surface polysaccharides of Escherichia coli isolated from 6 patients with recurrent urinary infection were studied serologically and chemically. In 4 patients multiple isolates were obtained. The first isolate from each of these patients was a smooth strain which could be serotyped with O antisera. The second isolates from 3 of these patients, obtained at intervals of 1-6 wk, were semi-rough strains. They could not be serotyped after culture on nutrient agar but could be serotyped after subculture on blood agar. In each patient the serotype remained the same. Gel column filtration of the polysaccharides, and gas-liquid chromatography (GLC) of the trimethyl-silylated sugars showed that smooth strains carried a preponderance of O-specific carbohydrate with little core carbohydrate. The semi-rough strains had lost nearly all their O-specific carbohydrate. The change from smooth to semi-rough involved the progressive loss of full length O-specific side-chains rather than a widespread 'shortening' of these side-chains. In patients chronically infected with the same strain of E. coli it has been shown that GLC analysis of the carbohydrates of different isolates of the same strain in one patient will vary because often the strain will undergo a smooth to semi-rough or rough variation. This variation indicates that GLC analysis of extracted carbohydrates would often not be able to determine whether multiple isolates of E. coli from one patient were the same or different strains.