Killing of Escherichia coli in the peritoneal cavity of convalescent mice; role of specific and non-specific immune mechanisms

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Abstract
Strains of Salmonella of serotype Sendai, producing a mannose-resistant and eluting haemagglutinin (MREHA) when cultured at 37°C but not at 18°C, were examined by electronmicroscopy after negative staining. Production of this MREHA, previously thought to be nonfimbrial, was correlated with the presence of thick fimbriae with an external diameter of 13.6nm. These fimbriae were readily fragmented and, when purified, had an estimated Mr of 28 Kda. Production of fimbrial MREHA by Sendai strains was associated with the ability to adhere to a wide range of substrates and to form a fimbrial pellicle at the surface of liquid media incubated statically in air. The origin of this unusual Sendai fimbrial MREHA is unknown. Thin filamentous structures produced independently of fimbrial MREHA by Sendai strains were also described. Fimbrial MREHA was not produced by strains of the antigenically similar serotype Miami which, however, and unlike Sendai strains, formed mannose-sensitive haemagglutinin and type-1 fimbriae. The ability to differentiate strains of Miami and Sendai (serotype 1, 9, 12:a:1, 5) by means of their fimbriae is noted.