Glycogen production by different Salmonella enterica serotypes: contribution of functional glgC to virulence, intestinal colonization and environmental survival

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Abstract
In enteric bacteria, the contribution of endogenous energy sources to survival both inside and outside the host is poorly understood. The contribution of glycogen production to the virulence, colonization and environmental survival of differentSalmonella entericaserotypes was assessed. Of 19 serotypes (339 strains) tested for glycogen production, 17 (256 strains) were positive. The avian-specific serovarsS. Gallinarum (62 strains) andS. Pullorum (21 strains) did not produce glycogen. The sequence ofglgCin threeS. Gallinarum strains tested revealed an identical deletion of 11 consecutive bases, which was not present inS. Pullorum, and a CCC insertion after position 597. Transduction ofS. Gallinarum andS. Pullorum to a glycogen-positive phenotype did not change the ability to colonize the intestine or affect virulence in the chicken. Mortality rates in chickens following oral infection with aS. Typhimurium glycogen mutant (glgC : : km) were not significantly reduced, although colonization of the intestine was reduced over the first 4 weeks of the trial. Growth and yield of theglgC : : km mutant were comparable to the parent. TheglgCmutant survived less well in faeces and in water at 4 °C when the strain was grown in LB broth containing 0·5 % glucose, and in saline it died off more rapidly after 7 days. The data suggest that glycogen has a complex but comparatively minor role in virulence and colonization, but a more significant role in survival.