TABLE 3.

SPI-1 and SPI-2 genotypes and invasivenesses of S. enterica Senftenberg strains and controlsa

StrainS. enterica serovarSourceSPI-1SPI-2% Invasion ± SDb
CI1SenftenbergClinical isolateNegativePositive0.0049 ± 0.00003
CI2SenftenbergClinical isolateNegativePositive0.176 ± 0.0225
SC1SenftenbergNICPBPositivePositive1.537 ± 0.0586
STMTyphimuriumLaboratory strainPositivePositive4.89 ± 0.3927
STMinvA−TyphimuriumLaboratory straininvA insertional mutantPositive0.3860 ± 0.0839
  • a The P values were as follows: 0.0840 for CI1 versus STMinvA−, 0.0000 for CI1 versus STM, 0.0000 for CI1 versus SC1, 0.4610 for CI2 versus STMinvA−, 0.0000 for CI2 versus STM, 0.0000 for CI2 versus SC1, 0.0000 for SC1 versus STMinvA−, and 0.0000 for SC1 versus STM. Note that CI1 and CI2 were stool sample isolates from the Shenzhen outbreak, SC1 was the control strain, STM was invasion-positive control, and STMinvA− was the invasion-negative control.

  • b Invasion is expressed as the percentage of the initial inoculum of bacteria that was insensitive to gentamicin because of cell invasion. The value represents the averages ± standard deviations for three experiments. The original data were analyzed by using SPSS software (version 13.0).