Characterization of Salmonella serovars by PCR-single-strand conformation polymorphism analysis

Abstract

PCR-restriction fragment length polymorphism (PCR-RFLP) and PCR-single-strand conformation polymorphism (PCR-SSCP) analyses were carried out on the 1.6-kb groEL gene from 41 strains of 10 different Salmonella serovars. Three HaeIII RFLP profiles were recognized, but no discrimination between the serovars could be achieved by this technique. However, PCR-SSCP analysis of the groEL genes of various Salmonella serovars produced 14 SSCP profiles, indicating the potential of this technique to differentiate different Salmonella serovars (interserovar differentiation). Moreover, PCR-SSCP could differentiate strains within a subset of serovars (intraserovar discrimination), as three SSCP profiles were produced for the 11 Salmonella enterica serovar Enteritidis strains, and two SSCP profiles were generated for the 7 S. enterica serovar Infantis and five S. enterica serovar Newport strains. PCR-SSCP has the potential to complement classical typing methods such as serotyping and phage typing for the typing of Salmonella serovars due to its rapidity, simplicity, and typeability.

FIG. 1.

PCR-RFLP profiles of groEL DNAs after HaeIII digestion for the 41 strains from 10 serovars run on a 1.5% TBE gel. Lanes 1 and 18, molecular weight markers (New England Biolabs Marker II). The strains and RFLP profiles are as follows: lane 2, S. enterica serovar Typhimurium strain 1, profile 1; lanes 3 and 4, serovar Infantis strains 17 and 18, respectively, profile 1; lane 5, serovar Newport strain 25, profile 1; lane 6, serovar Virchow strain 34, profile 1; lanes 7, 8, and 9, serovar Enteritidis strains 6, 7, and 8, respectively, profile 2; lane 10, serovar Infantis strain 22, profile 2; lane 11, serovar Newport strain 24, profile 2; lane 12, serovar Hadar strain 29, profile 2; lane 13, serovar Paratyphi A strain 37, profile 2; lane 14, serovar Paratyphi B strain 38, profile 2; lanes 15 and 16, S. enterica serovar Typhi strains 39 and 40, respectively, profile 2; and lane 17, serovar Arizona strain 41, profile 3. Strain numbers are as in Table 2.

FIG. 2.

PCR-SSCP profiles of groEL DNAs after HaeIII digestion for the strains from 10 serovars run on a CleanGel (10% polyacrylamide gel). Lane 1, New England Biolabs Marker II (with sizes in base pairs). The strains and SSCP profiles are as follows: lane 2, S. enterica serovar Typhimurium strain 1, profile 1; lanes 3 and 4, serovar Infantis strains 17 and 18, respectively, profile 11; lane 5, serovar Newport strain 25, profile 12; lane 6, serovar Virchow strain 34, profile 13; lanes 7, 8, and 9, serovar Enteritidis strains 6, 7, and 8, respectively, profiles 2, 3, and 4; lane 10, serovar Infantis 22, profile 7; lane 11, serovar Newport strain 24, profile 5; lane 12, serovar Hadar strain 29, profile 6; lane 13, serovar Paratyphi A strain 37, profile 8; lane 14, serovar Paratyphi B strain 38, profile 9; lanes 15 and 16, serovar Typhi strains 39 and 40, respectively, profile 10; and lane 17, serovar Arizona strain 41, profile 14. Strain numbers are as in Table 2. S1, single-strand bands of the denatured 850-bp HaeIII groEL fragment; S2, denatured 630-bp HaeIII groEL fragment; S3, denatured 620-bp HaeIII groEL fragments; S4, denatured 350-bp HaeIII groEL fragment; S5, denatured 250-bp HaeIII groEL fragment; S6, denatured 238-bp HaeIII groEL fragment.