Evaluation of PCR-Based Identification and Genotyping Methods for theiapGenes inListeria monocytogenesand otherListeriaspp.

Abstract

By using 181 Listeria spp. strains except for L. ivanovii, we evaluated the three distinct PCR methods targeting the iap genes encoding p60 proteins for genus or species identification, and the PCR-RFLP analysis for genotyping. Each of the two species-specific PCR methods yielded the expected amplicons from all of the 126 L. monocytogenes and 43 L. innocua strains tested. The genus-specific PCR method amplified the target regions (about 1.4 kb) from 178 Listeria strains other than3 L. grayi strains tested. The PCR-RFLP analysis with either HhaI or HindIII showed distinct several patterns: 97L. monocytogenes strains divided into 2 genotypes (types I and II) with Hind III and 5 genotypes (types A, B, C, D and E) withHhaI. On the other hand, 43 L. innocua strains showed an identical genotype (type I with Hind III and type F withHhal). Bot h L. seeligeri and L. welshimeri strains showed a distinct genotype (type I withHind III and type G withHhal). The L. monocytogenes genotypes correlated with the serovars. All 4b strains exhibited one genotype (type I and type A). 1/2b strains exhibited type I and types A or B. In contrast, 1/2a strains exhibited type II and types C, D, or E. 1/2c strains exhibited only type II and type C. Thus, these results suggest that the PCR and PCR-RFLP methods can identify or estimate the genus and species of listerial strains rapidly and are useful tools to genotype Listeria spp. strains phylogenetically.