Further consideration of the clonal nature of Salmonella typhi: evaluation of molecular and clinical characteristics of strains from Indonesia and Peru

Abstract

We examined envelope protein profiles, chromosomal restriction endonuclease digest patterns, and immune responses to envelope proteins for collections of Salmonella typhi strains isolated in Peru and Indonesia. Only minor differences in envelope protein patterns were apparent among strains. Strains from 7 of 20 Indonesian patients had a distinct chromosomal digest pattern compared with patterns of Peruvian and other Indonesian strains. Strains with this pattern carried the gene for thej flagellar antigen (Hi-j); differences in response to envelope proteins ofj and d strains were noted on immunoblot analysis. Our data suggest that there are genotypic and phenotypic differences among S. typhi strains. The clinical importance of these differences remains to be fully evaluated; however, in this study it was not possible to show a clear correlation between strain characteristics and disease severity.

Molecular analysis of isolates of Salmonella typhi obtained from patients with fatal and nonfatal typhoid fever

“…Few studies have been performed to determine if variations in clinical presentation are related to strain differences. Previous studies have, in fact, shown little correlation between strain characteristics and disease severity (6,8). This is perhaps not surprising, given the small number of strains studied and the well-known observation that S. typhi represents a single clone that has shown minimal intraspecies divergence in different parts of the world (14,16).…”

“…No association between the characteristics of these clones and disease severity was found (8). Franco et al, utilizing envelope protein profiles, restriction fragment length polymorphism of chromosomal DNA, and immune response to envelope proteins, also found no clear correlation between strain characteristics and disease severity (6). A more recent study, however, reported an association between flagellar serotypes and decreased severity of illness and invasiveness (7).…”

Analysis of Salmonella typhi isolates from Southeast Asia by pulsed-field gel electrophoresis

“…In contrast to these phenotypic approaches, genotypic techniques are believed to possess better reproducibility and discriminatory power (7). In a study of 69 S. typhi strains from Indonesia and Peru using envelope protein profiles, chromosomal restriction endonuclease digestion patterns, and immune response to envelope proteins, Franco et al (5) concluded that there are genotypic and phenotypic differences among S. typhi strains. Ribotyping studies of S. typhi isolates from different parts of the world, including those from the United States, Sicily, and Malaysia (1,9,11), have also indicated considerable genetic diversity.…”

“…It is also important to emphasize that the phenotypic correlates of these genetic differences are unknown and the clinical significance of these genetic differences and their importance with regard to the virulence of individual strains remain to be evaluated. This remains as an important issue in research on typhoid fever in view of the observation that the reported clinical manifestations of typhoid fever differ markedly in different parts of the world (5,6), including Southeast Asia.…”

Epidemiologic analysis of sporadic Salmonella typhi isolates and those from outbreaks by pulsed-field gel electrophoresis

“…More recently, there has been an increasing interest in the application of molecular techniques to type bacterial pathogens (35). With S. typhi, techniques such as multilocus enzyme electrophoresis (27,32), lipopolysaccharide (16) and envelope protein profiles (l1), chromosomal restriction endonuclease digestion patterns (11), and ribotyping (1, 24) have been used. Many of these techniques are not sufficiently sensitive for distinguishing individual strains and inves-tigators often find them tedious to perform.…”