rDNA fingerprinting as a tool in epidemiological analysis ofSalmonella typhiinfections

Abstract

SUMMARYCharacterization of 169 strains of Salmonella typhi of phage types C1, C4, D1 and D9 isolated in 1975-88 was carried out by rDNA gene restriction pattern analysis.Twenty-four isolates had been recovered during four large waterbone outbreaks in the last 20 years in Sicily; 145 strains, isolated from apparently sporadic cases of infection in Southern Italy in the same period of time, were also examined.Application of rRNA-DNA hybridization technique after digestion of chromosomal DNA with Cla I showed the identity of patterns of the epidemic strains of phage types C1 and D1, confirming attribution of the outbreaks to single bacterial clones. Patterns of the two available strains of lysotype Dg were slightly different, whilst the 12 epidemic strains of phage type C4 could be assigned to two distinct patterns scarcely related to each other and, consequently, to two different clones. A considerable heterogeneity was detected among all apparently sporadic isolates of the four phage types under study.This fingerprinting method appears a reliable tool to complement phage typing in characterizing isolates of S. typhi. In particular, epidemiological features of spread of this salmonella serovar in areas, where simultaneous circulation of indigenous and imported strains occurs, can be elucidated.

Endemic, Epidemic Clone of Salmonella enterica Serovar Typhi Harboring a Single Multidrug-Resistant Plasmid in Vietnam between 1995 and 2002

“…Boyd et al (4) investigated the genomic content of a set of isolates: they found such differences that they concluded the genomic reservoir was unstable, even within a highly clonal bacterial population. Several workers using ribotyping with or without PFGE (3,11,12,16,26,27,32) (26,27).…”

Ribotypes ofSalmonella entericaserovarGallinarumbiovarsgallinarumandpullorum

“…Ribotyping was introduced by Grimont & Grimont (1986). It has previously been used to separate biovars of the same species (Moureau et al, 1989;Hernandez et al, 1991;Kiehlbauch et al, 1991) and it has been demonstrated that ribotyping can provide useful epidemiological information concerning Salmonella enterica infections (Martinetti & Altwegg, 1990;Nastasi et al, 1991). Among the restriction enzymes EcoKL, Smal and Hindlll used in this investigation, only EcoKL was able to separate all biovar pullorum isolates from those of biovar galltnarum.…”

Clonal Expansion and Microevolution of Quinolone-Resistant Salmonella enterica Serotype Typhi in Vietnam from 1996 to 2004

“…PstI ribotyping is a stable, reproducible, and sensitive method that has been used since 1989 (1,12,18,20,27,28); but it has several limitations: (i) manual ribotyping is technically demanding and automated ribotyping is expensive; (ii) due to the high degree of plasticity of the S. enterica serotype Typhi genome, genetic rearrangements produced by homologous recombinations between rrn operons can occur during the emergence of an outbreak, leading to various ribotypes among outbreak isolates; and (iii) a single genetic rearrangement can substantially modify the banding pattern, precluding an accurate cluster analysis of epidemiologically related isolates (10,21). PstI ribotyping indicated that most of the Vietnamese isolates belonged to the same clonal expansion, confirming the results obtained with the SNP method.…”