Epidemiology ofSalmonella typhimurium: ribosomal DNA analysis of strains from human and animal sources

Abstract

SUMMARYSalmonella typhimurium is the most frequently identified serovar of Salmonella in Italy. This serovar is characterized by the widespread dissemination among human and non-human sources of phenotypically and genetically well-differentiated clones.In this study 457 strains of S. typhimurium isolated in Italy in the years 1982-91 from human and animal sources were submitted to characterization by the rDNA fingerprinting technique. Application of this typing method, after digestion of chromosomal DNA with HincIl endonuclease, confirmed the greatest genetic differentiation of clones of S. typhimurium, allowing reliable identification of 45 rDNA patterns linked into 9 major clusters. rDNA pattern clusters or ribotypes specific to man were not recognized, whereas some rDNA patterns were characteristically related to ducks, pigeons and pet birds. The ribotyping results for isolates from animal hosts suggest that pig and cattle are the main source of human infection. INTROD)UCTIONSalmonella typhimuriumn is the most frequently identified serovar of Salmonella at the Centres of Enterobacteriaceae in Italy. This serovar, which is characterized by a widespread dissemination and by its differentiation in phenotypically and genetically distinct clones, has been studied by various typing techniques to obtain reliable strain discrimination. In particular, combined use of biotyping and phage typing [1] and plasmid profile analysis [2,3] have proved to be useful tools in tracing of S. typhimurium infections.Because of the involvement of man and of a wide range of animal hosts in the spread of this serovar, possible relationships between bio-phage types of strains of S. typhimurium and sources have been investigated [4][5][6]. In our study, the rDNA fingerprinting technique, which has been applied in recent years to many bacterial species [7][8][9][10], was used on strains of S. typhimurium isolated over the last 10 years in Italy from human and non-human sources, in order to investigate the epidemiological features of interchange of clones between man and animal hosts. 19HYG 110

A three-way ribotyping scheme for Salmonella serotype Typhimurium and its usefulness for phylogenetic and epidemiological purposes

“…However, for different Salmonella serotypes, different REs have been found to be most useful in producing interpretable ribotypes [6,9,23, 241 and the present study identified HincII alone, or in combination with SaZI and PvuII, as the most useful RE in subtyping Typhimurium. H i n d ribotyping of xx H1 S1 P1 H2 S1 P1 H3 S1 P1 H4 S1 P1 H4 S1 P4 H11 S7 P1 H3 S1 P2 H3 S2 P2 H3 S8 P2 H3 S2 Typhimurium has been reported by Nastasi et al [6]; when results from that and the present series were compared, ribotypes numbered 8, 5, 1-14, 6, 2 and 16 found by Nastasi et aZ. [6] among Italian isolates seemed identical or very similar to ribotypes H1, H3, H4, H7, H13 and HI 1, respectively, among Asturian strains.…”

“…H i n d ribotyping of xx H1 S1 P1 H2 S1 P1 H3 S1 P1 H4 S1 P1 H4 S1 P4 H11 S7 P1 H3 S1 P2 H3 S2 P2 H3 S8 P2 H3 S2 Typhimurium has been reported by Nastasi et al [6]; when results from that and the present series were compared, ribotypes numbered 8, 5, 1-14, 6, 2 and 16 found by Nastasi et aZ. [6] among Italian isolates seemed identical or very similar to ribotypes H1, H3, H4, H7, H13 and HI 1, respectively, among Asturian strains. It should be pointed out, however, that the rates of the most frequent ribotypes in the two series were different.…”

Prevalence of antimicrobial resistance among pigeon isolates of Streptococcus gallolyticus , Escherichia coli and Salmonella enterica serotype Typhimurium

“…The MIC values were so homogeneous that it appeared as if replicates of a single clonal strain had been tested. Using a rDNA fingerprinting technique, Nastasi et al (1993) found that pigeon strains belong to clones of serotype Typhimurium that are only sporadically found in humans and other animals. The isolation of the same serotypes in humans, pigeons and other animals therefore does not imply that epidemiologically related Salmonella strains are involved.…”

Salmonella enterica Serotype Typhimurium and Its Host-Adapted Variants

“…Since the serological variant Copenhagen is also responsible for sporadic cases of disease in humans and other mammals, there was considerable concern in the first half of the 20th century that pigeons may be a reservoir for salmonellosis in mammalian species. However, subsequent studies have shown that serotype Typhimurium isolates from pigeons differ in their biotype and ribotype from those isolated from humans or other animals, suggesting that pigeons are not a source of infection for other host reservoirs (46,55,65,69). Based on these data, the existence of a serotype Typhimurium "pigeon type" that predominates in pigeons but is rarely transmitted to other host species has been proposed (25,31,35,38).…”