The identification, typing and fingerprinting of Salmonella: laboratory aspects and epidemiological applications

Abstract

Since the 1930s, traditional methods of strain identification based on serotyping and phage typing have been the foundation of salmonella epidemiology. Although the incidence of diseases such as typhoid and paratyphoid has decreased in recent years, food-poisoning caused by non-typhoidal salmonella strains has now reached epidemic proportions in many countries, despite improvements in sanitation and hygiene. Precise strain identification is an essential prerequisite for epidemiological investigations aimed at combating the spread of these strains and eradicating the sources of infection. Modern methods of genotypic typing, particularly those based on physical characterization of the plasmid content of the organism have already proved invaluable for the identification and differentiation of strains in many outbreaks. These plasmid typing methods are now increasingly used with serotyping and phage typing for many epidemiological investigations. Other methods of genotypic typing, particularly those based on recognition of small differences in chromosome structure, are not yet practical for the examination of large numbers of strains. Nevertheless, improvements in small-scale methods for chromosomal DNA extraction coupled with the increasing use of non-isotopic labels for identification of restriction fragment length polymorphisms may provide a new dimension to Salmonella epidemiology.

Genotype analysis of faecal and blood isolates of Salmonella dublin from humans in England and Wales

“…The latter two methods have pr-eviously been combined for-a typing analysis of S. enteritidis [23] and plasmid typing has been used extensively for a variety of applications [24]. IS8200 profiling has previously been combined with the analysis of restriction fragment length polymorphisms at several cloned chr-omosomal genes in a phylogenetic analysis of S. enteritidis [12].…”

Interrelationships between strains ofSalmonella enteritidis

“…Phage typing is used to subdivide strains within a particular serotype and phage typing schemes have been developed for the most common salmonella serotypes in the UK, namely S. enteritidis, S. typhimurium and S. virchow, and also for other serotypes of clinical and epidemiological importance such as S. typhi [7]. The 1-2 development in LEP of a phage typing scheme for S. enteritidis [8] has provided an invaluable means of differentiating strains of this organism, and has proved particularly useful for epidemiological studies.…”

Padrão de susceptibilidade a antimicrobianos e perfil plasmidial em Salmonella Muenster isoladas de suínos e do ambiente de abatedouros

“…Devido à conhecida instabilidade dos plasmídios, os quais podem ser perdidos ou adquiridos durante o processo evolucionário (Threlfall & Frost 1990), admite-se precariamente, a provável presença do perfil plasmidial P8 nas amostras pertencentes aos perfis P2, P4 e P6.…”

“…Devido a problemas relacionados à reprodutibilidade ou poder discriminatório associados a esses métodos de tipagem fenotípica, técnicas moleculares foram desenvolvidas propiciando uma boa discriminação entre cepas do mesmo sorotipo ou fagotipo (Threlfall & Frost 1990).…”