Salmonella Enteritidis
Salmonella evolution
Evolutionary trends associated with niche specialization as modeled by whole genome analysis of egg-contaminating Salmonella enterica serovar Enteritidis
from Jean Guard, Devendra Shah, Cesar A. Morales and Doug Call writing in Salmonella: From Genome to Function
The mosaic nature of the Salmonella enterica genome facilitates its access to multiple environments. Many large scale genomic events have been described that contribute to the combinatorial complexity of the pathogenic Salmonellae. However, the impact of small scale genetic change occurring at the level of single nucleotide polymorphism (SNP) on the emergence of niche specialization is just now becoming appreciated. A recent review describes concepts behind the evolution that culminated in the remarkable ability of Salmonella enterica serovar Enteritidis to contaminate and survive in the internal content of eggs produced by otherwise healthy hens. Evidence suggests that combinations of SNPs facilitate niche specialization by Salmonella enterica. However, few typing methods incorporate unbiased strategies for their detection. Selection of appropriate biological assays for ranking SNPs and combinations of SNPs for their impact on the ability of Salmonella enterica to propagate outbreaks, pandemics and disease will be a significant challenge to improve the safety of the food supply.
Further reading: Salmonella: From Genome to Function
from Jean Guard, Devendra Shah, Cesar A. Morales and Doug Call writing in Salmonella: From Genome to Function
The mosaic nature of the Salmonella enterica genome facilitates its access to multiple environments. Many large scale genomic events have been described that contribute to the combinatorial complexity of the pathogenic Salmonellae. However, the impact of small scale genetic change occurring at the level of single nucleotide polymorphism (SNP) on the emergence of niche specialization is just now becoming appreciated. A recent review describes concepts behind the evolution that culminated in the remarkable ability of Salmonella enterica serovar Enteritidis to contaminate and survive in the internal content of eggs produced by otherwise healthy hens. Evidence suggests that combinations of SNPs facilitate niche specialization by Salmonella enterica. However, few typing methods incorporate unbiased strategies for their detection. Selection of appropriate biological assays for ranking SNPs and combinations of SNPs for their impact on the ability of Salmonella enterica to propagate outbreaks, pandemics and disease will be a significant challenge to improve the safety of the food supply.
Further reading: Salmonella: From Genome to Function
Phages of Salmonella
Typing phages and prophages of Salmonella
from Wolfgang Rabsch, Sandra Truepschuch, Daniel Windhorst and Roman G. Gerlach writing in Salmonella: From Genome to Function:
Most Salmonella strains contain prophages or remnant phages and release them spontaneously. Special bacteriophages were developed and used in phage typing systems for epidemiological work all over the world since 1947 to control salmonellosis. This method provides fast and inexpensive characterization of frequent serovars such as S. Typhimurium or S. Typhi on the sub-serovar level and is especially useful for primary analysis before investigation by other, more expensive molecular techniques such as sequencing. Prophages are themselves not only variable elements in a chromosome but also variable by module exchange within the prophage genome, thus providing a high discriminating power. The availability of several genome sequences of different Salmonella serovars has recently led to the identification of new prophage-like elements. The prophages present in serovars Typhimurium, Enteritidis and Typhi are discussed. Salmonella phages frequently carry foreign DNA, so called morons. These morons are not necessary for phage functions but provide a benefit for the host. A list of some new morons found in different Salmonella serovars is presented. Recently, a monophasic variant of S. Typhimurium mainly belonging to Anderson phage type DT193 has become one of the dominant causes of salmonellosis in Germany and other European countries. These strains with the antigenic formula 4,[5],12:i:- do not express the 2nd phase flagellum. Investigation of their prophage attachment sites showed that the sites for Gifsy-1, Gifsy-2 and ST64B were occupied by the respective prophages. In about 90% of the monophasic DT193 strains the P22/ST64T attachment site was occupied by a novel 18.4 kb fragment, containing several open reading frames with significant similiarity to phage-related genes.
Further reading: Salmonella: From Genome to Function | Bacteriophage: Genetics and Molecular Biology
from Wolfgang Rabsch, Sandra Truepschuch, Daniel Windhorst and Roman G. Gerlach writing in Salmonella: From Genome to Function:
Most Salmonella strains contain prophages or remnant phages and release them spontaneously. Special bacteriophages were developed and used in phage typing systems for epidemiological work all over the world since 1947 to control salmonellosis. This method provides fast and inexpensive characterization of frequent serovars such as S. Typhimurium or S. Typhi on the sub-serovar level and is especially useful for primary analysis before investigation by other, more expensive molecular techniques such as sequencing. Prophages are themselves not only variable elements in a chromosome but also variable by module exchange within the prophage genome, thus providing a high discriminating power. The availability of several genome sequences of different Salmonella serovars has recently led to the identification of new prophage-like elements. The prophages present in serovars Typhimurium, Enteritidis and Typhi are discussed. Salmonella phages frequently carry foreign DNA, so called morons. These morons are not necessary for phage functions but provide a benefit for the host. A list of some new morons found in different Salmonella serovars is presented. Recently, a monophasic variant of S. Typhimurium mainly belonging to Anderson phage type DT193 has become one of the dominant causes of salmonellosis in Germany and other European countries. These strains with the antigenic formula 4,[5],12:i:- do not express the 2nd phase flagellum. Investigation of their prophage attachment sites showed that the sites for Gifsy-1, Gifsy-2 and ST64B were occupied by the respective prophages. In about 90% of the monophasic DT193 strains the P22/ST64T attachment site was occupied by a novel 18.4 kb fragment, containing several open reading frames with significant similiarity to phage-related genes.
Further reading: Salmonella: From Genome to Function | Bacteriophage: Genetics and Molecular Biology