Molecular Properties of Salmonella enterica Serotype Paratyphi B Distinguish between Its Systemic and Its Enteric Pathovars

Abstract

Salmonella enterica serotype O1,4,5,12:Hb:1,2, designated according to the current Kauffmann-White scheme as S. enterica serotype Paratyphi B, is a very diverse serotype with respect to its clinical and microbiological properties. PCR and blot techniques, which identify the presence, polymorphism, and expression of various effector protein genes, help to distinguish between strains with systemic and enteric outcomes of disease. All serotype Paratyphi B strains from systemic infections have been found to be somewhat genetically related with respect to the pattern of their virulence genes sopB, sopD, sopE1, avrA, and sptP as well as other molecular properties (multilocus enzyme electrophoresis type, pulsed-field gel electrophoresis [PFGE] type, ribotype, and IS200 type). They have been classified as members of the systemic pathovar (SPV). All these SPV strains possess a new sopE1-carrying bacteriophage (designated ⌽SopE309) with high SopE1 protein expression but lack the commonly occurring avrA determinant. They exhibit normal SopB protein expression but lack SopD protein production. In contrast, strains from enteric infections classified as belonging to the enteric pathovar possess various combinations of the respective virulence genes, PFGE pattern, and ribotypes. We propose that the PCR technique for testing for the presence of the virulence genes sopE1 and avrA be used as a diagnostic tool for identifying both pathovars of S. enterica serotype Paratyphi B. This will be of great public health importance, since strains of serotype Paratyphi B have recently reemerged worldwide.Salmonella enterica is one of the most diverse species in the bacterial kingdom. It is currently subdivided into six subspecies according to fermentative properties and into ca. 2,400 serotypes according to polymorphisms in the lipopolysaccharide (O antigen) and flagellar (H antigen) structures (20). Among S. enterica, two major pathogenic groups causing human infections have been identified: Salmonella strains restricted or adapted to humans (e.g., S. enterica serotype Typhi and S. enterica serotype Paratyphi A, B, and C) cause systemic clinical conditions such as septicemia and organ manifestation (typhoid fever), while the so-called enteritis salmonella strains (e.g., S. enterica serotype Enteritidis) cause local intestinal infections and originate epidemiologically from animal husbandry.However, human infections due to S. enterica serotype Paratyphi B with the O:H formula O1,4,5,12:Hb:1,2 are not restricted to systemic infections (paratyphoid fever) and humanto-human infection routes (15) but have been associated with gastroenteritis and food-borne infections as well (3,7,12). This clinical and epidemiological heterogeneity was regarded as a consequence of fermentative varieties among this serotype. Many such isolates do ferment d-tartrate and have been designated biovar S. enterica serotype Java, in contrast to non-dtartrate-fermenting strains, designated biovar S. enterica serotype Paratyphi B sensu stricto (3,12,13). Moreover, S. ent...

Characterization of Salmonella enterica Subspecies I Genovars by Use of Microarrays

“…For example, in serovar Paratyphi B, strains from systemic infections always lack the avrA gene but contain sopE1, whereas strains from enteric infections generally display different absence-presence patterns for these genes (24). All systemic isolates investigated by Prager et al belonged to MLEE type 1 (Pb1).…”

Genetic Determinants and Polymorphisms Specific for Human-Adapted Serovars of Salmonella enterica That Cause Enteric Fever

“…Serovar Paratyphi B isolate S1583 was d-tartarate positive (indicative of biovar Java). This serovar normally causes nonsystemic disease symptoms (35), so it was surprising that there was considerable similarity to the serovar Typhi-encoded alleles of trpS, sseC, and sseF. Notably, there are extensive genetic differences within strains of serovar Paratyphi B (27,35,39), so the observation of a single strain with alleles similar to those of the human-adapted serovars might be possible.…”

“…This serovar normally causes nonsystemic disease symptoms (35), so it was surprising that there was considerable similarity to the serovar Typhi-encoded alleles of trpS, sseC, and sseF. Notably, there are extensive genetic differences within strains of serovar Paratyphi B (27,35,39), so the observation of a single strain with alleles similar to those of the human-adapted serovars might be possible. Otherwise, use of the island from STY4217 to STY4222 for molecular identification of human-adapted typhoidal serovars resolved the cross-reaction with strain S1583, as this region was not encoded in any serovar Paratyphi B isolate.…”

Frequency and polymorphism of sopE in isolates of Salmonella enterica belonging to the ten most prevalent serotypes in England and Wales

“…5-fold increase in invasive ability compared with the wildtype (Ehrbar et al, 2002), which may be sufficient to result in a small increase in transmissibility of sopE-positive strains and increase prevalence over time. Prager et al (2003) found that all isolates of S. Paratyphi B associated with systemic infection carried sopE, compared with only a small number of S. Paratyphi B associated with enteric infection. These strains are distinguished phenotypically only by their ability to utilize D-tartrate, but show markedly different levels of virulence in man.…”