Characterization of Pathogenic and Resistant Genome Repertoire Reveals Two Clonal Lines in Salmonella enterica subsp enterica Serovar Paratyphi B (+)-Tartrate Positive

A total of 36 contemporary human, animal, and environmental (+)-tartrate-fermenting (dT+) Salmonella enterica serovar Paratyphi B isolates, formerly called Salmonella serovar Java, and five related monophasic S. enterica serovar 4,5,12:b:- isolates from Belgium, Germany, the Netherlands, and the United Kingdom were investigated for clonality and antimicrobial resistance profiles, as well as their virulence and resistance gene repertoire. Two major clonal lines, which could be phenotypically differentiated by the expression of the O:5 antigen, were identified. All O:5 antigen negative strains were multidrug resistant and originated (with two exceptions) from Belgian, Dutch, or German poultry. Strains exhibiting the O:5 antigen encoded by the oafA gene revealed a more heterogeneous group including multidrug-resistant and susceptible strains. Compared to O:5 antigen negative isolates, Salmonella Paratyphi B dT+O:5 positive strains possessed additional virulence determinants. The Salmonella genomic island 1 was only found in O:5 positive strains. Five monophasic Salmonella 4,5,12:b:- lacking the phase-2 flagellar antigen were assigned to Salmonella Paratyphi B dT+isolates of the O:5 positive group. The conclusion of the analysis is that Salmonella Paratyphi B dT+O:5 negative and O:5 positive isolates evolved from a different lineage. Salmonella Paratyphi B dT+O:5 positive strains possess additional fimbrial and virulence genes that probably enable this clone to interact with a broader range of hosts and the environment. Salmonella Paratyphi B dT+O:5 negative continuously persists in poultry across Western Europe, especially Belgium, the Netherlands, and Germany.