Antimicrobial Resistance in Salmonella enterica Serovar Paratyphi B Variant Java in Poultry from Europe and Latin America.

Salmonella enterica serovar Paratyphi B variant Java sequence type 28 is prevalent in poultry and poultry meat. We investigated the evolutionary relatedness between sequence type 28 strains from Europe and Latin America using time-resolved phylogeny and principal component analysis. We sequenced isolates from Colombia, Guatemala, Costa Rica, and the Netherlands and complemented them with publicly available genomes from Europe, Africa, and the Middle East. Phylogenetic time trees and effective population sizes (Ne) showed separate clustering of strains from Latin America and Europe. The separation is estimated to have occurred during the 1980s. Ne of strains increased sharply in Europe around 1995 and in Latin America around 2005. Principal component analysis on noncore genes showed a clear distinction between strains from Europe and Latin America, whereas the plasmid gene content was similar. Regardless of the evolutionary separation, similar features of resistance to ß-lactams and quinolones/fluoroquinolones indicated parallel evolution of antimicrobial resistance in both regions.

Improving Our Understanding of Salmonella enterica Serovar Paratyphi B through the Engineering and Testing of a Live Attenuated Vaccine Strain.

Enteric fever is caused by three Salmonella enterica serovars: Typhi, Paratyphi A, and Paratyphi B sensu stricto Although vaccines against two of these serovars are licensed (Typhi) or in clinical development (Paratyphi A), as yet there are no candidates for S. Paratyphi B. To gain genomic insight into these serovars, we sequenced 38 enteric fever-associated strains from Chile and compared these with reference genomes. Each of the serovars was separated genomically based on the core genome. Genomic comparisons identified loci that were aberrant between serovars Paratyphi B sensu stricto and Paratyphi B Java, which is typically associated with gastroenteritis; however, the majority of these were annotated as hypothetical or phage related and thus were not ideal vaccine candidates. With the genomic information in hand, we engineered a live attenuated S. Paratyphi B sensu stricto vaccine strain, CVD 2005, which was capable of protecting mice from both homologous challenge and heterologous challenge with S. Paratyphi B Java. These findings extend our understanding of S. Paratyphi B and provide a viable vaccine option for inclusion in a trivalent live attenuated enteric fever vaccine formulation.IMPORTANCE We developed a live attenuated Salmonella enterica serovar Paratyphi B vaccine that conferred protection in mice against challenge with S Paratyphi B sensu stricto and S Paratyphi B Java, which are the causes of enteric fever and gastroenteritis, respectively. Currently, the incidence of invasive S. Paratyphi B sensu stricto infections is low; however, the development of new conjugate vaccines against other enteric fever serovars could lead to the emergence of S. Paratyphi B to fill the niche left by these other pathogens. As such, an effective S. Paratyphi B vaccine would be a useful tool in the armamentarium against Salmonella infections. Comparative genomics confirmed the serovar-specific groupings of these isolates and revealed that there are a limited number of genetic differences between the sensu stricto and Java strains, which are mostly hypothetical and phage-encoded proteins. The observed level of genomic similarity likely explains why we observe some cross-protection.

Molecular characterization of Salmonella paratyphi B dT+ and Salmonella Heidelberg from poultry and retail chicken meat in Colombia by pulsed-field gel electrophoresis.

Salmonella Paratyphi B dT+ variant (also termed Salmonella Java) and Salmonella Heidelberg are pathogens of public health importance that are frequently isolated from poultry. As a step toward implementing the Colombian Integrated Program for Antimicrobial Resistant Surveillance, this study characterized molecular patterns of Salmonella Paratyphi B dT+ and Salmonella Heidelberg isolated from poultry farms, fecal samples, and retail chicken meat using pulsed-field gel electrophoresis (PFGE). The objective of this study was to determine the genetic relationship among isolates and to determine potential geographically predominant genotypes. Based on PFGE analysis, both serovars exhibited high heterogeneity: the chromosomal DNA fingerprints of 82 Salmonella Paratyphi B dT+ isolates revealed 42 PFGE patterns, whereas the 21 isolates of Salmonella Heidelberg revealed 10 patterns. Similar genotypes of both serovars were demonstrated to be present on farms and in retail outlets. For Salmonella Paratyphi B dT+, closely genetically related strains were found among isolates coming from different farms and different integrated poultry companies within two departments (Santander and Cundinamarca) and also from farms located in the two geographically distant departments. For Salmonella Heidelberg, there were fewer farms with genetically related isolates than for Salmonella Paratyphi B dT+. A possible dissemination of similar genotypes of both serovars along the poultry production chain is hypothesized, and some facilitating factors existing in Colombia are reviewed.