Molecular Characterization of Multiresistant d -Tartrate-Positive Salmonella enterica Serovar Paratyphi B Isolates

Abstract

ABSTRACT Since 1996, the National Salmonella Reference Laboratory of Germany has received an increasing number of Salmonella enterica subsp. enterica serovar Paratyphi B isolates. Nearly all of these belonged to the dextrorotatory tartrate-positive variant ( S . enterica subsp. enterica serovar Paratyphi B dT + ), formerly called S . enterica subsp. enterica serovar Java. A total of 55 selected contemporary and older S . enterica subsp. enterica serovar Paratyphi B dT + isolates were analyzed by plasmid profiling, antimicrobial resistance testing, pulsed-field gel electrophoresis, IS 200 profiling, and PCR-based detection of integrons. The results showed a high genetic heterogeneity among 10 old strains obtained from 1960 to 1993. In the following years, however, new distinct multiresistant S . enterica subsp. enterica serovar Paratyphi B dT + clones emerged, and one clonal lineage successfully displaced the older ones. Since 1994, 88% of the isolates investigated were multiple drug resistant. Today, a particular clone predominates in some German poultry production lines, poultry products, and various other sources. It was also detected in contemporary isolates from two neighboring countries as well.