Population Structure of Salmonella enterica Serovar 4,[5],12:b:− Strains and Likely Sources of Human Infection

Abstract

ABSTRACTSalmonella entericaserovar 4,[5],12:b:− is a monophasic serovar not able to express the second-phase flagellar antigen (H2 antigen). In Germany, the serovar is occasionally isolated from poultry, reptiles, fish, food, and humans. In this study, a selection of 67 epidemiologically unrelatedSalmonella entericaserovar 4,[5],12:b:− strains isolated in Germany between 2000 and 2011 from the environment, animal, food, and humans was investigated by phenotypic and genotypic methods to better understand the population structure and to identify potential sources of human infections. Strains of this monophasic serovar were highly diverse. Within the 67 strains analyzed, we identified 52 different pulsed-field gel electrophoresis XbaI profiles, 12 different multilocus sequence types (STs), and 18 different pathogenicity array types. The relatedness of strains based on the pathogenicity gene repertoire (102 markers tested) was in good agreement with grouping by MLST.S. entericaserovar 4,[5],12:b:− is distributed across multiple unrelated eBurst groups and consequently is highly polyphyletic. Two sequence types (ST88 and ST127) were linked toS. entericaserovar Paratyphi B (d-tartrate positive), two single-locus variants of ST1583 were linked toS. entericaserovar Abony, and one sequence type (ST1484) was associated withS. entericaserovar Mygdal, a recently defined, new serovar. From the characterization of clinical isolates and those of nonhuman origin, it can be concluded that the potential sources of sporadic human infections withS. entericaserovar 4,[5],12:b:− most likely are mushrooms, shellfish/fish, and poultry.