Genetic characteristics of emerging <i>Salmonella enterica</i> serovar Agona strains isolated from humans in the prior period to occurrence of the serovar shift in broilers

Abstract

Our previous studies found that a dominant serovar of Salmonella enterica isolates from three farms raising broilers in 2014 and 2015 was serovar Agona and the number of Infantis isolates decreased (the serovar shift). In this study, 52 S. Agona strains which isolated between 1993 and 2008, were compared to the serovar shift clone by molecular epidemiology and phylogenetic analyses, using pulsed field gel electrophoresis and whole genome sequence analyses. Of the 52 strains, one strain isolated from a human case in 1995 was genetically identical to the serovar shift clone, even though it was isolated prior to the serovar shift. These results suggested that the S . Agona serovar shift clone had existed in a source other than chicken penetrated chicken population.

Whole-Genome Sequence Analysis of an Extensively Drug-Resistant Salmonella enterica Serovar Agona Isolate from an Australian Silver Gull (Chroicocephalus novaehollandiae) Reveals the Acquisition of Multidrug Resistance Plasmids

“…In Japan, S . Agona has caused outbreaks of disease in humans and has risen to prominence, replacing Salmonella enterica serovar Infantis as the dominant serovar in the poultry industry ( 17 ). In Australia, S .…”

“…In 2015, S. Agona was also responsible for a small outbreak of gastrointestinal disease that was traced to contaminated sushi in Sydney, Australia (16). In Japan, S. Agona has caused outbreaks of disease in humans and has risen to prominence, replacing Salmonella enterica serovar Infantis as the dominant serovar in the poultry industry (17). In Australia, S. Agona has (i) been linked to Salmonella infections in humans originating from chicken eggs (18), (ii) been isolated from Australian layer hen sheds (19), and (iii) is a significant contaminant of grain in Australian feed mills, where it was the most frequently isolated serovar in raw feed (20), suggesting it may have an environmental reservoir.…”

Characterization of Salmonella Isolates from Wastewater Treatment Plant Influents to Estimate Unreported Cases and Infection Sources of Salmonellosis

“…Moreover, serovar Agona strain 14-8, which was isolated from human and clustered with the isolates from broilers in the Yamanashi Prefecture using whole-genome sequencing [24], was closely related to the isolates from two sewage and four human samples (Figure 1a). Murakami et al [36] and Torii et al [25] pointed out that the strains clustered with strain 14-8 were rarely obtained from broilers, other retail poultry, or humans in other regions. Furthermore, serovar Mbandaka, which caused an outbreak linked to cereal in the United States between March and August 2018 [37,38], was detected from sewage and humans in May and June 2018, respectively, although the relationship to the outbreak strain was not accounted for.…”

“…To estimate the sources of the isolates from sewage, the serovar Agona strain, designated as 14-8, which was isolated from a human in 2014 and clustered with strains isolated from broilers using PFGE analysis and whole-genome sequencing [24,25], was also analyzed. The PFGE pattern of the 14-8 strain was closely related to those of two and four isolates from sewage and humans, respectively, and the antimicrobial resistance pattern was consistent with these six isolates (Figure 1a).…”

Emergence of <i>Salmonella enterica</i> subsp. <i>enterica</i> serovar Chester in a rural area of Japan

“…We speculate that all the S. Chester isolates in this study may have been derived from the same genetic clone, and although there is no direct evidence that this is so, our previous reports support this hypothesis. In our previous reports of Salmonella serovar Agona, S. Agona strains were divided into several genetic clones based on a single nucleotide polymorphism (SNP) analysis of whole genome sequencing (WGS) data, and the grouping of those clones was identical to that found on PFGE using two types of restriction enzymes [26,31]. Moreover, Salmonella serovar Infantis strains were almost identically subdivided into several genetic clones based on SNP analysis of WGS data compared to those identified using PFGE [21,30].…”