分子疫学および薬剤耐性Molecular Characteristics and Antimicrobial Resistance
日本産鶏肉由来Salmonella enterica serovar Schwarzengrundの遺伝学的特徴と薬剤耐性 Molecular Characteristics and Antimicrobial Resistance of Salmonella enterica Serovar Schwarzengrund from Chicken Meat
in Japan.
Our previous study revealed that Salmonella enterica serovar Schwarzengrund-contaminated areas of broiler chickens have
expanded from West Japan to East Japan.
Comparing S. Schwarzengrund isolates obtained from chicken meat in 2008 and 2015-2019, an increase in the proportion of
those resistant to kanamycin [51.4-89.7% (p < 0.001)] was observed. In contrast, the proportion of isolates resistant to
both streptomycin and tetracycline and those that harbored a 1.0-kb class 1 integron, aadA1, and tetA, significantly
decreased from 100% in 2008 to 47.1% in 2015-2019 (p < 0.001).
A 1.0-kb class 1 integron containing aadA1, harbored by 78 isolates, was different from that reported in globally
distributed S. Schwarzengrund strains (1.9 kb, containing the dfrA12-aadA2 gene cassette).
Twenty-five isolates from different product districts and years of isolation were typed as sequence type (ST) 241 with
multilocus sequence typing.
Our results suggest that S. Schwarzengrund, which contaminates chicken meat in Japan, shares a common ancestor
regardless of the product district from 2008 to recent years. Moreover, S. Schwarzengrund ST241 may have spread from
western to eastern Japan.