Isolation of Serratia fonticola producing FONA, a minor extended-spectrum β-lactamase (ESBL), from imported chicken meat in Japan.

Five novel strains of Serratia fonticola that produce FONA, a minor extended spectrum beta-lactamase (ESBL), were isolated during the routine surveillance of ESBLproducing Enterobacteriaceae in imported chicken meat in Japan in 2017 and 2018. These strains exhibited a clear ESBL phenotype in susceptibility tests carried out in the presence of clavulanic acid; however, they were all negative in the multiplex polymerase chain reaction assay used to detect the TEM, SHV and CTX-M β-lactamase genes. After identification of the bacterial species as S. fonticola, full blaFONA genes were amplified and the DNA sequences were determined. The blaFONA genes from all five strains were different from those previously reported (blaFONA-1 to blaFONA-6); they clustered closely with one another but were distinct from previously reported blaFONA genes in a phylogenic analysis based on amino acid sequences.