FONA-7, a Novel Extended-Spectrum β-Lactamase Variant of the FONA Family Identified in Serratia fonticola.

Serratia fonticola is a human pathogen widely found in the environment, with birds being reported as possible natural hosts. During an epidemiological and genomic surveillance study conducted to monitor the occurrence of extended-spectrum β-lactamase (ESBL)-producing Enterobacterales in South American wild birds, we identified an ESBL-positive S. fonticola in a fecal sample collected from a Hudsonian Whimbrel, during its non-breeding range on the Pacific Coast of Chile. Whole genome sequencing analysis and "in silico" modeling revealed a novel variant of the class A ESBLs FONA family, designated FONA-7, which shows 96.28% amino acid identity with FONA-6; with amino acid substitutions occurring in the signal peptide sequence (Thr22→Ser), and in the mature protein (Ser39→Asn and Thr227→Ile). This finding denotes that migratory birds can be potential vectors for the transboundary spread of ESBL-producing bacteria, creating a further theoretical risk for the origin of novel plasmid-encoded β-lactamases.