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NCBI PD Serovar Link for Serovar Livingstone: https://www.ncbi.nlm.nih.gov/pathogens/isolates/#(taxgroup_name:%22Salmonella%20enterica%22)%20AND%20computed_types:(%22serotype=Livingstone%22)

Genetic characteristics: In a Serovar Livingstone has been found to be polyphyletic with four lineages identified and one stand-alone singleton that does not cluster with any other Salmonella Livingstone isolates. In a nosocomial outbreak associated with serovar Livingstone in Tunisia, all outbreak strains (n=16) exhibited resistance to ceftriaxone and ceftazidime, mediated by the production of an extended-spectrum β-lactamase (ESBL). Additionally, they showed resistance to multiple aminoglycosides (kanamycin, tobramycin, netilmicin, gentamicin, and amikacin) as well as sulfamethoxazole-trimethoprim. The ESBL resistance was encoded on a 40-kb conjugative plasmid. Genetic analysis revealed the presence of the mobile insertion sequence ISEcp1 upstream of bla_CTX-M-27, positioned similarly to its arrangement in bla_CTX-M-14. A novel trimethoprim resistance gene, dfrA21, was identified on a 90-kb plasmid. This gene was integrated as a single resistance cassette within a class I integron. Li et al. identified five clades of serovar Livingstone, with evidence suggesting that the global animal feed trade likely facilitated their introduction into China. Among these, Clade-5-I-a/b—the predominant lineage in China—demonstrated invasiveness in murine, avian (chicken), and zebrafish infection models. Antimicrobial susceptibility testing indicated that the vast majority (>96%) of Chinese Livingstone isolates exhibited multidrug resistance. In a comparative study, all Tunisian isolates exhibited resistance to amoxicillin, amoxicillin-clavulanic acid, ticarcillin, cefalotin, gentamicin, and kanamycin, as well as to third-generation cephalosporins (cefotaxime and ceftazidime). In contrast, Belgian isolates remained susceptible to all tested antibiotics. Genotypically, the Tunisian isolates were homogeneous, belonging exclusively to sequence type ST543, whereas the Belgian isolates exhibited greater diversity with eight strains typed as ST543, two as ST638, and one as ST457. All isolates including them from Tunisia and Belgium carried five chromosomal genes (agfA, hin/H2, iroB, phoP/Q, and slyA) but lacked the plasmid-encoded spvA and spvC.

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