Acinetobacter baumanniiis most well known for its role as a human pathogen and as a member of theAcinetobacter calcoaceticus-baumannii(ACB) complex. However, lesser characterised members of the ACB complex, have also been implicated in hospital-acquired infections. Once mainly considered opportunistic pathogens, manyA. baumanniiand non-baumanniistrains are being isolated from agricultural, water and food sources. The surveillance and tracking ofAcinetobacterspp. have been recently suggested to be part of the One Health consortium, to understand and prevent the spread of antimicrobial resistance. Here, we isolated fourAcinetobacterstrains from tank milk in Bogor, Indonesia and using ANI and dDDH techniques have identified them asAcinetobacter seifertii. MLST methods assigned theseA. seifertiistrains to a novel Sequence Types (ST), highlighting the diversity not only within the ACB complex but also in non-humanAcinetobacterspp. These fourA. seifertiistrains are colistin-resistant and while they do not harbour any known mechanism of colistin resistance, they do share amino acid substitutions in regulatory proteins, AdeS, PmrAB, H-NS, and the membrane associated proteins, LpxACD, MlaD, PldA, LpsB and EptA that may contribute to this phenotype. Furthermore, down-regulation of the RND efflux pump AdeAB, may also be a key factor in colistin resistance in these non-humanA. seifertiistrains. Lipidomics revealed an acyl-homoserine lactone (AHL) molecule, and lyso-phosphatidylethanolamine (lyso-PE) in significant abundance compared to colistin-sensitiveA. baumanniiATCC17978 revealing lipidomic differences between species. Finally, these four tank milkA. seifertiistrains are avirulent in an insect model of virulence. It is possible thatA. seifertiistrains are intrinsically resistant to colistin and require further study. By investigating these less understood Acinetobacter spp. from non-human sources, our study supports the One Health approach to combatting antibiotic resistance.
