Involvement of hpap2 and dgkA Genes in Colistin Resistance Mediated by mcr Determinants
Investigation published in Antibiotics
August 22nd, 2020
Plasmid-mediated colistin resistance (mcr) determinants are challenging the efficacy of polymyxins against Gram-negative pathogens. Among 10 mcr genes described so far, the major determinants mcr-1 and mcr-3 are found closely linked to hpap2 or dgkA genes, encoding a hypothetical phosphatidic acid phosphatase of type 2 (PAP2) and a diacylglycerol kinase, respectively, whose functions are still unknown. In this study, mcr-1, mcr-1–hpap2, mcr-3, and mcr-3–dgkA were expressed in Escherichia coli, and recombinant strains were analyzed to detect antimicrobial susceptibility and changes in the expression of genes involved in phospholipid metabolism. The mcr-1 or mcr-3 single genes were enough to drive growth on colistin selective media, although co-expression of linked genes conferred maximal antibiotic resistance. Expression of mcr determinants downregulated endogenous genes involved in lipopolysaccharide (LPS) modification or phospholipid recycling, although to different extents of repression: strong for arnB, ybjG, and pmrR; medium for eptA, lpxT, and dgkA; small for bacA and pgpB. Four of these genes (bacA, lpxT, pgpB, and ybjG) encode undecaprenyl pyrophosphate (UPP) phosphatases. In these conditions, cells presented resistance against bacitracin, an antibiotic that sequesters UPP from PAP2 enzymes. The hpap2 and dgkA genes might play a role in colistin resistance by compensating for phospholipid metabolism functions altered during LPS modification by colistin resistance determinants
Gallardo A., Ugarte-Ruiz M., Hernandez M., Miguela-Villoldo P., Rodriguez-Lazaro D., Dominguez L. and Quesada A.
 | Departamento de Bioquímica, Biología Molecular y Genética. Facultad de Veterinaria. Universidad de Extremadura (UNEX). |
 | Servicio de Zoonosis de Transmisión Alimentaria y Resistencia a Antimicrobianos (ZTA). Centro de Vigilancia Sanitaria Veterinaria (VISAVET). Universidad Complutense (UCM). |
 | Laboratorio de Biología Molecular y Microbiología. Instituto Tecnológico Agrario de Castilla y León (ITACyL). |
 | Unidad de Microbiología. Departamento de Biotecnología y Ciencia de los Alimentos. Universidad de Burgos (UBU). |
| Instituto Universitario de Biotecnología Ganadera y Cinegética (INBIO G+C). Universidad de Extremadura (UNEX). |
