Phenotypic and molecular investigation of polymyxin resistance in gram-negative bacilli

• Grant number: 22/07992-8
• Support Opportunities: Regular Research Grants
• Start date: April 01, 2023
• End date: March 31, 2025
• Field of knowledge: Biological Sciences - Microbiology - Applied Microbiology
• Principal Investigator: Ana Lúcia da Costa Darini
• Grantee: Ana Lúcia da Costa Darini
• Host Institution: Faculdade de Ciências Farmacêuticas de Ribeirão Preto (FCFRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil
• Associated researchers: Doroti de Oliveira Garcia

Abstract

In recent years, with the emergence of multidrug-resistant and extremely drug-resistant organisms, there has been an increase in the use of polymyxins, which in some situations are the last therapeutic option. Resistance to polymyxins has been described and the most common mechanism found in isolates resistant to polymyxins are mutations in chromosomal genes (for example, pmrA, pmrB, mgrB, crrB, phoP, phoQ) responsible for changes in lipid A of the outer membrane, in addition to the presence of plasmid mcr genes. In Brazil, there are still few studies demonstrating these mutations in these genes, and furthermore, data remain scarce regarding the impact on the virulent profile that these changes caused by mutations in these genes can cause, as well as the gene expression of the involved genes in the resistance to this class. In this context, the objective of this work is to investigate the genetics of polymyxin resistance and the virulence profile in members of the order Enterobacterales isolated from different infection sites of hospitalized patients in the State of São Paulo. The search for chromosomal and plasmid genes will be performed by PCR as well as the groups of plasmids (Inc) circulating among the isolates of the study. Plasmids detected carrying genes of interest will be characterized by hybridization. In addition, the gene expression of certain genes found will be performed by RT-PCR; the characterization of lipid A will be evaluated by MALDI-TOF and the virulent profile before and after exposure to different concentrations of the antimicrobial will be evaluated using the Galleria mellonella model. This knowledge becomes fundamental for the epidemiology of mcr genes as well as plasmids involved in their dissemination, mutations responsible for the phenotype presented, and the impact on the virulent profile to be known in isolates from Brazil since data remain scarce. With these results, we hope to contribute to the scientific community in order to better understand the genetics of polymyxin resistance in the study isolates as well as possible changes in the virulent profile caused by mutations in chromosomal genes and, possibly, contribute to better optimization of antibiotic therapy for infections caused by resistant multidrug organisms. (AU)