Base genética da resistência aos antimicrobianos em Pseudomonas aeruginosa isoladas de secreções respiratórias de indivíduos com fibrose cística

Abstract

Cystic fibrosis (CF) is a genetic disease that affects mainly respiratory and digestive system. It is caused by mutations in CFTR gene resulting in malfunction of the exocrine glands and thickness of mucus that obstruct the airways and makes digestion difficult. Pseudomonas aeruginosa is the main pathogens associated to pulmonary exacerbation and death in CF population. The ability to resist antimicrobials exhibited by P. aeruginosa is related to multiple factors, like efflux pump overexpression. Besides the microorganism can also acquire horizontal transferable genes and exhibit adaptative resistance as in biofilm conditions. In addition to this, P. aeruginosa samples acquired from Brazilian CF individuals were not associated to multidrug-resistance (MDR) profile, especially when compared to the rest of the world, where epidemic strains, capable of express resistance to various drugs, are commonly reported. Due to these characteristics and the recent observation of P. aeruginosa resistant to several drugs in ours centers, whole genome sequencing (WGS) is a tool capable of assisting in molecular analyzes related to antimicrobial resistance, through the search for mutations in intrinsic genes, acquisition of extrinsic genes and plasmids, as well as monitoring in the search for epidemic clones that circulates in these patients, which so far have not been described in Brazil. Almost all of the samples in this study exhibited resistance to imipenem and meropenem, however, as only samples resistant to polymyxin B were selected, this was an expected profile, since resistance to this class is associated with MDR profiles and extensively resistance. Using the WGS, we searched for intrinsic resistance genes, and identified evidence that suggests that alterations in the mexZ gene are overexpressing the MexXY efflux pump. Alterations in oprD, opdP and opdD genes, related to carbapenem resistance porins, are possibly related to resistance to this class. Modifications in the gyrA and parC genes, encoding DNA replication enzymes, have also been identified as associated with resistance to fluoroquinolones. Alterations in parS and pmrB, related to polymyxin B resistance, were also identified. The molecular typing were able to identify three new STs, 4051, 4052 and 4053 and when compared to epidemic CF clones, none of the samples included in this study showed association with them. The analysis of the genetic environment of P. aeruginosa resistant to polymyxin B allowed us to understand the different mechanisms of antimicrobial resistance, in addition to subsidizing the understanding of the possible relationships with the epidemic strains that circulates among individuals with CF, observed in other countries.